48
Additional Sequence of Operations
Supply Fan Operation
The supply fan will enable upon receiving a
24VAC input on the “G” terminal or upon a
call for compressor operation, unless an
alarm prevents the fan from operating.
There is a 30 second minimum off timer for
the fan. The supply fan is enabled for 15
seconds after the last stage of cooling,
heating, or dehumidification stages off.
Two Speed Electronically Commutated
Motor (ECM) if equipped with 1) EC motor
and 2) Fan-Speed Dehumidification or Hot
Gas Reheat
With a two speed ECM, the supply fan will
have two speed operations, “low speed” and
“high speed”. The supply fan speeds will
correspond to the below listed operating
functions.
• Supply Fan “G” call only - Low Speed
• Compressor low capacity “Y1” - Low
Speed
• Compressor full capacity “Y2” - High
Speed
• Supplementary Heating - High Speed
• Dehumidification - Low Speed
• Waterside Economizer - High Speed
With a “Y1” enable, the supply fan will run
at low speed, and with a “Y2” enable, the
supply fan will run at high speed. If there is
only one compressor capacity, the “Y1”
call from the thermostat must be wired to
the “Y2” terminal input on the unit
control board.
Compressor Operation
Unless an alarm is active, the compressor
will enable upon receiving a 24VAC input
on the “Y1” or “Y2” terminals, or upon
receiving a 24VAC input on the “TH_NS”
terminal if in night setback mode. If the
supply fan was not enabled prior to the
compressor call, then the supply fan will
enable for 5 seconds before the compressor
is started.
The compressor has a minimum on time and
a minimum off time of 180 sec and 120 sec
respectively to prevent short cycling. These
delays are shortened to 5 sec if the controller
is in test mode. If the unit goes into an
alarm, the minimum on time will be ignored
and the compressor will disable. Controller
includes built-in compressor inter-stage
delays.
All alarms will disable the compressor.
Auxiliary Heating Operation
Staged Heating
The heating stages will enable according to
thermostat inputs.
Dehumidification Operation
Fan Speed Dehumidification (requires EC
Motor)
For Fan Speed Dehumidification, switch 1,
position 9 must be set to “ON”.
Fan Speed Dehumidification Mode is
enabled based on a 24VAC input to the
“DH” terminal and a 24VAC input to the
“Y1” or “Y2” terminals.
Unit operates according to the cooling
sequence of operation, with the exception
that the supply fan low speed output is
enabled in lieu of high speed during cooling
mode. Compressor operates at full capacity
during dehumidification.
If a waterside economizer is included and
the entering water temperature falls below
the Entering Water Temperature setpoint,
the waterside economizer coil will be
enabled and operate as described in the
Waterside Economizer Operation section.
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