Thermostatic Controls - Central Boiler CL 4030 Owner's Manual

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. 26 for one
possible arrangement.
Fig. 26
Section 1 - Furnace Installation
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 line 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 building
(to prevent the water in the outdoor furnace from
freezing).
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