JRE-Series
R e v. : A u g u s t 1 9 , 2 0 2 0
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
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
31
Condenser Hot Water Reheat – Sequence of Operation, Cont’d.
• 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 (e.g. JRE036-072 units).
• 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.
JRE Component Functions
• Motorized Valve/Proportional Controller
• Supply Air Sensor
• Loop Pump
• Hydronic Coil
• Low Pressure Switch
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.
Application Considerations
The reheat coil adds a small amount of resistance to the
air stream. In some cases the high static option may be
required for applications with higher static ductwork.
Consult the submittal data or the Installation/Operation/
Maintenance (I.O.M.) manual for the specific heat pump to
review blower tables.
Unlike most hot gas reheat options, the condenser hot
water reheat option will operate over a wide range of
EWTs. Special flow regulation (water regulating valve) is
not required for low EWT conditions.
JRE units with the condenser hot water reheat option
shall have an antifreeze solution to protect the coil in low
ambient conditions. ASHRAE minimums for the region
shall be considered during the calculation of the antifreeze
solution.
In applications where antifreeze is not specified, a
secondary heat exchanger can be used to isolate the
JRE from the water loop, thus requiring less antifreeze
to be used with the JRE Secondary brazed plate heat
exchanger.
Water-source heat pumps with condenser hot water
reheat should not be used as make-up air units.
These applications should use equipment specifically
designed for make-up air.
