W A T E R - S O U R C E H E A T P U M P S
JRE-Series
R e v. : A u g u s t 1 9 , 2 0 2 0
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
16
Electrical – Low Voltage Wiring
Thermostat Connections -
The thermostat will be wired
to the DXM2 board located within the unit control box.
Refer to the unit wiring diagram for specific details.
Low Water Temperature Cutout Selection -
The DXM2
control allows the field selection of low water (or water-
antifreeze solution) temperature limit by clipping jumper
JW3, which changes the sensing temperature associated
with thermistor LT1. Note that the LT1 thermistor is
located on the refrigeravnt line between the coaxial heat
exchanger and expansion device (TXV). Therefore, LT1 is
sensing refrigerant temperature, not water temperature,
which is a better indication of how water flow rate/
temperature is affecting the refrigeration circuit.
The factory setting for LT1 is for systems using water
(30°F [-1.1°C] refrigerant temperature). In low water
temperature (extended range) applications with antifreeze
(most ground loops), jumper JW3 should be clipped as
shown in Figure 3 to change the setting to 10°F [-12.2°C]
refrigerant temperature, a more suitable temperature
when using an antifreeze solution. All Johnson Controls
WSHP units operating with entering water temperatures
below 60°F [15.6°C] must include the optional water/
refrigerant circuit insulation package to prevent internal
condensation.
Figure 3: LT1 Limit Setting
P1
Alarm
Relay
Comp
Relay
O
Y1
Y2
W
G
C
R
AL1
24Vdc
EH1
EH2
P6
R
C
Off On
JW3
A
OVR
ESD
C
R
NSB
AL2
JW1
Acc1
Relay
Acc2
Relay
H
COM
NC1
NO1
COM
NC2
NO2
P3
CO
RV
RV
LT1
LT1
LT2
LT2
LP
LP
HP
HP
P7
Status
Fault
R
R
CC
CCG
CO
S1
S2
1
12
1
4
Fa
cto
ry
U
se
(240Vac)
Com
N.O.
Fan Enable
5 1/2"
7"
6 1/2"
5"
Use 4 mounting screws
#6 sheet metal screw 1” long
1.5
3/8” standoff
Factory low
voltage Molex
connection for
unit harness
Factory low
voltage Molex
connection for
electric heat
harness
Micro
U1
Off On
P2
COH
COM
AO2
P11
Gnd T1
P10
T2 T2 T3 T3 T4 T4
T5
P9
T5 T6 T6
A0-1 A0-2
Off On
S3
RV
Relay
CCH
Relay
Test
P5
B-
Gnd
P4
A+ 24V
(240Vac)
Fan Speed
N.O.
N.C.
12V
OUT
Gnd
P8
IN
NC
P12
Note: There is only
one T1 connection
1 2 3 4
1 2 3 4 5 6 7 8
1 2 3 4 5 6 7 8
AO1 Gnd
1
DXM2 PCB
JW3-LT1 jumper should be clipped for low temperature
(antifreeze) operation
Accessory Connections -
A terminal paralleling the
compressor contactor coil has been provided on the
DXM2 control. Terminal “A” is designed to control
accessory devices. Note: This terminal should be used
only with 24 Volt signals and not line voltage. Terminal “A”
is energized with the compressor contactor.
The DXM2 controller includes two accessory relays ACC1
and ACC2. Each relay includes a normally open (NO) and
a normally closed (NC) contact. Accessory relays may be
configured to operate as shown in the tables below.
