Trane RTAA 215// circuit a,b intermittent low oil flow codes 199

[emcontrols]

My years may be off but did this year chiller have the black box guard pak controller??? I remember a SB that came out after I found a guard pak nusance tripping on compressor contactor pull in, creating an electrical inrush that tripped the guard pak. Ended up being a guard pak design flaw and had to replace all guard paks of that vintage. Same situation I got a hotel, lawn chair, 20 meters and 100 tattletales and watched this chiller for 3 days straight before I finally caught it in action. It was tripping but no safeties were telling it to the second the compressor contactor was engaged.

[R123]

My years may be off but did this year chiller have the black box guard pak controller??? I remember a SB that came out after I found a guard pak nusance tripping on compressor contactor pull in, creating an electrical inrush that tripped the guard pak. Ended up being a guard pak design flaw and had to replace all guard paks of that vintage. Same situation I got a hotel, lawn chair, 20 meters and 100 tattletales and watched this chiller for 3 days straight before I finally caught it in action. It was tripping but no safeties were telling it to the second the compressor contactor was engaged.

No, the Guard Pak was in the CGAA's and CGAC's which was before the RTAA.

[aggiechillertech]

No guard pak on this one..

[BKS60]

the number 1 cause of oil pressure trips is dirty condensers. the higher head pressure pushes the oil through the oil filter, piping and solenoids faster than normal and this causes the higher pressure drop which trips the unit.

you may still have a similar issue. perhaps the outdoor air temperature sensor is faulty or sometimes flaking out (it is used for pre-staging the fans). if it sees lower outdoor air temperatures than actual, then it may not be bringing on enough fans fast enough.

also check your saturated condenser and evaporator temperature sensors for accuracy. these are used to control the fans after start up. also, check to make sure that the fan contactors are wired properly. perhaps fewer contactors are coming on when the unit thinks/expects they are.

Since you stated the compressors are starting unloaded (about 40%) and load normaly I would recommend you take jayguys post and check each item thoughly.

[BKS60]

And also check the EXV's for proper operation.

[jayguy]

And also check the EXV's for proper operation.

i was thinking the same thing all day. we (me) have been focusing on the high side aspect of the switch. but there is a low side aspect as well! make sure that the low pressure isn't getting too low due to the exv's not working properly.

[BKS60]

Not to steal the thread but I ran into that this summer with a 240. One of the 70 ton exv's was not openning as it should and had to be replaced. Tripped on oil, low evap temp, and a few more I think. Of course that meant all three exv's and both modules when ambients were 100 degrees. Had to keep water on the 100 ton circuit to keep it on line with the high load ect,ect.

[aggiechillertech]

Ok pulled every temp sensor and verified accuracy. I put them in a cup of ice water at verified at 32 degrees and the temps on the UCM matched my fluke probe and unit temp sensors in cup of water. I then cross checked that to the resistance chart, all good. Every contactor is correct by wiring diagrams.

Fast forward to today it was cold last night in the 40's and the unit had tripped both circuits on oil. The maintenance guy checked for codes at 8:00 and there were none the chiller was satisfied and the circulating building water pump was off. When I got there at 8:30 both circuits were tripped so it looks like it happened on the first start after a long off cycle at night.

After digging way deeper I found the chiller barrel tape heaters were never hooked up to field installed 115v when the unit was installed brand new. Went ahead and ran power to them and hooked up correctly.

The barrel heaters have 115 volts constant feed and are not controlled by the UCM. According to the diagram it looks like it uses a thermostat hidden under the chiller barrel insulation i'm assuming) that opens and closes based off of the barrel temp. Does anyone know what the turn on and off temperatures are for the chiller barrel heat tape). As of now they show an open circuit with no continuity stands to reason if it's not cold enough for the barrel temp to turn them on.

[jayguy]

...As of now they show an open circuit with no continuity stands to reason if it's not cold enough for the barrel temp to turn them on.

yes. 35F is the switch temperature.

[BKS60]

Unless you pulled the gas out you did not pull the saturated condensor thermister. Have you compared the front panel condensor calculated pressure with the actual pressure!

[aggiechillertech]

I put the time in on this one I pulled the gas out of both circuits to check all of the sensors to be 100% sure. This has gone beyond charging people for every hour I've been pulling my hair out to fix it's personal now and I'm not walking away till the gremlin has been hunted down and terminated with extreme prejudice.

Thanks for the information.

[R123]

Fast forward to today it was cold last night in the 40's and the unit had tripped both circuits on oil. The maintenance guy checked for codes at 8:00 and there were none the chiller was satisfied and the circulating building water pump was off. When I got there at 8:30 both circuits were tripped so it looks like it happened on the first start after a long off cycle at night.

This indicates you have a slide valve piston leaking by and the compressor is starting loaded. If the compressor starts loaded, the fans can't stage up fast enough and the chiller trips on high pressure or low oil flow. When the piston first starts going bad, it will only do it on the first start after a long off cycle as the oil drains off the o ring on the piston. Then, it won't do it anymore as the oil on the o ring creates the seal. As it gets worse, it will start loaded more often and eventually it will do it all the time. To check this, you need to measure the amp draw at the first start of the day and it should start around 40 to 50% RLA and slowly increase as the chiller loads up. You can lock out one circuit the night before to insure you are there on the first start.

Although its important for the cooler heaters to be wired in, that is not your problem here.

[aggiechillertech]

10-4 I'll shut it down next time it looks like we are going to get a cool front in and check it out. I checked for them starting loaded but it has after they've been running. Man I hope this is it