LENNOX LF25-30-105 Compact Unit Heaters Instructions

RESIDENTIAL / COMMERCIAL
PRODUCT SPECIFICATIONS
UNIT HEATERS
LF25-30-105
COMPACT UNIT HEATERS
Low Profile – Horizontal Discharge – 60Hz
Bulletin No. 210892
November 2023
Supersedes October 2023
LF25-30-45 Models Shown
(LF25-60-105 models similar)
Steady-State Efficiency – up to 83.8%
Input – 30,000 to 105,000 Btuh

MODEL NUMBER IDENTIFICATION

APPROVALS AND WARRANTY

WARRANTY

• Heat Exchanger – Aluminized steel – ten year limited
• All other covered components:
• Five year limited – Residential installations
• One year limited – Non-residential installations
• Refer to Lennox Equipment Limited Warranty certificate included with unit for specific details

APPROVALS

• CSA International certified
• Certified for natural or LPG/Propane gas
• Units are approved for vertical or horizontal venting

FEATURE HIGHLIGHTS

1. Heavy Gauge Steel Cabinet
2. Tubular Heat Exchanger
3. Inshot Burners
4. Gas Control Valve
5. Combustion Air Inducer
6. Combination Ignition/Fan Timer Control
7. Direct Drive fan

FEATURES AND BENEFITS

APPLICATIONS

• Horizontal unit heaters are low profile, compact in design and easy to install
• Steady State Efficiencies – Up to 83.8%
• Ideal for economical heating systems in garages and non-confined living spaces
• Shipped completely assembled with controls factory installed and wired
• Hanging brackets are shipped loose for field installation
• Test operated at the factory to ensure proper operation and dependability

NOTE – Installer must locate unit, make unit gas supply, flue, electrical connections and mount thermostat to complete job.

1. CABINET
   • Constructed of pre-painted heavy gauge cold rolled steel
   • Hinged, reversible door for easy access
   • Adjustable louvers are furnished on cabinet for control of air flow direction
   • Wiring junction box is conveniently located outside unit cabinet for easy field wiring connections
   • Hanging brackets for suspending unit are furnished for field installation
   • Unit may be rotated 180 degrees (top for bottom) for ease of installation of gas, electrical and flue locations
   HEATING SYSTEM
   

2. Tubular Aluminized Steel Heat Exchanger
   • Tubular heat exchanger is constructed of aluminized steel for superior resistance to corrosion and oxidation
   • Curving design of heat exchanger allows complete exposure of heating surfaces to supply air stream
   • Dimpled tubes with wrinkle bends allow for maximum heat transfer
   • Compact design reduces space requirements in unit cabinet
   • Heat exchanger has been laboratory life cycle tested

3. Inshot Burner Assembly
   • Aluminized steel inshot burners provide efficient trouble free operation
   • Burner venturi mixes air and gas in correct proportion for proper combustion
   • Burner assembly is removable from the unit as a single component for ease of service

4. Gas Control Valve
   • 24 volt redundant combination gas control valve combines manual shut off switch (On-Off), automatic electric valve (dual) and gas pressure regulation into a compact combination control

5. Combustion Air Inducer
   • Prepurges heat exchanger and safely vents combustion products
   • Operates only during heating cycle
   • Blower motor has ball bearings and is thermally protected
   Pressure Switch
   • Pressure switch prevents unit operation in case of blocked flue outlet
   Limit Control(s)
   • Factory installed and accurately located
   • Limit control has fixed temperature setting and protects heating system from abnormal operating conditions
   Flame Rollout Switch
   • Automatic reset switch is factory installed on the top of the burner box
   HEATING SYSTEM (continued)
   Optional Accessories
   Natural Gas to LPG/Propane Conversion Kit
   • Required for field changeover from natural gas to LPG/ Propane
   NOTE – See Optional Accessories – Gas Heat for proper kit selection at different elevations.
   High Altitude Conversion Kit – Natural Gas
   • Required on all units for proper unit operation at altitudes from 5001 to 10,000 ft. (US) and 7501 to 10,000 ft. (Canada)
   High Altitude Pressure Switch Kit
   • Required for proper unit operation at various elevations

