Trane Compressor Overload
I was working on a hermetic Trane compressor ( 30 tons ) in a VAV system. The compressor has a six pin power connection with a solid state over load that just sense the amp draw in the three phase supply to just one contactor or one set of the three phase power supply. The power doesn't go thru the overload but is sensed by three current sensing metal loops that the wire passes thru. Checked with Trane these are expensive and hard to get , can you replace that with a regular three phase overload relay that the amp draw can be adjusted. Thanks Bob
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I'm not sure. I would think it would work. But I'd like to hear more about this from someone with a little more experience in this matter.
I'm assuming the compressor has multiple unloaders, right? I don't think I've ever seen a hermetic with unloaders, now that I think of it. If I have, I didn't know at the time.
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Originally Posted by jayhawker
keep trying to get that oem part, on that 30 ton you would be better off with original replacement.
hard to find doesnt mean they cant get it, that usually means someone is lazy!
i dont see why you could not put a standard heavy duty adjustable motor starter/overload combination,
but it wont be that much cheaper if any than the proper oem part.
they also make motor starters/overload combinations that you can change the heaters to your specified amperage.
Trane had an unloading tin can, think you could get 2 or 3 steps of unloading. They no longer make it, you can buy rebuilds from Trane still.
Originally Posted by BergerMech Rob
Are you talking about line transformers.
Originally Posted by skpkey9
I had the same problem with a trane overload sensor like the one you describe tranes replacement at that time was a solidstate motor overload with adjustible pot for motor current.The main difference was manual reset on the new relay.This didn't matter much to me since the oem caused a control circuit lockout with manuel reset at the unit.
the over load I think you are talking about if you peel back the corners of the sticker you will find an adjustable pot to change the setting there is a tool available but you can use a screw driver also if it is bad you should try to stick with OEM espically with those reset relay circuits,good luck.
If I understand you correct these are current transformers. These do exactly what their name describes. They have a ratio to them, if you’re lucky you can find out what this is and order something with the same ratio. These are not a voltage transformer. If the ratio is 100:1, when 100 amps flies through the wire to the comp, 1 amp will be present on the two leads. They work with current, voltage readings don’t mean much when dealing with these.
The O/L circuit is looking at the output of the CT and telling when it should trip. I would stick with OEM. If Trane can’t get it, ask them for the ratio or measure and calc it. Then find a source for a compatible CT. They are fairly common for power monitoring and easily obtained, pending you know the ratio.
Assuming this is 3 phase comp, you can verify a bad one by ohming it out. Compare it to the other 2 units, they should be close.
Btw installing these on a live circuit can blow your balls off. Be damm careful installing them on live circuits!! RTFM
Last edited by orion242; 03-24-2007 at 12:08 AM.
Yes, go with the oem part. Airmechanical is right about lazy parts people.
It's been a few years since I replaced a couple of them, But the OEM replacement purchased through trane parts at that time was made by siemens. It had a pot that has to be set per RLA of compressor and had a manual reset button. The only difference is if you buy it through trane parts for that unit, It comes with a adapter plate so it can be mounted in the same location using existing holes.