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The captain
26-11-2007, 11:47 AM
Any one had to replace the motor winding temp thermistor probe's on a Trane TRAD 50 ton screw compressor. Chiller is air cooled with 2 refrig circuits on R134a. Circuit B compressor is at well bellow 105 'C the trip out set point on the control panel. After Reset in diagnostics menu fault re appears after a fue seconds without a compressor start. Maybe i will return tomorrow morning and see if it will run.

Lowrider
27-11-2007, 12:27 AM
Winding/ motor sensors on RTAC's can't be done by yourself. You'll have to get Trane out, they have replacement sensors, but they have to be placed the right way, or you'll blow up the electro motor!

Have you checked to see if all 3 of them measure the same resistance and if the terminals are clean and making good contact?

The captain
27-11-2007, 01:31 AM
Where are the sensor terminals located on these compressors? I removed the electrical box cover from the compressor and traced out the sump heater and oil separator tank heater. Found the cables for the slide valve solenoids, 3 of them at front of compressor. Found another 2 wires connected to 2 of 4 spade terminals to the left of the 3 phase connections in the compressor box. The other 2 spade terminals where not connected to any wires. The resistance across the 4 terminals was 0.1ohms.

Lowrider
27-11-2007, 11:51 PM
If you have 4 terminals and just 2 used, then there are two spare sensors in the motor.

If all 3 sensors measure the same, place a wire across the terminals at the compressor module and if fault doesn't re-apear the module is at fault and you'll have to get the module changed out by Trane.

If the 3 sensors aren't the same, use one thats working.
One wire is common, other 3 are from each sensor.

Good Luck.

The captain
28-11-2007, 10:55 AM
Returned to site today to find circuit 2 compressor cool. Ambient temp today 26 'C. Refrigerant R134a. Reset fault once and managed to keep compressor running with good heat load, after pull down to design entering water 11 'C and leaving water 7 'C. Checked suction superheat of circuit 2 to find 12 'K, high for a late model screw chiller with EXV refrig control. Suction pressure 217 kpa. Suction saturation temp 2 'C. Suction temp 13 'C. First circuit running well with 4 'K suction superheat. Suction pressure 283 kpa. Suction saturation temp 7 'C. Suction temp 11 'C. The subcooling on each circuit was the same 11 'K, condenser outlet 30 'C and condensing saturation temp 41 'C. Discharge temp was also the same on each circuit 61 'C. Chiller has no sight glass!.

Circuit 2 looks to be short of refrigerant. Now i need to find a leak. :D

Lowrider
28-11-2007, 10:53 PM
Well that depends, did you check subcooling on both circuits?

If they are roughly the same, then check the sensors, because they can be off!

The captain
29-11-2007, 11:17 AM
The subcooling on each circuit is the same @ 11 'K, condenser outlet 30 'C and condensing saturation temp 41 'C.

Yeah checked both circuits subcooling @ 11 'K.

The sensors for the EXV appear to be threaded connection type screwed into a port on suction line.

Lowrider
30-11-2007, 11:40 PM
Sorry, missed the part about the subcooling! was reading too fast!

If you want to change the sensors, yes both saturated evaparation temp and suction temp sensor have to be changed at once, since they are a pair, you'll also need two connecters to replace the ones that are in there. Be carefull they are not in a bulb, but in direct contact with the refrigirant! Keep hight and position the same as it was before!

Mik Dundee
01-12-2007, 10:12 AM
wak your gauges on and get the actual sst compare that to the screen or ,you can check your ohms of the sensors relevant to a temp. its definately worth going over with your leak detektor

The captain
02-12-2007, 12:34 PM
checked with guages first up looks to be correct sst. Found leak on discharge service valve spindal gland. The cap was only on hand tight, removed the cap and found half full of oil. Service valve may require a new packing sleeve.

The captain
06-12-2007, 09:55 AM
Reclaimed 16 kgs of R134a, bloody short 18 kgs. 34 kg in the ckt. Time for a leak check.

The captain
11-12-2007, 12:37 PM
Unloader solenoid stem! bubble city.:D

Mik Dundee
15-12-2007, 05:22 AM
Nice one. Keep up the good work!!!