RTAA oil filter

[jemawalton]

How often do you guys have to change the "lifetime" oil filter on an RTAA? I guess it depends on how clean the system is kept during service. Just changed one out that the oil and filter looked good but was causing high diff trips. The filter was at least 5 years old.

[just_opinion]

according to Trane - never. Unless you have excessive amount of pressure drop, which means that compressor is about to die. Then you change both of them at the same time.

[Healey Nut]

You answered your own question it says life time and thats what it means unless excessive pressure drop tells you to or if you have a compressor failure. Graham Trane Tech.

[Trublshter]

Yep. That's the way Trane covered that in the service class I attended on those units.

[chiller rob]

your high diff pressure was probably more to do with head pressure problems than oil filter problems...

fan staginging... dirty condenser... compressor starting loaded... all will resurlt with this error...

high discharge pressure will push the oil thru the filter faster causing the pressure drop to increase...

if you continue to have probs post what is happening... there are alot of trane aces here on this site...

good luck...

[jayguy]

it depends on the system. we have a few systems that do not allow downtime...so we change them every year at shutdown PM. some have to be changed every year due to the number of starts/stops. remember that these units do not have an oil pump. they rely on differential pressure to move the oil. more starts equals more wear...as a general rule...but not always. but if you are looking for a starting place, that is how i do it.

but like rob said...lots of things can cause high oil pressure differential diagnostics. the easiest thing to start with is the oil filter. this will usually help you get it back online so that further troubleshooting can be performed. it is rare that the filter would be blocked up with debris and everything else would be ok. keep looking for other things. i personally write the date, starts and run hours on the oil filter after i change it. this really helps with future diagnosis.

good luck.

[txhvac]

These filters are oversized, 10-40 psi @ full load.

[jogas]

Check for Trane Service bulletins on this subject for your machine. I think some models may even trip on oil, but the filter is not the cause.
jogas

[Healey Nut]

when you get the oil flow diagnostic on an RTAA 99 times out of 100 it is NOT an oil filter problem,it could be any of the following :condenser coils dirty,fan motor issues,load/unload solonoid valves ,stuck slide valve, oil switch calibration [this is the most common in my experience].dont just assume its the filter.

[txhvac]

when you get the oil flow diagnostic on an RTAA 99 times out of 100 it is NOT an oil filter problem,it could be any of the following :condenser coils dirty,fan motor issues,load/unload solonoid valves ,stuck slide valve, oil switch calibration [this is the most common in my experience].dont just assume its the filter.

10-4 that!

[jemawalton]

I checked the condenser pressure transducer for accuracy, checked all fans for proper operation. I had just changed a fan motor on this circuit about a month ago. The coils are fairly dirty. They will be due an annual in Jan.

The machine does have a lot of starts on it and about the same number of running hours as starts on both circuits. Yuck! The diff pressure I was reading was about 40psi. As the machine loaded up it would stretch out to 45 just before staging on more cond fans. After changing the filter this dropped down to 15psi and stretching out to 20. Hopefully I will do the annual on this machine and can check it again after cleaning the coils.

Thanks for the replies!

[Manu1]

I checked the condenser pressure transducer for accuracy, checked all fans for proper operation. I had just changed a fan motor on this circuit about a month ago. The coils are fairly dirty. They will be due an annual in Jan.

The machine does have a lot of starts on it and about the same number of running hours as starts on both circuits. Yuck! The diff pressure I was reading was about 40psi. As the machine loaded up it would stretch out to 45 just before staging on more cond fans. After changing the filter this dropped down to 15psi and stretching out to 20. Hopefully I will do the annual on this machine and can check it again after cleaning the coils.

Thanks for the replies!

Maybe I'm a little late on this one as you replace the filter all ready but I'm confused :confused:, first of all RTAA's dont; have pressure transducers and second if this is and RTAA what size is it? RTAA 70-125 Tons. units use one system to check oil filter and RTAA 140-400 Tons. use another, before advising we need to know all the info. :cool:

[chiller rob]

30 min time out on a low oil flow diognostic can be a bugger!

[esdd]

RTAA's use the bottom 4" of the condenser coil as the oil cooler, I don't remember the exact number of passes, they also look at the temp differential through the cooler to verify oil flow as they do not have a pressure differential transducer or a flow switch. This bottom 4"-6" of the condenser needs the most attention when cleaning the condenser. I think you answered your own question as to the cause of this problem, you need to clean the coils.

[just_opinion]

First, I agree with Manu1 - different size RTAA has different method of low oil pressure.

Second, Jemawalton. High temperature oil has NOTHING to do with oil filter clogging. In fact, on the smaller RTAA (less than 125 tons) with a severe clogged oil filter will give you the opposite code "low oil temp". So that, in your case of changing filter is completely wrong diagnostic. Where as you need to look for dirty condenser coil, rotten fins, bad fan motor or something has to do with air flow on that condenser.

