OM 1280-2 • MICROTECH UNIT CONTROLLER 36 www.DaikinApplied.com
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 ships with an 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 Economizer function.
Temperature Comparison with OA
Enthalpy Setpoint Economizer (optional)
If the optional Expanded economizer function is selected, the
unit ventilator ships with an optional OA humidity sensor, which
is used along with the OA temperature sensor to calculate OA
Economizer Strategy and uses the Temperature Comparison
with OA Enthalpy Setpoint Economizer function. Refer to Table
19 and Table 20.
NOTE: Temperature Comparison with OA Enthalpy Setpoint
Economizer requires an optional OA humidity sensor.
Temperature Comparison with Enthalpy
Comparison Economizer (optional)
If the optional Leading Edge economizer function is selected, the
unit ventilator ships with an optional IA humidity and OA humidity
sensor, which are used along with the IA temperature and OA
temperature sensors to calculate IA enthalpy and OA enthalpy. In
this case, the UVC is factory set for the Leading Edge Economizer
Strategy and uses the Temperature Comparison with Enthalpy
Comparison Economizer function. Refer to Table 19 and Table
20.
NOTE: Temperature Comparison with Enthalpy Comparison
requires both an optional OA humidity sensor and an
optional IA humidity sensor.
Table 19: Economizer Enable/Disable Tests Dened
Tests
Economizer Enable/
Disable Tests
Enable Test Disable Test
A OA temp setpoint
B
C OA enthalpy setpoint
D
enthalpy
Table 20: How Economizer Enable/Disable Tests are Selected
Economizer
Strategy
Control Temp Sensor OA Temp Sensor Space Humidity Sensor OA Humidity Sensor
Economizer Enable/
Disable Tests
All
Unreliable Ignored Ignored Ignored OA damper closed
Ignored Unreliable Ignored Ignored OA damper closed
Basic
Reliable Reliable Ignored Unreliable Test B
Reliable Reliable Ignored Reliable Test C
Expanded Reliable Reliable Ignored Reliable Test C and Either Test B or Test A
Leading Edge
Reliable Reliable Reliable Reliable Test D and Test B
Reliable Reliable Reliable Unreliable Test B
Reliable Reliable Unreliable Unreliable Test B
Reliable Reliable Unreliable Unreliable Test B
NOTE: The hard-wired sensor and the equivalent input must both be unreliable for the value to be considered unreliable.
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