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Millivolt flame proving and safety magnet checks
What happens, in order
- Pilot heats the thermopile (or thermocouple); the output energizes the safety magnet so the pilot stays on after the knob is released
- Thermocouple (non-millivolt valves) closed-circuit output below 8 mV means replace the thermocouple
- Thermopile and magnet, circuit open should read above 325 mV; below that, clean connections and adjust the pilot, otherwise replace the thermopile
- Valve operator with thermostat contacts closed: should read above 100 mV; if above 100 mV and the valve will not open, replace the operator
- Thermostat leads with contacts closed drop should stay under 80 mV; more means wire too long or thin, dirty connections or a bad thermostat
- Magnet drop-out with the pilot out, the magnet should hold until the reading falls to 120 mV or less; a good thermocouple magnet holds for a drop of at least 5 mV from steady reading
Timings and thresholds
| Item | Value |
|---|---|
| Thermocouple minimum closed circuit | 8 mV |
| Thermopile open circuit minimum | 325 mV |
| Operator closed circuit minimum | 100 mV |
| Thermostat circuit drop maximum | 80 mV |
| Magnet drop-out | 120 mV or less |
| Thermostat wire 14 / 16 / 18 / 20 / 22 ga | 100 / 64 / 40 / 25 / 16 ft |
Applies to: Flameworks millivolt gas valves
Models
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Source: Flameworks gas valve installation manual v3, Operating and Service instructions - Service instructions, Test results A to C. 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.