valent PVG Indirect Gas Fired Furnaces Heat Modules Dedicated Outdoor Air System Installation Guide

: June 15, 2024
: VALENT

Table of Contents

PVG Indirect Gas Fired Furnaces Heat Modules Dedicated Outdoor Air System
Product Information
Specifications
General Safety Information
Warnings
- Product Usage Instructions
Receiving
Unit Identification
- FAQs
Q: What should I do if I smell gas?

PVG Indirect Gas Fired Furnaces Heat Modules Dedicated Outdoor Air System

Product Information

Specifications

Model: PVG
Type: Indirect Gas-Fired Furnaces/Heat Modules Dedicated
Outdoor Air System
Installation, Operation and Maintenance Manual: Document
483594

General Safety Information

These indirect gas-fired furnaces are commonly used in many
different manufacturer’s ventilating products. For unit-specific
information, refer to the Installation, Operation and Maintenance
manual (IOM) for the unit in which this furnace is installed.

Warnings

FIRE OR EXPLOSION HAZARD

Failure to follow safety warnings exactly could result in
serious injury, death or property damage.
Be sure to read and understand the installation, operation and
service instructions in this manual.
Improper installation, adjustment alteration, service or
maintenance can cause serious injury, death or property
damages.
Do not store or use gasoline or other flammable vapors and
liquids in the vicinity of this or any other appliance.
If you smell gas, follow the provided instructions.
Installation and service must be performed by a qualified
installer, service agency or the gas supplier.

Product Usage Instructions

Receiving

Unpacking:

If the unit is to be installed, tested and operated right away,
locate and remove all packing materials from the furnace, including
any protective coverings that may be on the combustion air intake
and on the furnace exhaust. Follow the Unpacking Instructions as
found in the unit-specific IOM.

Storage:

If the unit must be stored after it is received, take steps to
protect the furnace from damage, moisture, and extreme
temperatures. Verify that gas piping is plugged.

Unit Identification

It is necessary to know the unit model number, the burner
control turndown, and the serial number. This information is needed
when ordering replacement parts and is available on labels located
on the unit.

Furnace Model Number:

On the furnace access door or immediately next to the door is a
Mylar data label. Locate the furnace model number at the top of the
label.

Furnace Model Number: _____

Burner Control Turndown:

Burner turndown ratio is used in many places and must be
calculated. On the data label, locate the INPUT BTU/HR (the largest
number on the label) and also the MINIMUM INPUT BTU/HR. Calculate
the burner turndown ratio and record it.

INPUT BTU/HR MINIMUM BTU/HR = Burner Control Turndown Ratio

Example: 150,000 / 75,000 = 2 (The turndown ratio is 2:1 in this
example.)

Burner Turndown: ___

Furnace Serial Number:

On the furnace access door is a plate identifying the unit
serial number.

Furnace/Unit Serial Number: _____

FAQs

Q: What should I do if I smell gas?

A: If you smell gas, follow the provided instructions in the
manual. Make sure to contact a qualified installer, service agency,
or the gas supplier for installation and service.

Document 483594 Model PVG
Indirect Gas-Fired Furnaces/Heat Modules Dedicated Outdoor Air System
Installation, Operation and Maintenance Manual
Please read and save these instructions for future reference. Read carefully before attempting to assemble, install, operate or maintain the product described. Protect yourself and others by observing all safety information. Failure to comply with these instructions will result in voiding of the product warranty and may result in personal injury and/or property damage.
Technical Support Call: 1-800-789-8550 Email: support@doas.com
Recognized Component

Model PVG
General Safety Information
These indirect gas-fired furnaces are commonly used in many different manufacturer’s ventilating products. For unit-specific information, refer to the Installation, Operation and Maintenance manual (IOM) for the unit in which this furnace is installed.
· Both the furnace units are listed for installation in the United States and in Canada.
· Installation of gas-fired duct furnaces must conform with local building codes. In the absence of local building codes, installation must conform to the National Fuel Gas code, ANSI Z223.1 or in Canada, CAN/CGA-B149 Installation codes.
· All electrical wiring must be in accordance with the regulations of the National Electric Code, ANSI/ NFPA-70.
· Unit is approved for installation downstream from refrigeration units. In these conditions, condensate could form in the duct furnace and provision must be made to dispose of the condensate.

WARNING
FIRE OR EXPLOSION HAZARD
Failure to follow safety warnings exactly could result in serious injury, death or property damage.
Be sure to read and understand the installation,operation and service instructions in this manual.
Improper installation, adjustment alteration, service or maintenance can cause serious injury, death or property damages.
— Do not store or use gasoline or other flammable vapors and liquids in the vicinity of this or any other appliance.
— WHAT TO DO IF YOU SMELL GAS
· Do not try to light any appliance. · Do not touch any electrical switch; do not use
any phone in your building. · Leave the building immediately. · Immediately call your gas supplier from a
phone remote from the building. Follow the gas supplier’s instructions. · If you cannot reach your gas supplier, call the fire department.
— Installation and service must be performed by a qualified installer, service agency or the gas supplier.
DOAS Indirect Gas-Fired Heat Modules/Furnaces 1

NOTE
Model PVG is an indirect gas-fired heat module that will be referred to in this manual as a furnace.
Receiving
Upon receiving the product, check to ensure all items are accounted for by referencing the delivery receipt or packing list. Inspect each crate or carton for shipping damage before accepting delivery. Alert the carrier of any damage detected. The customer will make notation of damage (or shortage of items) on the delivery receipt and all copies of the bill of lading which is countersigned by the delivering carrier. If damaged, immediately contact your manufacturer’s representative. Any physical damage to the unit after acceptance is not the responsibility of the manufacturer.
Unpacking
If unit is to be installed, tested and operated right away, locate and remove all packing materials from the furnace, including any protective coverings that may be on the combustion air intake and on the furnace exhaust. Follow Unpacking Instructions as found in the unit-specific IOM.
Storage
If unit must be stored after it is received, take steps to protect furnace from damage, moisture, and extreme temperatures. Verify that gas piping is plugged.
Unit Identification
It is necessary to know the unit model number, the burner control turndown and the serial number. This information is needed when ordering replacement parts and is available on labels located on the unit.
Furnace Model Number
On the furnace access door or immediately next to the door is a Mylar data label. See images below. Locate the furnace model number at the top of the label and record it here:
Furnace Model Number: _____

Burner Control Turndown

Burner turndown ratio is used in many places and must be calculated. On the data label, locate the INPUT BTU/HR (the largest number on the label) and also the MINIMUM INPUT BTU/HR. Calculate the burner turndown ratio and record it.

INPUT BTU/HR MINIMUM BTU/HR

=

Burner Control Turndown Ratio

Example:

150,000 75,000

=2

The turndown ratio is 2:1 in this example.

Burner Turndown: ___

Furnace Serial Number On the furnace access door is a plate identifying the unit serial number. Record that information here. Furnace/Unit Serial Number:

ETL Listing Model PVG furnaces have been ETL tested as gas-fired heat modules intended for installation as a component within heating equipment in duct or cabinet mounted applications. They are ETL Recognized Components.

Product Overview
Burner Assembly

Heat Exchangers

Typical Furnace Data Labels each unit will be different
2 DOAS Indirect Gas-Fired Heat Modules/Furnaces

