Old holly wall furnace wired wrong?

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Old 12-18-07, 08:21 PM
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Old holly wall furnace wired wrong?

Hello all, I have a very old wall furnace that is working but not with the thermostat. It is currently working with a valve at the bottom that you turn to lo. Med, or Hi. anyways the gas valve has two studs on it which has two wires going to the thermostat and two wires going to the thermopile thingy. My question to you is, Is this thing wired right? it looks like some one mickey moused it to get it to work. I would like it to work with the thermostat.
 
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Old 12-18-07, 09:31 PM
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Doesn't sound right..picture available?
 
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Old 12-19-07, 06:54 AM
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First we need to confirm my suspicions that this is a millivolt powered furnace. Is there any external source of power going to the furnace? If not.....

If the gas valve terminals are marked, one thermostat wire goes to the TH terminal, the other to the TH/TP terminal. It is important the the thermostat is meant for millivolt applications.
 
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Old 12-19-07, 09:27 PM
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Thank you guys for the replys. There is no external power source and the terminals are not marked, One terminal has a wire from the thermostat and one wire from the pilot generator. the other terminal has the other thermostat wire and the other generator wire hooked up to it. It does not make any sense to me because how could a thermostat possibly work like that. The wire from the generator are red and white, and the wires from the thermostat are both black. If I short the two wires together at the thermostas the heater shuts off. It is like it is doing the opposite it is supposed to do. I will try and post some pics tomorrow. Thank you guys for your help.
 
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Old 12-20-07, 04:16 PM
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I'm gong to venture a guess: You have an old B-60 gas valve.
One terminal tstat wire, other terminal PG wire, the remaining tstat and PG wires are wire nut together. Now you have a complete circuit. There is no pilot safety on this system. If the pilot goes out the PG quits generating and the burner can't come on.
You may also have a 3rd terminal above the other two. That is a convenience terminal to attach the remaing tstat and PG wires instead of using a wire nut.
 
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Old 12-21-07, 09:20 PM
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So, if I understand everyone correctly, it is NOT wired correctly the way it is now. He should have the thermostat and Pilot Generator wired in SERIES to the two terminals on the valve. Right?

Just to play it safe I would use a wire nut just in case you are not sure which screw is the isolated junction point terminal.

Haven't seen this system yet. Thanks mbk3 for teaching an ole fart like me something new.

Charlie
 
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Old 12-22-07, 10:26 AM
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boilersrus, the thermostat is not wired in series to the pilot generator. There are three terminals on the control valve (TH, TP, TH/TP). The pilot generator wires into the TP and TH/TP legs to energize the magnet in the gas valve. The thermostat gets wired to the TH and TH/TP terminals to close the circuit for the main burner.
 
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Old 12-22-07, 06:37 PM
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Originally Posted by hankhill6018 View Post
boilersrus, the thermostat is not wired in series to the pilot generator. There are three terminals on the control valve (TH, TP, TH/TP). The pilot generator wires into the TP and TH/TP legs to energize the magnet in the gas valve. The thermostat gets wired to the TH and TH/TP terminals to close the circuit for the main burner.
I was referring to an old General Controls B-60 valve that were very popular in Holly wall furnaces. And yes it is a series setup. Remember there is no pilot safety magnet (power unit) to energize in that valve.
 
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