120-24volt step down transformer, is it supposed to get HOT?


Old 07-25-03, 10:49 AM
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120-24volt step down transformer, is it supposed to get HOT?

Been having problems with my a/c unit running while the fan shuts off inside. Changed out contactor which had really burnt terminals but also decided to change out the thermostat after talking with my friend who is a tech. Anyway while I was putting the inside furnace back together I noticed that the 120-24 volt transformer seemed HOT is it supposed to be? The reason I ask is that when I put the new contactor in I did not notice that the actuator terminals where 180 degrees apart (old contactor had both terminals side by side), thought it was just an extra pair of terminals based on mounting - well I ended up putting the hot and ground on the same terminal for probably a minute until I noticed what I had done. Really never noticed the transformer being hot but wanted to confirm if it should be or not. It is putting out the correct voltage. Thanks for the help.

I take back the correct voltage. Before a load it is a little over 24 volts. When load applied and is hot it is around 17 volts. Is that good or does it indicate a faulty transformer? Thanks again.
Old 07-25-03, 06:56 PM
Ed G
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you seem to have a better than average understanding of this, so replace the transformer. It costs about $5-$10. Get at least a 50VA and you should be fine. It should not be that hot, and the voltage drop should not happen.
Old 07-25-03, 08:50 PM
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Your transformer will get hot if there is too much current draw too. There should only be 2 contactors (relays) powered from that transformer. They should not cause the voltage to drop past 24v. The voltage may be higher than 24 with no load, but if it goes below 24 with load, either the va rating of the transformer is too low, it is shorted internally, or there is a wiring problem in the low voltage wiring to the fan or condensing unit. It might be where the wire goes through the wall to the outside unit.


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