Combustion Blower

Collector Box

Table of Contents
General Safety Information . . . . . . . . . . . . . . 1 Receiving, Unpacking, Storage . . . . . . . . . . . . 2 Unit Identification . . . . . . . . . . . . . . . . . . . 2 Furnace Model Number . . . . . . . . . . . . . . . . 2 Burner Control Turndown . . . . . . . . . . . . . . . 2 Furnace Serial Number . . . . . . . . . . . . . . . . 2 ETL Listing . . . . . . . . . . . . . . . . . . . . . . . 2 Product Overview . . . . . . . . . . . . . . . . . . . 2 Furnace Control Center
Furnace Control Center Components. . . . . . . . 4 Typical Furnace Control Logic. . . . . . . . . . . . 4 Typical Furnace, Electrical and Control Components . . . . . . . . . . . . . . . . 5 Gas-Fired Burner Turndown . . . . . . . . . . . . 6 Electronic Modulation . . . . . . . . . . . . . . . . 6 Combinations . . . . . . . . . . . . . . . . . . . . 6
Available Turndown Control Options . . . . . . . 6 Installation of Venting for Outdoor Units . . . . . 7 Installation of Venting for Indoor Units . . . . . . 7
Venting Methods . . . . . . . . . . . . . . . . . . 8 Installation of Standard Indoor Venting
Horizontal . . . . . . . . . . . . . . . . . . . . . . 8 Vertical . . . . . . . . . . . . . . . . . . . . . . . . 8 Installation of Concentric Venting Two- Pipe Venting – Horizontal. . . . . . . . . . . . 9 Two-Pipe Venting – Vertical . . . . . . . . . . . . 10 Installation of Control Wiring . . . . . . . . . . 10 Installation of Discharge Air Sensor . . . . . . 10 Installation of Gas Piping. . . . . . . . . . . . . 11 Gas Supply Requirements . . . . . . . . . . . . 11 Connect the Supply Gas Line . . . . . . . . . . . 11 Installation of Additional Regulator . . . . . . . . 11 Test the System for Leaks. . . . . . . . . . . . . 11 Gas Pressure Test Ports. . . . . . . . . . . . . . 11 Sequence of Operation . . . . . . . . . . . . . . 12 Start-Up / Standby . . . . . . . . . . . . . . . . 12

Heat Mode. . . . . . . . . . . . . . . . . . . . . 12 Recovery from Lockout . . . . . . . . . . . . . . 12
Performance Data . . . . . . . . . . . . . . . . . 12
Start-Up – Furnaces (all units) . . . . . . . . . . 13 4:1 Turndown Electronic Modulation . . . . . . . 13 Adjust High Fire and Low Fire Settings . . . . . 14 Modulating Valve High Fire Setting . . . . . . . 14 Modulating Valve Low Fire Setting . . . . . . . 14 With High Turndown Electronic Modulation . . 15
Troubleshooting Ignition Controller . . . . . . . . . . . . . . . . . 16 4:1 Modulating with Stand-Alone Controller . 17-21 4:1 Modulating with Microprocessor Controller 22-25
Reference: Controls Furnace Control with Microprocessor. . . . . . . 26
Maintenance Combustion Blower Motor . . . . . . . . . . . . 27 Burners and Orifices . . . . . . . . . . . . . . . 27 Heat Exchanger . . . . . . . . . . . . . . . . . . 27 Flue Collector Box. . . . . . . . . . . . . . . . . 27 Electrical Wiring . . . . . . . . . . . . . . . . . . 27 Gas Train . . . . . . . . . . . . . . . . . . . . . 27 Replacement Parts . . . . . . . . . . . . . . . . 27
Maintenance Log . . . . . . . . . . . . . . . 28-29
Our Commitment . . . . . . . . . . . . . Backcover

DOAS Indirect Gas-Fired Heat Modules/Furnaces 3

Furnace Control Center

Each ventilating unit containing one or more furnaces will have a furnace control center located on the furnace vest plate. The control center receives high voltage AC from the main unit control center and in most cases, also receives low voltage control signals (call for heat) from the main unit control center. In all cases, see the unit-specific wiring schematic located inside the furnace door. Furnace Control Center Components
(Components and their locations will vary.)
Components shown are for a typical 4:1 turndown electronic modulation configuration.

12 9

2

13

High Voltage Side
1. Inducer Relay (controls combustion fan) 2. Combustion Blower 3. Power Transformer

3
7
14 4 8
5 6 1

11

10

Low Voltage Side 4. Ignition Controller (also has high voltage present) 5. Furnace Controller (modulates heat and switches entire furnace on/off) 6. 24 volt Terminal Strip
Control Sensors 7. High Temperature Sensor (auto reset) 8. Airflow Switches 9. Flame Sensor
Gas Train 10. Combination Valve 11. Modulating Valve 12. Burner Manifold 13. Collector Box 14. Spark Rod

Typical Furnace Control Logic In all cases, refer to the unit-specific wiring diagram located on the unit control center door. This illustration is only for a typical 4:1 turndown electronic modulation configuration.

Optional Microprocessor Controller Configuration
Microprocessor Controller Located in unit main control center

Expansion Board
Activates Ignition Controller

Activates and modulates Modulating Valve
Controls speed of Combustion
Blower

Ignition Controller
Activates Combination Valve

Activates Combustion Blower
Spark to Igniter

Furnace Controller
Activates Ignition Controller
Ignition Controller
Activates Combination Valve

1. Microprocessor with pCOe

Temperature Sensor
If there is no Microprocessor Controller, the sensor is connected
to the furnace Controller

(if present) or furnace controller senses low temperature from the

temperature sensor, then

sends an enable signal to

the ignition controller, and

Activates and modulates Modulating Valve

0-10 VDC signal to the modulating valve.

Controls speed of Combustion
Blower
Activates Combustion Blower Spark to Igniter

2. Ignition controller receives call for heat from pCOe expansion board or furnace controller, sends spark to igniter, and activates the combination valve. It looks for verification that the combustion blower is running.

3. Flame sensor detects flame and the trial for ignition ends.

4 DOAS Indirect Gas-Fired Heat Modules/Furnaces

Typical Furnace, Electrical and Control Components

Microprocessor
The microprocessor provides the call for heat to the ignition controller and also monitors the discharge air temperature. It is found in the unit’s main control center. On units with electronic modulation, it also determines the required burner firing rate.
Discharge Air Temp Sensor
This sensor is shipped with all units and must be field-installed in the discharge air duct. This may be shipped in the main unit control center or in the furnace control center, depending on the control type.
pCOe Expansion Board
Used on all 4:1 or high turndown electronic modulating controls when a microprocessor controller is present in the unit.
The pCOe acts as an interface between the furnace and microprocessor controller. It sends the signal to enable the ignition controller, modulate the gas valve, speed up the combustion fan, and it monitors the furnace for alarms. The expansion board has no built-in logic since the main microprocessor controller contains the built-in logic.
Furnace Controller
Used on all stand-alone 4:1 electronic modulating controls
The furnace controller provides power to the gas valve(s) and electronically adjusts the valve(s). It will also enable the ignition module. The furnace controller has a digital readout and six push buttons: Enter, Alarm, Program, Escape and arrows for Up or Down. It is pre-programmed at the factory for each specific furnace configuration and it may be used to control up to three furnaces at the same time.
Ignition Controller
This controller is found only in the furnace control center. It has an LED indicator light on the top right of the controller that will flash GREEN for normal operation or RED for an error. Some furnace configurations have two of these controllers.

Airflow Switch
Airflow switches are used on both furnaces and are found on the furnace vest plate. If the combustion blower is multi-speed, there will be two airflow switches and each will switch in response to a different pressure. The switch is connected to the combustion blower by means of a vacuum tube and is used to sense operation of the combustion blower. The internal switch is Normally Open (NO). If the blower fails to operate, the open circuit will cause the ignition controller to disable the furnace.
Flame Igniter
The igniter receives a high voltage input from the ignition controller to produce a spark between the two electrodes. It operates only during the ignition phase. On split burner manifolds, there will be two igniters.
Flame Sensor
The flame sensor is identical to the flame igniter. It is located on the opposite end of the burner manifold from the igniter. On split burner manifolds, there will be two flame sensors.
Auto Reset High Temperature Limit Switch
This limit switch is installed through the vest plate into the supply air plenum.
Burner Manifold

Single Section Burner Manifold

Split Burner Manifold

DOAS Indirect Gas-Fired Heat Modules/Furnaces 5

Gas-Fired Burner Turndown

Furnaces are available in electronically modulated configurations. Electronically modulated furnaces have continuously variable firing rates. Turndown is the capability of the furnace to operate at less than full capacity, accomplished by reducing the amount of gas flow when the unit is operating. The advantage of turndown is that at partial-load conditions, the furnace will not cycle as often.Turndown is expressed as a ratio and is found by dividing the maximum BTU input by the minimum BTU input.

Electronic Modulation

The most common electronic

modulation involves the use

of an electronically-controlled

gas valve which provides

a 4:1 turndown. The entire

furnace is sized appropriately

for the maximum heat output

ordered by the customer, but

it can operate as low as 25%

of its maximum capacity. The electronically-controlled gas valve will modulate the combustion rate continuously,

Low Fire and High Fire adjustments are made on printed circuit board behind removable cover

dependent on the output from the furnace controller.

With this method, all the burners fire at the same time

but at a varying capacity. The Modulating Valve is

used in conjunction with a furnace controller and a

combination valve which provides an ON/OFF function.

