Instruction manual

www.DaikinApplied.com 31 OM 751-4
desCrIptIon of operatIon
Indoor Air Fan interlock with Compressor Operation
The IA fan will turn on with compressor operation if congured for fan cycling. When
the compressor turns off, if the indoor air coil DX temperature is less than 50°F (10°C),
then the IA fan will remain on at the current user or auto fan speed selection. When
the indoor air coil DX temperature becomes greater than 50°F (10°C) the IA fan will be
allowed to turn off.
Off Delay
When the UVC is placed into off mode or shutdown mode, the UVC is congured to
continue fan operation for a short time period and then shutdown.
Outdoor Air Damper Operation
The UVC is congured for an OA damper operated by a oating-point actuator. The OA
damper actuator contains a spring that ensures the OA damper is closed upon loss of
power. The oating-point actuator is driven by the UVC using two binary (Triac) out-
puts. The OA damper typically is open to the current minimum position during the oc-
cupied and bypass occupancy modes and closed during the unoccupied and standby
occupancy modes.
A Triac output is best tested under load using a 24 V relay for verication. To verify:
1. Put a relay across the Triac outputs.
2. Cycle the power.
3. Verify the relay’s closed contacts during calibration.
Minimum Position
The UVC is congured to maintain three OA damper minimum positions based on the
operation of the IAF fan. This allows each unit to be eld congured to provide the
amount of fresh air required to the space at each of the three IA fan speeds.
Table 17: Default OA damper minimum positions
IAF speed Without CO
2
With CO
2
High 20% 5%
Medium 25% 5%
Low 30% 5%
Note: if the CO
2
Demand Controlled Ventilation (DCV) option is used, the UVC only uses the IA
fan high speed OA damper minimum position regardless of fan speed. The DCV function
adjusts the OA damper above this minimum as needed to maintain CO
2
set point.
Economizer Operation
The economizer function is used by the UVC to determine if the OA is adequate for
economizer (primary) cooling. When both the economizer and mechanical cooling are
available, the economizer is used as primary cooling and the UVC adds mechanical
cooling only if the economizer is not adequate to meet the current cooling load (e.g.,
the OA damper reaches 100% and cooling is still required).
The UVC supports three economizer functions:
• Basic (default)—Temperature Comparison Economizer
• Expanded (optional)—Temperature Comparison with OA Enthalpy Setpoint
Economizer
• Leading Edge (optional)—Temperature Comparison with Enthalpy Comparison
Economizer
Temperature Comparison Economizer (default)
If the default Basic economizer function is selected, the unit ventilator is provided from
the factory without the optional IA and OA humidity sensors. In this case, the UVC is
factory set for the Basic Economizer Strategy—the UVC automatically detects that no
OA humidity sensor is present and adjusts to use the Temperature Comparison Econo-
mizer function.