6. CONTROLS
   Combination Direct Spark Ignition/Fan Timer Control
   • Electronic direct spark ignition control provides positive and safe main burner ignition
   • Spark is intermittent and occurs only when required
   • Separate electronic flame sensor control assures safe and reliable operation
   • Should loss of flame occur, flame sensor controls will initiate 5 attempts at re-ignition before locking out unit operation
   • Control board contains all necessary controls and relays to operate unit
   • Includes: Fan timer control – fan on 30 seconds (fixed), fan off 150 seconds (fixed), terminal strip plug for thermostat connections, diagnostic LED for troubleshooting
   • Direct plug-in wiring harness
   Transformer
   • 120V/24V transformer furnished as standard
   Optional Accessories
   Remote Diagnostic LED Kit
   • Allows for remote status updates and diagnosis of the unit
   Thermostats
   • For thermostat options, see Optional Conventional Temperature Control Systems on Page 8
   VENTING
   • Units may be vented horizontally or vertically
   • Residential Vertical Venting – Units are approved for installation when vented in compliance with the latest edition of the National Fuel Gas Code (NFPA 54 / ANSI Z223.1) in the USA and with CSA-B149.1 codes in Canada
   • Residential Horizontal Venting – Units are approved for residential installation only with UL listed, Cat III stainless steel vent kits
   • Commercial Vertical Venting – Units are approved for installation with single wall metal vent pipe
   • Commercial Horizontal Venting – Units are approved for single-wall metal vent pipe or optional UL listed, Cat III stainless steel vent kits
   NOTE – See installation instructions for detailed venting requirements.
   Optional Accessories
   Horizontal Vent Kits
   • UL listed, Cat III stainless steel vent kits are required for horizontal venting
   • Available for upward or downward slope
   • Vent kits snap together
   • Kits include unit transition, vent termination and wall thimble
   • Upward slope vent kits have a drain connection
   • Provisions for hanging must be field supplied
   • Optional 45° or 90° elbow available for ease of vent connection
   • Straight pipe sections in various lengths are available
   NOTE – See Horizontal Vent Kits / Elbow table for Horizontal Vent Kits and accessories on Page 5.
   NOTE – See drawings for additional information.
   Vent Adaptor Kits
   • Mounting Plate Kit – Required for 4 inch to 3 inch vent pipe applications
   • Vent Adaptor Kits (Upslope and Downslope) for 4 inchunit flue pipe to 3 inch Category III vent pipe

7. DIRECT DRIVE FAN
   • Efficient and quiet operating direct drive propeller type fan
   • Permanently lubricated fan motor
   

SPECIFICATIONS

Gas Heating **Model No.**

Performance Heating Capacity Input Btuh

Heating Capacity Output Btuh – Natural
Steady State Efficiency – Natural
Temperature rise – °F

| LF25-30A| LF25-45A| LF25-60A| LF25-75A| LF25-90A| LF25-105A
---|---|---|---|---|---|---
30,000| 45,000| 60,000| 75,000| 90,000| 105,000
25,020| 37,665| 50,220| 62,550| 75,420| 87,675
83.4%| 83.7%| 83.7%| 83.4%| 83.8%| 83.5%
37| 52| 47| 56| 43| 54
Connections      Flue size(round) in. Gas Piping Size – in.| 4| 4| 4| 4| 4| 4
1/2| 1/2| 1/2| 1/2| 1/2| 1/2
Fan Data Number of fans
Fan Diameter – in.
Number of blades
Motor Output – hp
rpm
Air Volume – cfm
Air throw at 8 ft. mounting height – ft.| 1| 1| 1| 1| 1| 1
10| 10| 14| 14| 16| 16
4| 4| 4| 4| 4| 4
1/25| 1/25| 1/15| 1/15| 1/10| 1/10
1550| 1550| 1075| 1075| 1075| 1075
625| 665| 1000| 1050| 1600| 1500
27| 29| 34| 41| 46| 43
Weight Data       Net Weight – lbs. (kg)
Shipping Weight – lbs. (kg)| 55 (25)| 60 (27)| 85 (39)| 90 (41)| 115 (52)| 120 (54)
60 (27)| 65 (29)| 90 (41)| 95 (43)| 120 (54)| 125 (57)