The high turndown option uses the same functionality as the 4:1 modulation described above in conjunction with a split manifold to provide higher turndown capabilities. When less heat is needed, a portion of the manifold is turned off and the remaining portion continues to modulate. This provides seamless modulation at very high turndown ratios. High turndown is classified as 8:1 turndown or greater per furnace.

Combinations
Various combinations of the methods outlined may be used to accomplish the turndown required by the application.
Available turndown control options include:

Single Furnace Unit
Two Furnace Unit

Electronic Modulation
4:1- uses modulating valve and furnace controller
High turndown – uses 4:1 modulating valve with split manifold and furnace controller
4:1 – uses two 4:1 modulating furnaces controlled in parallel
High turndown furnaces in a parallel configuration – use two high turndown furnaces, controlled in parallel

6 DOAS Indirect Gas-Fired Heat Modules/Furnaces

Installation of Venting for Outdoor Units
Follow Guidelines
All of the following guidelines must be followed when installing the unit.
WARNING
Do not install units in locations where flue products can be drawn into adjacent building openings such as windows, fresh air intakes, etc. Distance from vent terminal to adjacent public walkways, adjacent buildings, operable windows and building openings shall conform with the local codes. In the absence of local codes, installation shall conform with the National Fuel Gas Code, ANSI Z223.1 or the Canadian CAN/CGA B-149 Installation Codes.
WARNING
The following guidelines must be followed for all outdoor units: 1. Building materials that will be affected by flue
gases should be protected. 2. Maintain minimum horizontal clearance of 4 feet
from electric meters, gas meters, regulators and relief equipment. In Canada, the minimum clearance is 6 feet. 3. The combustion blower discharge on outdoor units must be located a minimum of 42 inches from any combustible materials. 4. Do not modify or obstruct the combustion air inlet cover or the combustion blower weatherhood. 5. Do not add vents other than those supplied by the manufacturer. 6. During the winter, keep the unit clear of snow to prevent any blockage of the combustion venting.
Install Stack (optional) Clearance may require an exhaust stack. Install an exhaust stack as needed to the exhaust connection on the unit. Install a vent terminator on the exhaust pipe.
Exhaust transition and vent termination must be purchased from the factory for proper operation. Exhaust pipe is by others.

Installation of Venting for Indoor Units
WARNING
The following guidelines must be followed for all indoor units: 1. Installation of venting must conform with local
building codes. In the absence of local codes, installation must conform with the National Fuel Gas Code, ANSI Z223.1 or in Canada, CAN/ CGA-B149 installation codes. 2. For the exhaust pipe, use pipe approved for a Category III appliance or galvanized vent pipe sized 26 gauge or heavier. The piping is required to be gas-tight by ANSI. 3. For the combustion air pipe on separated combustion units, sealed single-wall galvanized air pipe is recommended. 4. The joints must be sealed with a metallic tape or SilasticTM suitable for temperatures up to 350°F. 5. A minimum of 12 inches of straight vent pipe is recommended after the exhaust connection and before any elbows. 6. Vertical combustion air pipes should be fitted with a tee, drip leg and clean-out cap to prevent any moisture in the combustion air pipe from entering the unit. 7. To reduce condensation, insulate any vent runs greater than 5 feet. 8. All vent pipe connections should be made with at least three corrosion-resistant sheet metal screws. 9. Refer to the National Fuel Gas Code for additional piping guidelines.
NOTE
Vent piping is supplied by others and not supplied by manufacturer.
NOTE
The drip leg should be cleaned out periodically during the heating season.
NOTE
Clearances from combustible material for indoor units are determined by the National Fuel Gas Code and/or other local codes.

DOAS Indirect Gas-Fired Heat Modules/Furnaces 7

Venting Methods
There are two venting methods for indoor mounted units. For each method, the units can be vented horizontally through an exterior wall or vertically through the roof. Specific venting instructions are provided for each method and shown in the following pages. Construct the vent system as shown in these instructions. Refer to your unit specific submittal to determine the applicable venting option.
The venting method options are:
Standard Indoor Venting · uses building air for combustion · vents exhaust to outdoors · one exterior roof or wall penetration
Separated Combustion 2-Pipe Venting · uses outside air for combustion · vents exhaust to outdoors · two exterior roof or wall penetrations
NOTE
For each method, the units can be vented horizontally through an exterior wall or vertically through the roof. Refer to the specific venting instructions for your unit. Construct the vent system as shown in these instructions.
Installation of Standard Indoor Venting
Standard indoor venting uses one penetration through an exterior wall or roof for venting the flue exhaust. The combustion air is supplied from the air inside the building. Units must not be installed in a potentially explosive, flammable, or corrosive atmosphere. To prevent premature heat exchanger failure, do not locate unit where chlorinated, halogenated or acid vapors are present.
When units are installed in tightly sealed buildings, provisions should be made to supply an adequate amount of infiltration air from the outside. The rule of thumb is that an opening of one square inch should be provided for every 1000 BTUs per hour of input rating.
Vent terminals must be used. Construct the vent system as shown in the drawings. Reference the Vent Pipe Diameter table and Exhaust Vent Pipe table for additional details.

A = 12 inch minimum

Pitch vent pipe downward from furnace ¼ inch per foot
EXHAUST
Air Inlet

Exterior Wall
A
Exhaust Vent
Terminal

Standard Indoor Venting – Horizontal

A = 12 inch minimum B = 12 inch minimum, but size according to expected snow depth
B
Roof Line

Exhaust Vent Terminal

EXHAUST

A

Air Inlet

Standard Indoor Venting – Vertical

Vent Pipe Diameter
Select the vent pipe diameter. Use only the specified pipe diameter.
Installing Exhaust Vent Pipe

Standard Indoor Venting Vent Pipe Diameter

Furnace Size Exhaust Pipe (MBH) Diameter (inches)

75-175

4

200-400

6

Install the vent pipe with a minimum downward slope

(from the unit) of 1/4-inch per foot (horizontal venting

only). Securely suspend the pipe from overhead

structures at points no greater than 3 feet apart.
The minimum vent length is 5 feet for horizontal

Standard Indoor Venting Exhaust Vent Pipe

Vent Minimum Maximum

Length

(feet)

and 10 feet for vertical. Horizontal 5

70

The maximum vent

Vertical

10

70

length is 70 feet. The

total equivalent vent length must include elbows. The

equivalent length of a 4 inch elbow is 6 feet and the

equivalent length of a 6 inch elbow is 10 feet.

Attach the vent terminal to the end of the exhaust pipe.

8 DOAS Indirect Gas-Fired Heat Modules/Furnaces

Installation of Two Pipe Venting Horizontal
Refer to the diagram for venting on horizontal two pipe systems. Maintain at least 12 inches of clearance between the exhaust pipe termination and the exterior surface of the exterior wall.
The combustion air pipe must be a minimum of 12 inches from the exhaust pipe and 2 inches from the exterior surface of the outside wall.
A maximum of 48 inches of building wall thickness is required for separated combustion vent pipe.

A = 12 inch minimum B = 2 inch minimum C = 12 inch minimum
Pitch vent pipe downward from furnace ¼ inch per foot

Exterior Wall

Exhaust Vent
Terminal

EXHAUST
COMBUSTION AIR B

A

C

Combustion Air Inlet Terminal

Install Combustion Air Pipe
Run a combustion air pipe from the unit’s combustion air intake through the exterior wall to the outdoors. The combustion air pipe must terminate at least 12 inches from the exhaust vent pipe and 2 inches from the exterior surface of the outside wall. Attach the combustion air inlet guard to the end of the combustion air pipe. Using field-supplied mounting brackets, support the combustion air pipe as needed.
Seal Wall Openings
Using an appropriate method, seal the wall openings around the piping.

Vent Connection Diameter

Vent terminals must be used. The vent kit includes two

terminals per furnace. Construct the vent system as shown in the drawings and refer to the

Horizontal Two Pipe Venting Vent Connection Diameter

Furnace Size Exhaust Combustion

(MBH)

(inches) (inches)

table for the correct

75-175

4

vent connection

200-400

6

diameters.

Vent Length

Refer to table for

Horizontal Two Pipe Venting

minimum and maximum

Vent Length

vent lengths. The

Vent Minimum Maximum

minimum vent length is

Length

(feet)

5 feet and the maximum Horizontal 5

50

vent length is 50 feet.

