Thermo Electron 8600 Series, Troubleshooting Service Manual

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2.15 Symptom: Troubleshoot compressor
Order Possible Cause Verification
Action
Verify compressor starts and run continuously.
If yes, install gauges and go to next step.
If no, go to order 3 of “Compressor starting problem”.
Verify suction pressure is above:
High Stage – 0 psig
Low Stage – 10” vac
If suction pressure is “ok”, proceed to next step.
If suction pressure is below limits, conduct equalization test: if
equalization test fails – blocked cap tube; recondition refrigeration
system.
If equalization test passes, warm unit, go order 2 “unit at room
temp, heat exchanger at room temp”.
Verify discharge pressure is below 175 psig – conduct
efficiency test. Suspect bad compressor (values): replace compressor…recondition
refrigeration system.
1
Low suction pressure
problem
If discharge pressure is above:
LS 175 psig
HS 250 psig
Suspect non-condensables: recondition the refrigeration system in
question.
Verify static pressures are acceptable. Recondition low stage (suspect partial restriction in cap tube).
Compare high stage static and low stage static
pressures. Are the static pressures on high and low
stages identical? Yes, replace interstage and recondition both the high and low
stages.
No, go to next verification.
2
Unit at room temperature,
heat exchanger at room
temperature
Static pressure unacceptable. Suspect under- or overcharge. Recondition refrigeration system for
system in question.
Measurements of wall voltage
Unit off
Unit at start-up.
If unacceptable, work with customer to correct.
If acceptable, go to next step.
3
Compressor Starting
Problem
Verify compressor attempts to start (draws L.R.A. or
turns over briefly).
If no attempt to start –
Check voltage to compressor
No voltage at compressor LD5 (HS) or LD6 (LS) is on.
No voltage at compressor LD5 (HS) or LD6 (LS) is
off. If compressor attempts to run and draws L.R.A., check start relay
for proper operation and values on start and run capacitors.
If voltage at compressor, isolate compressor. Ohm compressor
windings at compressors and compare to nominal values (Appendix
B).
Check connections: enclosure, high pressure cutout switch. Ohm
out pressure switch. Switch to be closed.
Voltage between U13-15 (HS) or U13-16 (LS) and J11-1 on micro
board is less than 10VDC, replace micro board. Else if DC voltage
across D12 (HS) or D13 (LS) on high voltage board is less than
10VDC, replace high voltage board.