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79•dap4UserManual

 3. TheEnergySaver/AuxiliaryChilledWaterCoolinglogicwillbethesameand

compressor rules for short-cycle time will not be violated.

4. Low discharge temperature alarm limit must be set in menu K-Alarms & Limits.

If Discharge temperature drops below this limit, compressors will be inhibited for at

least 15 minutes and discharge temperature rises above this limit.

5. If discharge temperature drops below the limit while the variable speed compressor

  nishingitsminimumruntimetheCWshouldcloseuntildischargetemperaturerises

above the limit.

6. When DX cooling requires, the compressors will stage on as follows:

Compressors on cycle

-- Variable speed compressor C1 comes on at Temperature Setpoint + Temperature

Deadband + 1+ STS DB. For instance: SP=72, DB=2 and STS=0.3, the C1

compressor will on at 75.3°.

 -- Oncevariablespeedcompressorcomesonitwillrampupitsspeedmaximum 

speed for delay modulation then uses PI logic to maintain setpoint +1°F.

 -- FixedspeedcompressorC2comesonatTemperatureSetpoint+Temperature 

Deadband + 2ºF + STS DB and variable speed compressor has run at 95% speed

for a C2on delay. This step only applies to dual compressor system.

For instance: SP=72, DB=2 and STS=0.3, the C2 compressor will on at 76.3°.

Compressors off cycle

 -- FixedspeedcompressorC2cyclesoffatTemperatureSetpoint+2ºF,variablespeed

compressor C1 continues to run at 100%. For instance: SP=72, the C2 compressor

goes off at 74 degrees.

-- Variable speed compressor C1 starts to ramp down to minimum speed when return

temperature reaches setpoint + 1°F.

-- Variable speed compressor cycles off at Temperature Setpoint.

-- CW Valve will close 10% for every 0.1 Deg F below the setpoint plus 1°F and

completely close at setpoint.

-- Compressor will not violate its minimum runtime.

* This applies on dual compressor system.

2. Discharge Air Temperature Control Mode

a) Single DX circuit - One variable speed compressor system

-- Compressor settings type in dap4 Factory Settings menu is programmed to “Var. Sp”

and Control mode is set to “Supply”.

 -- Thereisave(5)minutedelaybetweenstart-to-startofthecompressor.Thedelay

  willbeincreasedtosix(6)minutesforone(1)hourfollowingthedetectionofa

short-cycle condition even if the short cycle alarm is disabled using a short cycle

alarm menu.

-- There is a two (2) minute delay between stop-to-start of the compressor.

-- Once compressor C1 comes on, it must remain on for a minimum runtime even

  setpointsatises.

Data Aire dap 4 User Manual

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