Bad transformer in air handler?


Old 09-03-03, 07:54 AM
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Bad transformer in air handler?

I had a contactor short out in the outside compressor unit due to a lizard. Fortunately I've had this happen before and knew what to pick up from Grainger to replace. However, it was odd in that even the air handler fan was inoperative.

After replacing contactor with exact same make and model AC unit is still inoperative. Both inside and outside units. Since even the fan in the air handler was inoperative I suspected additonal failures from the short inside the air handler itself.

Inside I noticed that the 24V transformer was cold, rather than warm, and read no voltage off of the 24V side. 240V going in was fine. I then did a continuity test between the 24V and common on the secondary and it reads shorted with the 240V main disconnected.

I haven't worked on transformers before, so before I buy a replacement wondered if the above results do point to the transformer being bad?

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Old 09-03-03, 08:22 AM
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Sure could. Most 24v transformers have a non replaceable fuse built inside of it and more than likely blew the fuse.

Are you sure it's 240v going in and not 120v?
Old 09-03-03, 10:39 AM
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Like matt said make sure if it 220 or 120 to the transformer. You also want to ask for a 40 VA or better transformer. ED
Old 09-03-03, 10:46 AM
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It's a 208V/240V in on the primary and 24V 40VA out on the secondary. Solid 239V reading into the transformer.
Old 09-03-03, 05:42 PM
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no brainer

voltage in, no voltage out, replce transformer. put a fuse in line, 5 amp at most.
Old 09-04-03, 02:59 AM
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Replaced with an 8.00 part from Grainger. Everything works again. Thanks.

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