View Full Version : RTAA Oil Pressure Problem
11-01-2010, 12:41 PM
Guys- we have a RTAA300 that has been tripping on oil flow. With the service bulletins we have, we found out that the compressor won't unload. We went through the service bulletins and replaced the load solenoid. Still starts loaded. I have read about a lip seal problem on these 100 ton compressors. Does anybody know if there is a service bulletin on that? One of the other compressors has a plate under the load and unload solenoids. Don't know what that is for, either.
Yes, I'm new. Thanks.
11-01-2010, 01:15 PM
This service bulletin is for lip seal problems with the 100ton compressors. Can you provide the serial number? Can you provide more information on what the pressures and amps are on start up? Does the compressor lock out on oil flow at start up or after the compressor is running for a while?
11-01-2010, 03:34 PM
1. the reason is tripping on oil flow is because the oil is being flush out from the oil separator (sump) due to hi discharge pressure being that the compressor is starting loaded.
3.blown lip seals
to approx. discharge
increase to approx.
Gradually increase to
approx. discharge pressure
11-01-2010, 04:23 PM
The oil flow switch senses pressure drop across the oil filter and oil solinid. If the pressure drop is more than 50# the switch will open. High dischrge pressure at start up increses oil velocity which can cause a high pressure drop thru the filter.
11-01-2010, 05:03 PM
if the machine starts loaded, might want to check ur seals,. maybe worn.,
or like what was already posted., high discharge pressure, oil filter clogger, dont know reccommend pd across filter., in iom., also check oil solenoid at compressor
11-01-2010, 06:50 PM
Phisher- the S/N: U98H02252. The discharge pressure starts above 200 and quicly climbs to 350 PSIG. The amps are 50% of FLA right after startup. The amps and pressures rise even during the 30 second unload period at startup.
The compressor locks out on oil flow after about 2-3 minutes.
Thanks for the bulletin-that looks like what I need.
11-01-2010, 07:33 PM
Ther is a condenser fan upgrade for chillers built prior to July 1998. The upgrade starts condenser fans faster to lower the head pressure on start up. Your chiller was built prior to July 1998. High head pressure is whats tripping the circuit off on low oil flow. I'm attaching the bulliten that explanes the upgrade. A shorted condenser fan motor can cause the same probelm. The fan motors are powered thru the same fuses. If one motor shorts out and blowes the fuses it can keep other fans from runnig which makes the problem worse. I would check the fuses first.
11-01-2010, 08:36 PM
He already said the compressor is starting loaded , no amount of fans or staging eproms is going to fix that . The amperage should be less than 40% at start up period .
11-01-2010, 10:06 PM
You are absolutly correct graham. I'm just giving rsneck some other things to look at if the lip seal checks out good. The oil flow switch is opening from high condenser pressures wheather it's from starting loaded or fans not running.
11-01-2010, 10:38 PM
...One of the other compressors has a plate under the load and unload solenoids...
anybody else see this?
describe 'plate' to us.
there should only be gaskets, kind of a paper/fiber type...not metal. and only 1 of each under each solenoid. metal 'shims' or thin pieces of metal are usually used to test for a leaking slide valve piston. they are then REMOVED and new gaskets installed. with this 'plate', the compressor can not unload and it can only load up depending on the severity of the leaking piston.
11-01-2010, 10:46 PM
Check out the "RTAA lip seal" PDF and you will see the plate he's referring to. It's a retrofit to repair a leaking lip seal.
rsneck, If the compressor your working on is a 100 ton compressor built in 98 then chances are good that you will need the lip seal re-route kit.
11-01-2010, 11:02 PM
ahhhhhh...block....plate....potato....potatoe....a nybody remember dan quayle?
11-01-2010, 11:16 PM
The plate under the solinoids is part of the lip seal kit. Also, if I remember right, should have a 1/4 or 3/8 line running from it to the underside of the compressor. Are your solinoids working? Check your differential pressure across your filters and of course head pressure.
11-01-2010, 11:20 PM
Probably going to need a lip seal kit on that compressor. It relieves the pressure back to the crankcase so the slide valve piston can move to the unload position. But if that compressor already has one then your looking at something else.
11-02-2010, 12:14 PM
When we ran checks under service bulletin #4 checking the load and unload solenoid, the piston pressure actually increased when we energized the unload solenoid. This makes me think it is a lip seal failure. BUT in service bulletin #18 on lip seal problems, an increase of piston pressure on call for unload would indicate a leaking piston. I am quite sure I don't want to replace the piston.
11-02-2010, 05:00 PM
Changing the piston really is not that bad. Just be careful how far you spread the sections of the compressor. If you hear a heavy "thunk" you have a boat anchor.
11-02-2010, 05:16 PM
Just be careful how far you spread the sections of the compressor. If you hear a heavy "thunk" you have a boat anchor.
Im not sure how you are attempting to change the piston but it sounds very wrong to me . All you need to do is dissconect the discharge line and remove the end plate ...
Unless of course the nut on the piston wont unscrew then you have another whole different set of problems !!!!!!!
11-02-2010, 07:13 PM
Did the load and unload solenoids test ok? If the load/unload valves are holding then you can connect a manifold set to the schrader on piston cavity and on the suction line. Open the gauge set to relieve the pressure on the piston cavity back to the suction line. The piston pressure should drop close to suction pressure. If the pressure doesn't drop or drops and comes back up to discharge pressure then the lip seal is leaking. The piston could be leaking but it's more probable that the lip seal is leaking. The lip seal re-rout is a easy install. Trane had problems with the lip seal leaking.
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