The total equivalent vent length must include elbows.

The equivalent length of a 4 inch elbow is 6 feet and the

equivalent length of a 6 inch elbow is 10 feet.

Install Exhaust Pipe

Run an exhaust pipe from the unit’s combustion exhaust through the exterior wall to the outdoors. The exhaust pipe must terminate at least 12 inches from the outside surface of the outside wall. Attach exhaust vent terminal to the end of the exhaust pipe. Using field-supplied mounting brackets, support the exhaust pipe as needed.

DOAS Indirect Gas-Fired Heat Modules/Furnaces 9

Installation of Two Pipe Venting Vertical

Refer to the diagram for venting vertical two pipe systems. The combustion air pipe must terminate at least 12 inches above the roof. This clearance may need to be increased to accommodate for snow accumulation. The exhaust must terminate at least 12 inches above and 12 inches horizontally from the combustion air inlet.

A = 12 inch minimum, but size

C

according to expected snow depth

Exhaust Vent

B = 12 inch minimum

Terminal

C = 12 inch minimum D = 12 inch minimum

B

Combustion Air Inlet Terminal

A Roof Line

EXHAUST COMBUSTION AIR

D D

Tee with drip leg and
clean-out cap

Vent Connection Diameter

Vent terminals must be used. The vent kit includes two terminals per furnace. Construct the vent system as shown in the drawings and refer to the table

Vertical Two Pipe Venting Vent Connection Diameter

Furnace Size Exhaust Combustion (MBH) (inches) (inches)

75-175

4

200-400

6

for the correct vent connection diameters.

Vent Length

Refer to table for minimum and maximum vent lengths.

The minimum vent length is 10 feet and the maximum

vent length is 70 feet. The total equivalent vent length

must include elbows. The equivalent length of a

Vertical Two Pipe Venting Vent Length

4 inch elbow is 6 feet and the equivalent length of a

Vent Minimum Maximum

Length

(feet)

6 inch elbow is 10 feet.

Vertical

10

70

Install Exhaust Pipe

Run an exhaust pipe from the unit’s combustion exhaust through the roof to the outdoors. The exhaust pipe must terminate at least 24 inches above the outside surface of the roof. This clearance may need to be increased to accommodate snow accumulation. Attach the exhaust vent terminal to the end of the exhaust pipe.

Install Combustion Air Pipe
Run a combustion air pipe from the unit’s combustion air intake through the roof to the outdoors. The combustion air pipe must terminate at least 12 inches horizontally and vertically from the combustion exhaust pipe and at least 12 inches from the exterior surface of the roof. These clearances may need to be increased to accommodate for expected snow accumulation. Attach the combustion air terminal to the end of the combustion air pipe.
Seal Roof Penetration
Using an appropriate method, seal the roof openings around the vent pipes.
Installation of Control Wiring
Disconnect power supply before making any wiring connections to prevent electrical shock and equipment damage.
All appliances must be wired strictly in accordance with the wiring diagram furnished with the unit. Any wiring different from the diagram could result in a hazard to persons and property.
Any original factory wiring that requires replacement must be replaced with wiring material having a temperature rating of at least 105° C.
1. Installation of wiring must conform with local building codes. In the absence of local building codes, installation must conform to the National Electrical Code and ANSI/NFPA 70 – Latest Edition. Unit must be electrically grounded in conformance with this code. In Canada, wiring must comply with CSA C22.1, Canadian Electrical Code.
2. All furnaces are provided with a wiring diagram located on the inside of the access panel or door to the unit’s furnace. Refer to this diagram for all wiring connections.
Installation of Discharge Air Sensor
Every furnace has a Discharge Air Sensor included. It is typically attached to the terminal strip on the furnace control center. If the ventilating unit has a microprocessor controller, the discharge air sensor will be connected to the microprocessor controller. See the unit-specific wiring diagram. Install sensor in the supply air duct, as far downstream as possible for accurate temperature measurement. Additional wire may be added to the sensor as necessary.

10 DOAS Indirect Gas-Fired Heat Modules/Furnaces

Installation of Gas Piping
IMPORTANT
All gas piping must be installed in accordance with the latest edition of the National Fuel Gas Code ANSI/Z223.1 and any local codes that may apply. In Canada, the equipment shall be installed in accordance with the Installation Code for Gas Burning Appliances and Equipment (CGA B149) and Provincial Regulations for the class. Authorities having jurisdiction should be consulted before installations are made.
IMPORTANT
All piping should be clean and free of any foreign material. Foreign material entering the gas train can cause damage.
WARNING
All components of this or any other gas fired heating unit must be leak-tested prior to placing the unit into operation. A soap and water solution should be used to perform this test. NEVER test for gas leaks with an open flame.
IMPORTANT
Do NOT connect the unit to gas types other than what is specified and do NOT connect the unit to gas pressures that are outside of the pressure range shown on the label.
WARNING
When leak testing pressures equal to or less than 14 in. wg (3.5 kPa), first close the field-installed shutoff valve to isolate the unit from the gas supply line.
WARNING
When leak testing pressures above 14 in. wg (3.5 kPa), close the field- installed shutoff valve, disconnect the furnace and its gas train from the gas supply line and plug the supply line before testing.
NOTE
When connecting the gas supply, the length of the run must be considered in determining the pipe size to avoid excessive pressure drop. Refer to a Gas Engineer’s Handbook for gas pipe capacities.
NOTE
Each furnace has a single 3/4-inch connection.

Determine the Gas Supply Requirements
The data label located on the face of the furnace lists the requirements for the gas being supplied to the unit.

Typical Furnace Data Labels each unit will be different
Connect the Supply Gas Line
A manual shut off valve, a 1/8 inch plugged test port and a drip leg must be installed between the gas supply pipe and the start of the gas train. The valve and test port must be accessible for the connection of a test gauge. Supply gas connections must be made by a qualified installer and are not furnished by manufacturer.

Manual Shut Off Valve

Ground Joint Union

Gas to Controls

From Gas Supply
Bleeder Valve or 1/8 in Plugged Tap

8 in. Trap

Typical Gas Supply Piping Connection
IMPORTANT Before applying gas to the valves, test the gas pressure to make sure it is less than 14 in. wg. Pressures greater than 14 in. wg will damage the gas valves.
Install Additional Regulator (if required) If the gas supply pressure exceeds 14 in. wg, an additional regulator must be installed to reduce the pressure. The additional regulator is to be provided and installed by others. The regulator must have a Listed leak limiting device or it must be vented to the outdoors.
Test the System for Leaks After installing the gas supply piping, perform a leak test in accordance with the instructions in this manual. The leak test must be performed before placing the unit in service.
DOAS Indirect Gas-Fired Heat Modules/Furnaces 11

Gas Pressure Test Ports Burner manifolds and gas valves used in the furnaces are supplied with test ports for temporary connection of a pressure gauge or a magnehelic gauge.
Test Ports
Gas Supply In Typical Split Burner Manifold
Sequence of Operation
Start-Up / Standby Prior to start-up, verify that all field-installed sensors have been installed. This includes a room temperature sensor (optional) and a discharge air temperature sensor (standard). Heat Mode When the unit or furnace controller calls for heat: 1. The ignition control will check that the pressure switch
for the combustion blower is open. 2. The combustion blower will energize and the
15 second pre-purge begins. 3. The gas valve is energized and the igniter will spark for
up to 10 seconds. If a flame is not sensed during the trial for ignition, two additional tries will be attempted before going into lockout for one hour.
Performance Data

4. When a flame is sensed, sparking stops immediately. The gas valve and combustion blower remain energized.
5. Ignition
4:1 Electronic Modulation – The burner will light at 100% fire and remain there for 10 seconds. The main burner gas valve will then modulate from 100% down to a minimum of 25%, as needed. The combustion blower will change between high and low speed to maintain acceptable combustion airflow. If the high speed pressure switch does not pull in when required, the furnace will lock out.
High Turndown Electronic Modulation – The furnace controller will ignite the necessary manifold(s) at 100% for 10 seconds. The main burner gas valves will then modulate from 100% down to a minimum of 25% as needed. The combustion blower will change between high and low speed to maintain acceptable combustion airflow. If less heat is needed, a manifold section will be turned off. Each time a manifold section is initialized, the manifold section will ignite at 100%.
6. The ignition control constantly monitors the call for heat, the pressure switch and the burner flame to assure proper operation.
7. When the unit or furnace controls are satisfied, the main gas valve is then de-energized and the combustion blower shuts off following a 30 second post-purge period.
Recovery from Lockout
If the furnace goes into lockout, the ignition control will automatically reset after one hour if the thermostat is still calling for heat. If needed, a manual reset can be accomplished by either shutting off the power or turning off the call for heat (turn off the thermostat) for a period of five seconds.

