•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 cooling.
•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
There is a
After a compressor is staged off, it may be restarted again after a normal
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
•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
speed. Should this be insufficient, and the SAT rises further reaching the maximum heating SAT limit, the fan will be indexed to the maximum speed. If the SAT still continues to rise 5° F above the maximum limit, all heating stages will be disabled.
During Heating mode, the reversing valve output will be held in the heating position (either B or O type as configured) even after the compressor is stopped. The valve will not switch position until the Cooling mode is required.
The configuration screens contain the maximum SAT parameter as well as heating lockout based on
There is a
After a compressor is staged off, it may be restarted again after a normal
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. Also, if auxiliary heat is available (see below), the auxiliary heat will operate to replace the reverse cycle heating and maintain the space temperature as required.
AUXILIARY HEAT — The WSHP Open controller can con- trol a
Auxiliary Modulating Hot Water/Steam Heating Reheat
—The control can modulate a hot water or steam valve con- nected to a coil on the discharge side of the unit and supplied by a boiler in order to maintain the desired heating set point should the compressor capacity be insufficient or a compressor failure occurs. Unless a compressor fault condition exists, the valve will only operate to supplement heat provided by com- pressor if the space temperature falls more than one degree be- low the desired heating set point. The valve will be controlled so the SAT will not exceed maximum heating SAT limit.
Single Stage Electric Auxiliary Heat — The control can op- erate a
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