RTAA 125 Starter Transition

[mountainman]

I have asked this question before and have tried some of the suggestion. I'm still having problems with 3 RTAA-1254YL01A3D0BFGJKN Starter Transition. This problem comes and goes. Some of the things I have tried are bending the pins on the board to get a better connection; I have replaced all aux contacts and have used Trane parts. I have also call Trane to have a representative come and look and was told to replace the coils on the main contactors (1K1 & 1K2). This did not help. The pumps for this unit are on all the time 24/7. They are used for production for cooling rolls. The chiller is set up to maintain 44 deg water. The E proms have been updated. Thanks for your help. If you need any more info I will try to get it to you.

[milkyway]

Did u check the CT's?., sound like u are in the right area..,.,
good luck!

[jayguy]

so i am assuming that you are getting a 'Starter Transition - Cprsr A' or 'B' fault...correct? let's just say that i heard you say 'YES'!

my next question is: Are you transitioning and the unit doesn't know it or are you not transitioning at all? does the unit finish the start up or does it 'die' half way through it?

have you checked your 12 VDC test point?

[deltap10]

How old are the chillers? Do they have the brown CH contactors? If you can shut down and do a bunch of starter dry runs maybe the problem will reveal itself. Sometimes a small washer installed under the aux. mounting screws will help. A relay can be installed parallel to a suspected aux. contact. Shading rings still in the contactors? All connections to starter mod. tight?

[mountainman]

Did u check the CT's?., sound like u are in the right area..,.,
good luck!

I have not checked the CT's but I will. Thanks

[mountainman]

so i am assuming that you are getting a 'Starter Transition - Cprsr A' or 'B' fault...correct? let's just say that i heard you say 'YES'!

my next question is: Are you transitioning and the unit doesn't know it or are you not transitioning at all? does the unit finish the start up or does it 'die' half way through it?

have you checked your 12 VDC test point?

Yes you are right Im getting a "Starter Transition -Cprsr A or B" fault.
One time it stop half way through. Thanks

[mountainman]

How old are the chillers? Do they have the brown CH contactors? If you can shut down and do a bunch of starter dry runs maybe the problem will reveal itself. Sometimes a small washer installed under the aux. mounting screws will help. A relay can be installed parallel to a suspected aux. contact. Shading rings still in the contactors? All connections to starter mod. tight?

The chillers are about 10 years old. They do have the white CH contactors which I have rebuilt. Thanks for the other info I will look into these as well.

[jayguy]

...One time it stop half way through. Thanks

AH HA! a failure to transition rahter than a failure to 'sense' transition is a clue!

failure to actually transition is caused by a few things...

1. the 12 VDC or 5 VDC logic is dropping out which causes the internal module relays to drop out...check your test points.
2. there is an electrical failure occuring within the 115 VAC which pulls in the contactors that is either at the module connections pins or within the auxillaries and wires that allow the chiller to perform its magical contactor-dance.
3. the high pressure switch is dropping out or is causing a loss of voltage that is great enough to cause some issues. the contactors get their voltage from teh module, however, the module gets this 115 VAC from the high pressure switch.

[double bogey]

+1 on what Jayguy said. Personally got bit on #3 when I had an intermittant high pressure switch. Drops out and gives transition diagnostic.

[Nuclrchiller]

+1 on what Jayguy said. Personally got bit on #3 when I had an intermittant high pressure switch. Drops out and gives transition diagnostic.

I've seen this countless times on Trane centrifugals. Never saw it myself on an RTAA. Unless I did.... and didn't realize it....

[mountainman]

Ok I had so time this morning to go up and check some things. Checked connection at the compressor (High Pressure and thermo connection). Then went and checked the CT's. Want are the CT's going to read? Also is the High Pressure swith have a sherader fitting or will have to pump down to change?. Tried the chiller circuit #1 and it started and switch over but then shut down with Starter transition fault. Tried it again and it started fine. Im still checking other things but any comments would be great. Thanks

[SFTB]

Just a shot in the dark but one time I had one that had either transition or phase loss and it turned out to be the terminal strip. Some of the screws had backed out where all the jumper bars are on the terminal strip. I lucked into finding that one and I'm going back 10 years or so, not remembering the exact diagnostic but it was power/starter related. I think the high pressure switch sounds like the most likely but that may be phase loss.

[moideen]

hi mountain, recently we faced same issue. on the configuration(service setting)the partwind/star delta was delated. so we replaced eprom.now it is ok.you should check the configuration of the starting mode whether it is partwind or stardelta.please go to service setting,password +-,+-,+- entre.

moideen-dubai