Liebert Question

[nukepuke]

got an early 90's vintage liebert, seems to be loosing voltage to liquid line sol.
on # 1 compressor intermittently/erratically. seems to happen when near setpoint temp. coil on LLS could be going open intermittently but I doubt it.
could the motherboard be the culprit?? any thoughts would be appreciated.

[coolwhip]

Get your meter out and start checking.

[Airmechanical]

Get your meter out and start checking.

ditto;

a leibert is the best system made but its still a glorified a/c




.

[whec720]

Check your control voltage starting at the transformer. Work your way through the circuit till you find the problem.

[Wire-by-Colors]

Control xfrmr is the best place to start. If its from the early 90s I'm guessing its either an SM (Standard Microprocessor) or perhaps a level 3 or 10 board. If you look on the schematic you can look and identify the board type in the lower right corner. Most boards have the option of jumpering the output triac and testing the auxillary components. With that said, you should be able to energize the solenoid and see if the coil is responding to the board. Be sure to pull the compressor contactor coil because it may energize the compressor when the low pressure switch closes. The triac is the only point on the board or output to this device. If you have any books on the system, you may be able to test the input and output optos to confirm the semiconductors aren't beginning to fail. There is always the possibility the other devices are pulling down the voltage at the coil, but again if this is the case, I would suspect the compressor contactor would possibly chatter since the VA on the compressor contactor is slightly greater than that of the LLS coil. And finally, if this is a dual circuit machine, how does the other circuit respond when circuit 1 is running? There is again a greater overall VA demand on the XFMR than in the case of only circuit 1.

[The Doctor]

got an early 90's vintage liebert, seems to be loosing voltage to liquid line sol.
on # 1 compressor intermittently/erratically. seems to happen when near setpoint temp. coil on LLS could be going open intermittently but I doubt it.
could the motherboard be the culprit?? any thoughts would be appreciated.

more info would help.
what else could be the culprit-- sensitivity? you mentioned it seems to happen near setpoint temp.

[whec720]

Temperature sensitivity default, if I remember correctly, is 2.0. As the Doctor stated, check your settings.