DIY Home Improvement, Remodeling & Repair Forum > Appliances > HVAC > 24vac transformer burns out




Reply
 
LinkBack Thread Tools Search this Thread Display Modes
Old 09-02-2010, 06:52 PM  
paponertelo
Junior Member
 
Join Date: Sep 2010
Location: Washington, DC, Virginia
Posts: 12
Default 24vac transformer burns out

Hi. I have a Trane gas heat/ AC unit thats about 18 years old. Untill 2 weeks ago it was working perfectly. Sudenly, it stopped working and nothing would come on. I checked the control unit and there was no power. My trane has a white-Rodgers 50A50-403 control unit. I bought a new 50A55-843 which is the replacement and still nothing worked. After checking everything, I noticed that the transformer was dead and ordered and replaced said transformer. I installed the old control unit back and when I switched on the power, the unit's light started flashing normally. I also heard a humm from the transformer.

I went upstairs and turned the AC T-stat on. The blower started running but the compresor/condenser unit did not kick in. I went to the control unit and noticed that the red light was flashing very rapidly and then it went out. I verified all conections and even checked the breaker and all was okay. When I touched the new transformer and it was hot. The diagnostic light does not come on and not even the blower will work. The old control unit does not have a fuse to protect the transformer. I'm at a loss, what can I test next?

One last thing, last year I replaced the contactor for the compresor/condenser unit because it would not stop running.

Thanks for your help.



__________________
paponertelo is offline  
 
Reply With Quote Quick reply to this message
Old 09-03-2010, 12:31 PM  
kok328
Supporting Member
HRT_SUPPORTER.png
 
Join Date: Nov 2007
Location: Grand Blanc, MI
Posts: 2,167
Liked 100 Times on 88 Posts
Likes Given: 61

Default

I suppose you could try the new control unit with a new transformer and there's nothing stopping you from installing an inline fuse to protect your components.



__________________
kok328 is offline  
 
Reply With Quote Quick reply to this message
Old 09-08-2010, 05:48 PM  
paponertelo
Junior Member
 
Join Date: Sep 2010
Location: Washington, DC, Virginia
Posts: 12
Default

I was about to try that. Got a new transformer and the new control unit has a fuse for the transformer circuit. Will report after try.

__________________
paponertelo is offline  
 
Reply With Quote Quick reply to this message
Old 09-25-2010, 11:34 AM  
RichCPZ
Junior Member
 
Join Date: Sep 2010
Location: Atlanta, Georgia
Posts: 5
Default

paponertelo,

I was wondering what your out come is? I have the same problem and was considering a new system. But if it is the board then I may spring for the part. I have already changed and tested the t-stat, replaced a broken switch and went through 2 transformers.
The only thing is seems to slowly burning out the transformer. When I test I got the 24 volts needed but it slowly get cut down to about 10-13 volts and doesn't blow the fuse either. I guess the fact that the transformer slowly heating up, building up resistances, and burning itself out. I had a HVAC guy out and he suggest I change the circuit board his cost to do it about 500.00...but, I can do it myself for about 100.00.
Please give me an update, and any suggestion on what else I may try..

__________________
RichCPZ is offline  
 
Reply With Quote Quick reply to this message
Old 10-01-2010, 11:59 AM  
silentdub
Junior Member
 
Join Date: Jun 2010
Location: Wilmington, Delaware
Posts: 16
Default

A transformer would NOT have a voltage drop from 24 to 13 from heating up.

Something is bring it down. I am betting that there is some kind of short on the outside unit.

I would disconnect the outside board and see if you get the 24 volts back and also make sure the inside unit works properly.

Remove the board, check for any burn marks or places where it can be touching metal. Check all connections too, especially out to the unit.

__________________
silentdub is offline  
 
Reply With Quote Quick reply to this message
Old 10-02-2010, 06:14 AM  
RichCPZ
Junior Member
 
Join Date: Sep 2010
Location: Atlanta, Georgia
Posts: 5
Default

Quote:
Originally Posted by silentdub View Post
A transformer would NOT have a voltage drop from 24 to 13 from heating up.

Something is bring it down. I am betting that there is some kind of short on the outside unit.

I would disconnect the outside board and see if you get the 24 volts back and also make sure the inside unit works properly.

