Magic fireplace?

[Arbutus]

Well, maybe. So we are in the middle of a west coast windstorm and inevitably the power is out again.

We have a Napoleon brand gas fireplace which has a wall switch to turn it on and off.

To my surprise it started just fine. But there is no power. There are no batteries anywhere. The wall switch is a standard 115ac SPST light switch. There is no energy across the switch at all.

At the connection point the black& white wires are from the switch, the other pair are from the piezo igniter.

So how does it work??????

 

[Downwindtracker2]

On mine I'm converting our to a themoplile from a thrmocoupling. as parts are no longer available. The Thermopile generates voltage from the heat of the pilot.

The first winter in our house we had some nasty outflow winds. As we were on the edge of town, the circuit we were on was a rural one with trees crossing the lines. The next summer we bought a gas fireplace and a freestanding gas heater/fireplace. Of course they then switched us to urban underground circuit .

 

[TorontoBuilder]

Well, maybe. So we are in the middle of a west coast windstorm and inevitably the power is out again.

We have a Napoleon brand gas fireplace which has a wall switch to turn it on and off.

To my surprise it started just fine. But there is no power. There are no batteries anywhere. The wall switch is a standard 115ac SPST light switch. There is no energy across the switch at all.

At the connection point the black& white wires are from the switch, the other pair are from the piezo igniter.

So how does it work??????

thermopile

 

[TorontoBuilder]

sorry I had to run out and pick up my pizza...

so a thermopile generates a small voltage... thanks to a pilot light. This then powers the low voltage gas valve and thermostat.

the ignitor just helps start the pilot light which tend to be buried inside sealed combustion chamber.

This design is specifically made to be reliable back up heating during power failures.

 

[Arbutus]

So that also explains why the switch is very 'iffy'. A basic light switch probably has poorly matching contacts and a relatively high resistance. According to WIKI, a thermopile produces a few millivolts - barely enough to measure but presumably sufficient to open the valve. Clever design.

 

[TorontoBuilder]

So that also explains why the switch is very 'iffy'. A basic light switch probably has poorly matching contacts and a relatively high resistance. According to WIKI, a thermopile produces a few millivolts - barely enough to measure but presumably sufficient to open the valve. Clever design.

Yeah typically about 750 millivolts, so switches can sometimes create issues.

Back in the day many standard natural venting gas furnaces used to run on millivolt ignition systems. Very clever design that now survives only in gas fireplaces because they can be back up heat requiring zero power to work

 

[Downwindtracker2]

I did a study up, a thremocoupleing also generates voltage, but only enough to hold the safety valve open. If any of us older guys who have lived with gas, you know the routine, hold the knob down on the pilot setting until the thermocoupling heats up, about a minute. It's enough to hold the safety valve open when you switch over . With a thermopile you can add a small battery powered thermostat. Then the thermopile voltage will open and close the main valve.