RTAA low evap ref. temp. hair falling out!

[MrSlim]

MN: RTAA0804YN01A3D0BD
SN: U02M07829
This thing is driving my nuts. Tied into Summit. Continual low evap ref. temp faults, mostly in the winter months. I have done everything I can think of, from checking the charge to replacing the EEV. Has anyone had this problem?

I get about one fault a month.

(from RTAA IOM):
Low Evap Rfgt Temp - Ckt 1 or 2 CMR a. The Saturated Evap Rfgt Temp - Circuit 1 or 2 dropped below
the Low Rfgt Temp Cutout Setpoint while the circuit was
running for 30 deg F seconds.
b. See the low ambient ignore time on startup.

Yes, I've gotten this fault before and it turned out to be a fan staging problem. I'll post a thread with information from the RTAA troubleshooting manual titled: RTTA - Variable Speed Fan System

[Healey Nut]

He doesnt have inverters thats the problem , cant keep the head pressure up in low ambient conditions .
Running the chillers in series is no big deal as long as they are set up correctly ie first in line 58/48 2nd 48/38 could be for a process application .

[MrSlim]

I've never worked on an RTAA without fan inverters. I understand this is a factory option. Is it possible to add the inverters in the field? And what all is involved?

[Healey Nut]

And what all is involved?


Buy em ,mount em , wire em, programme UCM . Done

[allstar08]

who has the passcodes for these machines?

[scott_RWS48]

Ok, let’s back up.

++--++ Field start up
--++-- Configuratiuon (be careful, know what you are doing!)


Check very accurately the sub-cooling. RTAA chillers need sub-cooling to be correct at full load as per the IOM.

Another area to check is the load-unload and step loader. Insure NONE of the coils are burned out. Also Insure the output (triac) is working correctly and not shorted. In many cases the coil shorts out and then takes out the output board trac.

Be sure (as another person posted) to check RLA on start up. Normal RLA should be 35-38%. If one or more circuits start and transition (assuming Y-Delta) and immediately show 42-48% OF RLA there is no doubt the PID loop for the EXV will not respond well and tripping off on low evap refrigerant temperature will be a frequent event. The best solution is to install a adjustable LPS and set it to 40 PSI. This will allow the switch to trip, (auto reset) which will flood the evaporator, and on the next start the unit will run fine because plenty of refrigerant will have migrated to the evaporator, allowing time for the EXV to catch up on the next start. This is A LOT cheaper than a new compresser.

Understanding the sequence of operation and knowing what options this chiller has is the key. I suggest you look at these items and post back. 4-degrees superheat and 22 degrees for low refrigerant temp trip.

I’m rather busy these days but if I get a chance to look at this post I’ll try to help you further. RTAA chillers of this vintage usually work well but are very temperamental if anything is not working perfectly well. The algorithms developed for this chiller assume everything is working correctly. As soon as a mechanical, electrical issue arises these chillers become problematic.

Good luck 

[scott_RWS48]

This upload interface is a little clunky. Hopefully the troubleshooting guide uploaded. Hope this helps.

[scott_RWS48]

And another one. Is this panel the older one with the numeric codes? Or the clear L display?

[climpro]

Is this job Mds Pharma ?

[Healey Nut]

And another one. Is this panel the older one with the numeric codes? Or the clear L display


The 80ton RTAA was never manufactured with a numeric code display .
Is posting confidential service bulletins a good idea Scott ???

[scott_RWS48]

They are "GENERAL" Service not confidential. The RTAA is out of production and I'm sure Trane would like to help wherever possible.

I usually jump in one time, and post with as good information as possible, and then leave the thread. I don't have much time to visit here. I want all Trane equipment to work properly, so just providing what I can. I did not download those TSB off the Trane Tech side of the site. He could have downloaded them himself.

[jayguy]

And another one. Is this panel the older one with the numeric codes? Or the clear L display?

looks like a confidential service bulletin to me. trane wants all of their equipment running well. but they will not release any confidential bulletins...most confidential bulletins anymore do not contain a lot of "special-super-secret" info...

[scott_RWS48]

LOL...way to go guys, been at Trane a very long time, no need to stick my neck out to help. Don't worry about getting information from this Trane guy anmore. Good job

I remember trying this forum years ago and ended up in all these side battles. I realized I didn't need to be in the middle of it. After all I don't need to be. Guess what I did the 1st time is what I'll do again. Say good bye

[jayguy]

LOL...way to go guys, been at Trane a very long time, no need to stick my neck out to help. Don't worry about getting information from this Trane guy anmore. Good job

I remember trying this forum years ago and ended up in all these side battles. I realized I didn't need to be in the middle of it. After all I don't need to be. Guess what I did the 1st time is what I'll do again. Say good bye

if you want your panties in a wad then fine...the questioning of the confidential service bulletin posting was for your benefit. if you really are a trane technician (still anyway) then you are probably violating the 'never tell any of the super secret info' clauses that you signed.

i do not care if any service bulletin gets out...i really don't. but i don't post them because i want to keep my job. if you don't or you are not worried then fine...post away.

[cooolguy]

ok my advice check your

check suction and saturated sensor
check your connectors on the module
circuit unit charge
compressor starts unloaded at around 40 percent should jump up to 60 percent when female is energized
check expansion valve control response

[milkyway]

if you want your panties in a wad then fine...the questioning of the confidential service bulletin posting was for your benefit. if you really are a trane technician (still anyway) then you are probably violating the 'never tell any of the super secret info' clauses that you signed.

i do not care if any service bulletin gets out...i really don't. but i don't post them because i want to keep my job. if you don't or you are not worried then fine...post away.

im not a trane employee, however i am always studying trane ioms and i have been to many traing classes as well a teardown schools., i like sb and i wish i could get some more so when i do go out and work on a machine i am prepared., ,. any input

[milkyway]

There aren't vfds on the condenser fans, just fan cycle controls based on head pressure

Bingo !!!!!!! Houston we have a problem .

hey graham, can u explain this, if temp is cold outside and there is a call for cooling, i know cond fan will come on for cooling the cond, which would drive head and suction down , i know what a vfd does , and i know what fan cycle does., and if oat sensor set correctly,.
idk ., what really is goning on, also the fans are already cycling i think.,

[supertek65]

what part dont you understand???

hey graham, can u explain this, if temp is cold outside and there is a call for cooling, i know cond fan will come on for cooling the cond, which would drive head and suction down , i know what a vfd does , and i know what fan cycle does., and if oat sensor set correctly,.
idk ., what really is goning on, also the fans are already cycling i think.,

[Healey Nut]

hey graham, can u explain this

No head pressure = no suction pressure = no oil movement = no chiller ..Done

[supertek65]

hey graham!!!!!!!!!!!!!!!!!!!!!!!

hows it goin??????????????????

hey graham, can u explain this

No head pressure = no suction pressure = no oil movement = no chiller ..Done