User Guide
42
Design Guide - HZH/HZV Series
ClimaDry
®
II - Sequence of Operation
1st Stage Heating: A simultaneous call from (G) and (Y1)
to the (G) and (Y1) terminals of the DXM control board
will bring the unit on in 1st stage Heating.
2nd Stage Heating: A simultaneous call from (G), (Y1),
and (Y2) to the (G), (Y1), and (Y2) terminals of the
DXM control board will bring the unit on in 2nd Stage
Heating. When the call is satisfied at the thermostat
the unit will continue to run in 1st Stage Heating until
the call is removed or satisfied, shutting down the
unit. NOTE: Not all units have two-stage heating
functionality.
Reheat Mode: A call from the Humidistat/Dehumidistat to
the (H) terminal of the DXM control board will bring the
unit on in Reheat Mode if there is no call for cooling at
the thermostat. When the Humidistat/Dehumidification
call is removed or satisfied the unit will shut down.
NOTE: Cooling always overrides Reheat Mode. In the
Cooling mode, the unit cools and dehumidifies. If the
cooling thermostat is satisfied but there is still a call for
dehumidification, the unit will continue to operate in
Reheat Mode.
Note: Care must be taken when using a humidistat
to operate ClimaDry
®
. When the DIP switch on the
DXM controller is set for ‘humidistat’ it reverses the
control logic so that an “open” control circuit initiates
a ClimaDry
®
run cycle. If a humidistat is not connected,
or if a manual switch on the humidistat is set to
“off”, ClimaDry
®
will see the open circuit and call for
dehumidification.
ClimaDry
®
II Component Functions
The ClimaDry
®
II option consists of the following components:
Motorized Valve/Proportional Controller
Supply Air Sensor
Loop Pump
Hydronic Coil
Low Air Temperature Safety
The Proportional Controller operates on 24 VAC power
supply and automatically adjusts the water valve based
upon the Supply Air Sensor. The Supply Air Sensor senses
supply air temperature at the blower inlet providing the
input signal necessary for the proportional control to drive
the motorized valve during the reheat mode of operation.
The Motorized Valve is a proportional actuator/three-way
valve combination used to divert the condenser water
from the coax to the hydronic reheat coil during the reheat
mode of operation. The proportional controller signals the
motorized valve based on the supply air temperature of the
supply air sensor.
The Loop Pump circulates condenser water through the
hydronic reheat coil during the reheat mode of operation.
In this application, the loop pump is only energized during
the reheat mode of operation. The Hydronic Coil is utilized
during the reheat mode of operation to reheat the air to
the setpoint of the proportional controller. Condenser
water is diverted by the motorized valve and pumped
through the hydronic coil by the loop pump in proportion
to the control setpoint. The amount of reheating is
dependent on the setpoint and how far from setpoint
the supply air temperature is. The factory setpoint is 72°F
[22°C], generally considered “neutral” air.
ClimaDry
®
II Application Considerations
The reheat coil adds a small amount of resistance to the
air stream. Consult the submittal data or the Installation/
Operation/Maintenance (I.O.M.) manual for the specic
heat pump to review blower tables.
Unlike most hot gas reheat options, the ClimaDry
®
II
option will operate over a wide range of EWTs. Special ow
regulation (water regulating valve) is not required for low
EWT conditions.
Unit mimimum entering air temperature while in the
dehumidication, cooling, or continuous fan modes is 65ºF
DB/55ºF WB. Operation below this minimum may result in
nuisance faults.
Water-source heat pumps with ClimaDry
®
II should not be
used as make-up air units. These applications should use
equipment specically designed for make-up air.