Page 20 / IM 742
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 cir-
cuit that only requires a set of dry contacts for operation.
The contacts shown on the Boilerless System board (ter-
minals 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
temperature 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).
Boilerless System Kit (BSK) – P/N 062522204 for sizes 007 - 070
RD
1
2
3
Auxiliary Relay
Orange
Yellow
White
1 2 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
Signal to remote
duct heater
control circuit
F L W1 V
Mark IV Board Terminals
9.66
(245 mm)
(007 – 042)
14.50
(368 mm)
(048 – 060)
6.5 (165 mm) (007 – 042)
4.12 (105 mm) (048 – 060)
1.75
(44.5 mm)
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 cir-
cuit.
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 func-
tions 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.
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).
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