Gas and Oil Home Heating Furnaces - Gas Heater won't start with thermostat
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Grizzle
12-28-03, 07:15 PM
I've got an old gas in-floor heater. I've accessed it from the crawlspace and it has a fairly shiny new looking control valve. It is the millivolt style.
It used to work but stopped.
I shorted the terminals at the valve and it started right up so I replaced the thermostat and no joy.
When I shorted the wires at the thermostat side, it would sometimes start and sometimes not. So I replaced the wires with Cat 5 ( I had it in stock in the truck) and used two pairs for each terminal and still no luck.
So I ran bell wire just in case there was some issue with Cat5 and it still would't fire up.
If I connected it all up and then shorted the valve, it would start and the thermostat would hold it open until it reached its set temp and shut off. If I tried to restart it immediately ifrom the thermostat it would restart. But if I waited 5 minutes or so, then it would not restart with the thermostat.
So what is wrong?
It used to work but stopped.
I shorted the terminals at the valve and it started right up so I replaced the thermostat and no joy.
When I shorted the wires at the thermostat side, it would sometimes start and sometimes not. So I replaced the wires with Cat 5 ( I had it in stock in the truck) and used two pairs for each terminal and still no luck.
So I ran bell wire just in case there was some issue with Cat5 and it still would't fire up.
If I connected it all up and then shorted the valve, it would start and the thermostat would hold it open until it reached its set temp and shut off. If I tried to restart it immediately ifrom the thermostat it would restart. But if I waited 5 minutes or so, then it would not restart with the thermostat.
So what is wrong?
mattison
12-29-03, 09:05 AM
I'm not the pro at these systems but it sounds as if you're not getting a good millivolt signal through. You may need to relace the thermopile. Hopefully one of the other guys will chime in soon.
Ed Imeduc
12-29-03, 02:10 PM
Your working down to a 750 millivolt Generator or call also thermopile. So if the unit there in the pilot dont put this out the valve dont have the power there to open . Id get a new one . Take it with you so you get the right one. You said old ,If the tstat has points in it take a business card and run it back and forth in them as you hold them together;) ED
I think when it would start after being on. It worked cause the unit was hotter from the burner being on and had more out put .
I think when it would start after being on. It worked cause the unit was hotter from the burner being on and had more out put .
hvac4u
12-29-03, 06:16 PM
ed is right, millivolts generated are not enough to pull in valve after going through wire and points, but will when jumped straight to valve, is this a floor furnace? (one big grate in the floor?)
Grizzle
12-29-03, 08:37 PM
Yes, it is about a 16" square grate in the floor. It is a 100 year old house but the valve on there looks to be less than 10 years old.
So which piece do I need to actually replace, not the entire valve right?
So which piece do I need to actually replace, not the entire valve right?
hvac4u
12-30-03, 07:09 AM
the part that sticks in the pilot flame is the generator
Ed Imeduc
12-31-03, 05:51 PM
Id be sure and get the ###off of it or take it with me to get the part that goes in the pilot there as they run from 750 millivolt on down to 250 millivolt. Also do forget that the thermostat has to be just for this millivolt set up.;) ED