Description of Operation
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OM 1280-2 • MICROTECH UNIT CONTROLLER
Face and Bypass Damper Control
When the freeze-stat cuts-out:
1. The OA damper closes immediately.
2. The space fan is allowed to run normally.
3. The wet heat and chilled water EOC valves open
immediately.
4. If heating is required and available, the F&BP damper
modulates normally to maintain room temperature.
Auxiliary heat may be used as needed.
When the freeze-stat cuts-in the UVC returns to normal
operation.
The UVC ignores the low temperature thermostat when the
OA temperature is greater than Compressor Cooling Lockout
Setpoint (e.g., the low temperature thermostat is ignored during
the cooling season).
2-Pipe Changeover Heating/
Cooling Availability
The UVC uses a Source (Water-In) temperature sensor to
determine if the water-in temperature is adequate for heating or
cooling. If the Source (Water-In) temperature is inadequate for
heating or cooling, the UVC does not use the water for heating
or cooling.
Source (Water-In) Temperature Sensor
The Source (Water-In) Temp Differential (5°F/2.78°C default )
configuration is used by the UVC to determine if the water can
be used for heating or cooling. The Source (Water-In) Temp
Differential is the minimum differential between water-in and
room temperature before water is used for heating or cooling.
Network Source (Water-In) Temperature
Capability
A Network Source (Water-In) temperature sensor can be
configured using the Source (Water-in) Temp Input variable.
When the Source (Water-In) Temp Input variable is used (valid
value), it automatically overrides the hard-wired Source (Water-
In) temperature sensor.
Source (Water-In) Temperature Sampling
When heating or cooling is required, the UVC checks first to
verify that the Source (Water-In) temperature is adequate for
the desired mode. For face and bypass damper applications
with an end-of-cycle valve, the valve opens but the face and
bypass damper remains in the bypass position until the water
temperature meets setpoint conditions. For valve control
applications, the valve will stay at 10% open until water is
deemed adequate.
If the water is deemed inadequate, the valve closes for the
EWT RetryTime (default 120 minutes) before sampling again. If
the demand for heating or cooling goes away, the unit samples
the Source (Water-In) temperature again with the new call for
heating or cooling.
Summary of Contents for MicroTech
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