modulation valve (SMV) and suction solenoid valve (SSV) with the compressor energized.
When pulling down from a control temperature that is more than 5_C (9_F) above set point, both valves will be open to reduce the pulldown time unless suction solenoid override or current limiting is activated. See section 2.10 for explanation of suction solenoid override. The current limit function will restrict the valves if the current is above the selected value. When the controlling probe temperature reaches set point, the suction solenoid valve will close.
When the controlling probe temperature enters the
The Controller logic is designed so the suction modulation valve will begin to close as the set point is reached. The modulation valve will close to restrict refrigerant flow until the capacity of the unit and the load are balanced, unless the compressor reliability enhancement logic on the first compressor start prevents closure.
If the temperature drops below the set point, the compressor will remain running for a few minutes. This is to accommodate any initial undershoot which might occur. After this time, and at 0.2_C (0.4_F) or greater below the set point, the compressor will be turned OFF.
The heaters will be energized if the temperature drops to 0.5_C (0.9_F) below the set point. The heaters will
b.Operation in the dehumidification mode (Code 33 value selected)
The dehumidification mode is activated by selecting Code 33, choosing a desired relative humidity value, and pressing the ENTER key. The control probe LED (supply 1) will flash ON and OFF every second to indicate that the dehumidification mode is active. Once the Mode is active and the following conditions are satisfied, the Controller will activate the heat relay to begin dehumidification.
1.The humidity sensor reading is above the set point and valid (AL67).
2.The pulldown mode is NOT active. (ie., The SSV valve is closed, and the control temperature is less than 5_C above set point.)
3.The control probe (i.e.; Supply 1) temperature is less than set point, plus 0.25_C.
4.Temperature control set point is greater than
5.The heater debounce timer (three minutes) has timed out.
6.Heater termination thermostat (HTT) is closed.
7.The Controlled Atmosphere (CA) option VENT or
8.Humidity sensor alarm is not active (AL67).
9.High pressure switch (HPS) is not open.
If the above conditions remain true for at least one hour the evaporator fans will switch from high to low speed operation (on units so equipped). The evaporator fan speed will switch every hour thereafter as long as all conditions are met (see Bulb Mode section for different evaporator fan speed options). If any condition except for item (1.) becomes false OR if the relative humidity sensed is 2% below the dehumidification set point, the high speed evaporator fans will be energized.
The dehumidification mode applies power to the defrost and drain pan heaters. This added heat load causes the Controller to open the modulating valve to match the new total heat load while still holding the supply air temperature very close to the set point.
Opening the modulating valve reduces the temperature of the evaporator coil surface, which increases the rate at which water is condensed from the air passing through the coil. Removing water from the air reduces the relative humidity. When the relative humidity sensed is 2% below the set point (function code Cd33), the Controller
Two timers are provided in the Dehumidification mode to prevent rapid mode switching and consequent contactor wear. They are:
SHeater debounce timer (three minutes). S
The heater debounce timer is activated whenever the heat contactor status is changed. The heat contactor remains energized (or
