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T8624C,D
SELECTION/APPLICATION
Selection/Application
The T8624 Thermostat uses the latest microelec-
tronic design and control technology to provide home
and building owners with the highest level of comfort
available and optimal energy savings in a package that is
easy to use and easy to live with.
The following section is a guide to selection and
application of the best thermostat to meet individual
needs.
PROGRAMMING
Does the thermostat selected accommodate the
customer’s daily schedule, lifestyle or work schedule?
Device Programming
Daily
Temperature
Selection
T8624C,D 5-1-1 (Mon-Fri,
Sat, Sun)
4 heat and
4 cool
T8621A,C,D 7-day (each
day different)
4 heat and
4 cool
T8600,01,02,03* 5-1-1 (Mon-Fri,
Sat, Sun)
4 heat and
4 cool
The choices are:
*Model not currently available to control multistage
equipment.
IF NEW CONSTRUCTION APPLICATION, CON-
SIDER:
• Equipment type (see manufacturer specifications).
—Staging required.
—System switching required.
—Fan switching required.
• Control wiring—number of conductors required
to operate equipment and thermostat.
IMPORTANT: The T8624 requires an additional con-
ductor to transformer common to provide continu-
ous 24V power for thermostat operation.
IF RETROFIT/REPLACEMENT APPLICATION,
CONSIDER:
• Equipment requirements.
—Staging (heat stages, cool stages).
—System switching (manual: HEAT-OFF-COOL;
automatic: HEAT-AUTO-COOL-OFF). Emer-
gency heat for heat pump application not pro-
vided on T8624.
—Fan switching; does fan come on automatically
from thermostat on cooling only (typical gas/
oil heating), or on call for cool and heat (typical
electric heat with single speed fan)?
• Existing wiring
—Are there enough conductors to operate the equip-
ment and the thermostat? Can a new cable be
pulled?
IMPORTANT: The T8624 requires an additional con-
ductor to transformer common to provide continu-
ous 24V power for thermostat operation.
SECURITY
Does the thermostat selected provide access to
Access
Typical
Application Device
Free access to
programming
and adjustment/
override.
Home or
owner-occupied
commercial
building.
T8624A,C,D
Restricted
access to
device.
Public
building.
T8624 with
TG512 Locking
Guard or
TG586A
Locking Cover.
programmming and the override features that will best
suit the application? The choices are:
SINGLE-STAGE HEAT PUMPS
If home/building owner has a single-stage heat pump,
one option is to use a T8624C or D (see Fig. 8).
The T8624C is a two-stage heating, one-stage cool-
ing programmable thermostat. The T8624D is a two-
stage heating, two-stage cooling programmable thermo-
stat. What both thermostats have in common is separate
W1 and W2 (first and second stage heat) terminals. In
both cases, the W1 can be used for changeover in heat-
ing.
For single-stage compressor applications (both first-
stage heating and first-stage cooling energized through
the Y terminal), simply jumper Y1 and W1.
Note that the recovery algorithm of the T8624 may
cause the compressor to cycle on and off during recov-
ery.
Although the cycle rate for the first stages of heat and
cool are set for hot water systems, the second stage of the
T8624 must be adjusted. Turn the cycle rate adjustment
screws to the hot water setting on both the T8624C and
D to achieve the cycle rate appropriate for heat pumps.
If changeover is utilized in the cooling mode, apply a
normally closed relay.
The above application should be used only on single-
stage heat pumps.