Installation Instructions for use by heating contractor Auxilliary Low Gas Pressure Switch Part No. 7842158 CM2 186 Part No. 7842159 CM2 246 to 620 (TX) for use with: Vitocrossal CM2 boilers 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. Refer to the applicable boiler Installation Instructions. 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. 03/2018 Please file in Service Binder
Installation - CM2 186 to 311 (equipped with Vitotronic 100 GC1/300 GW2) Installation steps 1. Disconnect boiler power supply. 2. If the boiler has already been installed, shut off main gas supply to the boiler and disconnect gas supply piping. 3. Supply and install gas piping components as required (see illustration on page 5). 4. Route cable beneath the top rail 1 as shown. Secure using plug-in cable retainers as shown. 5. Make electrical s as shown below. 6. Set the low gas pressure switch to 4.5 wc. 1 Low gas pressure cable (field supplied) 7. Open gas supply to the burner. Note: The setting must be higher then the GW1 pressure switch (4 w.c.) located on the gas valve. If a 4 w.c. setting is required then the GW1 pressure switch must be set below 4 w.c. 8. Using an approved gas leak detector, check gas line and low gas pressure switch. 9. Reconnect 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. CM2 Boiler G Low pressure gas switch 21 (through COM LWCO) 22 NO A A Low gas pressure switch (Honeywell C 6097A 1012) 2
Installation - CM2 400 to 620 TX (equipped with Vitotronic 300 GW5B) Installation steps 1. Disconnect boiler power supply. 2. If the boiler has already been installed, shut off main gas supply to the boiler and disconnect gas supply piping. 3. Supply and install gas piping components as required (see illustration on page 5). 4. Route supplied cable beneath the top rail 1 as shown. Secure using plug-in cable retainers as shown. 5. Remove jumper from terminals 19 and 20 and make electrical s as shown between the boiler and the low gas pressure switch as required. 6. Set the low gas pressure switch to 4.5 wc. 1 Low gas pressure cable (supplied) 7. Open gas supply to the burner. Note: The setting must be higher then the GW1 pressure switch (4 w.c.) located on the gas valve. If a 4 w.c. setting is required then the GW1 pressure switch must be set below 4 w.c. 8. Using an approved gas leak detector, check gas line and low gas pressure switch. 9. Reconnect 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. A CM2 Boiler Low pressure gas switch Cable color G Green (GN) 19 COM Black (BK) 20 NO White (WT) A Low gas pressure switch (Honeywell C 6097A 1012) 3
Installation - CM2 186 to 620 TX (equipped with Vitotronic 300 GW6B) Installation steps 1. Disconnect boiler power supply. 2. If the boiler has already been installed, shut off main gas supply to the boiler and disconnect gas supply piping. 3. Supply and install gas piping components as required (see illustration on page 5). 4. Route supplied cable beneath the top rail 1 as shown. Secure using plug-in cable retainers as shown. 5. Remove jumper from terminals 26 and 27 and make electrical s as shown between the boiler and the low gas pressure switch as required.. 6. Set the low gas pressure switch to 4.5 wc. 1 Low gas pressure cable (supplied) 7. Open gas supply to the burner. Note: The setting must be higher then the GW1 pressure switch (4 w.c.) located on the gas valve. If a 4 w.c. setting is required then the GW1 pressure switch must be set below 4 w.c. 8. Using an approved gas leak detector, check gas line and low gas pressure switch. 9. Reconnect 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. CM2 Boiler Low pressure gas switch Cable color 26 (G) Green (GN) 26 (L) COM Black (BK) 27 (L) NO White (WT) 4 A DIN rail (junction box) B Auxiliary low gas pressure switch (Honeywell C 6097A 1012)
Operation 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 sufficient gas pressure is no longer available, the low gas pressure switch contact terminals 3(COM) and 2(NO) will open. The burner control will stop operating and generate a fault C1 at the boiler control. To restart the boiler, press the low gas pressure switch reset button (only once) and reset the boiler control fault. If the fault persists, verify the gas supply pressure. There should be a minimum operating pressure of 4.5 w.c., if not contact your local gas company. Gas Piping Components A Nipple (supplied with boiler) B Elbow (supplied with boiler) C Reducing tee (kit part) D Short nipple kit (field supplied) E Manual gas shutoff valve (supplied with boiler) F Ground joint union (recommended) (field supplied) G Reducing bushing kit (only for 7842159) H Short nipple (kit part) I Low gas pressure switch* * the switch can be installed in the gas line anywhere near the boiler. Note: Typical gas piping shown. 5
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