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Honeywell T874H Installation Instructions Manual page 2

Multistage thermostats and subbases

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T874H,Q,W MULTISTAGE THERMOSTATS AND Q674B,C,G,L SUBBASES
CAUTION
1.
Disconnect the power supply to prevent
electrical shock or equipment damage.
2.
Run the wires as close as possible to the
subbase. To prevent interference with the
thermostat linkage, keep the wire length to a
minimum. Push the excess wire back into the
hole, and plug the hole to prevent drafts from
affecting the thermostat operation.
3.
Do not tighten the thermostat captive mount-
ing screws to the point of damaging the
subbase threads.
4.
Do not short across the coil terminals on the
relay. This can burn out the heat anticipator.
5.
Never install more than one wire per terminal
unless a factory-supplied jumper with a spade
terminal is used.
IMPORTANT
These thermostats are calibrated at the factory
by using subbases mounted at true level.
Inaccurate subbase leveling causes thermostat
control deviation.
Location
Install the thermostat about 5 ft (1.5m) above the floor in
an area with good air circulation at average temperature.
Do not install the thermostat where it can be affected by:
— drafts, or dead spots behind doors and in corners.
— hot or cold air from ducts.
— radiant heat from sun or appliances.
— concealed pipes and chimneys.
— unheated (uncooled) areas behind the thermostat
such as an outside wall.
Mounting and Wiring the Subbase
Mount the subbase on a wall or horizontal outlet box. If
you mount it on a vertical outlet box, order Honeywell part
no. 193121A Adapter Assembly, which includes an
adapter ring with two screws, and a cover plate to cover
the marks on the wall.
All wiring must comply with local electrical codes and
ordinances. Follow the equipment manufacturer wiring
instructions, when available.
To install the subbase:
Prepare a hole for the thermostat wires at the
chosen location. Run wires to the location.
Pull about 6 in. (152 mm) of wire through the hole.
IMPORTANT
Use 18 gauge, color-coded thermostat cable for
proper wiring.
When mounting the subbase on a vertical outlet box,
install an adapter ring with the two screws provided
with the adapter assembly. See Fig. 1.
Pull the wires through the cover plate (if used) and
the subbase wire opening. Secure the cover plate
and subbase with the two screws provided, but do
not fully tighten.
The subbase mounting slots provide for minor out-
of-level adjustments. Level the subbase by using a
spirit level and tightening the subbase mounting
screws. See Fig. 2.
69-0087—6
1
HORIZONTAL
OUTLET
BOX
SUBBASE
SUBBASE
MOUNTING SCREWS (2)
CAPTIVE
MOUNTING SCREWS (2)
1 NOT INCLUDED WITH UNIT.
2 ACCESSORY PARTS AVAILABLE (193121A).
Fig. 1. Installation on vertical or horizontal outlet box.
TOP
MOUNTING
HOLES (2)
SPIRIT LEVEL
MOUNTING
HOLES (2)
Fig. 2. Leveling subbase.
Connect the system wires to the subbase. See Fig.
4 through 9. A letter code for identification is
located near each terminal. The terminal barrier
permits straight or conventional wraparound wiring
connections. See Fig. 3. Either method is accept-
able. Run the wires as close as possible to the
subbase, keeping the wire length to a minimum.
Push the excess wire back into the hole. Plug the
hole to prevent drafts.
IMPORTANT
An incorrectly leveled subbase causes the
temperature control to deviate from the setpoint.
2
VERTICAL
MOUNTING
OUTLET
SCREWS (2)
1
BOX
ADAPTER
RING
2
O L
C O
8 0
7 0
6 0
5 0
8 0
7 0
6 0
5 0
A T
H E
6 0
5 0
THERMOSTAT
WIRING
CABLE OPENING
TERMINAL
POST (2) FOR
TO SPRING FINGER
MOUNTING
CONTACTS ON THE
THERMOSTAT
THERMOSTAT
(UP TO 12)
COVER
PLATE
2
THERMOSTAT
THERMOSTAT
COVER
8 0
7 0
M6009
M927

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