LOW VOLTAGE CONNECTIONS
HEAT PUMP APPLICATION
FIGURE 11
Comfort Plus Hydronic 12 Position Low Voltage Terminal Block Coding
R = Low Voltage Hot
C = Low Voltage Common
Y = Compressor/Stage 1 Heat Call
W = Stage 2 Heat Call
Y2 = Compressor Output
G = Fan Call
O = Reversing Valve Input
O2 = Reversing Valve Output
H= Hydronic Heat
OS = Outdoor Temperature Sensor
SC = Temperature Sensor Common
DS = Duct Temperature Sensor
Wiring:
Route low voltage wire from the outdoor
sensor to the electrical compartment
through one of the low voltage wire
knockouts.
Connect to "OS" and "SC" as shown in
Figure 11-13.
If the sensor wiring is routed through an
external wall, the opening through which the wire is routed MUST be sealed. Failure to
do so may affect the accuracy of the outdoor temperature sensor.
The outdoor sensor is supplied with a lead length of 40 ft. If a greater wire length is
needed, it can be extended to a total of 250 ft.
No other loads can be controlled or supplied through this cable. It is for connection of the
outdoor sensor ONLY.
This low voltage cable MUST not enter any line voltage enclosure.
Unshielded Class II (thermostat) wire can be used as extension wire provided it is segre-
gated from any line voltage cabling.
LOW VOLTAGE ELECTRICAL CONNECTIONS - ROOM
THERMOSTAT
A low voltage (24VAC) room thermostat is required for room temperature control with the Comfort Plus Hy-
dronic system. Steffes recommends using a digital thermostat. If utilizing a mechanical thermostat, a load resistor
may be necessary due to the low current draw (.01 amps) on the heat call input circuit of the Comfort Plus
system. Contact the factory for information on thermostats available from Steffes.
IMPORTANT
Outdoor sensor wire MUST NEVER be
combined with other control wiring in a
multi-conductor cable.
12 Position Terminal Block
H
Y2
R
Y
C
O O2
G
W
Optional Freeze Protection
RS
OS SC
Room Sensor
Honeywell TH5220D
Aux
E
L
C
G O/B
Hydronic Heat Thermostat, Zone
Valve, End Switch, or Pump Control
W
R
Y
R
c
R
C - Low Voltage Common
Outdoor Sensor
R - Low Voltage Hot
O - Reversing Valve
Y - Compressor
To Heat Pump
In
st
al
la
ti
on
Installation
3.09
Comfort Plus Hydronic
Low voltage wires MUST never enter
any line voltage enclosure.
IMPORTANT
