Mount Thermostat; Temperature Setting - Honeywell T874 Quick Start Manual

MOUNT THERMOSTAT

1. Remove the thermostat cover by pulling the bottom
edge of the cover upward until it snaps free of the mount-
ing slots.
NOTE: The cover is hinged at the top and must be removed
by pulling up at the bottom.
2. Carefully remove and discard the polystyrene packing
insert that protects the mercury switches during shipment.
3. Turn over thermostat base and note the spring fingers
that engage the subbase contacts. Make sure the spring
fingers are not bent flat, preventing proper electrical con-
tact with the subbase.
4. Note the two tabs on 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 ther-
mostat base with the posts on the subbase. See Fig. 10.
Tighten both screws. Do not overtighten screws or damage
to subbase posts can result.
Fig. 10—Mounting thermostat on subbase.
THERMOSTAT
MOUNTING SLOTS (2)
SUBBASE
THERMOSTAT
M936
INSTALL OR REMOVE TG504A KEY LOCK
COVER
To install the TG504A:
—hang the upper edge of the cover on the thermostat
subbase.
—swing cover downward.
Spring-loaded locking mechanism will automatically
engage mounting posts and secure cover in final position
without use of key provided.
To remove the TG504A:
— insert the key provided.
— rotate the key clockwise until locking mechanism
releases from thermostat posts.
— swing cover upward and off.
THERMOSTAT
MOUNTING POST (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
CAPTIVE MOUNTING
SCREWS (2)
SET THE HEAT ANTICIPATOR
Move the indicator to match the current rating of the
primary control. See Fig. 11. When using the T874 Ther-
mostat with two stages of heating, set each heat anticipa-
tor to match its respective primary control current draw. If
you cannot find the current rating on the primary control,
or if further adjustment is necessary, see NOTE below and
use the following procedure to determine the current draw
of each stage.
The current draw of each heating stage must be mea-
sured with the thermostat removed and the power on to the
heating system.
1. Connect an ac ammeter of appropriate range between
the heating terminals of the subbase:
Stage 1—between W
Stage 2—between W
2. Move the system switch to HEAT or AUTO.
3. After one minute, read the ammeter and record the
reading:
Stage 1—__________ amperes.
Stage 2—__________ amperes.
4. After mounting the thermostat, set the adjustable
heat anticipator to match the readings measured in Step 3.
NOTE: If equipment cycles too fast, set the indicator to a
higher current rating, not more than one-half division at
a time, and recheck cycle rate. Most conventional two-
stage heating equipment is designed to operate at three
cycles per hour per stage and one-stage heating equip-
ment at six cycles per hour, at 50 percent load condition.

TEMPERATURE SETTING

Move the heating and cooling setpoint levers to the
desired comfort positions. See Fig. 12. One lever controls
all stages of heating, and the other lever controls all stages
of cooling. The minimum differential between heating and
cooling setpoint is 3° F [1.7° C], which means the setting
levers are designed so they cannot be set closer together
than 3° F [1.7° C].
Fig. 11—Adjustable heat anticipator scales.
1.2.8
STAGE TWO
ANTICIPATOR
HEATING CONTROL
4
Settings
and R ;
1 H
and R .
2 H
STAGE ONE
ANTICIPATOR
HEATING CONTROL
MOVE INDICATOR TO
MATCH CURRENT RATING
OF PRIMARY CONTROL
M5069