Originally Posted by tnbna
the 24vac transformer in my inside unit of A/C system was burned out 3 times in this winter. one month ago, the unit did not work, no heating, no blowing. we found out the transformer burned out and replaced it. one week ago, burned out and replaced it again. yesterday (worked for 5 days) it was burned out again.
there is no fuse on the inside unit board. this is a electric heating system. any suggestion to figure out this issue is appreciated. thanks.
Anytime a transformer burns out and you go to change it, like you have been told , use the right size VA rating transformer. You also have to assume that there is a reason that it burned out. so the very first thing you need to do is take a amp draw when its calling for heat and blower start. Lets say you have a 40 VA transformer and its secondary power is 24 volts. Divide the voltage into the VA and that will tell you how many amps the transformer will handle. 40 divided by 24 is 1.6 amps. that's how much that transformer is good for. If you try to use 3 amps through it, it will burn up.
Do you have a amp probe?
Most amps probes don't have a small enough scale to check amperage for 1 amp or less. Take your amp probe that has maybe 6 amp scale and use a wire with 10 loops in a circle, so 10 wires are going through the amp probe. This way you readings are divided by 10, so if you get a reading of 4 that would .4 amps.
Most relays only use about .2 amps when powered . You might have to check all your 24 volt loads one at a time to see which one is drawing too much power. Check all low volt wires for bare spots and lose connections. Paul