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Originally Posted by Screwit

Something else it may pay to check before you change out the Micro.

What would happen if power was lost through the HP switch normally closed circuit from 1J2-1 to 1J2-3 if the switch bounced but not enough for a HP fault indication was not signaled to 1J2-4.

I have experienced this problem causing phase loss diagnostic on later generation controls/chillers but not on RTHA with UCP1. If the false phase loss diagnostic only occurs under loaded summer conditions this could be a possible cause.

It worth a try I will be back on that job site Tuesday due to fireworks always plug up the tower. Thank you

I think Screwit has a good idea here. I also have seen this on other Trane chillers (CVHE/CVHF), but don't recall if I've seen it on RTHA. It could also be happening if condensor water is getting too warm either due to setpoint too high or, maybe more likely, cooling tower has become less efficient/more dirty and needs cleaning.

Something else it may pay to check before you change out the Micro.

What would happen if power was lost through the HP switch normally closed circuit from 1J2-1 to 1J2-3 if the switch bounced but not enough for a HP fault indication was not signaled to 1J2-4.

I have experienced this problem causing phase loss diagnostic on later generation controls/chillers but not on RTHA with UCP1. If the false phase loss diagnostic only occurs under loaded summer conditions this could be a possible cause.

The phase loss errors started last summer.(not after the contactors were changed, another tech. tried to change them again but the unit still tripped so they went back to the old ones) The DDC logs show the chiller usually trips while running not on start up based on chilled water temps.(not a fuse, open contactor leg, or burned windings) I have SB-5a and already checked power supply boards and transformer. All readings were in range. It would usually trip when running loaded or close to fully loaded. I only suspect the 1U3 due to the only logical problem. I do appreciate the feedback though, at lest I have been going the same direction.

Originally Posted by hvac2tech

Contactors were changed about 3 yrs ago with new auxiliary. Chiller phase monitoring is done with CTs the factory monitor is just a phase reversal monitor, so i added ICM 450 Just to see if one was acting up, but have yet to log a error. I have it set low at 2% with out a delay. The unit will start normally when ever I have been onsite. The unit will transition flawlessly and haven't had any trouble with start components. A dry run cycled normal and tripped on oil failure like you would expect. This chiller may be the death of me! I hate the idea of replacing the the control boards just to try and eliminate possible problems(even though every thing points to the control board 1U3)that may not fix anything. There is always a logical way to test and confirm what is wrong.(At lest there should be)

By any chance did the phase loss problem start occurring following changeout of the contactors and are the new contactors the same as original. In the absence of a mains power supply problem there are a number of possibilities but two that come to mind are in relation to the phase loss protection timing to sense current draw on any leg > the required 15%

1) Contactor reaction time lag - this could be borderline with UCP1 diagnostic causing nuisance trips on start-up

2) Power supply issue to the UCP1 (1U3) This check should be performed before you think about changing out the 1U3 anyway.

transformers review 2T5, 6 and 7 they send voltage to the module 1U3

occurrence of this latching diagnostic indicates that 1 leh of the 3 phases power supply has been lost the phase lost "threshold" recognized by the UCM is any phase that drops below 15% of the RLA for more 1 second.

A variety of causes can result in PHASE LOST condition,three of the include:

1 a below fuse o breaker is one leg.

2 an incomplete or open line conector to one leg.

3 a burned of open motor winding

Contactors were changed about 3 yrs ago with new auxiliary. Chiller phase monitoring is done with CTs the factory monitor is just a phase reversal monitor, so i added ICM 450 Just to see if one was acting up, but have yet to log a error. I have it set low at 2% with out a delay. The unit will start normally when ever I have been onsite. The unit will transition flawlessly and haven't had any trouble with start components. A dry run cycled normal and tripped on oil failure like you would expect. This chiller may be the death of me! I hate the idea of replacing the the control boards just to try and eliminate possible problems(even though every thing points to the control board 1U3)that may not fix anything. There is always a logical way to test and confirm what is wrong.(At lest there should be)

make a dry starter test, to ensure that the phase monitor is OK, and confirm the sequence of the starter while

Is it a wye-delta starter? Ditto on auxillaries. If contractors are original (brown) they may be worn. Look for white dust when you open contactor. Contactor shading rings may have fallen out resulting in a lot of vibration/hum. Jump out phase monitor output to test that function.

For RTHA UCP1 an issue existed with an RC timing circuit component that was corrected by setting S3 Dip switch 6 to on for the 50 hz setting to prevent nuiscance b E4 phase loss diagnostics.

Not sure what is causing your issue but anything that interrupts control power to the motor start contactors can cause a phase loss condition be it a faulty auxillary contact, interlock or micro relay.

Rtha E4 Phase loss

I am fighting a 92' chiller. the unit will randomly fail but always with a E4 (phase loss) The system had a compressor change about 5yrs ago and the main control board was also changed (1U3). Trane tech. support pushed for oil problems but none of the tests every showed any sign of an oil problem. I have logged the power supply to see if it was actually dropping out even for a split second, however it was normal when the chiller would trip. All the Service bullion listed was changing the unit to run at 50hz instead of 60hz as per Trane it make no sense. This also made no difference. The only thing that logs a failure is the Main control board by inputs from the CT's witch test normal.
My current working theory is the board overheats. I logged the cabinet temps and only peaked at 98. Added cooling fan and the chiller has yet to trip. Has anyone ever had this problem or more important solve it permanently? Any help or thoughts would be great.