Sequence of Operation
WSHP Open v3
CARRIER CORPORATION ©2021
Integration Guide
All rights reserved
25
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 temper
ature 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
–
When 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°F 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
–
When 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°F
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. When 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 st
atus 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 or ZS) 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 or ZS is greater than the occupied cooling setpoint
•
Space temperature reading is valid
•
If unoccupied, the SPT or ZS is greater then the unoccupied cooling setpoint
•
If economizer cooling is available and active, and the economizer alone is insufficient to provide enough
cooling
•
OAT >
Cooling Lockout Temperature
if OAT is available
•
Source Water Pump
is on (if
Source Water Linkage
is active)
