Operating instructions

IMM AGSB-60 55
CAUTION
The unit has a one-time pumpdown operation. When the CS switches are in the off
position the unit will pumpdown once and not run again until the switches are moved to
the on position. If the CS switches are in the on position and the load has been
satisfied, the unit will go into one-time pumpdown and will remain off until the
MicroTech II control senses a call for cooling and starts the circuit. Under no
circumstance use the compressors for pumpdown of the system with the liquid line
valves closed.
CAUTION
It is important that the water flow to the unit is not interrupted before the compressors
pump down to avoid freeze-up in the evaporator.
CAUTION
If all power is turned off to the unit, the compressor heaters will become inoperable.
Once power is resumed to the unit, it is important that the compressor and oil separator
heaters are energized a minimum of 12 hours before attempting to start the unit. Failure
to do so could damage the compressors due to excessive accumulation of liquid in the
compressor.
Start-up After Temporary Shutdown
1. Insure that the compressor heaters have been energized for at least 12 hours prior to
starting the unit.
2. Start the chilled water pump.
3. With system switch S1 in the "on" position, move the circuit pumpdown switches CS to
the on position.
4. Observe the unit operation until the system has stabilized.
Extended (Seasonal) Shutdown
1. Move the CS switches to the off position.
2. After the compressors have pumped down, turn off the chilled water pump.
3. Turn off all power to the unit and to the chilled water pump.
4. If fluid is left in the evaporator, confirm that the evaporator heaters are operational.
5. Move the emergency stop switch S1 to the off position.
6. Close the optional compressor suction valve (if so equipped) as well as the liquid line
shutoff valves.
7. Tag all opened compressor disconnect switches to warn against start-up before opening the
compressor suction valve and liquid line shutoff valves.
8. If glycol is not
used in the system, drain all water from the unit evaporator and chilled
water piping if the unit is to be shutdown during winter and temperatures below -20°F can
be expected. The evaporator is equipped with heaters to help protect it down to
-20°F. Chilled water piping must be protected with field installed protection. Do not leave
the vessels or piping open to the atmosphere over the shutdown period.
9. Do not
apply power to the evaporator heaters if the system is drained of fluids as this can
cause the heaters to burn out.