HVACopediaSIT · Gas fireplace · Ignition
NOVA 820 millivolt start-up and flame proving
What happens, in order
- Bleed air from the gas lines and confirm inlet pressure is within the appliance maker's range
- Thermocouple and thermo-generator fully inserted; thermocouple hand-tight plus a quarter turn
- Wire the thermo-generator to the TPTH and TP terminals, and thermostat or wall switch to TPTH and TH
- Turn the knob to PILOT, press it, and light the pilot with a match or piezo igniter
- Keep holding until enough current builds to engage the safety magnet
- After about 3 minutes with only the thermo-generator connected, open-circuit voltage should be 500-750 mV; trim the pilot screw if outside range
- With a jumper from TPTH to TH, closed-circuit voltage should stay above 300 mV; with thermostat wires connected it should stay above 175 mV
- Turn the knob to ON and the main burner lights; cycle the thermostat and switch to check them
- Turning the knob to OFF puts out both the pilot and the main burner
- Safety interlock after OFF the pilot cannot be relit until the thermocouple has cooled (30 s or less)
Timings and thresholds
| Item | Value |
|---|---|
| Thermo-generator open circuit | 500-750 mV |
| Closed circuit (jumper) | Above 300 mV |
| Closed circuit (with thermostat) | Above 175 mV |
| Pilot burn before reading | About 3 min |
| Thermocouple open circuit (MV Plus) | 18-28 mV, replace under 14 mV |
Applies to: SIT 820 NOVA millivolt, MV Plus vented and un-vented valves
Models
Related
Take it to the job
Sequences of operation, error codes and tips work offline in the HVACopedia app.
Source: SIT 820 NOVA millivolt troubleshooting guide (fido-manual_1453404727), set-up and system checks. Written in our own words; timings can differ by model and software version, so check the manual for your exact unit.
For licensed technicians. Gas, electrical and refrigerant work must be done by a qualified, licensed person. Shut off power and gas before servicing, never bypass a safety control, and follow the manufacturer’s manual for the exact model; it and local codes always take priority. HVACopedia is not affiliated with any manufacturer; brand and model names only identify the equipment.