Page 20 / IM 778
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 enclo-
sure with cover, wire harness, boilerless system board, aux-
iliary 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 tem-
perature 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.
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 thermo-
stat (not included).
Boilerless System Kit (BSK) – P/N 062522204 for sizes 007 - 060
RD
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
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)