Model
50 75 100 125 150 175 200 225 250 275 300 325 350 400

Input (BTU/hr) 50,000 75,000 100,000 125,000 150,000 175,000 200,000 225,000 250,000 275,000 300,000 325,000 350,000 400,000

20°F
1875 2813 3750 4688 5625 6563 7500 8438 9375 10131 11250 12188 13125 15000

30°F
1250 1875 2500 3125 3750 4375 5000 5625 6250 6875 7500 8125 8750 10000

40°F
938 1406 1875 2344 2813 3281 3750 4219 4688 5156 5625 6094 6365 7500

Supply Air Temperature Rise

50°F

60°F

70°F

CFM

750 1125 1500 1875 2250 2625 3000 3375 3750 4125 4500 4875 5250 6000

625 938 1250 1563 1875 2188 2500 2813 3125 3438 3750 4063 4375 5000

536 804 1071 1339 1607 1875 2143 2411 2679 2946 3214 3482 3750 4286

80°F
469 703 938 1172 1406 1641 1875 2109 2344 2578 2831 3047 3281 3750

90°F
417 625 833 1042 1250 1458 1667 1875 2083 2292 2500 2708 2917 3333

100°F
375 563 750 938 1125 1313 1500 1688 1875 2063 2250 2438 2625 3000

12 DOAS Indirect Gas-Fired Heat Modules/Furnaces

Start-Up – Furnaces (all units)
IMPORTANT
For the unit to function properly, ALL gas valves must have their high fire and low fire settings adjusted for field conditions.
IMPORTANT
Confirm the discharge air sensor is installed at least three duct diameters downstream of the furnace.
IMPORTANT
Multi-furnace units may use a combination of the available turndown options. Each furnace must be set-up per the specific instructions for its control type. For additional information, see Gas-Fired Burner Turndown in this manual.
After the gas piping has been installed and leak tested, verify that all field-installed components such as an air temperature sensor have been installed. Verify that ON/ OFF gas control knob on each stage-type gas valve is turned to the “ON” position (see image).

With 4:1 Turndown Electronic Modulation

Furnace Controller

Discharge Temperature Sensor

Ignition Controller

Test Port

ON / OFF Gas Control Knob
Test Port

Typical Single Stage Gas Valve
Verify the unit turndown ratio as shown on page 2 of this manual. Consult the specific start-up instructions as shown on the following pages to accomplish the following steps:
Set Airflow
Airflow adjustment is done at the time of unit start-up. Refer to the unit- specific Installation, Operating and Maintenance manual (IOM) for instructions.

EXA Valve Single Stage Valve
Single Section Burner Manifold
Furnaces with electronically modulated 4:1 turndown use a combination valve for primary gas control. It controls the high fire gas supply and acts as an on/off switching device. The combination valve is normally closed. It requires 24 VAC to hold it open.
The modulating valve is located just after the combination valve. The modulating valve is the device that modulates or changes the gas volume that is being supplied to the furnace manifold. It has a built-in digital controller that will accept user settings for High Fire and Low Fire. During normal use, the amount of combustion gas will vary constantly to regulate the heat output from the furnace. The modulation is controlled by the microprocessor controller through the pCOe expansion board or by the furnace controller. The controller sends a 0-10 VDC analog signal to the modulating valve that causes the valve to send more or less gas to the furnace. The valve also requires a 24 VAC power supply to operate.
When a call for heat is provided to the furnace controller or the pCOe expansion board, the controller will first provide a 10 VDC signal to the modulating valve so that it will always start in a high fire condition. After ignition, the controller will change its output signal, causing the volume of combustion gas to be reduced to as little as 25% of full flow (4:1 turndown) based on demand.
Both of these valves require adjustment at the time of unit start-up.
DOAS Indirect Gas-Fired Heat Modules/Furnaces 13

Before making furnace adjustments, enter the Commissioning Menu on the unit or Furnace Controller. The Commissioning Menu is located under Service > Overrides > Control Loops. Reference the controller IOM for more information about navigating through the controller menus. The Commissioning Menu offers a step by step guide to setting up the furnace. Follow the instructions on the screen. The following sections of this IOM offer detailed information about setting the gas pressures.

Combination Valve Adjustments

Conduct this step when the Commissioning Menu reaches the High Fire Setting screen.

Connect a manometer to the outlet pressure tap on the Honeywell combination

Combination Valve Outlet Settings

valve and remove the cover Natural Gas 5 in. wg

over the outlet pressure adjustment screw. Use the

LP Gas 11.5 in. wg

outlet pressure adjustment screw on the combination

valve to adjust the outlet pressure to the value listed in

the table.

ON / OFF Gas Control Knob

Outlet Pressure Tap

Outlet Pressure Adjustment

Typical Single Stage Gas Valve

Modulating Valve Adjustments
At start-up, remove the cover from the circuit board housing by loosening the two Phillips head retaining screws. Identify Button #1 and Button #2 and also locate the LED indicator light.

Terminals 1 & 2 (signal)

Terminals 3 & 4 (power)

Button #1

Button #2 LED Light

EXA Modulating Gas Valve (with cover removed)

Modulating Valve High Fire Setting

Conduct this step with the Commissioning Menu on the High Fire Setting screen.

1. Connect a manometer to the test port on the burner manifold.
2. Press and hold button #1

Modulating Valve High Fire Settings
Natural Gas 3.5 in. wg

until the LED lights solid

LP Gas 10.0 in. wg

red. Release the button.

Observe the gas pressure on the manometer.

3. Adjust the modulating valve by pushing button #1 to increase the pressure or by pushing button #2 to decrease the pressure.

4. Save the High Fire setting by simultaneously holding down buttons #1 and

2 until the LED turns off. If the new setting is not saved within five

minutes, the modulating valve will default back to its last saved setting.

NOTE
During the adjustment process, each push of either button will increase or decrease the pressure in steps. Holding down either button auto-steps and eliminates the need to repeatedly push the button. Use this feature to rapidly increase or decrease the gas flow.

Modulating Valve Low Fire Setting

Conduct this step when the Commissioning Menu reaches the Low Fire Setting screen.

1. With a manometer installed at the burner manifold test port, press and hold down button

Modulating Valve Low Fire Settings
Natural Gas 0.3 in. wg

2 until the LED blinks

LP Gas

1.0 in. wg

red. Release the button.

Observe the gas pressure on the manometer.

2. Adjust the Low Fire setting by pushing button #1 to increase the pressure or by pushing button #2 to decrease the pressure.

3. Save the Low Fire setting by simultaneously holding down buttons #1 and #2 until the LED turns off. If the new setting is not saved within five minutes, the Modulating Valve will default back to its last saved setting.

Continue through the Commissioning Menu to verify proper furnace operation. If additional furnaces are present, the Commissioning Menu will step through setting up those furnaces as well. Reference the appropriate section in this IOM for detailed information about each furnace.

Reinstall the cover on the modulating valve, remove the manometer and reinstall the plug in the manifold test port.

