HVAC 24v Transformer Blowing

[aimpulsive]

Help!

My 24v transformer blew on my 10 year old Trane system. I replaced it and the unit ran for a few seconds and then the transformer started smoking and everything stopped. This transformer is now shot too!

I checked the wires coming from the control unit to the motor relay on the compressor and got 0 ohms resistance across the wires. I then went to the compressor and removed the leads from the control unit to make sure that the wires weren't shorted somewhere (the wires were 24v yellow and orange/control t-stat wires) and the relay measured 0 ohms across the 24v terminals.

Should the relay measure 0 ohms across the 24v terminals? This seems like it would be bad as it basically is like a shorting my two 24v leads together (since no resistance is there).

I checked for cross shorting of all t-stat wires and found no shorts. The problem only happens when the t-stat tells the AC to turn on. Just in case, I replaced the t-stat but that did not fix the problem.

Where else (or what else) should I be looking for? What is causing this thing to short out?

Thanks for ANY help!

[Mr Bill]

Originally posted by aimpulsive
Where else (or what else) should I be looking for?

http://www.MyOnlineImages.com/Members/mrbillpro/images/yellow.jpg

[keepitsimplestupid]

Zero is a figment of the imagination. It usually only exists in mathematics. Shorts are funny things - they are open when you look for them, but they short because of heat vibration and other factors and then they open again just when your staring right at it.

How about shorts to ground? To power? Fuses and energy limiting transformers exist so that the majic smoke can be contained to a cheap element.

Sorry, can't be of much help because of THE "RULES".

[waynesrefrigeration]

>>>EDIT...

Regardless of expertise this is NOT a DIY site.

DIY threads, questions and answers have a life of their own. What happens, if we post repair instructions that injures the person whom we thought was qualified?

We have Forum Rules (http://hvac-talk.com/vbb/showthread.php?threadid=1241) not to anger you, but because they are well thought tried and true.

We all want to help, but we just can't due to the difficulties of working on the other end of the computer and safety. If we tell you, we tell everyone once it’s posted. It’s here for all to read and try.

Thanks for looking at it from our point of view.

Forum Rules (http://hvac-talk.com/vbb/showthread.php?threadid=1241)




[Edited by jrbenny on 08-24-2006 at 05:21 PM]

[jim baughman]

Originally posted by mrbillpro

Originally posted by aimpulsive
Where else (or what else) should I be looking for?

http://www.MyOnlineImages.com/Members/mrbillpro/images/yellow.jpg


I am still rolling over this one...LOL

great job!

[aimpulsive]

Keeptitsimple and Wayne: Thanks for the direction. I have installed a fuse already, but I wanted more information about the desired resistance across the 24v coil on the relay before turning power back on.

MrBillPro: Cute. Not helpful. But cute. :)

[Mr Bill]

Originally posted by aimpulsive

MrBillPro: Cute. Not helpful. But cute. :)

I bet you will change you mind about not helpful soon as it gets to about 95 inside you home, and I really was trying to help I was not trying to be mean.

[keepitsimplestupid]

Coils have a characteristic impedance, not resistance. Wire is wire. Resistance of wire R = pl/A. The p thing is rho and is resistivity of the material. l is it's length and A is the cross-sectional area. Zero ohms doesn't exist except mathematically.

[brooklyntech]

Yellow pages----hahahahahahah, brilliant