ELECTRICAL DATA

Voltage
Fan motor full load amps
Maximum overcurrent protection (MOCP)| 115 volts – 60 hertz – 1 phase
---|---
2.0| 2.0| 2.0| 2.0| 3.0| 3.0
15| 15| 15| 15| 15| 15

OPTIONAL ACCESSORIES – MUST BE ORDERED SEPARATELY

OPTIONAL ACCESSORIES – GAS HEAT

NATURAL GAS TO LPG/PROPANE CONVERSION KITS

HIGH ALTITUDE CONVERSION KITS – NATURAL GAS

HIGH ALTITUDE PRESSURE SWITCH KITS

Model No.| LF25- 30A| LF25- 45A| LF25- 60A| LF25- 75A| Model No.| LF25- 90A| LF25- 105A
---|---|---|---|---|---|---|---
0-3000 ft.| Factory| Factory| Factory| Factory| 0-2000 ft.| Factory| Factory
3000-5000 ft.| Factory| Factory| Factory| 22K44| 2001-4000 ft.| 22K44| Factory
5001-6000 ft.| Factory| Factory| 22L26| 22K44| 4001-6000 ft.| 22L26| 22K44
6001-9000 ft.| 22L27| 22L27| 22L26| 22L27| 6001-7000 ft.| 22L27| 22K44
9001-10,000 ft.| 22L27| 22L27| 22L28| 22L27| 7001-10,000 ft.| 22L27| 22L27

HORIZONTAL VENT KITS AND ELBOWS

REQUIRED FOR RESIDENTIAL HORIZONTAL VENTING APPLICATIONS

Unit Heater Model No.| Vent Diameter (in.)| Upslope Vent Kit Catalog No.| Downslope Vent Kit Catalog No.| 45° Elbow Catalog No.| 90° Elbow Catalog No.| 1 Minimum Vent Length (ft.)
---|---|---|---|---|---|---
LF25-30A, LF25-45A LF25-60A, LF25-75A LF25-90A, LF25-105A|

4

|

75W63

|

75W67

| 87W80

(Optional)

| 75W71

(Optional)

|

5

Length does not include termination (or elbow if used).

STRAIGHT VENT PIPE – FOR HORIZONTAL VENTING

Unit Heater| Vent Diameter (in.)| Length (in.)| Catalog No.
---|---|---|---
LF25-30A, LF25-45A LF25-60A, LF25-75A LF25-90A, LF25-105A| 4| 6| 75W77
4| 12| 75W78
4| 36| 75W79

VENT ADAPTOR KITS (FOR RETRO-FIT INSTALLATIONS)

LF25-30A
LF25-45A| Vent Adaptor Kit (Upslope) – 4 inch unit flue pipe to 3 inch Category III vent pipe| 19V95
Vent Adaptor Kit (Downslope) – 4 inch unit flue pipe to 3 inch Category III vent pipe| 19V96

INSTALLATION CLEARANCES

| in.| mm
---|---|---
Top| 1| 25
Side opposite control box/access panel| 1| 25
Control Box/Access Panel Side| 24| 610
Back| 18| 457
Bottom| 1| 1
¹ Flue| 6| 152

1 See Installation Instructions for further installation considerations.
Single-Wall vent clearance. Type B Double-Wall vent clearance is in accordance with the manufacturer’s listing.