14 DOAS Indirect Gas-Fired Heat Modules/Furnaces

High Turndown Electronic Modulation
IMPORTANT High turndown furnaces use a split burner manifold with a shutoff and a modulating valve on each manifold section. High and low fire manifold pressure must be checked and properly set on each manifold section
High turndown furnace patent pending.
Furnaces with electronically modulated high turndown control use two combination valves for primary gas control one valve controls each manifold section. They control the high fire gas supply and act as on/off switching devices. The combination valves are normally closed and require 24 VAC to hold them open. A modulating valve is located just after each combination valve. The modulating valve is the device that modulates or changes the gas volume that is being supplied to the furnace manifold. Its function is described in the 4:1 Turndown Electronic Modulation section. When a manifold section is initiated, the furnace controller will first provide a 10 VDC signal to the modulating valve so that it will always start in a high fire condition. After ignition, the controller will change its output signal, causing the volume of gas to be reduced to as little as 25% of full flow (4:1 turndown) based on demand. If less heat is needed, a manifold section is turned off and the remaining manifold section is allowed to modulate based on demand. Adjustment of the high turndown modulation system follows the same steps as the 4:1 modulation system. The same settings must be performed on each manifold section. Refer to the 4:1 modulation section for proper adjustment of each section of the high turndown modulating furnace.
DOAS Indirect Gas-Fired Heat Modules/Furnaces 15

Troubleshooting – Ignition Controller

NOTE
The green LED light indicates NORMAL operation while the red LED light indicates an ERROR operation.
The ignition controller has a diagnostic LED light at the top right of the controller. The LED light will flash GREEN for normal operation or RED for an error.
The following are the green LED codes of operation:

GREEN LED Indications – NORMAL OPERATION

Flash Code

Flash Code Indication

Steady on

Flame detected, main burner on

0.1 second on/off

Controller is generating spark

0.5 second on/off

Purge or inter-purge time

0.5 second on/4.5 second off Retry or recycle time

The following are the red LED codes of error:

RED LED Indications – ERROR OPERATION

Flash Code

Flash Code Indication

Blinks 1 time

No flame in trial time error

Blinks 2 times

Flame sense circuit error

Blinks 3 times

Valve circuit error

Blinks 4 times

Flame loss error

Blinks 6 times

Airflow error

Blinks 7 times

Ground or internal error

Steady on

Line voltage/frequency error

Airflow Fault (6 red flashes)
An airflow fault may occur for the following reasons:
· During the start-up sequence, the controller relay turned the combustion blower on, but the blower did not prove airflow in 30 seconds.
· During the start-up sequence, the airflow was proven before the controller turned the combustion blower on. If this condition lasts for 30 seconds, the control will error out.
To fix fault, determine which error above is occurring, remove power from controller, fix problem and re-power controller.
Flame Fault (2 red flashes)
If the main gas valve fails to close completely and maintains a flame, the full-time flame sensor circuit will detect it and energize the combustion blower. Should the main valve later close completely and remove the flame signal, the combustion will be de-energized.

Ignition lockout (1 red flash for start-up, 4 red flashes for during operation)

Possible Cause

Solution

Manual gas valve not open

Open manual valve. If combination valves are used, verify that switch on top is in “ON” position.

Air in the gas line Bleed gas line.

Supply gas pressure Check that supply pressure is too high or too low between 6 and 14 in. wg for natural
gas and between 11 and 14 in. wg for LP gas.

Loose wire connections

Check for tight wire connections.

No Spark:

Ensure spark gap is 1/8 inch and

a. Spark electrode ceramic insulator is not cracked.

Replace if necessary.

b. Spark cable shorted to ground

Replace spark cable.

c. Ignition controller not grounded

Ground ignition controller.

High Limit Control Check unit airflow and manifold

tripped

pressure.

Faulty combination valve

Measure voltage between terminals MV and Common. If 24 volts is present but valve remains closed, replace valve.

Faulty ignition control

Check diagnostic LED on controller for “steady on”. If LED remains on constantly and there is NO voltage between valve and round, replace ignition controller.

Valve Circuit Error (3 red flashes)
Check that the valve is a 24 volt AC valve. Check that the valve is wired correctly.
Internal Control Error (7 red flashes)
Check all ground connections including the entire unit.
Line Frequency/Voltage Error (solid red)
Check that the controller power is 24 volt AC (+10%/-15%). Check for 60 Hz or 50 Hz.
If all checks have been made using the troubleshooting guide and you have confirmed there are no other defective components, and the red LED error light is flashing or on, then the ignition controller may need to be replaced.

16 DOAS Indirect Gas-Fired Heat Modules/Furnaces

Troubleshooting – 4:1 Modulating Furnace
4:1 Modulating Furnace with Stand-Alone Controller Will Not Light In all cases, verify correct terminals as shown on the unit-specific wiring diagram.

Line voltage across L1 & L2,

L2 & L3, and L1 & L3 on main

No

disconnect (DS1)?

Yes

Line voltage across T1 & T2,

T2 & T3, and T1 & T3 on main

No

disconnect (DS1)

Yes

24 VAC across R and C?

No

Yes

Main incoming power not connected Connect proper supply power to unit
Main disconnect (DS1) open or defective Close, repair, or replace
Main transformer (TR1) fault Reset or replace main transformer Phase Monitor (PM) Contact Open
Correct incoming phase order Fuse (FU6) Blown
Test and replace blown fuse(s)

24 VAC across G and C?

No

Yes

Fan Switch (S2) open or not wired Close or wire fan switch
(If fan switch is not required, place jumper from R to G)

Supply fan running?

No

Yes

24 VAC across W1 and C?

No

Yes

24 VAC across A2 and A1

No

on the RH relay?

Unit Main

Yes

Furnace Board

Freeze protection tripped Cycle disconnect to reset
Supply fan overload tripped Push reset button on overload or VFD to reset. Check motor amp draw and correct as necessary
Damper limit switch (D1L) not closed Damper stuck closed or actuator failed Repair damper interference or replace actuator
Exhaust fan contactor not powered Close or wire exhaust switch, reset exhaust overload, or replace faulty
exhaust contactor.
Heat Switch (S4) open or not wired Close or wire heat switch
(If heat switch is not required, place jumper from R to W1)
Starter interlock (ST1) not closed Replace contactor

Continues on next page…

DOAS Indirect Gas-Fired Heat Modules/Furnaces 17

Troubleshooting – 4:1 Modulating Furnace
4:1 Modulating Furnace with Stand-Alone Controller Will Not Light In all cases, verify correct terminals as shown on the unit-specific wiring diagram.
…continued from previous page

Line voltage at primary side of

No

furnace transformer (TR5)?

Yes No
24 VAC across 20 and 101?

Yes

24 VAC across C1 and G0 on

No

furnace controller (SC1)?

Yes

Blank screen

Yes

on furnace controller?

No

Furnace Controller Alarm:

Yes

`Furn Alarm – Check Log’?

No

Furnace Controller Alarm:

Yes

`Supply Sensor (U2) Err’?

No

Fuse (FU7) Blown Test and replace blown fuse(s)
Fuse (FU9) Blown Test and replace blown fuse Furnace Transformer (TR5) fault Replace Heating Transformer
Discharge temperature was above high limit control (HLC) Wait for high limit to cool and reset
High limit control (HLC) does not close when at room temperature Replace high limit control
Furnace controller defective or not powered Replace or wire furnace controller
New furnace alarm(s) have been logged Press the down arrow to scroll to the end of the alarms menu.
Press enter to go to the data logger and review alarms.
Discharge air sensor (U2) not wired or defective Wire or replace discharge air sensor (U2)

Furnace Controller Alarm:

Yes

`Inlet Sensor (U1) Err’?

No

Inlet air temperature above

Yes

heating lockout setting?

No

Continues on next page…

Inlet air sensor (U1) not wired or defective Wire or replace outdoor temperature sensor (U1)
Increase heating lockout setting to above inlet air temperature (Be sure to return this setting to the proper temperature after testing furnace)

18 DOAS Indirect Gas-Fired Heat Modules/Furnaces

Troubleshooting – 4:1 Modulating Furnace
4:1 Modulating Furnace with Stand-Alone Controller Will Not Light In all cases, verify correct terminals as shown on the unit-specific wiring diagram.
…continued from previous page

Supply air temperature above

Yes

Supply Temp Set Point?

No

Ignition Controller (IC#) red LED Yes blinks 7 times or is on?

No

120 VAC at 120/240 terminal on No Ignition Controller (IC#)?

Yes

Ignition Controller (IC#) red LED

blinks 6 times

Yes

or

Furnace Controller Alarm:

`Comb fan not proved’?

No

Furnace Controller Alarm:

Yes

`Low PSW with no call’?

No

Furnace Controller Alarm:

Yes

`High PSW with no call’?

