26
Thermostatic Controls
There are several methods for installing thermostatic
controls for this type of installation.
1. If the forced air furnace has connections for
control of the blower from a thermostat or switch,
the simplest method is to add a second 24-volt
thermostat. Wire the thermostat to the forced air
furnace so that upon a call for heat, the thermostat
closes the connection between power (usually 'R'
or red) and the fan terminal (usually 'G' or green).
By setting the new thermostat to the desired room
temperature, it will control when the blower
operates, drawing heat from the outdoor furnace.
The existing thermostat should be set a few degrees
below the new thermostat. This setting will be the
temperature at which the existing forced air heating
system will operate if the outdoor furnace is out of
fuel. Refer to Fig. 34 for one possible arrangement.
2. An alternative method is to install a line voltage
thermostat to control the blower on the forced air
furnace. In this installation, a 120-volt wire is run
from the thermostat to the forced air furnace. One
wire is connected to the hot (line feed) and the
other wire is connected to the forced air furnace
blower wire. A low water temperature switch may
be installed to shut off the blower if the temperature
of the water is too low. The switch is connected
in series to the wire coming from the line voltage
thermostat and must be installed so that it does not
affect the forced air system thermostat.
NOTE: If the low water temperature switch
is not installed, the fan will run continuously
even when the outdoor furnace is out of fuel.
This will keep the water in the outdoor furnace
approximately the same temperature as the air
in the house (to prevent the water in the outdoor
furnace from freezing). This will also work with
the thermostatic valve installed.
Fig. 34
RC
Y
B
O
RH
G
W
RC
Y
B
O
RH
G
W
FAN
TIME PRGM RUN HOLD
SYSTEM
COOL
ON AUTO
OFF HEAT
FAN
TIME PRGM RUN HOLD
SYSTEM
COOL
ON AUTO
OFF HEAT
Existing thermostats may vary in
style. This is an example
illustration only.
The additional thermostat is
set to a higher temperature
to allow the blower fan to run
without running the furnace.
NOTE
NOTE
Existing
Thermostat
(Heat-Cool)
(Heat Only)
Additional
Thermostat
24-Volt
Thermostat
(p/n 8200008)
To Existing
Furnace
NOTE
In order for this system
to operate properly, a
minimum of 3 wires are
required on the existing
thermostat. The "G"
terminal on the existing
thermostat must be
connected to the
furnace fan relay.
Wiring Diagram for p/n 8200008
(Forced Air Application)
Connect a wire from "R" on your existing thermostat to "R" on
the additional thermostat then connect a wire from "G" on your
existing thermostat to "W" on the additional thermostat.
This is one of several variations.
If air conditioning is present, a
temperature control should be
installed on the heat exchanger
manifold to provide an interlock
for the air conditioner. This
prevents the air conditioner from
operating when the water
temperature is higher than 140˚F.
Section 6 - System Installation
