VIESSMANN 7842160 Auxiliary Low Gas Pressure Switch Instruction Manual
- June 9, 2024
- VIESSMANN
Table of Contents
VIESSMANN 7842160 Auxiliary Low Gas Pressure Switch
Safety and Installation Requirements
Please ensure that these instructions are read and understood before starting
any service work. Failure to comply with these instructions may cause
product/property damage, severe personal injury and/or loss of life.
Working on the equipment
The installation, adjustment, service and maintenance of this product must be
performed by a licensed professional heating contractor who is qualified and
experienced in the installation, service, and maintenance of hot water
boilers. There are no user serviceable parts on the boiler, burner or control.
Ensure that main power to the equipment being serviced is off.
Ensure that the main fuel supply valve to the boiler is closed.
Take precautions to avoid accidental activation of power or fuel during
service work.
Do not perform service work on any component part without ensuring safe
operation of the heating system. When replacing parts, use original Viessmann
or Viessmann approved replacement parts.
Installation Steps
IMPORTANT
Low pressure switches are suitable for making and/or breaking a circuit when
the medium pressure changes relative to the setpoint. The setpoint can be set
in the field by an adjustable dial with an integrated scale.
CAUTION
Low gas pressure can cause the heating system to shut down.
Codes
Refer to current CAN/CSA B149.1 and .2 or National Fuel Gas Code ANSI
Z223.1/NFPA 54, as well as local codes for gas piping requirements and sizing.
Pipe size to the boiler must be determined based on:
- pipe length
- number of fittings
- type of gas
- maximum input requirements of all gas appliances in the residence.
IMPORTANT
Design piping layout in such a way that piping does not interfere with
serviceable components.
All electrical wiring is to be done in accordance with the latest edition of
CSA C22.1 Part 1 and/or local codes. In the U.S. use the National Electrical
Code ANSI/NFPA 70.
Installation steps
- Disconnect boiler power supply.
- If the boiler has already been installed, shut off main gas supply to the boiler and disconnect gas supply piping.
- Supply and install gas piping components as required (see illustration).
- Make electrical connections as shown between the boiler and the low gas pressure switch as required.
- Set the low gas pressure switch to 4.5” w.c.
- Open main gas supply.
- Using an approved gas leak detector, check gas line and low gas pressure switch.
- Restore power to the boiler.
Note: External vent line is not required. If necessary the d” NPT vent opening on the Honeywell low gas pressure switch can be used.
Operation
When sufficient gas pressure is available, the low gas pressure switch contact
terminals 3(COM) and 2(NO) will close. The burner control is then energized
and the system will operate normally.
When there is insufficient gas pressure, the low gas pressure switch contact
terminals 3(COM) and
2(NO) will open and the burner will stop operating.
Check the boiler control display for a fault message. If no fault message is
displayed on the boiler control, verify that the boiler is not operating due
to low gas pressure. Access coding level 2, enter the ‘Boiler’ submenu and
scroll to coding address 38. If coding address 38:29 is displayed, restart the
boiler.
For details on accessing coding levels, refer to Vitodens Service
Instructions.
To restart the boiler, press the low gas pressure switch reset button (only
once). Return to the home screen and access coding level 2, enter the ‘Boiler’
submenu and scroll to coding address 38. Coding address 38 should now display
38:0. If coding address 38:29 continues to be displayed, verify the gas supply
pressure.
There should be a minimum operating pressure of 4.5” w.c. If the operating
pressure is lower than 4.5” w.c., contact your local gas company.
Gas Piping Components
Legend
- A Coupling 1”
- B Nipple 1”x 3”
- C Reducing tee 1”x1”xa
- D Manual gas shutoff valve 1″ (supplied with boiler) E Nipple a”x1b”
- F Low gas pressure switch
- G Nipple 1”x2”
- H Pressure switch harness (not shown)
Fault Generation
When connected in a Multi-boiler system using a Vitotronic 300 MW2C, a boiler fault signal is required.
Installation steps
-
Disconnect boiler power supply.
-
If the boiler has already been installed, shut off main gas supply to the boiler and disconnect gas supply piping.
-
Install relay (field supplied) by connecting the coil side of the relay to the Normally Closed (NC) position
(120VAC) of the LGPS, and the Neutral terminal of the ‘MULTI’ plug -
Connect the Normally Open (NO) position of the relay to terminals DE1, DE2 or DE3 (terminals 1 and 2) of the internal EA1 module.
-
Open main gas supply.
-
Using an approved gas leak detector, check gas line and low gas pressure switch.
-
Restore power to the boiler.
-
Access coding level 2 and set address 3A:0 to 3A:4 (for DE1, for DE2 and DE3 set addresses 3B:4 or 3C:4 respectively.
Legend
- A Relay (field supplied)
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