No

Continues on next page…

Wait for discharge temperature to cool or increase supply temp setpoint sufficiently above inlet air temperature. (Be sure to return this setting to the proper temperature after testing furnace)
Faulty ground connection to ignition controller (IC#) Repair or install proper ground
Incorrect voltage supplied to ignition controller Rewire transformer or correct main voltage supply to unit
(Voltage to controller must be 24-29 VAC) Intermittent Controller Fault Reset power to unit
Ignition Controller(s) (IC#) failed Replace faulty ignition controller(s)
Fuse (FU8) Blown Test and replace blown fuse Furnace Transformer (TR5) fault Replace heating transformer
Pressure switch tubing kinked, disconnected, plugged, or filled with water/ice.
Straighten, connect, clear or replace pressure switch tubing Pressure switch (PS2) failure
Repair or replace pressure switch (PS2) Combustion blower (CM) not functioning Replace fusing (FU7), combustion blower(CM), or relay (IR)
Combustion blower operating with no call for heat to ignition controller
Check wiring to combustion fan and correct as necessary Ignition Controller (IC#) BLWR relay fault (relay stuck closed)
Replace ignition controller Pressure switch (PS2) failure Repair or replace pressure switch (PS2)
Pressure switch (PS5) failure Repair or replace pressure switch (PS5)

DOAS Indirect Gas-Fired Heat Modules/Furnaces 19

Troubleshooting – 4:1 Modulating Furnace
4:1 Modulating Furnace with Stand-Alone Controller Will Not Light In all cases, verify correct terminals as shown on the unit-specific wiring diagram.

…continued from previous page

Furnace Controller Alarm:

Yes

`High Speed PSW Fault’?

No

24 VAC between 24 VAC

No

terminals on mod valve?

Yes

Does the 0-10 VDC signal at the

SIG+/- terminals on the mod

No

valve correspond to the heat %

shown on the controller?

Yes
Ignition Controller (IC#) red LED blinks 1 time, 2 times or 4 times Yes
or Furnace Controller Alarm:
`No flame 3 trials’?

No

Flame lights but doesn’t travel all the way across

Yes

the burner manifold

No

Flame flashes back

Yes

during light off?

No

Continues on next page…

Pressure switch tubing kinked, disconnected, plugged, or filled with water/ice.
Straighten, connect, clear or replace pressure switch tubing Pressure switch (PS5) failure
Repair or replace pressure switch (PS5) Combustion blower (CM) not functioning Replace fusing (FU7), combustion blower or relay (CM)
Connection fault between terminal 20 and mod valve Check and repair connection issue
Connection fault between pCOe and mod valve Check and repair connection issue Furnace controller defective Replace defective parts
Manual supply gas valve off or combo valve (MV) switch turned off Turn supply gas valve or combo valve on Inlet gas pressure incorrect
Adjust inlet gas pressure to the range specified on the furnace label Improper manifold pressure
Set high and low manifold pressure (refer to 4:1 Electronic Modulation Start- Up section) Faulty spark rod or spark gap does not equal 1/8 inch
Replace spark rod or adjust gap to 1/8 inch Spark wire or connections faulty Repair connections or replace wire
Flame sensor faulty, grounded, or faulty connection to flame sensor
Replace or unground flame sensor or repair connection
Flame spread gap on outlet of burner pinched or blocked Spread gap or remove debris
One or more orifices fully or partially plugged Inspect and clean or replace orifices
Heat exchanger cracked Inspect and replace heat exchanger if necessary Combustion air inlet or discharge passageway restricted
Inspect and remove restriction

20 DOAS Indirect Gas-Fired Heat Modules/Furnaces

Troubleshooting – 4:1 Modulating Furnace
4:1 Modulating Furnace with Stand-Alone Controller Will Not Light In all cases, verify correct terminals as shown on the unit-specific wiring diagram.
…continued from previous page

Furnace Controller Alarm:

Yes

`High Temp. Alarm’?

No

Discharge temperature was above high limit control (HLC) Wait for high limit to cool and reset
Pressure switch (PS2) trip due to high discharge temp (Check pressure at combustion fan pressure tap with furnace running and
compare reading to pressure setting of pressure switches.) 1. If Pressure switch trips at wrong pressure, replace pressure switch. 2. If the combustion fan does not generate enough pressure, consult the
factory.

Furnace Controller Alarm:

Yes

`IG furnace max retry’?

No

Everything is working properly, consult factory.

Furnace has reached its maximum number of automatic error resets
1. Review alarm history and correct any issues identified
2. Reset the max retry alarm by holding the alarm button on the furnace controller for 3 seconds. Verify proper furnace operation.

DOAS Indirect Gas-Fired Heat Modules/Furnaces 21

Troubleshooting – 4:1 or High Turndown Modulating Furnace
4:1 or High Turndown Modulating Furnace with Microprocessor Controller Will Not Light In all cases, verify correct terminals as shown on the unit-specific wiring diagram.

Line voltage across L1 & L2,

L2 & L3, and L1 & L3 on main

No

disconnect (DS1)?

Yes

Line voltage across T1 & T2,

T2 & T3, and T1 & T3 on main

No

disconnect (DS1)

Yes

Main incoming power not connected Connect proper supply power to unit
Main disconnect (DS1) open or defective Close, repair, or replace

24 VAC across R and C?

No

Main transformer (TR1) fault Reset or replace main transformer

Yes

24 VAC across G and C?

No

Yes

Fan Switch (S2) open or not wired Close or wire fan switch
(If fan switch is not required, place jumper from R to G)

Blank screen on

Yes

microprocessor controller?

No
Unit Main Furnace Board

Line voltage at primary side of

No

furnace transformer (TR5)?

Yes

24 VAC across 20 and 101?

No

Yes

24 VAC across C1 and G0 on

No

pCOe (SC1)?

Yes
Continues on next page…

Microprocessor controller defective or not powered Replace or wire furnace controller
Fuse (FU7) Blown Test and replace blown fuse(s)
Fuse (FU9) Blown Test and replace blown fuse Furnace Transformer (TR5) fault Replace heating transformer
Discharge temperature was above high limit control (HLC) Wait for high limit to cool and reset
High limit control (HLC) does not close when at room temperature Replace high limit control

22 DOAS Indirect Gas-Fired Heat Modules/Furnaces

Troubleshooting – 4:1 or High Turndown Modulating Furnace
4:1 or High Turndown Modulating Furnace with Microprocessor Controller Will Not Light In all cases, verify correct terminals as shown on the unit-specific wiring diagram.

…continued from previous page

Microprocessor Alarm:

Yes

pCOe offline’ orIG furnace

Offline’, red blinking

or no light on pCOe?

No

Microprocessor Alarm:

Yes

`Discharge temperature

sensor (U04) failure’?

No

Microprocessor Alarm:

Yes

`Outdoor temperature

sensor (U05) failure’?

No

Inlet air temperature above

Yes

heating lockout setting?

No

Supply air temperature above

Yes

Supply Temp Set Point?

No

Ignition Controller (IC#)

Yes

red LED blinks 7 times or is on?

No
Continues on next page…

pCOe not powered Power the pCOe
pCOe not connected to main controller Wire to main controller pCOe defective Replace pCOe
Discharge air sensor (U04) not wired or defective Wire or replace discharge air sensor (U04)
Outdoor air sensor (U05) not wired or defective Wire or replace outdoor temperature sensor (U05)
Increase heating lockout setting to above inlet air temperature (Be sure to return this setting to the proper temperature after testing furnace)
Wait for discharge temperature to cool or increase supply temp setpoint sufficiently above inlet air temperature. (Be sure to return this setting to the proper temperature after testing furnace)
Faulty ground connection to ignition controller (IC#) Repair or install proper ground
Incorrect voltage supplied to ignition controller Rewire transformer or correct main voltage supply to unit
(Voltage to controller must be 24-29 VAC) Intermittent Controller Fault Reset power to unit
Ignition Controller(s) (IC#) failed Replace faulty ignition controller(s)

DOAS Indirect Gas-Fired Heat Modules/Furnaces 23

Troubleshooting – 4:1 or High Turndown Modulating Furnace
4:1 or High Turndown Modulating Furnace with Microprocessor Controller Will Not Light In all cases, verify correct terminals as shown on the unit-specific wiring diagram.
…continued from previous page

120 VAC at 120/240 terminal on

No

Ignition Controller (IC#)?

Yes

Ignition Controller (IC#) red LED

blinks 6 times

or

Yes

Microprocessor Alarm:

`Combustion fan not proved’?

No

Microprocessor Alarm:

`Pressure Switch closed

Yes

with combustion fan off’?

No

Microprocessor Alarm:

Yes

`IG furnace high pressure’?

No

24 VAC between 24 VAC

No

terminals on mod valve?

Yes

Does the 0-10 VDC signal at the

SIG+/- terminals on the mod

No

valve correspond to the heat %

shown on the controller?

