Carrier WSHP Open v3 Integration Manual

Also see for WSHP Open v3: Integration guide

WSHP Open v3 17If all the above conditions are met, the heating outputs are energized as required, otherwise they are de-energized. If the heating is active and the SAT approaches the maximum SAT limit, the fan is indexed to the nexthigher speed. If this is insufficient, and if the SAT rises further and reaches the Maximum Heating SAT limit, thefan is indexed to the maximum speed. If the SAT still continues to rise 5° F above the maximum limit, all heatingstages are disabled.During Heating, the reversing valve output is held in the heating position (either B or O-type, as configured), evenafter the compressor is stopped. The valve does not switch position until the cooling mode is required.The configuration screens contain the Max SAT parameter as well as heating lockout based on outdoor airtemperature (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 theSAT to achieve a stable temperature before energizing a second stage of capacity. Likewise, a 45 second delay isused when staging down.After a compressor is staged off, it may be restarted again after a normal time-guard period of 5 minutes and ifthe supply air temperature has fallen below the maximum supply air temperature limit.The WSHP Open provides a status input to monitor the compressor operation. The status is monitored todetermine if the compressor status matches the commanded state. This input is used to determine if a refrigerantsafety switch or other safety device has tripped and caused the compressor to stop operating normally. If thisoccurs, an alarm is generated to indicate the faulted compressor condition. Also, if auxiliary heat is available (seebelow), the auxiliary heat replaces the reverse cycle heating and maintains the space temperature as required.Auxiliary heatThe WSHP Open can control a 2-position or modulating water or steam valve, connected to a coil on the dischargeside of the unit and supplied by a boiler, or a single stage ducted electric heater, in order to maintain the desiredheating setpoint. If the compressor capacity is insufficient, or a compressor failure occurs, the auxiliary heat isused. Unless the compressor fails, the auxiliary heat only operates to supplement the heat provided by thecompressor, if the space temperature falls more than 1° F below the desired heating setpoint. (This amount isconfigurable.) The heat is controlled so the SAT does not exceed the Maximum Heating SAT limit.The same conditions required for Reverse Cycle Heating must be true in order for the Auxiliary Heat algorithm torun.Auxiliary Modulating Hot Water / Steam Heating Reheat - The control can modulate a hot water or steam valveconnected to a coil on the discharge side of the unit, and supplied by a boiler in order to maintain the desiredheating setpoint, if the compressor capacity is insufficient, or a compressor failure occurs. Unless a compressorfault condition exists, the valve only operates to supplement the heat provided by the compressor if the spacetemperature falls more than 1° F below the desired heating setpoint. The valve is controlled so the SAT does notexceed the Maximum Heating SAT limit.2- Position Hot Water / Steam Heating Reheat - The control can operate a 2-position, NO or NC, hot water orsteam valve, connected to a coil on the discharge side of the unit and supplied by a boiler, in order to maintain thedesired heating setpoint, if the compressor capacity is insufficient or a compressor failure occurs. Unless acompressor fault condition exists, the valve only opens to supplement the heat provided by the compressor, if thespace temperature falls more than 1° F below the desired heating setpoint. The valve is controlled so the SATdoes not exceed the Maximum Heating SAT limit and is subject to a 2-minute minimum OFF-time to preventexcessive valve cycling.Single Stage Electric Auxiliary Heat – The control can operate a field-installed single stage of electric heat that isinstalled on the discharge side of the unit, in order to maintain the desired heating setpoint, if the compressorcapacity is insufficient or a compressor failure occurs. Unless a compressor fault condition exists, the heat stageonly operates to supplement the heat provided by the compressor if the space temperature falls more than 1° Fbelow the desired heating setpoint. The heat stage is controlled so the SAT does not exceed the MaximumHeating SAT limit and is subject to a 2-minute minimum OFF-time to prevent excessive cycling.