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2. Firmly tighten each terminal screw.
3. Fit wires as close to the subbase as possible. Push
excess wire back into hole.
4. Plug hole with nonflammable
insulation to prevent
drafts from affecting the thermostat.
Fig. 6-Wiring
conneciions.
MOUNTING
THE THERMOSTAT
1. Remove the thermostat cover by pulling the bottom
edge of the cover upward
until it snaps free of the
retaining posts.
NOTE: The covar is hinged at the top and must be
removed by pulling up at the bonom.
2. Carefully
remove
and discard
the polystyrene
packing
insert which
protects the mercury
switches
during shipment.
3. Turn the thermostat base over and note the spring
fingers which engage the subbase contacts. Make sure
the spring fingers are NOT bent flat, preventing proper
electrical contact with the subbase.
4. Note the tabs along the top inside edge of the
thermostat base. The tabs fit into corresponding
slots on
top of the subbase. Mount the thermostat on the subbase.
5. Align
the two captive
mounting
screws
in the
thermostat base with the oosts on the subbase fFia. 7).
Tighten both screws. DO NOT OVERTIGHTEN SCREWS
or damage to subbase posts may result.
t
:ig. 7-Mounling
thermostat
on subbase
(T874R
shown).
SETTING
TEMPERATURE
SETTING
COOL-cooling
system is controlled by the thermo-
On the T874G, move the heating and cooling set point
stat. Heating system is off.
levers to the desired positions. The minimum differential
AUTO
(T874G
only)-thermostat
automatically
between heating and cooling set points is 3 F [1.7 C]. On
changes between
heat
and cool modes, depending
the T874R one lever controls both heating and cooling.
upon the indoor temperature.
SUBBASE
SETTING
System switching
positions
control thermostat oper-
ation as follows:
EM. HT.-emergency
heating system is energized.
Red EM. HT. LED on subbase is on. Cooling system
is off.
HEAT-heating
system is controlled by the thermo-
stat. Cooling system is off.
OFF-both
the heating and cooling systems are off.
Fan switching
positions
control
fan operation
as
follows:
ON-fan
operates continuously.
AUTO-fan
operates with equipment as controlled by
the thermostat.
To switch positions, usethumband
indexfingertoslide
lever to desired position. Switch lever must stop in detent
directly over desired function indicator mark for proper
circuit operation.
CHECKOUT
HEATING
Move the system switch on the subbase to HEAT and
the fan switch to AUTO. Move the heating set point lever
on the thermostat about 10 F [56 C] above room temper-
ature. Heating should start, providing there is no time
delay or outdoortemperature
limiting system, and the fan
should run after a short delay. Move the heating set point
lever about 10 F [56 C] below room temperature. The
heating equipmentshould
shutoff, and
the
fan should run
for a short time, then shut off.
Move the system switch on the subbase to COOL.
Move the cooling set point lever on the thermostat about
10 F [56
C] below
room temperature.
The cooling
equipment and fan should start. Move the cooling set
point lever about 10 F [5.6 C] above room temperature.
The cooling equipment and fan should stop.
NOTE: On the T874R, the same lever controls
both
heating and cooling.
COOLING
below 50 F [lo Cl. Refer to manufacturer's
recom-
Move the subbase system switch to OFF, and the fan
switch to ON.
The
fan should run continuously. When the
is in the AUTO position, fan operation
is
controlled by the heating or cooling system.
4
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