Carrier 50PSH, PSD006-070, PSV guide

NOTE: Scheduling can either be controlled via the unit or the BAS, but not both.

INDOOR FAN — The indoor fan will operate in any one of three modes depending on the user configuration selected.

Fan mode can be selected as Auto, Continuous, or Always On. In Auto mode, the fan is in intermittent operation during both occupied and unoccupied periods. Continuous fan mode is intermittent during unoccupied periods and continuous dur- ing occupied periods. Always On mode operates the fan con- tinuously during both occupied and unoccupied periods. In the default mode, Continuous, the fan will be turned on whenever any one of the following is true:

•The unit is in occupied mode as determined by its occu- pancy status.

•There is a demand for cooling or heating in the unoccu- pied mode.

•There is a call for dehumidification (optional).

When power is reapplied after a power outage, there will be a configured time delay of 5 to 600 seconds before starting the fan. There are also configured fan delays for Fan On and Fan Off. The Fan On delay defines the delay time (0 to 30 seconds; default 10) before the fan begins to operate after heating or cooling is started while the Fan Off delay defines the delay time (0 to 180 seconds; default 45) the fan will continue to op- erate after heating or cooling is stopped. The fan will continue to run as long as the compressors, heating stages, or the dehu- midification relays are on. If the SPT failure alarm or conden- sate overflow alarm is active; the fan will be shut down imme- diately regardless of occupancy state or demand.

Automatic Fan Speed Control — The WSHP Open controller is capable of controlling up to three fan speeds using the ECM (electronically commutated motor). The motor will operate at the lowest speed possible to provide quiet and efficient fan op- eration with the best latent capability. The motor will increase speed if additional cooling or heating is required to obtain the desired space temperature set point. The control increases the motor's speed as the space temperature rises above the cooling or below the heating set point. The amount of space tempera- ture increase above or below the set point required to increase the fan speed is user configurable in the set point. Also, the control will increase the fan speed as the supply-air tempera- ture approaches the configured minimum or maximum limits.

Fan Speed Control (During Heating) — Whenever heat is re- quired and active, the control continuously monitors the sup- ply-air temperature to verify it does not rise above the config- ured maximum heating SAT limit (110 F default). As the SAT approaches this value, the control will increase the fan speed as required to ensure the SAT will remain within the limit. This feature provides the most quiet and efficient operation by oper- ating the fan at the lowest speed possible.

Fan Speed Control (During Cooling) — Whenever mechani- cal cooling is required and active, the control continuously monitors the supply-air temperature to verify it does not fall be- low the configured minimum cooling SAT limit (50 F default). As the SAT approaches this value, the control will increase the fan speed as required to ensure the SAT will remain within the limit. The fan will operate at lowest speed to maximize latent capacity during cooling.

COOLING — The WSHP Open controller will operate one or two stages of compression to maintain the desired cooling set point. The compressor outputs are controlled by the PI (propor- tional-integral) cooling loop and cooling stages capacity algo- rithm. They will be used to calculate the desired number of stages needed to satisfy the space by comparing the space tem- perature (SPT) to the appropriate cooling set point. The water side economizer, if applicable, will be used for first stage cool- ing in addition to the compressor(s). The following conditions must be true in order for the cooling algorithm to run:

• Cooling is set to Enable.

•Heating mode is not active and the compressor time guard has expired.

•Condensate overflow input is normal.

•If occupied, the SPT is greater than the occupied cooling set point.

•Space temperature reading is valid.

•If unoccupied, the SPT is greater than the unoccupied cooling set point.

•If economizer cooling is available and active and the economizer alone is insufficient to provide enough cool- ing.

•OAT (if available) is greater than the cooling lockout temperature.

If all the above conditions are met, the compressors will be energized as required, otherwise they will be deenergized. If cooling is active and should the SAT approach the minimum SAT limit, the fan will be indexed to the next higher speed. Should this be insufficient and if the SAT falls further (equal to the minimum SAT limit), the fan will be indexed to the maxi- mum speed. If the SAT continues to fall 5° F below the mini- mum SAT limit, all cooling stages will be disabled.

During Cooling mode, the reversing valve output will be held in the cooling position (either B or O type as configured) even after the compressor is stopped. The valve will not switch position until the Heating mode is required.

The configuration screens contain the minimum SAT parameter as well as cooling lockout based on outdoor-air temperature (OAT) Both can be adjusted to meet various specifications.

There is a 5-minute off time for the compressor as well as a 5-minute time delay when staging up to allow the SAT to achieve a stable temperature before energizing a second stage of capacity. Likewise, a 45-second delay is used when staging down.

After a compressor is staged off, it may be restarted again after a normal time-guard period of 5 minutes and if the sup- ply-air temperature has increased above the minimum supply- air temperature limit.

The WSHP Open controller provides a status input to moni- tor the compressor operation. The status is monitored to deter- mine if the compressor status matches the commanded state. This input is used to determine if a refrigerant safety switch or other safety device has tripped and caused the compressor to stop operating normally. If this should occur, an alarm will be generated to indicate the faulted compressor condition.

HEATING — The WSHP Open controller will operate one or two stages of compression to maintain the desired heating set point. The compressor outputs are controlled by the heating PI (proportional-integral) loop and heating stages capacity algo- rithm. They will be used to calculate the desired number of stages needed to satisfy the space by comparing the space tem- perature (SPT) to the appropriate heating set point. The follow- ing conditions must be true in order for the heating algorithm to run:

•Heating is set to Enable.

•Cooling mode is not active and the compressor time guard has expired.

•Condensate overflow input is normal.

•If occupied, the SPT is less than the occupied heating set point.

•Space temperature reading is valid.

•If unoccupied, the SPT is less than the unoccupied heat- ing set point.

•OAT (if available) is less than the heating lockout temperature.

If all the above conditions are met, the heating outputs will be energized as required, otherwise they will be deenergized. If the heating is active and should the SAT approach the maxi- mum SAT limit, the fan will be indexed to the next higher