Yes

Continues on next page…

Fuse (FU8) Blown Test and replace blown fuse Furnace Transformer (TR5) fault Replace heating transformer
Pressure switch tubing kinked, disconnected, plugged, or filled with water/ice.
Straighten, connect, clear or replace pressure switch tubing Pressure switch (PS2) failure
Repair or replace pressure switch (PS2) Combustion blower (CM) not functioning Replace fusing (FU7), combustion blower or relay (CM)
Combustion blower operating with no call for heat to ignition controller
Check wiring to combustion fan and correct as necessary Ignition Controller (IC#) BLWR relay fault (relay stuck closed)
Replace ignition controller Pressure switch (PS2) failure Repair or replace pressure switch (PS2)
Pressure switch tubing kinked, disconnected, plugged, or filled with water/ice.
Straighten, connect, clear or replace pressure switch tubing Pressure switch (PS5) failure
Repair or replace pressure switch (PS5) Combustion blower (CM) not functioning Replace fusing (FU7), combustion blower or relay (CM)
Connection fault between terminal 20 and mod valve Check and repair connection issue
Connection fault between pCOe and mod valve Check and repair connection issue
Microprocessor controller or pCOe defective Replace defective parts

24 DOAS Indirect Gas-Fired Heat Modules/Furnaces

Troubleshooting – 4:1 or High Turndown Modulating Furnace
4:1 or High Turndown Modulating Furnace with Microprocessor Controller Will Not Light In all cases, verify correct terminals as shown on the unit-specific wiring diagram.
…continued from previous page

Ignition Controller (IC#) red LED

blinks 1 time, 2 times or 4 times

or

Yes

Microprocessor Alarm: `IG

furnace no flame after 3 trials’?

No

Flame lights but doesn’t

Yes

travel all the way across

the burner manifold?

No

Flame flashes back during light off?

Yes

No

Microprocessor Alarm: `High temp. alarm – pressure fault Yes with excessive discharge temp.
Check for high limit trip.’?

No

Microprocessor Alarm:

Yes

`IG furnace max retry’?

No

Everything is working properly, consult factory.

Manual supply gas valve off or combo valve (MV) switch turned off Turn supply gas valve or combo valve on Inlet gas pressure incorrect
Adjust inlet gas pressure to the range specified on the furnace label Improper manifold pressure
Set high and low manifold pressure (refer to 4:1 Electronic Modulation Start- Up section) Faulty spark rod or spark gap does not equal 1/8 inch
Replace spark rod or adjust gap to 1/8 inch Spark wire or connections faulty Repair connections or replace wire
Flame sensor faulty, grounded, or faulty connection to flame sensor
Replace or unground flame sensor or repair connection
Flame spread gap on outlet of burner pinched or blocked Spread gap or remove debris
One or more orifices fully or partially plugged Inspect and clean or replace orifices
Heat exchanger cracked Inspect and replace heat exchanger if necessary Combustion air inlet or discharge passageway restricted
Inspect and remove restriction
Discharge temperature was above high limit control (HLC) Wait for high limit to cool and reset
Pressure switch (PS2) trip due to high discharge temp (Check pressure at combustion fan pressure tap with furnace running and
compare reading to pressure setting of pressure switches.) 1. If Pressure switch trips at wrong pressure, replace pressure switch.
2. If the combustion fan does not generate enough pressure, consult the factory.
Furnace has reached its maximum number of automatic error resets
1. Review alarm history and correct any issues identified 2. Reset the max retry alarm by pressing the alarm button on the
Microprocessor twice. Verify proper furnace operation.

DOAS Indirect Gas-Fired Heat Modules/Furnaces 25

Reference – Controls

Furnace Control with Microprocessor Control
If the unit is equipped with a microprocessor control, the expansion board acts as an interface between the microprocessor controller and the furnace. In this case, the pCOe has no logic built into it since the logic is already contained in the microprocessor controller. On this type of controller, the LED status lights show the following:

LED Color Yellow Red Green

Status Powered
Error Operational

Significance The pCOe has power. The pCOe is not connected to the microprocessor controller. Check connection and the microprocessor controller power. The pCOe has power and is connected to the microprocessor controller.

If the controller detects a fault, it will go into alarm mode and a message code will appear on the microprocessor controller. Message codes that may appear include:

Alarm Descriptions

IG furnace no flame after three trials

Indicates a furnace failure to light or properly sense flame after 3 trials.

IG combustion fan high pressure switch failure

Indicates a call for high speed combustion fan but high pressure switch did not close.

IG furnace ignition control

Indicates an alarm from the ignition controller.

Pressure switch closed with combustion fan off

Indicates low pressure switch was closed with no call for combustion fan.

Combustion fan not proved

Indicates a call for low speed combustion fan but low pressure switch did not close.

IG furnace max retry

Indicates that the max number of retries was reached.

High temp. alarm pressure fault with excessive discharge temp. Check for high limit trip.

Indicates upon a pressure fault, there was a high discharge temperature which could indicate a high limit trip.

IG furnace offline

Indicates communication with furnace control has failed.

26 DOAS Indirect Gas-Fired Heat Modules/Furnaces

Maintenance
Combustion Blower Motor
Motor maintenance is generally limited to cleaning. Cleaning should be limited to exterior surfaces only. Removing dust and grease build-up on the motor housing assures proper motor cooling. Use caution and do not allow water or solvents to enter the motor or bearings. Under no circumstances should motors or bearings be sprayed with water, steam or solvents. The motor bearings are pre-lubricated and sealed, requiring no further lubrication.
WARNING
Turn off all gas and electrical power to the unit before performing any maintenance or service operations to this unit. Remember that if the unit is equipped with electric heat, there may be a second high voltage source that must also be disconnected.
Burners and Orifices
Before each heating season, examine the burners and gas orifices to make sure they are clear of any debris such as spider webs, etc. Clean burner as follows:
· Turn off both electrical and gas supplies to the unit. · Disconnect the union between manifold and gas
valve. · Remove burner manifold and burner assembly. · Inspect and clean orifices and burners as necessary.
Avoid using any hard or sharp instruments which could cause damage to the orifices or burners. a. Remove any soot deposits from the burner with a
wire brush. b. Clean the ports with an aerosol degreaser or
compressed air. c. Wipe the inside of the burner clean. Cleaning
the burner with a degreaser will slow the future buildup of dirt. · Before reinstalling the burner assembly, look down the heat exchanger tubes to make sure they are clear of any debris. · Reinstall manifold and burner assembly, reconnect wire leads and gas supply piping. · Turn on the electrical power and gas supply. · Follow the start-up procedure to light the burners and verify proper operation.
Heat Exchanger
The heat exchanger should be checked annually for cracks and discoloration of the tubes. If a crack is detected, the heat exchanger should be replaced before the unit is put back into operation. If the tubes are dark gray, airflow across the heat exchanger should be checked to make sure the blower is operating properly.

Flue Collector Box
The flue passageway and flue collector box should be inspected prior to each heating season and cleared of any debris.
Electrical Wiring
The electrical wiring should be inspected annually for loose connections or wiring deterioration.
Gas Train
The gas train connections, joints and valves should be checked annually for tightness.
Replacement Parts
When ordering replacement parts, include the complete unit model number and serial number as shown on the unit labels.

DOAS Indirect Gas-Fired Heat Modules/Furnaces 27

Maintenance Log
Date ___Time _ AM/PM Notes:

Date ___Time _ AM/PM Notes:

28 DOAS Indirect Gas-Fired Heat Modules/Furnaces

Maintenance Log
Date ___Time _ AM/PM Notes:

Date ___Time _ AM/PM Notes:

DOAS Indirect Gas-Fired Heat Modules/Furnaces 29

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DOAS Indirect Gas-Fired Heat Modules/Furnaces 31

Contact Us

Contact Us / More Information

Technical Support and Service 800-789-8550 support@doas.com

Valent Dedicated Outdoor Air Systems 6028th Avenue North Minneapolis, MN 55411 Main: 612-877-4800

More Information
Unit Schematics For configuration and connection questions, see the schematics that shipped with your unit. They can typically be found attached to the main control panel door.
Mechanical and Controls Manuals Find current mechanical and controls manuals here: www.valentair.com/resources

© 2023 Valent
Continuous product improvement is a policy of Valent; therefore, product functionality and specifications are subject to change without notice. For the most recent product information visit the product website.

PVG Part number: 483594 Rev. 4 October 2023