Initial Start-up
CAUTION
I
Initial start-up must be performed by McQuayService personnel.
1.
2.
3.
Set up control as described in the initial conditions.
Turn front panel switch to Auto position (chilled water flow pump relay will energize).
If the field installed flow indicator does not indicate chilled water flow after 30 seconds, the
alarm output wi
I l be
energized.
4.
5.
6.
The chiller will start w hen the leaving water temperature is
above the Active Setpoint.
The controller starts the compressor W ith the least starts while in auto Iead-lag setting. energizes
the liquid in_jection solenoid and motor coolin g solenoid. energizes the suction injection
solenoids. and de-energizes the crank case heaters.
Suction injection will turn off when the following conditions have been met:
The discharge superheat drops below “F. the Liquid Presence sensor shows liquid, and the
Absolute Pres. ratio is greater than I.2
Abs.
Condenser Psia Abs. Evaporator Psia)
7.
The unit status moves from:
If additional cooling capacity is required then the controllers will add capacity by changing the
capacity control solenoids outputs 7. 8. and 9 and maintaining a close balance in amp capacity
between compressors after both compressor are running. The lag compressor will come on after the
lead compressor amps have exceeded the setpoint to turn on the lag for the defined lag time (see menu
23 on the master controller).
Load Recycle
As the load drops. the controls will unload the compressors until the compressors amps drop below
the lag cutoff point for the delay time required. The control will then shut off the lag compressor and
further reduction in load will cause the leaving water ternperature to drop 3 F below the active
setpoint which will cause the compressor to turn off on Load Recycle and the display will show
Waiting For Load and the chilled water pump will remain on.
EvapOn-Recirc **Sec to All Systems Off to MCR Started to Pre-purge to Open
Solenoid to Running Min Amp Lim to Running: % Cap 50
IM 663
27
