Unit installation

64 ACZ / AGZ-BM IOMM ACZ/AGZ-3
Unit Test Mode
The unit test mode allows manual testing of controller outputs. Entering this mode requires the
following conditions:
• Unit OFF input = OFF (i.e., entire chiller is shut down).
• Manager password active.
• Available Unit Mode setpoint = TEST.
A test menu can then be selected to allow activation of the outputs. It is possible to switch each
digital output ON or OFF and set the analog outputs to any value.
When in test mode, the compressors may be turned on but they will automatically shut off after 10
seconds.
Chilled Water Pump Control
Operation of the evaporator pump is controlled by the state-transition diagram shown below.
The evaporator pump is cycled by the controller. If the unit is enabled and at least one circuit is able
to run, the controller sends a signal to start the pump (terminals #33 and #35 on TB1). If water flow
is sensed for a period of time from the flow switch (terminals #44 and #61 on TB1), the unit will
start at a call for cooling. This time delay is set in Set menu #5 with a default of 30 seconds.
Compressor Control
Compressor Sequencing
This section defines which compressor is the next one to start or stop. The next section defines
when
the start, or stop, is to occur.
Compressor sequencing is based primarily on compressor run-hours and starts. Compressors with
fewer starts will start before those with more starts. Compressors that have more run-hours will shut
off before those with less run-hours. In the event of a tie on number of starts, the lower numbered
compressor starts first. In the event of a tie on run-hours, the lower numbered compressor shuts off
first.
If possible, the number of running compressors on each circuit will be balanced. If a circuit is
unavailable for any reason, the other circuit is allowed to stage on all compressors.
OFF
RUN
START
TEST: Flow OK for
Evap Recirc Time
TEST: Unit State=OFF &
All Comp State=OFF &
N
O Evap water freeze condition
TEST: Unit State = AUTO AND
At least one circuit is enabled for start
OR
Evap water freeze condition
TEST: Unit State=OFF &
All Comp State=OFF &
N
O Evap water freeze condition
Power ON