RTAA 185 Trane

[bcooling]

Hey Guys,
I have a Trane Rtaa 185 that has problems. Ive posted in the past about a code 198, loss of oil flow, you guys so generously responded. Update, I have gone through all the service publications from trane about the high head pressure and the lip seal failure, I even put the lip seal failure kit on, to no avail.

Now to the real kicker, the unit will trip on 198 with the pressure switch jumped out. It is my understanding that the switch is normally closed and opens on a failure, how the )&*&^& can it see a failure if it is jumped out. The funny thing is somtimes it runs fine and will run till it satisfies the water and then it goes bonkers again. I have swapped out the two boards that contol the compressors and that did not help. Sounds like I may have have a failure in the main board, what are your thoughts.

Thanks
bcooling

[flemsteele]

Check all your condenser fans and make sure they are all running. Also take compressor amperage @ startup should be no more than 30% RLA. If it is higher you either got a lip seal failure or a stuck slide valve.

By the way I believe the UCP needs to see that switch open then close, jumping it out wont help your cause>

[bulldogker lu74]

I had a similar problem on a rtaa 200. chiller would run fine but every now and then would go out on 198 low oil flow. you need to check pressure differential across the switch to verify if it is correct. If pressure diff. is good then i would replace the switch. That fixed my problem. If not then you need to monitor the start up of the unit trane has specific instructions as to how unit needs to start and if you are not staging the fans properly then this could lead to oil failure because the head pressure getting to high could cause oil problems that was on a service bulletin posted by trane. If you do not have correct pressure diff. across switch check oil filter to see if it is restricted i think trane said if it drops more than 5 or 10Lbs it is clogged ( check on that pressure drop i can not quite remember). also need to check oil level of unit to verify you are not low and depending on age of unit oil should be changed every 5 years. Hopefully this helps and before you change the board i would cover your bases because that board is not cheap and if does not fix the problem that could be bad

[pa2jonah]

Where have you jumpered the switch out. I would look for possible bad wiring, or bad connector at the board. Also, do not leave it jumpered when the unit is powering down the compressor. It's looking for an open switch then, and will generate another diagnostic if you leave it jumpered.

[bcooling]

Ok fellows here it goes,
I still have the code 198 coming up. Here are the unit stats:
Oil Level in separator correct.
Clean condenser coils.
All fans working.
Ambient temp 46.
Entering water temp 61.
suction pressure 65.
suction line temp 49.
sat. evap refrig. temp 35.
I monitored S/H ran from 9 to ll degrees.

Discharge Pressue 178.
Liquid line pressure at angle valve 140.
Liquid line temp 66.
Sat. cond refrig. temp 91.
S/C was 13 +/-.
Pressure drop across the filter drier was around 10 psig. No noticable temp difference.

Amp draw around 100 amps, 163 Full Load at full load.
Unit starts out at 40 or so % and increases as unit loads to full load amps.
Slide valve moves freely.
Compressor loads and unloads properly.
Oil differential switch calibrated and functions properly.
Presure drop across oil filter well within the 10 to 40 psid drop range as stated in s/b 12.

Wiring to the differential switch ohms out. No nicks or cuts.
All connections at the board are good.
All sensors ohm out correct and correspond with thermomoter.
Saturated condenser sensor has correct depth.
All fan contactors working.

Ok, On start up, if i hold the first fan contactor in, until the unit runs a few minutes, it will run untill it satisfies the water temp. It appears the first stage fan is not coming on early enough to reduce the pressure drop at the switch. This is only happening on start up, and does not happen every time.

Since the condeser fan is staged by the processor, I am unsure when the first stage fan is supposed to come on due to the ucm seeing the difference in the satuarated condenser and evap. temps. The sensors are good.

By the way, its not a lipseal falure, cause I invested in one of those, lol.

Does the tracer system do more indepth diagnostics than the unit itself. If so I may have to call in the Calvary!!!!

Well Guys and Gals theres what I have. You know a blind hog finds an acorn every now and then, hopefully you guys see better than I do.

Thanks,
Bcooling

[scott123]

These design sequence have always had this problem. Oil level doesn't matter because they only shut down on high DP (via the switch). The units with the external oil filter are problematic. In the hot summer months (105 degrees +) its common for this design sequence to drip off on low oil flow due to excessive DP across the filer (new filter or not). There was an EPROM update available to help with the fan staging, but my experance with this update, is nothing more than a marginal improvement in the algorithm.

I've delt with these units since their beginning (been at Trane for 15 yrs.), and unfortunatly its never been fully resolved. I recommend the EPROM update for low ambiant conditions, and for hi ambiant conditions, set the current limit to 95% or lower until the diagnostic no longer happens. DP settings (not Trane recommended) is to set it higher then IOM default (I wont say how high :) ).

Fortunatly all supsequent RTAA / RTAC have resolved this problem.

[bulldogker lu74]

Using the same gauge what is the actual pressure diffrential across the oil psid switch? I remember reading that on start up the head pressure should not exceed 325psig and if it does that is a problem because head pressure that is to high would cause the oil switch to trip on start up. you should monitor what the trane sensors says head pressure is on start up and verify fans are staging properly and verify there reading to your gauges. Another issue is that if your are running at a reduced capacity for a long period of time this will cause oil flow issues. @ 46 degrees ambient i would think outside air could do the job the chiller is performing but i do not know the situation there but the 2 rtaa's that i take care of lock out on ambient at 43 and that was set from the trane people that worked on them previous to me. there is a setting in one of the p menu functions where you need to specify if the unit is to run in low ambient conditions I would check that because the head pressure seems slighty low to me. let me know how you make out.

[bcooling]

Thanks to all that have replied,
Scott, shew, I am sure glad to read your post, I have pulled my hair out over this one. I had an idea that that the processer may be the problem. I will get the updates tommorrow.
Bulldogker, the head presure never gets near the 325 , it would trip at 160 to 175 most of the time. It did it summer and winter. I hope the update and adjustments lol, will cure my ails.

Hey guys I will update the hopefully with good news. Any other tips will be greatly appreciated.

Thanks again, I love this forum, its all about helping one another, hey maybe hvac techs should run for public office. well maybe thats a bad thought.
Thanks
bcooling

[pa2jonah]

Some of the earlier units had weird logic control for the condensor fan sequence. Eprom update should take care of it.

[hvacgirl1488]

Get a hold of your local Trane office and ask for a copy of RTAA-SB-21

[joeywpittman]

you can download it here
http://members.cox.net/epittman2/hvac-talk/rtaasb21.pdf

[enart9591]

What is the serial nuber of this machine? Their are a number of things that can cause this diagnostic other than an actual oil flow problem. Have you contacted your local Trane office for the troubleshooting bulletin for this machine?

[bcooling]

Thanks for the replies,
I have service bulletin numbers 4,5,12,21,18,in regard to this unit. The serial # is U98K03874. I have ordered the emprom kit from Trane, hope that will do the trick.
Will update when I get the parts. Thanks all.
Bcooling