77•dap4UserManual
For instance: SP = 72, DB = 2, STS = 0.3. Compressor will be on at 74.3 deg.
Return air temperature is dropping (Off cycle):
-- FixedspeedcompressorC2turnsoffwhenreturnairtemperaturedropsbelow
temperature setpoint – STS band (default STS band=0.3 deg F) for duration of C2
off delay (default =5s). For instance: SP = 72, STS = 0.3 Compressor goes off at
71.7 degrees after 5 seconds delay.
-- AfterFixedspeedcompressorC2turnsoff,variablespeedcompressorC1ramps
uptoitsmaximumspeedandoperatesatmaximumspeedfora“DelayModulation”
period (default=60s). The Delay modulation is set in the Compressor/Factory
settings menu.
-- Variable speed compressor C1 will then modulate to maintain setpoint and turns
off when return air temperature drops to temperature setpoint – C1offset
(default=2degF); and C1 has operated for at least minimum runtime period.
For instance: SP= 72, C1 offset = 2, compressor goes off at 70 deg if it has ran for
6 minutes (minimum runtime is set to 6 minutes).
c) Energysaver/auxiliarycoolingwithoutDXcoolingassist.
1. EnergySaver/AuxiliaryChilledWaterCoolingwillbeavailablewheneverthe
incoming water supply is below the setpoint of the Energy saver Water Thermostat
in menu B-setpoint – Energy Saver
2. TheEnergySaver/AuxiliaryChilledWatermodewilloperatewhenspace
temperature is between the return air setpoint plus deadband and plus Energy
saver to DX change-over band. If the temperature rises above this range, Energy
Saver/AuxiliaryChilledWaterCoolingwillbeinhibitedforatleast15minutetoan
hour (see Energy saver Lockout setting in Factory settings menu for details) and
only DX cooling will be available. After a lockout time delay, system will try Energy
Saver/AuxiliaryChilledWaterCoolingagain.
3. The chilled water valve proportionally opens 10% for each 0.1ºF above the
temperature setpoint + temperature deadband.
4. If the temperature is consistently rising, then the valve will be opened wider.
Likewise, if the temperature is consistently falling, then the valve will be close
gradually. However, if temperature movement changes directions, then it must
change the amount of the deadband before the valve will be repositioned.
The temperature can be slowly drifting back and forth within a deadband window
at any point in the adjustment period and no valve position changes will be made.
5. If the current temperature is higher than temperature setpoint, the following
sequence is used to determine the new valve position.
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