Trane rtac 170

[El Padre]

Hi,
I just had to get out of the sun for a couple of minutes as my client is going to wonder why my face is tanned and not the back of my neck!

I have a site with the above chiller, during the winter or prolonged periods of low demand, circuit number two fails on low oil pressure/flow, I can understand why as the compressor runs unloaded for extended periods of time, I left the circuit locked out on the control panel, I pumped the circuit down today and then ran it and monitored it carefully;

Sat. Suction = 4 Sat. Condensing = 39 SH = 5 SC = 6 Oil Pressure = 763 Kpa Oil Temp. = 54 Current = 92 95 98 %FLA = 57 59 60.

As you can see with enough load the circuit runs fine, what I cannot understand is why does circuit number one run "perfectly" all year round and cope with the variations in load? Could it be the way that the evaporator is designed?

Anyone else had the same?

Cheers

[centrecipew]

Hi, sounds like internal oil pressure relief valve is faulty. This is a repair that should be looked at by a local Trane Service Agency. Cheers.

[El Padre]

Thanks centrecipew,

I have changed oil filter, checked strainers on oil return lines etc. Shall suggest a Trane engineer, I did'nt want to miss something obvious.

Cheers

[Lowrider]

What's the serial number and type, could be it was just not designed to work in low ambiant! Is the first fan stage y/delta or VSD?

[El Padre]

Hi Lowrider,

the model number just says RTAC 170, there are no other letters after the model number, I think that the fan stages are all DOL, there is definately no converter/inverter.

Thanks for replying

Cheers

[Lowrider]

Inside the panels there should be a long code starting with ERTAC170. There after start the option codes. Since it has no VFD it is not a Low Ambiant version.

Reasons why the compressor would shut down on low oil flow:

Could be the oil return from the bottom off the evaporator, there's a check valve in there.

The oil heater in the separator of that compressor could be working at a lower temperature or not producing enough heat!

Did you check to see if the intermediate oil pressure sensor is measuring correct all the time? If you run the unit in part load with a gauge on the oil line you'll be able to see if it doesn't.

Official explaination of the diagnostic:

The intermediate oil pressure transducer for this compressor was out
of the acceptable pressure range for 15 seconds, while the Delta
Pressure was greater than 35 Psid.: Acceptable range is 0.50 > (PC-PI)
/ (PC-PE) for the first 2.5 minutes of operation, and 0.25 > (PC-PI) / (PCPE)
thereafter,