Gas Fireplace: SIT 820 Nova millivolt valve: main burner will not come on or will not cycle
SIT 820 Nova millivolt valve: main burner will not come on or will not cycle on a gas fireplace: Pilot is fine but the burner will not light with the switch/thermostat, lights intermittently, or the flame looks wrong.
Applies to: Fireplaces and gas logs with SIT 820 Nova MV / Millivolt Plus valves
Common causes of sit 820 nova millivolt valve: main burner will not come on or will not cycle
- Knob not on ON, thermostat not calling
- Too much resistance in the millivolt circuit (wire length, thermostat, corroded connections)
- Weak thermo-generator (thermopile)
- Failed main operator
- Wrong orifice, inlet or outlet pressure, partly blocked burner, bad regulator/diaphragm
How to fix sit 820 nova millivolt valve: main burner will not come on or will not cycle: step by step
- Make sure the knob is on ON and the wall switch/thermostat is calling.
- Millivolt circuits are very sensitive to resistance: use a thermostat rated for millivolt, keep connections clean and tight, and keep total thermostat wire length within limits (14 ga 100 ft, 16 ga 64 ft, 18 ga 40 ft, 20 ga 25 ft, 22 ga 16 ft).
- Thermopile test: only the thermopile leads on the operator, pilot lit about 3 minutes, TPTH to TP open circuit should be 500-750 mV; adjust the pilot to reach it.
- Closed-circuit: jumper TPTH to TH - reading must stay above 300 mV. Then remove the jumper and reconnect the thermostat/switch - must stay above 175 mV (below 150 mV = too much resistance in the thermostat circuit; find and fix it).
- Operator test: remove all operator wires and measure resistance TP to TH; out of spec (see SIT table) = replace the valve.
- Burner lights but flame is poor: check the regulator matches the fuel, orifice size, inlet and outlet pressure, partial burner blockage; replace the valve if the diaphragm is bad.
If the unit shows an error code, look it up: Heat & Glo Gas Fireplace codes Napoleon Gas Fireplace codes Skytech Gas Fireplace codes
Source: SIT 820 Nova MV Troubleshooting Guide; SIT Gas Control Valve troubleshooting flow chart (Fireparts). Written in our own words as a summary; always check the original manual.
General guidance for qualified technicians. The manufacturer's installation and service manual and local codes always take priority. Aurora Star Tech is not affiliated with, endorsed by or sponsored by any equipment manufacturer; brand and model names are used only to identify equipment and belong to their owners.