I n s t a l l a t i o n , O p e r a t i o n , M a i n t e n a n c e
43
JE-Series
I s s u e D a t e :
M a y 1 0 , 2 0 2 1
T H E S M A R T S O L U T I O N F O R E N E R G Y E F F I C I E N C Y
Condenser Hot Water Reheat Option
Condenser Water Reheat Sequence of Operation
A heat pump equipped with condenser water reheat
can operate in three modes; cooling, cooling with reheat
(dehumidification), and heating. The cooling/heating
modes are like any other Johnson Controls WSHP. The
reversing valve (“O” signal) is energized in cooling, along
with the compressor contactor(s) and blower relay. In the
heating mode the reversing valve is de-energized. Almost
any thermostat will activate the heat pump in heating
or cooling modes. The DXM2 microprocessor board will
accept either heat pump (Y,O) thermostats or non-heat
pump (Y,W) thermostats. The reheat mode requires
either a separate humidistat/dehumidistat or a thermostat
that has an integrated dehumidification function for
activation. The DXM2 board is configured to work with
either a humidistat or dehumidistat input to terminal
“H”. Upon receiving an “H” input, the DXM2 board will
activate the cooling mode and engage reheat.There are
four operational inputs for single stage units and six
operational inputs for dual stage units:
- Fan Only
- 1st Stage Cooling
- 2nd Stage Cooling
- 1st Stage Heating
- 2nd Stage Heating
- Reheat Mode
• Fan Only:
A (G) call from the thermostat to the
(G) terminal of the DXM2 control board will bring
the unit on in fan only mode. 1st Stage Heating: A
simultaneous call from (G) and (Y1) to the (G) and (Y1)
terminals of the DXM2 control board will bring the unit
on in 1st Stage Heating.
• 1st Stage Cooling:
A simultaneous call from (G), (Y1),
(Y2), and (O) to the (G), (Y1), (Y2), (O/W2) terminals
of the DXM2 control board will bring the unit on
in 2nd Stage Cooling. When the call is satisfied at
the thermostat, the unit will continue to run in the
1st Stage Cooling until the 1st Stage Cooling call is
removed or satisfied, shutting down the unit.
• 2nd Stage Cooling:
A simultaneous call from (G),
(Y1), and (O) to the (G), (Y1), (O/W2) terminals of the
DXM2 control board will bring the unit on in 1st Stage
Cooling.
• 1st Stage Heating
: A simultaneous call from (G) and
(Y1) to the (G) and (Y1) terminals of the DXM2 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
DXM2 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 DXM2 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 condenser water reheat. When the DIP
switch on the DXM2 controller is set for ‘humidistat’
it reverses the control logic so that an “open” control
circuit initiates a reheat run cycle. If a humidistat is not
connected, or if a manual switch on the humidistat is
set to “off”, reheat will see the open circuit and call for
dehumidification.
System 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.
