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Old 12-02-2013, 07:36 PM   #1
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Furnace electrical transformer fried??


Yesterday I moved my thermostat to a more convenient location. I got everything moved and hooked up and it awash all working great. A few hours later I noticed that the furnace stopped working. The pilot is on but the electrical system seems to be messed up. I tried turning the furnace switch off and on to no avail.

I think I could have blown some electrical components because I accidentally touched the wires from the thermostat before I remembered to turn off the electrical switch to the furnace.

Can anyone help me diagnose the problem?

I have a comfortmaker guf100a012an gas furnace

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Old 12-02-2013, 07:44 PM   #2
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Furnace electrical transformer fried??


You probably just blew the transformer fuse on the furnace circuit board. It is ususally a 3 or 5 amp that looks like a plug in car fuse under one of the furnace access panels. Open the circuit breaker to the furnace, make sure your wires are connected properly, replace the fuse, and switch the breaker back on.

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Old 12-02-2013, 08:05 PM   #3
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Furnace electrical transformer fried??


There doesn't appear to be a fuse just a black and a yellow box with all of the cables around it.
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Old 12-02-2013, 08:12 PM   #4
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Furnace electrical transformer fried??


Never seen one withour a fuse. Did you remove both panels? Do you not see a circuit board? It would help if you take a couple of pics and post them.
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Old 12-02-2013, 08:16 PM   #5
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Furnace electrical transformer fried??


Can you post some pics of the inside showing your control board and transformer area. Thanks. Do you own a multimeter and know how to use it? Others will be along shortly with more advice.

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Old 12-02-2013, 09:04 PM   #6
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Furnace electrical transformer fried??


Quote:
Originally Posted by raylo32
Never seen one withour a fuse. Did you remove both panels? Do you not see a circuit board? It would help if you take a couple of pics and post them.
This model has no circuit board it is an old style standing pilot and almost never had a fuse for low voltage. It would appear that the transformer is blown but I'd double check by putting a meter across the terminals on the secondary side and look for 24 volts AC.
If you haven't seen this type of unit before you haven't been to many older houses with original furnaces. They stopped making standing pilot furnaces in 1993

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Old 12-02-2013, 09:27 PM   #7
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Furnace electrical transformer fried??


I was hoping this would not be the case. Looks like its the transformer. Where would be the best place to find a replacement part?
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Old 12-02-2013, 09:34 PM   #8
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Furnace electrical transformer fried??


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I was hoping this would not be the case. Looks like its the transformer. Where would be the best place to find a replacement part?
As a contractor ive always bought from any hvac supply places but they may or may not sell to you so trainers would be my suggestion. As long as the transformer it 120 VAC primary and 24VAC secondary. You can even get a multi tap one that will work with different supply voltages and is more of a universal one.
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Old 12-03-2013, 06:08 AM   #9
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Furnace electrical transformer fried??


The box stores sell 24vac doorbell transformers that might work but they won't have the exact same mounting holes as your original.
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Old 12-03-2013, 08:42 AM   #10
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Furnace electrical transformer fried??


Doorbell transformers are too weak and will not work. Transformers are rated in VA=volt amps like horsepower for the layman. Doorbell ones are 10 VA or close and you need a 35-40 VA if you have AC. 20 VA minimum for heat only. try americanhvacparts.com
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Old 12-03-2013, 08:51 AM   #11
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Furnace electrical transformer fried??


I think the ones I get are in the 40-50 range. Maybe they are really multi-purpose transformers sold in the doorbell aisle? I've got one at home I can check later but hopefully the OP will have his issue resolved by then. Hopefully he lives somewhere that the winter has eased up a bit. It would have been tough going w/o heat here last week, but not so bad this week.
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Old 12-03-2013, 10:08 AM   #12
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Furnace electrical transformer fried??


Yuri is correct as usual... the doorbell xfmr I got from the orange box store is only 20 VA. I have a plug-in wall wart one I got online that is 50, that is what I was remembering...
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Old 12-03-2013, 11:02 AM   #13
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Furnace electrical transformer fried??


I got a new transformer and changed out the old one and nothing has changed. I can hear a slight hum. when all the electrical is on, but it is behaving just as it did before.

Anyone have any ideas?

Thanks!
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Old 12-03-2013, 11:51 AM   #14
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Furnace electrical transformer fried??


post some closeup and well lit pics of it with both doors off and the wiring. you need a voltmeter to test for voltages and if you don't know how to use it etc then better to call a Pro. Those old furnaces usually have cracked heat exchangers so it should be inspected by a Pro for safety. Google cracked heat exchanger>Images for more info.
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Old 12-03-2013, 12:49 PM   #15
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Furnace electrical transformer fried??




Here is the picture I have on hand (I hope I am uploading it right). I replaced the transformer on the right.

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