Please help me with the furnace wiring!


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Old 12-02-12, 04:28 PM
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Please help me with the furnace wiring!

Can you and any knowledgeable people help me in tracing down
the wiring of my old air forced gas heater made from Payne Company,
if there is any mistake; because it did'nt have any power of
voltage coming out across the terminals of the gas valve at all and
when I turned the thermostat to call for heat, the burner did'nt fire;
but when I connected directly two wires from the transformers to the
thermostat, the burner fired right away. I did check all the parts,
they're working fine like: transformer, limit control, gas valve, thermopile,
thermostat.


The present wiring as described below:


Starting from the terminals of the transformer, one terminal is wiring
to limit control and from limit control coming out wiring to one wire
of thermopile; the remaining thermopile's wire going to the terminal of
gas valve. The remaining of terminal of gas valve is wired to one wire
of the thermostat and the other thermostat's wire is going to the
remaining terminal of the transformer.


I don't know whether the wiring is correct or not, but it's not working.
The burner doesn't fire!


I am welcome to your advices and thank you all for your helps.

Read more: http://www.doityourself.com/forum/ga...#ixzz2DwWhybQn
 
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Old 12-02-12, 04:40 PM
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If you have a transformer, you don't have a thermopile.

A thermopile is a way of powering a gas valve and furnace without a transformer and without a 120 volt power supply.

You might want to look more carefully at what you are calling a thermopile and see if you can describe what it is in more detail.

What is the model number of the furnace, which you can get off the furnace rating plate in the burner compartment of the furnace.

Do you have a multimeter and understand how to use it?
 
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Old 12-02-12, 05:24 PM
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Thank you very much for your prompt reply!

I thought the term thermopile is just a small thermocoupler just like one used in gas water heat;
its use is for sensing and keeping the pilot flame. I saw two wires coming out from the standing
pilot flame and I thought it's called thermopile. Sorry if I called it wrong.

I try to get the model number of the furnace when I come there.

Yes SeattlePioneer, I have a multimeter and understand how to use it as a novice user.

I don't think the present wiring is correct and I don't know either what is the right connection.
I described the route of wiring going from one terminal of the 24v transformer to the limit control and from limit to pilot flame control_ instead of calling thermopile_ and from here to terminal of the gas valve, the remaining gas valve terminal wiring to one wire of the thermostat, and the other remaining wire of thermostat going back to the remaining terminal of the transformer.
That was axactly what I saw the wiring route going in detail.

Thank you so much for your further inputs.
 
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Old 12-02-12, 05:57 PM
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Not knowing the correct terminology is not a problem. But I try to get these things straightened out so we are all in agreement about the facts. If you suppose something is one thing and it's something else, you can have serious problems.

Does this furnace have a standing pilot light that is lit all the time, or does it have a pilot that is lit each time the thermostat calls for heat?

Payne has a lot of intermittent pilot ignition system that have three wires going to the pilot light and that connect to the furnace with a white plastic plug. Does that sound like what you have?

The model number of the furnace will reveal a lot of information about the furnace when you have it.
 
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Old 12-02-12, 06:56 PM
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I think it might be a standing pilot safety switch that is wired in series with the main gas valve. OP, can you post a picture. If you do have a standing pilot switch and no control to turn off the pilot gas if the pilot goes out then you need to STOP. Shut off the gas and call a pro to have a 100% shutoff gas gas valve installed or to have your very old furnace replaced.
 
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Old 12-03-12, 06:55 PM
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Some pictures of the wiring from my air forced gas furnace

I just noted down a model number and a serial number as following, so you
can have more useful details to give me advice_ model: 80 FAU-12,
serial no: 565 55702. And the furnace has the standing pilot that lit all the
time.

Beside I took some more pics so you can have a glue of what I tried to
describe in the last post.

Thank you again to all of you for your kindness in helping me to correct the
wiring problem!
 
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Old 12-03-12, 07:13 PM
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yep, That is a unsafe gas valve using a pilot switch. It is also a very old furnace that should have its heat exchanger examined by a professional before you put any money into it.
 
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Old 12-04-12, 03:35 AM
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Can you and any knowledgeable people help me in tracing down
the wiring of my old air forced gas heater made from Payne Company,
if there is any mistake; because it did'nt have any power of
voltage coming out across the terminals of the gas valve at all and
when I turned the thermostat to call for heat, the burner did'nt fire; >>


HVAC Tech's earlier post was correct. Your furnace is older than I was supposing.

You have a two wire pilot switch. The main burner wont turn on unless the pilot burner keeps the bimetal switch built in to the pilot burner hot enough to verify that the pilot light is lit.

And that's very likely the problem ---- the pilot burner is dirty and needs to be cleaned. Once that's done the pilot burner will operate better, will keep the pilot switch closed and allow the burners to turn on.

As HVAC tech warns, this isn't as safe as is available on newer furnaces. For example, the pilot switch can seize up in the "on" position so it wont shut the burner off. If the pilot goes out, the thermostat will turn on the main burner and the burner will turn on and stay on with no pilot burner to light the gas.

However, it's as safe as it was when designed by the manufacturer, except for being 40+ years old.

Having the furnace heat exchangers inspected and the burners cleaned and having the pilot burner cleaned by a pro would be a good practice. The fan is probably past due for being oiled as well. Have the furnace vent and chimney checked and cleaned of debris, especially if it's a brick chimney.
 
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Old 12-04-12, 10:08 AM
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Don't waste your money on an inspection - that unit should have been replaced 20 years ago. It was dangerous 40+ years ago and it's even more dangerous now.
 
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Old 12-04-12, 02:05 PM
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Thank you very much for your instructional advice. So all I need is cleaning the pilot burner to
work better in giving out the signal to the gas burner to fire. So what about the wiring of the
furnace that i described and attached all the pictures; do you think the way of wiring is correct,
because I did try to wire the way I thought it right, but still it didn't work either. I just want your
verification on the wiring itself of the furnace.
 
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Old 12-04-12, 02:39 PM
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If you insist on keeping that old furnace running, please call a pro instead of tinkering with it.

The type of ignition system your unit has is not safe. If the pilot goes out, the pilot gas will keep on flowing. If the pilot goes out and the safety switch fails, unburned fuel will accumulate in the furnace and surrounding area, resulting in explosion.

The heat exchanger is most likely bad, meaning that co containing exhaust can leak into the the supply air and kill you.
 
 

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