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When power is reapplied after a power outage, there is a configurable delay of 5 - 600 seconds (default 60)
before starting the fan. You must configure the fan delay:
•
The Fan On Delay defines the delay time (0 - 30 seconds, default 10) before the fan begins to operate after
heating or cooling is started.
•
The Fan Off Delay defines the delay time (0 - 180 seconds, default 45) the fan continues to operate after
heating or cooling is stopped.
NOTE The fan continues to run as long as the compressors, heating stages, or the dehumidification relays are on.
If the SPT failure alarm or condensate overflow alarm is active, the fan is shutdown immediately, regardless of
occupancy state or demand.
Automatic Fan Speed Control - The WSHP Open can control up to 3 fan speeds using the ECM (Electronically
Commutated Motor). The motor operates at the lowest speed possible to provide quiet and efficient fan operation
with the best latent capability. The motor increases speed if additional cooling or heating is required to reach the
desired space temperature setpoint. The control increases the motor's speed as the space temperature rises
above the cooling or below the heating setpoint. The amount of space temperature increase above or below the
setpoint required to increase the fan speed is configurable in the setpoint. Also, the control increases the fan
speed as the Supply Air Temperature approaches the configured minimum or maximum limits.
Fan Speed Control
•
During heating – Whenever heat is required and active, the control continuously monitors the supply air
temperature to verify it does not rise above the configured Maximum Heating SAT Limit (110° default). As
the SAT approaches this value, the control increases the fan speed as required to ensure the SAT remains
within the limit. This provides the most quiet and efficient operation by running the fan at the lowest speed
possible.
•
During cooling – Whenever mechanical cooling is required and active, the control continuously monitors the
supply air temperature to verify it does not fall below the configured Minimum Cooling SAT Limit (50°
default). As the SAT approaches this value, the control increases the fan speed as required to ensure the SAT
will remain within the limit. Fan operates at the lowest speed during dehumidification to maximize latent
capacity during cooling.
Fan Status - You can configure an optional input as either an occupancy input contact or a fan status input. If
configured as fan status, the controller compares the status of the fan to the desired commanded state.
Whenever the fan is commanded to run (ON), the fan status is checked and verified to match the commanded
state. If the fan status is not on, then a fan status alarm is generated after 1 minute and the equipment's
compressor(s) and auxiliary heat is disabled and the optional OA damper closes.
Cooling
The WSHP Open operates 1 or 2 stages of compression to maintain the desired cooling setpoint. The compressor
outputs are controlled by the PI (Proportional-integral) cooling loop and cooling stages capacity algorithm. The
algorithm calculates the desired number of stages needed to satisfy the space by comparing the space
temperature (SPT) to the appropriate cooling setpoint.
NOTE The waterside economizer, if applicable, is used for 1st stage cooling, in addition to the compressor(s).
The following conditions must be true for the cooling algorithm to run:
•
Cooling is set to Enable
•
The Fire/Smoke Input and Shutdown modes are inactive
•
Heat mode is not active and the compressor time guard(s) have expired
•
Condensate Overflow input in Normal
•
Fan Status is True (if option is enabled)
•
If occupied, the SPT is greater than the occupied cooling setpoint
WSHP Open v3
15
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