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Originally Posted by wika_boy

The 460v to 24v 4amp transformer overload keeps tripping about every 4 hours. Unit is a dx system. Any ideas why. Thanks

Every Four hours eh ? That should be helpful in tracing down your faulty component to some degree.

You could isolate components one at a time while monitoring current on R. Transformers tripping usually wind up being something simple.

One of my customers at a local server farm who likes to trouble shoot and "repair" electrical problems ran one leg of 460 through the thermostat wire on a Trane 2 stage 20 ton split and then called me.

Of course it smoked various low voltage components and compromised the insulation on the plenum rated thermostat wire.

Didnt start having issues with the t-stat wire until a month later.

Just yanked it out and pulled new wire. Not a big deal.

If you have something like Fluke 189, this is where it gets useful.

Another option is to hookup a needle volt meter to monitor the voltage between R and C at the thermostat that's controlling this and monitor it with security camera, so that it can see both the thermostat and the needle.

The fuse blowing current level will cause a significant voltage drop. See if there is a relationship between what the thermostat is calling for and the voltage.

Sorry "time builder",I can be alittle long winded in my answers sometimes, but yes it was in the control circuit for 2nd stage condenser fan bank. just read where I wrote "cf motor", my mistake. Thanks for calling my attention to that, proper terminology is a must.
I will be more careful in the future.

Let me explain,in fl. we can have power swings up/dn in excess of 10-15%,(summer). So as a precaution I would add TDR relay's(var.10min.) and adjust times to protect all my loads. Also,served to stage eqpt.in (1-2m.)increments. Because of the added TDR's, 45'-60' mornings that year,left it lurking in the background. There is a method behind the madness, I hope that explains it. Take care guys, bklyntek.

If this is a rooftop with an economizer, there is always the possibility of a short in the circuits going through econo wiring/modules.

Originally Posted by Bklyntek

Hi guys, it's bklyntek, same thing has happened turned out it was the cf motor on the 2nd stage ck. On a air cool chiller. Moderate temps. Kept me from diagnosing it faster. At the time, I had removed the 3.2amp from an old decommissioned carrier rtu & used it to isolate the coil problem. Now, It's part of my tool bag, don't have to stock up on the small glass fuses in my truck. It's worth having with you. Hope this helps out.

You mean it was in the control circuit for the CF motor, right?

Hi guys, it's bklyntek, same thing has happened turned out it was the cf motor on the 2nd stage ck. On a air cool chiller. Moderate temps. Kept me from diagnosing it faster. At the time, I had removed the 3.2amp from an old decommissioned carrier rtu & used it to isolate the coil problem. Now, It's part of my tool bag, don't have to stock up on the small glass fuses in my truck. It's worth having with you. Hope this helps out.

Stick your amp probe on 24v side to see the draw at restart then you can watch the load grow towards overload. You can also put the probe on different component coils and see the individual draw. If the power side is in series you use temp wire direct from trans to each component coil to isolate the draw from each. Having chased this ghost before I even found it hiding in a normally closed high limit that built more resistance the longer it was energized.

Originally Posted by timebuilder

New transformer?

Correct tap?

Measured load on secondary?

Hello.......?

I'm with timjimbob. Best way to start isolating the problem since it is intermittent.

Drop a fuse on each control load. See which load is popping fuse. Y1 , G, Y2 loads.

Check the time delay. I have seen time delays do this several times.

I'd check the amp draw on the secondary side with all components energized. If not overamping, replace thermostat wire. Sometimes that is the quick fix.

Akelesis, did you read his post carefully? He said the 4 amp transformer overload keeps tripping. That overload is in the 24V circuit. What would the breaker or the motor in the 460V circuit have to do with that?

Wika_boy, are you a DIY. An HVAC tech would know how to diagnose that.

sorry buddy. i misread the thread. i was too quick to respond. sorry guys i do look like an idiot now

Originally Posted by hvac69

Measure the amp draw on the 24 volt side as the unit runs, somethings coil could be overheating then shorting or the amp draw is close to the breaker trip point that it takes that long to heat up and trip. Had an unloader coil do that a while back, unit would run a good 30 minutes.

I've run in to the same situation with run contactors. Thank you NAFTA!

Measure the amp draw on the 24 volt side as the unit runs, somethings coil could be overheating then shorting or the amp draw is close to the breaker trip point that it takes that long to heat up and trip. Had an unloader coil do that a while back, unit would run a good 30 minutes.

once you verify correct voltage on the primary side of your xfmr id check the loads like already mentioned. you could ohm each holding coil but depending on size of system & amount of components it might take a while but it beats repeat trips to location

Originally Posted by wika_boy

The 460v to 24v 4amp transformer overload keeps tripping about every 4 hours. Unit is a dx system. Any ideas why. Thanks

New transformer?

Correct tap?

Measured load on secondary?

Originally Posted by wika_boy

The 460v to 24v 4amp transformer overload keeps tripping about every 4 hours. Unit is a dx system. Any ideas why. Thanks

Originally Posted by akelesis

the first thing you look at is the max fused/breaker size on unit and see if it has the correct one in. then start looking at the motors see if they are over amping then see any loose connections.. start eliminating components!

Akelesis, did you read his post carefully? He said the 4 amp transformer overload keeps tripping. That overload is in the 24V circuit. What would the breaker or the motor in the 460V circuit have to do with that?

Wika_boy, are you a DIY. An HVAC tech would know how to diagnose that.

the first thing you look at is the max fused/breaker size on unit and see if it has the correct one in. then start looking at the motors see if they are over amping then see any loose connections.. start eliminating components!