Remove the board, check for any burn marks or places where it can be touching metal. Check all connections too, especially out to the unit.
The tech and I checked the unit outside and anywhere a wire may be shorting out against the unit inside and out. He still thinks it's the board and I just bought one for 69 bucks..So, I'm in the process of installing it. If it not the problem I'm just gonna spring for a new unit.
I'll update this later ....
__________________
RichCPZ is offline  
 
Reply With Quote Quick reply to this message
Old 10-03-2010, 05:39 AM  
RichCPZ
Junior Member
 
Join Date: Sep 2010
Location: Atlanta, Georgia
Posts: 5
Default

OK, Here is my update, Installed new board and the fan started blowing..GREAT..then switched to the A/C setting, blew fuse, replaced fuse - blew again..Called Tech then replaced contactor in the A/C unit... same result...check all wires for grounding without any success and then started system up again, Transformer blew? So, ...Gonna install a full new system this week and call it a day! Lucky it was only about 200 bucks to make this decision...

__________________

Last edited by RichCPZ; 10-03-2010 at 05:44 AM.
RichCPZ is offline  
 
Reply With Quote Quick reply to this message
Old 10-03-2010, 09:47 AM  
silentdub
Junior Member
 
Join Date: Jun 2010
Location: Wilmington, Delaware
Posts: 16
Default

Quote:
Originally Posted by RichCPZ View Post
OK, Here is my update, Installed new board and the fan started blowing..GREAT..then switched to the A/C setting, blew fuse, replaced fuse - blew again..Called Tech then replaced contactor in the A/C unit... same result...check all wires for grounding without any success and then started system up again, Transformer blew? So, ...Gonna install a full new system this week and call it a day! Lucky it was only about 200 bucks to make this decision...
That sucks, sorry to hear that.

If you are looking for an excellent system, check out my thread on the goodman, I love it.


I had an issue where I ran new wires from the inside unit to the outside, brand new from the box and something was wrong with them. They were shorted somewhere, I replaced them again and all was ok.

Pick yourself up an ohm meter, a cheap 4 dollar one will do from harbor freight tools. It will help you ohm out the lines.

something that the board is connected to is cauing the problem. What you could do, just for the hell of it, disconnect the board from all of the components, plug everything in, then plug each one in one at a time, when the fuse blows, you found the problem.
__________________
silentdub is offline  
 
Reply With Quote Quick reply to this message
Old 10-04-2010, 09:57 AM  
RichCPZ
Junior Member
 
Join Date: Sep 2010
Location: Atlanta, Georgia
Posts: 5
Default

Yeah, we kind of did the process of elimination, and found the wire. Cut off part of the wire that was "worn" and then blew out the transformer. The Tech and I are replacing the whole HVAC unit...I will assist him with the tear-out and install for $3500.00.
For me it's a cool deal... I get a new system ( Goodman ) and an education in HVAC. I have an ohm meter but, never use it beyond checking batteries.
Thanks for your help...!

__________________
RichCPZ is offline  
 
Reply With Quote Quick reply to this message
Old 01-04-2011, 11:48 AM  
paponertelo
Junior Member
 
Join Date: Sep 2010
Location: Washington, DC, Virginia
Posts: 12
Default Got it!!

Sorry for the delay and thank you to kok328 for his help in logically determining what was wrong with my system. As we discussed, I replaced the transformer and the control unit (the new control unit is fused) and the system is now working.

Like to note that the fan speed is now lower but the heat is operating beautifully. I believe the fan speed is now lower because I did not change any of the switches on the new control unit which serves as the replacement for a large number of Trane systems. And because this speed is lower and thus, much quieter, I do not intend to change the setting as its easier to listen to the TV now.

Thanks and I wish all of you a very prosperous new year.



__________________
paponertelo is offline  
 
Reply With Quote Quick reply to this message
Reply


Quick Reply
Message:
Options

Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are On
Refbacks are On


Similar Threads
Thread Thread Starter DIY Home Repair Forum Replies Last Post
Oil Burner Transformer jgilpin HVAC 12 03-07-2012 11:17 AM
Weatherproof Low Voltage transformer Hardwired vistav Electrical and Wiring 4 08-05-2009 04:54 AM
Transformer crazy bbyyll General Home Improvement Discussion 2 08-01-2008 06:11 PM
LP range burns too hot guyod General Appliance Discussion 7 04-14-2008 12:24 AM