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Chances are that your gas valve is powered by 750 millivolts. That power is generated by the pilot flame burning on the pilot power generator. There are several items that connect the electrical parts to make the millivolts open the gas valve.

• First there is the power generator sometimes called a power pile.
• Next there is a Gas Valve that uses that power
• Then there is the thermostat that opens and closes the electric current based on the room temperature
• Then there may be a Limit switch or even more limit switches placed in different locations around the furnace in order to keep the furnace from overheating.

Some of these limit switches may have a manual reset. If you have a manual reset limit, that may be the reason you have no heat. Follow the wires to see if there are any limit switches. See if those switches have a tiny button between the wire connectors and press it. If you feel a slight click when you push it then it was tripped. If you do not feel a slight click then it was not tripped.

Another reason for no heat is the power generator thermopile may be defective.

Here is a wiring diagram that might be close to what you have in your floor furnace.

If you are not comfrotable playing with the safety controls on a gas appliance then i would suggest you call a professional for service. but pushing a reset button on a limit control is usually a DIY first step. If the limit trips again, then you need to find the cause. The safety switches are there to let you know something is wrong and needs further attention. Don't bypass them.

Hi @borecrazy , What region or city in CA are you in? I keep trying to be retired, so am not looking for work, but am near Monterey and have experience with floor furnaces.

Yours, Larry

As long as its not leaking, I'm more concerned about the distance/height to that window...Mad Dog

Got it. So it's an either/or thing.

So, update: the new relay arrived from Supply House during dinner. I got a dispensation from the lady of the manor to interrupt dinner and quickly head downstairs along with two very excited kids to install it. After I plugged the new relay in, I returned power to the boiler and the damper opened. That was it.

My 8-year old: "Nothing's happening."

I turned to my 12-year old and told him to go upstairs, set the thermostat to Heat, hold the up arrow until it flashed above the room temperature, then press the up arrow repeatedly until it was 2 degrees higher than the room temperature.

My 12-year old: "But you said never touch the thermostat."

Me: "This is an exception."

My 8-year old: "How come he gets to do it?"

Me: "You can both do it." I told the 12-year old to let his brother do it, and "supervise." They ran up the basement stairs.

I expected the next sounds I heard to be kids fighting in the living room but after a half a minute or so, I heard the boiler click and the burners fire up. Then two kids stampeding down the basement stairs.

"Did it work?" the 8 year old asked.

I told him it did.

Thank you to everyone who pitched in to help us out. It's very kind of you all to offer your time and your expertise to help strangers. My wife wanted me to extend her gratitude as well. I've learned a lot. This site is a great resource. I'm sure I'll have more questions in the future.