76 • dap4 User Manual
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When return air temperature = Temperature se temperature deadband
variable speed compressor starts and ramp up to maximum speed. For instance:
SP = 72, DB = 2. Compressor will be on at 74°.
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Variable speed compressor will then use PI (Proportional and Intergral) control
algorithm to main the setpoint. Proportional band is the same as deadband. The
Intergral band is programmed in Factory settings menu. In most cases there is no
need to change the P and I value as the result of temperature control fluctuation.
Return air temperature is dropping (Off cycle):
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As the return air temperature reaches setpoint, the compressor will ramp down
to its minimum speed. (Note: If variable speed compressor runs at the minimum
speed for a long period of time, it will automatically ramp up to the maximum speed
for one minute to maintain the minimum compressor oil level. The temperature may
drop slightly during this override period).
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Compressor continues to run at minimum speed then turns off when return air
temperature drops to temperature setpoint – C1 offset. C1 offset is programmed
in Compressor/Factory settings menu, default value is 2°F. For instance: SP= 72,
C1 offset = 2, compressor goes off at 70°.
b)
Dual DX circuit : Combination of a variable speed compressor (C1) and a fixed speed
compressor (C2)
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Compressor settings type in dap4 Factory Settings menu is programmed to
“V fixed” and Control mode is set to “Return Temp”.
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There is a five (5) minute delay between start-to-start of the same primary stage.
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.
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There is a two (2) minute delay between stop-to-start of the same compressor.
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There is minimum two (2) minutes delay between the start of variable speed
compressor and start of fixed speed compressor.
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Once variable speed compressor C1 comes on, it must remain on for a minimum
runtime even setpoint satisfies.
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Compressor cycles on and modulate as follows:
Return air temperature is rising (On cycle):
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When return air temperature rises to temperature se temperature deadband,
Variable speed compressor C1will start and ramp up to its maximum speed.
For instance: SP = 72, DB = 2. Compressor will be on at 74°.
--
Variable speed compressor will then use PI (Proportional and Integral) control
algorithm to main the setpoint. Proportional band is the same as deadband.
The Integral band is programmed in Factory settings menu. In most cases there is
no need to change these P and I settings.
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Fixed speed compressor C2 cycles on when return air temperature rises to
temperature se temperature DB + stage-to-stage Band and compressor C1
has operated at above 95% of its maximum speed for the “C2 on delay” period. C2
on period is programmed in Compressor/Factory settings menu (default=60s).
