Instruction manual

OM 751-4 34 www.DaikinApplied.com
desCrIptIon of operatIon
Compressor Operation
The UVC is congured to operate the compressor as secondary (mechanical) cooling
when the economizer is available. When the economizer is not available and the com-
pressor is available, the UVC uses the compressor when cooling is required.
Compressor Envelope
The compressor envelope protects the compressor from adverse operating conditions
that can cause damage and or shortened compressor life by ending compressor opera-
tion if coil temperatures exceed the dened operating envelope.
For self-contained units, the UVC is congured to monitor both the inside air/refriger-
ant and outside air/refrigerant coil temperatures to prevent compressor operation under
adverse conditions.
For split-system units, the UVC is congured at the factory to only monitor the inside
air/ refrigerant coil as part of the compressor envelope function.
Figure 21: Compressor envelope in self-contained units
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or compressor operation envelope.Area for compressor operation envelope.
120 ˚ F (48.9˚C)
28
˚ F (-2.2˚C)
40˚F (4.2˚C) 160˚F (71.1˚C)
Evaporator temperature
(indoor air coil)
(outdoor air coil)
Note: 1. For split-system units the Condenser temperature value will be xed at 122°F (50°C).
Compressor Cooling Lockout
The UVC is congured to lockout compressor cooling when the OA temperature falls
below the Compressor Cooling Lockout set point (63.5°F/17.5°C). Below this point,
only economizer cooling is available.
Compressor Minimum On and Off Timers
The UVC is provided with minimum On (3-minute default) and minimum Off (5-minute
default) timers to prevent adverse compressor cycling.
Compressor Start Delay
The UVC is provided with a Compressor Start Delay conguration variable, which is
intended to be adjusted as part of the start-up procedure for each unit. This variable is
used to delay compressor operation each time the compressor is required.
Note: To prevent strain on a building’s electrical supply system from multiple unit compressors
all starting at the same time after a p wer failure or after an unoccupied-to-occupied
changeover, Daikin strongly recommends conguring each unit or groups of units at start-
up with different start delays.
Outdoor Air Fan Operation
For self-contained units, the UVC is congured with a fan on delay that delays OA fan
operation for a time period (10 seconds, default) after the compressor starts. The OA
fan stops with the compressor.