Outdoor Air Damper Operation; Minimum Position; Economizer Operation - Daikin MicroTech II Operation And Maintenance Manual

OM 752-4

Outdoor Air Damper Operation

The UVC is configured for an OA damper operated by a floating-point actuator. The OA
damper actuator contains a spring that ensures the OA damper is closed upon loss of
power. The floating-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 verification. 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 configured to maintain three OA damper minimum positions based on the
operation of the IAF fan. This allows each unit to be field configured 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
High
Medium
Low
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.
Temperature Comparison with OA Enthalpy Setpoint Economizer (optional)
If the optional Expanded economizer function is selected, the unit ventilator is provided
from the factory with the optional OA humidity sensor, which is used along with the
OA temperature sensor to calculate OA enthalpy. In this case, the UVC is factory set
for Economizer Strategy 1 and uses the Temperature Comparison with OA Enthalpy
Setpoint Economizer function.
Note: Temperature Comparison with OA Enthalpy Setpoint Economizer requires an optional OA
humidity sensor.
Without CO 2 With CO 2
20% 5%
25% 5%
30% 5%
32
d o
esCrIptIon of peratIon
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