[jonzo]

A "knowledgeable" person told me it was ok to downsize my blown 25 year old Carrier air handler transformer from 60va to 40va, cos it was "probably oversized " to begin with in the original specs. It worked for less than 10 mins, before it got really hot and blew. Does this make any sense? Original spec was for 60va.
Also..if the original prob is NOT that the old one just gave up the ghost on its own..what coudl possibly cause the transformer to blow?
Thanks so much!!

[SteveKJR]

Downsizing a transformer is not a good idea. The manufacturer specs that size for a reason.

With regard to your transformer blowing - you might have a contactor that is bad - but not completely. Sometimes contactors will still work even though the coil has deteriorated internally.

Part of the coil may be ok and provide enough of a magnetic pull to engage the contactor. However, over a period of time it begins to heat up and will start to draw more current and eventually cause the transformer to overheat and blow the internal fusable link.

I would start by disconnecting all the wires from the thermostat and start connecting one at a time. Turn the unit on and let it run for a period of time. Connect the next wire and do the same thing. Eventually you should eleiminate the problem.

You also need to check the thermostat as that could be the culprit. If the problem still persists after you connect all the wires then bypass the thermostat and do the same thing. If the problem goes away, it's most likely the thermostat.

SteveKJR

Originally Posted by jonzo

A "knowledgeable" person told me it was ok to downsize my blown 25 year old Carrier air handler transformer from 60va to 40va, cos it was "probably oversized " to begin with in the original specs. It worked for less than 10 mins, before it got really hot and blew. Does this make any sense? Original spec was for 60va.
Also..if the original prob is NOT that the old one just gave up the ghost on its own..what coudl possibly cause the transformer to blow?
Thanks so much!!

[paul52446m]

Originally Posted by jonzo

A "knowledgeable" person told me it was ok to downsize my blown 25 year old Carrier air handler transformer from 60va to 40va, cos it was "probably oversized " to begin with in the original specs. It worked for less than 10 mins, before it got really hot and blew. Does this make any sense? Original spec was for 60va.
Also..if the original prob is NOT that the old one just gave up the ghost on its own..what coudl possibly cause the transformer to blow?
Thanks so much!!

When you hook up a new transformer , put your am-prob on it and fire it up and check your amp draw. A 60va will handle 2.5 amps, a 40 va will handle 1.6 amps.
Do you have a fuse in the low volt line leaving the tran.? If you are drawing more than the2.5 amps then you have a problem with a control. bad contacts in a switch or some bad wires. Paul

[icehouse]

Originally Posted by paul52446m

When you hook up a new transformer , put your am-prob on it and fire it up and check your amp draw. A 60va will handle 2.5 amps, a 40 va will handle 1.6 amps.
Do you have a fuse in the low volt line leaving the tran.? If you are drawing more than the2.5 amps then you have a problem with a control. bad contacts in a switch or some bad wires. Paul

VA = Supply voltage x total amp draw

Carrier's specs call for 60 VA never go smaller.