MAXIMUM MOUNTING HEIGHT

MAXIMUM HORIZONTAL VENT LENGTHS

NOTES – Minimum horizontal vent length is 5 ft.
Horizontal venting requires the use of a UL listed, Cat III Horizontal Vent Kit and Vent Pipe.
Horizontal venting must terminate in a tee.
Maximum total length of vent pipe must not exceed 30 ft.
One elbow is equivalent to 5 ft. of vent pipe.
Residential Vertical Venting – Units are approved for installation when vented in compliance with the latest edition of the National Fuel Gas Code (NFPA 54 / ANSI Z223.1) in the USA and with CSA-B149.1 codes in Canada
Residential Horizontal Venting – Units are approved for residential installation only with UL listed, Cat III stainless steel vent kits Commercial Vertical Venting – Units are approved for installation with single wall metal vent pipe
Commercial Horizontal Venting – Units are approved for single-wall metal vent pipe or optional UL listed, Cat III stainless steel vent kits

DIMENSIONS – UNIT

VENT KITS AND ACCESSORY DRAWINGS

|
---|---
|

OPTIONAL CONVENTIONAL TEMPERATURE CONTROL SYSTEMS

CS7500 Commercial 7-Day Programmable Thermostat

• Four-Stage Heating / Two-Stage Cooling
• Universal Multi-Stage
• Intuitive Touchscreen Interface
• Automatic Changeover between Heating and Cooling
• Full Seven-Day Programming
• Four Time Periods Per Day
• Temperature and Humidity Control
• One-Touch Away Mode
• Holiday Scheduling
• Smooth Setback Recovery (SSR)
• Performance Reports
• Notifications/Reminders
• Economizer Relay Control
• Backlit Display
• Wallplate Furnished
• FDD, ASHRAE and IECC Compliant

CS3000 Commercial 5-2 Day Programmable Thermostat

• Two-Stage Heating / Two-Stage Cooling
• Conventional Systems
• Intuitive Interface
• 5-2 Day Programming
• Program Hold
• Remote Indoor Temperature Sensing
• Smooth Setback Recovery (SSR)
• Economizer Relay Control
• Maintenance/Filter/Service Reminders
• Backlit Display
• Wallplate Furnished
• Simple Up and Down Temperature Control

CS7500 Commercial 7-Day Programmable Thermostat
CS7500 7-Day Thermostat| 17G74
Sensors/Accessories| ¹ Remote non-adjustable wall-mount 20k| 47W36
| ¹ Remote non-adjustable wall-mount 10k| 47W37
| Remote non-adjustable discharge air (duct mount)| 19L22
| Outdoor temperature sensor| X2658
CS3000 5-2 Day Programmable
CS3000 5-2 Day Thermostat| 11Y05
Sensor/Accessories| Remote non-adjustable wall mount 10k averaging| 47W37
| Thermostat wall mounting plate| X2659
Universal Thermostat Guard with Lock (clear)
| Inside Dimensions (H x W) 5 7/8 x 8 3/8 in.| 39P21
1 Remote wall-mount sensors can be applied in any of the following combinations:|

1 R emote wall-mount sensors can be applied in any of the following combinations:
One Sensor – (1) 47W36, Two Sensors – (2) 47W37, Three Sensors – (2) 47W36 and (1) 47W37
Four Sensors – (4) 47W36, Five Sensors – (3) 47W36 and (2) 47W37

REVISIONS

models

Visit us at www.Lennox.com
For the latest technical information, www.LennoxCommercial.com
Contact us at 1-800-4-LENNOX

NOTE – Due to Lennox’ ongoing commitment to quality, Specifications, Ratings and Dimensions subject to change without notice and without incurring liability.
Improper installation, adjustment, alteration, service or maintenance can cause property damage or personal injury.
Installation and service must be performed by a qualified installer and servicing agency.
©2023 Lennox Industries, Inc.

References

• Air Conditioning and Heating Solutions | Lennox
• Commercial Air Conditioning & Heating Units | Lennox Commercial

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