Boilerless System Kit (BSK)
P/N 062522204 for sizes 070 - 108 and 121 & P/N 0061251501 for sizes 180, 215 and 290
The BSK option for use with the Mark IV/AC control board
provides the capability to control a remote duct heater. The
duct heater must be provided with a low voltage control
circuit that only requires a set of dry contacts for operation.
The contacts shown on the Boilerless System board (termi-
nals 1, 2, and 3) are used to control the remote duct heater,
the N.O. contacts will close on a call for duct heater heat.
POT1 provides a means to manually adjust the water tem-
perature setpoint (adjustment range is 43
O
F to 60
O
F). The
Normal/Override switch provides a means to manually force
electric heat to always be used in place of heat pump heat
when in the override position (default position is normal - heat
pump heat).
When the water temperature drops below the value of POT1,
then the duct heater will be used instead of heat pump heat
on a call for heat from the low voltage thermostat (not
included).
The BSK field installed kits include the sheet metal enclosure
with cover, wire harness, boilerless system board, auxiliary
relay, and water temperature sensor. When used, one BSK is
required for each unit. To use the BSK kit you attach the sheet
metal enclosure to the unit as shown, route the 4-wire
harness through knockouts and connect to the Mark IV/AC
board, mount and connect and insulate the water tempera-
ture sensor on the water supply line, and then connect the
duct heater control contacts to the duct heater control
circuit.
If night setback (U-terminal) is used, the duct heater will
respond to the occupied W1 thermostat signal. The load
shed input (L-terminal) cannot be used for other control
functions when being used with the BSK.
The BSK is a DC voltage device, when the BSK is used the
thermostat must be wired for VDC operation, one example is
provided below. This example is for a 2-circuit WSHP, R1 is
a field supplied 24vdc relay. R1 is not required on 1-circuit
units.
Control Box
Boilerless System Kit
Page 20 / IM 439
RD
WSHP Mark IV/AC Board Low Voltage Terminal Strip
1
2
3
Auxiliary Relay
Orange
Yellow
White
12
3
4
5
RD
BR
WH
OR
OR
WH
WH
YE
GR
GR
BK
WH
RD
OR
Normal
Override
Pot 1
Boilerless
System
Board
43 Ohm
4-pin
Plug
Water
Temperature
Sensor
Wire Ends to be Field
Connected to the
Mark IV/AC Board
Signal to remote
duct heater
control circuit
O
W2 G W1 Y1
F
E
L
U
A
P
V
R
C
Thermostat T
erminals
WSHP Mark IV/AC Board Low
Voltage Terminal Strip
Strip
RC
W
1
Y1
W2
Y2
G
O
W2 G W1 Y1
F
E
L
U
A
P
V
R
C
WSHP Mark IV/AC Board Low
Voltage Terminal Strip
Strip
OR
BR
RD
WH
R1
+
43 Ohm
R1
Wire ends
from
Boilerless
System Kit
