how to test the transformer


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Old 07-12-12, 06:53 PM
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how to test the transformer

Can someone tell me how to test the transformer to see if its putting out 24 volts from 240?
 
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Old 07-12-12, 07:07 PM
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call a pro if you dont have a volt meter or know how to use one.
 
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Old 07-12-12, 10:46 PM
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If I had the money to call a pro I would not be here in this forum looking for help.
 
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Old 07-13-12, 12:39 AM
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First you need a voltmeter with both a high range (300 volts AC) and a lower range (around 50 volts AC). Then you have to locate the transformer in the furnace or air handler. It could be attached to the inner cabinet or the circuit board. It will have two colored wires coming from each side.

The two black wires are the primary side and where they connect on the circuit board should have approximately 240 volts when all the safety switches are closed. Don't forget to close the safety switch on the blower compartment that is normally closed by the compartment door.

The secondary side of the transformer will have wires colored other than black, usually, but not always blue and yellow. Where these wires connect to the circuit board should read approximately 24 to 28 volts when the primary has the aforementioned 240 volts. If you have the 240 but not the 24 the transformer is probably toast but before condemning it look closely for a fuse in the secondary wiring.
 
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Old 07-13-12, 09:50 PM
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Does my thermostat have to be connected to test the transformer? If so I will have to wait till I go into town to buy one since my original one got melted down. I was hoping to know if my transformer had to be replaced so I could kill 2 birds with one stone. And thank you for your reply as I do appreciate it.
 
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Old 07-14-12, 02:29 AM
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No, the thermostat does not need to be in place. Be sure that none of the thermostat wires are touching each other before testing. Best to have the thermostat completely removed.
 
 

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