RTAC Phase Reversal

[SystemWhisperer]

Last summer i had an RTAC 200 comp2 phase reversal alarm. We know there was not a true phase reversal because the chiller is 4.5 years old, other circuit runs fine, all high voltage was triple checked. Comp motor megs good, CT's check good starter module was replaced with a new one and the cross line starter was replaced. Still locks out on in about .3 seconds. Trane tech support had me remove the suction line from compressor and turn the compressor by hand (Yes you can turn a 100 ton Trane screw compressor with you bear hand) to determine if we had locked rotor, which we did not.. At this point Trane tech support said we don't what is wrong, call your local Trane dealer. Working with my local Trane dealer we decided to connect the working comp 1 to the comp 2 starter, we started the comp 1 and ran it about 45 t0 60 seconds. Compressor 2 was replaced and the problem was solved. Now at a building next door (same campus about 300 yards away) i have a RTAC 250 with the same symptoms. Has anyone had this type of problem, any in put would be great.

[SystemWhisperer]

Hey Guys
I don't understand no one is responding to my question. i can not be the only guy in the USA with this problem

[jayguy]

Hey Guys
I don't understand no one is responding to my question. i can not be the only guy in the USA with this problem

well, ok...let's get into this then, shall we? since i had a choice to pick between which 2 posts to respond to, i picked this one.

today, i was at my daughters state gymnastics meet. i peeked into this thread between events and saw that it was going to take a little more time than my iphone would really allow. however, since i got home you decided that ME responding to your post was more important than my daughter and that i should have responded, ON MY OWN PERSONAL TIME ON THE WEEKEND, in about 7 hours to your post (which is missing some key and important information) was more important.

even though you seem to think that you have already solved the issue.

you are the whisperer...you should be able to figure it out.

[Tommy knocker]

Was it starting fully loaded perhaps?

[SystemWhisperer]

The screen name is for humor only, even with 30 plus years in this industry I know there is a lot i don't know. This is my 1st time on any form so i may not know all of the proper etiquette. Help from anyone would be great of course at their convenience.

I don't know if it was trying to start fully loaded, not sure i know how to determine that.

[R123]

I find it very unusual that a faulty compressor will be the cause of a phase reversal alarm. Especially since it wasn't locked up and megged good. Those compressors ain't cheap!

You need to check everything you stated in your first post. In addition, you need to check all electrical connections and polarity of ct's. Also, if you have multiple incoming electrical conduits running to the chiller, all 3 phases and ground must be run in each conduit equally. Not all phase A run in one conduit, B in another conduit, and C in a third conduit.

[SystemWhisperer]

Thanks for your response R123
I agree the comp is about $19k. That is why i want to know the true root cause of phase reversal alarm when i know that the comp phasing is correct from line side to comp terminals. The incoming conductors are paralleled ABC in one conduit and ABC in the other. The chiller is an 05 model and i PMed it 2 weeks ago and found no problems. The #2 circuit is working properly now. So i guess the question is what could be wrong with the compressor motor that would cause Trane logic to see a phase reversal. I will be returning to the site this week to make a few more checks. I did check ohm of CTs but i did not check polarity, if polarity of CTs is reversed than that means sabotage in the past two weeks!!

[SystemWhisperer]

Thanks for your response R123
I agree the comp is about $19k. That is why i want to know the true root cause of phase reversal alarm when i know that the comp phasing is correct from line side to comp terminals. The incoming conductors are paralleled ABC in one conduit and ABC in the other. The chiller is an 05 model and i PMed it 2 weeks ago and found no problems. The #2 circuit is working properly now. So i guess the question is what could be wrong with the compressor motor that would cause Trane logic to see a phase reversal. I will be returning to the site this week to make a few more checks. I did check ohm of CTs but i did not check polarity, if polarity of CTs is reversed than that means sabotage in the past two weeks!!

[R123]

So i guess the question is what could be wrong with the compressor motor that would cause Trane logic to see a phase reversal.

Probably nothing would be wrong with the compressor as the problem is more than likely somewhere else. A phase loss will sometimes call out a phase reversal alarm.

Does the compressor run at all or was that an isolated incident? This question is for this current chiller and the one last summer.

[SystemWhisperer]

The Trane logic opens the contactor in 0.3 seconds when it detects a phase reversal. In both cases i can not tell if the compressor starts rotating in that short amount of time. I don't have the balls to push in the contactor by hand!! Remember last summer after a week of Trane tech support and trouble shooting the problem did turn out to be the compressor. I have not condemned the comp yet but i am trying to understand because i have about 12 more of this comps on this campus.

[motoguy128]

Any chance a phase imbalance can cause this? Maybe check voltage on each phrase and double check for high resistance connections.



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[R123]

The Trane logic opens the contactor in 0.3 seconds when it detects a phase reversal. In both cases i can not tell if the compressor starts rotating in that short amount of time. I don't have the balls to push in the contactor by hand!! Remember last summer after a week of Trane tech support and trouble shooting the problem did turn out to be the compressor. I have not condemned the comp yet but i am trying to understand because i have about 12 more of this comps on this campus.

That's not what I'm asking. Let me rephrase it.....do you get a phase reversal every time you try to start the compressor, or is this an intermittent problem?

[SystemWhisperer]

Sorry
The one from last summer was not intermittent, each time Trane made a recommendation we would do that and attempt to start the compressor. At least 8 or 10 times in a week period and every time the contactor would pop in and out in less than 1 second. So far i have only tried to start the current one, one time with same symptoms

[SystemWhisperer]

Sorry
The one from last summer was not intermittent, each time Trane made a recommendation we would do that and attempt to start the compressor. At least 8 or 10 times in a week period and every time the contactor would pop in and out in less than 1 second. So far i have only tried to start the current one, one time with same symptoms.

I guess it is possible that Trane logic would see a phase imbalance as phase reversal. All connections were tightened on Friday prior to the attempted start. The contacts in the contactor look in fair to good condition to me.

[CCSPIERCE]

Are you sure that the CT polarity and actual mounting direction over the wire are correct. Had this happen on a Trane before. Look VERY closely at how those CT's are wired and mounted.

[R123]

I can tell you from experience that a phase loss or imbalance can cause the chiller to call out a phase reversal. Also ct polarity and orientation can cause this. Bad compressor is extremely unlikely.... I've never seen that before. Poor power quality.....very possible. You could also have a bad starter module. You can swap starter modules with the other compressor AND REBIND THEM USING TECHVIEW to verify that.

[Nuclrchiller]

I can tell you from experience that a phase loss or imbalance can cause the chiller to call out a phase reversal. Also ct polarity and orientation can cause this. Bad compressor is extremely unlikely.... I've never seen that before. Poor power quality.....very possible. You could also have a bad starter module. You can swap starter modules with the other compressor AND REBIND THEM USING TECHVIEW to verify that.

There's really no point in looking elsewhere until these things have been checked. Nice post, R123.

[stanbyyourword]

I was sent out on an RTAc monday "PHASE LOSS" alarms , check the modules etc, Would go through first contactor sequence of wye delta and shut down on first, puzzled for about 2 hours with no wiring diagrams, finally checked HP switch, internal reset, bingo. hope this may help stan

[FixItRight]

Have you checked your compressor terminals.

[CV_Geardrive]

I agree with stabyyourworld. HP switch handles the current for main contactor coil.
Check the HP switch, for bad contacts and clean if necessary, and check for possible liquid hammering when the compressor starts. (Discharge check valve and operation of compressor oil heater)
CV