Temperature Comparison With Enthalpy Comparison Economizer (Optional); Networked Space Humidity Sensor Capability; Networked Outdoor Humidity Sensor Capability; Co 2 Demand Controlled Ventilation (Optional) - McQuay MicroTech II Operation & Maintenance Manual

Temperature Comparison with Enthalpy Comparison
Economizer (optional)
The UVC uses four configuration variables to determine if the
economizer can be used: Economizer OA Temp Setpoint, Economizer
Temp Differential and Economizer OA Enthalpy Setpoint, and
Economizer EnthalpyDifferential. See Table 19.
Table 19. Economizer Available Calculation – Enthalpy and
Temperature Comparison
Economizer Available
NOTICE
Temperature Comparison with Enthalpy Comparison requires both
an optional OA humidity sensor and an optional IA humidity sensor.

NETWORKED SPACE HUMIDITY SENSOR CAPABILITY

A networked space humidity sensor can be interfaced with the Space
Humidity Input variable. When the Space Humidity Input variable is
used (valid value), it will automatically override the hard-wired space
humidity sensor (if present).
NETWORKED OUTDOOR HUMIDITY
SENSOR CAPABILITY
A networked outdoor humidity sensor can be interfaced with the
Outdoor Humidity Input variable. When the Outdoor Humidity Input
variable is used (valid value), it will automatically override the hard-
wired outdoor humidity sensor (if present).
CO DEMAND CONTROLLED VENTILATION (OPTIONAL)
2
Ventilation equipment typically uses fixed damper positions to
determine the amount of OA for proper ventilation within the space.
Most commonly, the fixed position of the OA damper is based upon the
maximum number of occupants the space is designed to accommodate.
This fixed OA damper operation however ignores the fact that most
spaces during the day have varying occupancy levels, and may only
rarely reach maximum design occupancy levels. This type of fixed
damper control for ventilation is energy wasteful as you are treating
OA not actually needed for ventilation during low occupancy levels.
People produce CO when they breath. The CO
2
has a direct relationship with the number of people within that space.
The UVC can optionally be factory configured to provide CO
Demand Controlled Ventilation (DCV). The CO
useful in saving the energy typically wasted in treating OA that is not
actually needed for ventilation within a space during occupancy levels
below maximum design. The CO
to adjust the OA damper above the minimum position as needed to
maintain the Space CO Setpoint (1200 PPM default). The minimum
2
damper position used with CO
minimum position that would be used without CO
should then provide enough ventilation to keep odors within the space
in check for most applications.
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EffectiveOutdoorEnthalpy <
(EconomizerOAEnthalpySetpoint –
EconomizerEnthalpyDifferential)
AND
EffectiveOutdoorTemp <
(EffectiveSpaceTemp –
EconomizerTempDifferential)
level within the space
2
DCV function is very
2
DCV function uses a PI-loop control
2
DCV can typically be set at 20% of the
2
DCV, this number
2
The CO DCV function can increase the OA damper position past
2
that required by the economizer and vice versa.
If odors within the space become a problem, increase the OA
damper minimum position as needed to eliminate these odors. It
may be necessary with new construction or after renovation to raise
the minimum position for some time period to help reduce odor
buildup due to the out-gassing of new construction material, and
then return the minimum OA damper position at a later date.
If the CO Demand Controlled Ventilation (DCV) option is used,
2
then the UVC will only use the IA fan high speed OA damper
minimum position regardless of fan speed, the DCV function will
adjust the OA damper above this minimum as needed.
NETWORKED SPACE CO
A networked space CO
Input variable. When the Space CO
value), it will automatically override the hard-wired space CO
(if present).

ASHRAE CYCLE II

The UVC supports ASHRAE Cycle II operation. The basis of ASHRAE
Cycle II is to maintain the required minimum amount of ventilation
whenever possible, which can be increased during normal operation
for economizer cooling or CO
to prevent excessively cold discharge air temperatures.
A discharge air temperature sensor is installed in all unit ventilators. If
necessary, the ASHRAE II control algorithm will override room
control and modify the heating, ventilating, and cooling functions (as
available) to prevent the discharge air temperature from falling below
the VCLL setpoint.

Compressor Operation

The UVC is configured to operate the compressor as secondary
(mechanical) cooling when the economizer is available, when the
economizer is not available and the compressor is available then the
UVC will use the compressor when cooling is required.

COMPRESSOR ENVELOPE

-based
2
The compressor envelope protects the compressor from adverse
operating conditions which can cause damage and or shortened
compressor life by ending compressor operation if coil temperatures
exceed the defined operating envelope.
For self-contained units, the UVC is configured to monitor both the
inside air refrigerant and outside air/refrigerant coil temperatures to
prevent compressor operation under adverse conditions.
For split-system units, the UVC will be configured at the factory to only
monitor the inside air/refrigerant coil as part of the compressor envelope
function.
NOTICE
NOTICE
NOTICE
SENSOR CAPABILITY
2
sensor can be interfaced with the Space CO
2
Input variable is used (valid
2
DCV control, but can also be reduced
2
2
sensor
2
OM 750