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Old 12-03-2013, 12:56 PM   #16
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Furnace electrical transformer fried??


You might also want to re-check your thermostat wires since you said you just relocated it. Maybe a wire popped off its terminal or somesuch...

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Old 12-03-2013, 01:00 PM   #17
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Furnace electrical transformer fried??


the primary side/120 volts side is the black and white wires. the secondary 24 volt side is the blue and yellow. You should get 24 volts from them, check that. after that you should get 24 volts from the W wire from the tstat when it is calling for heat to the C terminal or yellow wire, if not then it is shot or you got a bigger wiring problem or broken wire. you can also take the W wire and R wire off at your box and using an ohmmeter with alligator clips on your meter ends put them on those wires and have it call for heat. should get 0 ohms or very low resistance. if it is infinity or OL open line then you got an open circuit for some reason. don't use the ohmmeter while holding the probes with your fingers as it will read continuity thru your body and give a false positive result. I am pretty sure yellow is common but really need to see the wiring diagram to be sure. post a pic of that box with the other side facing out so we can read what the terminals are or you list them from top to bottom starting at the transformer and going down to where that blue wire attaches.
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Old 12-03-2013, 11:24 PM   #18
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Furnace electrical transformer fried??


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The box stores sell 24vac doorbell transformers that might work but they won't have the exact same mounting holes as your original.
Im thinking a doorbell transformer is normall between 12-18v depending on how old it is anyway,wont work.
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Old 12-03-2013, 11:26 PM   #19
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Furnace electrical transformer fried??


Its usally pretty hard to smoke a transformer by bumping the wires together on the thermostat end of circuit,if you bump the wires against something metal inside the furnace on the other hand Id say all bets are off though!
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Old 12-04-2013, 02:04 AM   #20
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Furnace electrical transformer fried??


I get voltage across the blue and yellow wires off of the transformer, seems to be doing its job. The furnace won't switch on still. I tested using a spare thermostat and that didn't change anything so it is not the thermostat. What is the best way to find where the electrical fails?

Here are so pictures for you to look at.

This is the electrical box with the new transformer installed.



Here is the front of the electrical box.



Here is a larger view of the furnace



Is there any sort a wiring diagram that I could use for a reference? Its hard for me to follow what the different electronics do.
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Old 12-04-2013, 05:13 AM   #21
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Furnace electrical transformer fried??


Disconnect the thermostat wires at the furnace.
Then put a jumper wire from the red/r to the white/w terminals,furnace should come on(you might have to hold in the door switch,couldnt tell from picture)
If that brings the furnace on its time to hook low voltage back up at furnace and check the wires at the stat,can you post a picture of the wires at the stat?
Did you splice anything when you moved stat?
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Old 12-04-2013, 06:30 AM   #22
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Furnace electrical transformer fried??


This is a little OT since the OP seems to have a working transformer now... but for us DIYers who might not be able to get a real HVAC xfmr fast these might be the only things we can get in a hurry on a cold day to get the heat back up and running. They are multi-voltage (different taps) and do have 24vac, 20VA output. Would this work in a pinch? What would happen if 20VA wasn't enough? Would it hurt the circuit board or just burn out the xfmr?

http://www.homedepot.com/p/IQ-Americ...x#.Up8RN8RwqSo



Quote:
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Im thinking a doorbell transformer is normall between 12-18v depending on how old it is anyway,wont work.
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Old 12-04-2013, 06:35 AM   #23
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Furnace electrical transformer fried??


Quote:
Originally Posted by raylo32 View Post
This is a little OT since the OP seems to have a working transformer now... but for us DIYers who might not be able to get a real HVAC xfmr fast these might be the only things we can get in a hurry on a cold day to get the heat back up and running. They are multi-voltage (different taps) and do have 24vac, 20VA output. Would this work in a pinch? What would happen if 20VA wasn't enough? Would it hurt the circuit board or just burn out the xfmr?

http://www.homedepot.com/p/IQ-Americ...x#.Up8RN8RwqSo

The transformer would burn out. 20 VA at 24 volts is .83 amp.
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Old 12-04-2013, 10:01 AM   #24
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Furnace electrical transformer fried??


Quote:
Originally Posted by plummen View Post
Disconnect the thermostat wires at the furnace.
Then put a jumper wire from the red/r to the white/w terminals,furnace should come on(you might have to hold in the door switch,couldnt tell from picture)
This doesn't kick the furnace on, where is the next place to check?

Quote:
Originally Posted by plummen View Post
If that brings the furnace on its time to hook low voltage back up at furnace and check the wires at the stat,can you post a picture of the wires at the stat?


Quote:
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Did you splice anything when you moved stat?
I did not I just got a new wire and hooked everything up where it was before.
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Old 12-04-2013, 10:36 AM   #25
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Furnace electrical transformer fried??


Quote:
Originally Posted by raylo32 View Post
This is a little OT since the OP seems to have a working transformer now... but for us DIYers who might not be able to get a real HVAC xfmr fast these might be the only things we can get in a hurry on a cold day to get the heat back up and running. They are multi-voltage (different taps) and do have 24vac, 20VA output. Would this work in a pinch? What would happen if 20VA wasn't enough? Would it hurt the circuit board or just burn out the xfmr?

http://www.homedepot.com/p/IQ-Americ...x#.Up8RN8RwqSo
A furnace transformer is generally going to be 24v 40-50va if I remember right without digging one up.
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Old 12-04-2013, 10:38 AM   #26
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Furnace electrical transformer fried??


do you get 24 volts across R and C on the terminal strip with the door switch pressed in. looks like somebody altered some of the factory wiring. R is fed by that pink wire and you may need to trace where it comes from, I suspect the limit control.
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Old 12-04-2013, 10:41 AM   #27
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Furnace electrical transformer fried??


there are 2 types of OEM furnace transformers. 20 VA and 35-40 VA none larger than that.
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Old 12-04-2013, 10:46 AM   #28
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Furnace electrical transformer fried??


Yep I was having a brain cramp,40va is what I was thinking but couldnt remember for sure.
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Old 12-04-2013, 11:24 AM   #29
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Furnace electrical transformer fried??


you ought to see what a mess and disaster using telephone wire instead of #18 wire can do to a modern circuit board. blows their brains and logi circuits. hate that stuff when I run into it.
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Old 12-04-2013, 06:21 PM   #30
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Furnace electrical transformer fried??


Doubt its a problem with the thermostat. More likely a limit or roll out tripped.

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