The oil cooling circuit is on the top section of the condenser coil. It is always the hardest place or last place anyone ckeck or clean. It always rotten there first if you live near the ocean area. Cheap POS Trane.

[stickerhead]

One other item to be aware of. When the RTAA came out in the early 90's they had a poor algorithium for starting the condenser fans. Us living in the southwest found this out the hard way. The chiller would come on, condenser pressure would be 350 + and trip on low oil pressure delta P. Trane provided us with the "southwest kit" which staged the condenser fans on by ambient temperature I believe starting at 55 degrees. If you have an older chiller that has not had the eprom upgrade and outside air sensor, this could be the problem. On the later chillers, it became standard. Dirty condenser coils seems to be the biggest culprit.

[chiller rob]

on the smaller rtwa's i have had to install a 1500 ohm resistor in series with the condenser temp sensor... this will electrically lower the condenser pressure untill the tubes can be cleaned... to prevent trip out...

[pete_d]

You answered your own question it says life time and thats what it means unless excessive pressure drop tells you to or if you have a compressor failure. Graham Trane Tech.

Graham, Please let me have your email. Thanks;
pete@pvt-worldwide.com

[jemawalton]

Sorry for the lack of info. To clarify:

1. The oil pressure diff that the machine measures is the differential across the oil filter, not across the compressor.

2. The machine is a RTAA185. It uses an ordinary mechanical Alco pressure diff sensor set to trip at 50psi and reset at 47psi.

3. Manu1, you are correct, the condenser has a temp probe about 2/3rds of the way down that converts the temp to pressure. I misspoke.

4. just-opinion, I agree that oil temp has nothing to do with an oil filter clogging. Not quite sure where you got the impression that I did. However, high pemp has a great deal to do with the differential pressure across the filter. High temp = high pressure = higher delta P across the filter.

[Healey Nut]

the oil diff switch measures the delta P across the oil circuit not just the filter theres a solonoid in there to[master oil solonoid].

[jemawalton]

the oil diff switch measures the delta P across the oil circuit not just the filter theres a solonoid in there to[master oil solonoid].

....and a shutoff valve.

[Manu1]

What is the chiller serial number? I can tell you by the serial number if your chiller has or not the latest software for fan staging, the old RTAA 140-400 use only saturated condenser temp for fan staging, then Trane came-up with a fix for that and consist on a software retrofit along with the outdoor temp sensor (if your machine is doesn't have it all ready) but if once again the serial number will tell.

How many hours and starts you have on both compressors? which circuit was showing the low oil flow diagnostic? 100 ton compressors have the tendancy to show it more often and sometimes fan staging or dirty filter has nothing to do with it. ;)

[jemawalton]

Serial #U94J24091.

It had an e-prom upgrade in 1999. It was the 100 ton circuit that had the problem. As far as starts and run time, I can't remember te exact numbers but starts were in the 44,000 range for both circuits. As well as runtime.

[Manu1]

Serial #U94J24091.

It had an e-prom upgrade in 1999. It was the 100 ton circuit that had the problem. As far as starts and run time, I can't remember te exact numbers but starts were in the 44,000 range for both circuits. As well as runtime.

Check if the compressor starts loaded, measure the current and compare witht the compressor nameplate RLA, if the compressor is not unloading all the way it will show this condition moslty at start-up before all the fans kick-in. :cool:

[kentucky hillbilly]

140-400 ton RTAA? Are condenser fans all turning the right direction? Was unit built prior to July 1997? could be a timing issue if it was. Unit doesn't start out running off referigerant pressures but timing to stage up unit.

[OzziePedro]

Might pay to double check you oil level if you haven't already.

[always looking]

A little trick I started doing several years ago on some of these units that may have problems is to go in the P4 menu and change the % of condensor pressure setpoint down to 82 from 90. This slows down loading on startup and allows fans to catch up.

[Manu1]

A little trick I started doing several years ago on some of these units that may have problems is to go in the P4 menu and change the % of condensor pressure setpoint down to 82 from 90. This slows down loading on startup and allows fans to catch up.

This will take the chiller into condenser limit sooner than normal at 82% of the HPCO (82% of 405) meaning that will reduce your system DP, but that is just a band-aid not a cure!! I don't like this solution as reduces the capacity of the chiller. :cool:

[Healey Nut]

Yes True .But how much capacity does the chiller have when its tripped off and its 85f outside and its a critical application ?????????????????????????

[jayguy]

A little trick I started doing several years ago on some of these units that may have problems is to go in the P4 menu and change the % of condensor pressure setpoint down to 82 from 90. This slows down loading on startup and allows fans to catch up.

i kinda like that! i think that i will use it on units that maint won't clean until the unit refuses to work normally anyway. thanks.

good luck.