WattMaster MUA II - Manual (Page 19)

Technical Guide
MUA II Controller
19
Sequence of Operations
Cool
This mode occurs when the controller reads an OAT one Cooling
Deadband above the Supply Air Setpoint and a Dewpoint Tempera-
ture below the Dewpoint Setpoint. The migration table for this mode
is shown below.
Condition Mode
Outside Dewpoint rises above the
Dewpoint Setpoint
Dehumidifi cation
OAT drops below the Cool Setpoint Vent
During this mode, the controller will maintain the SAT between a ±
Cooling Deadband from the Supply Air Setpoint. This is achieved
by activating and deactivating the stages of cooling.
Figure 19: Cool Mode Staging
Vent Mode
This mode occurs when the controller reads an OAT between the
Cooling and Heating Deadband from the Supply Air Setpoint and a
Dewpoint reading below the Dewpoint Setpoint. The migration table
for this mode is shown below.
Condition Mode
OAT falls below the Heat Setpoint Heat
OAT rises above the Cool Setpoint Cool
Dewpoint Temperature rises above
the Dewpoint Setpoint
Dehumidifi cation
During this mode, the controller will shut off heating and cooling, but
will allow the blower to continue its normal operation.
Dehumidifi cation Mode
This mode occurs when the controller reads a Dewpoint Temperature
above the Dewpoint Setpoint. The migration table for this mode is
shown below.
Condition Mode
OAT falls below the Heat Setpoint
and Dewpoint Temperature falls
below the Dewpoint Setpoint
Heat
OAT rises above the Cool Setpoint
and Dewpoint Temperature falls
below the Dewpoint Setpoint
Cool
Dewpoint Temperature falls below
the Dewpoint Setpoint
Vent
In this mode, the controller will use the Outside Enthalpy to calculate the
number of compressors needed to extract the moisture from the air. At the
same time, the Reheat Control will be active to avoid over-cooling.
Reheat Control
The controller can utilize a combination of different heating methods to
reheat the supply air during dehumidifi cation mode. The following is the
method the controller will use to try to reheat the supply air:
Dehumidifi cation Heat
You can elect to use the unit heating source to reheat the air dur-
ing dehumidifi cation or to supplement Hot Gas Reheat dehumid-
ifi cation control. If the HVAC unit is not equipped with Hot Gas
Reheat or the Hot Gas Reheat is not able to bring the Supply Air
Temperature to the desired setpoint, the MUA II Controller will
activate the heat source to maintain the Supply Air Temperature
Setpoint. The heat source can be either internal or external to the
HVAC unit.