Honeywell T8090A User Manual
TRADELINE
and Heating-Cooling Thermostat,
®
T8090A Heating, Cooling,
Wallplate and Subbase
Preparation
Check thermostat and subbase (if used) suitability for
the heating, cooling, or heating/cooling system. Refer to
Table 1.
Assemble tools required: flat bladed screwdriver, hand
or power drill with 3/16 in. drill bit, wire cutter/stripper or
sharp knife, bubble level or plumb bob and line.
TABLE 1—SYSTEM COMPATIBILITY FOR NON-BATTERY POWERED THERMOSTATS.
Type of Heating System to be Controlled Conditions/Compatibility
Electric (Line Voltage)—Typical baseboard and
radiant
Fan Coil Unit • Compatible. Assure correct subbase identity selected for
Gas—Direct Spark Ignition (DSI), Intermittent
Pilot (IP), and Standing Pilot (SP)
Heat Pump • Compatible. Assure correct subbase identity is selected
Hot Water Zone • Honeywell 2-wire valves are compatible.
Oil • If not using battery backup, assure that the 24V control
Vent Damper • Honeywell damper motors are compatible.
Warm Air Zone • Most are compatible.
a
If thermostat is not compatible with the system being controlled, the system will not operate. No hazard exists. The thermostat
will not be damaged unless it is used to directly control a line voltage system. For proper system operation, a Honeywell R841
or R8239D1015 Isolating Relay must be added to the thermostat control circuit.
b
Cut the two black heat anticipator jumper wires before installing the thermostat. See Set Heat Anticipator section.
c
Consult manufacturer for installation requirements.
• The R8239D1015 Isolating Relay or R841 Silent
• Compatible. If not using battery backup, assure that the
• Some non-Honeywell 2-wire valves will require an
• Some 3-wire valves will require an R8239A1052
• Some non-Honeywell damper motors will require an
Assure power is off to the heating, cooling, or heating/
cooling system at the main fuse panel. Most buildings have
a separate switch box or circuit breaker for disconnecting
power to the heating and cooling (if applicable) equipment.
This thermostat is compatible with all heating, cooling or
heating/cooling systems when thermostat is powered by
batteries. If thermostat is not powered by batteries, refer to
Table 1 for thermostat and system compatibility information.
Switching Center must be installed in the thermostat
control circuit.
fan control.
24V control transformer common is accessible for
connection to thermostat cable conductor and power to
the transformer is not regularly interrupted by high
temperature or limit operation.
for fan control and changeover control (O terminal for
cool and B terminal for heat).
R8239D1015 Isolating Relay in the thermostat control
circuit.
Isolating Relay in the thermostat control circuit.
transformer common is accessible for connection to
thermostat cable conductor and power to the transformer
is not regularly interrupted by high temperature, purge
cycle, or limit operation.
R8239D1015 Isolating Relay in the thermostat control
circuit.
a,b
b
b
c
b
a,b
b
a
Check control amperage requirement.
b
a,c,b
b
c
D.F. • Rev. 10-94 • • ©Honeywell Inc. 1994 • Form Number 69-0750—1
1 69-0750—1
M3375
M3375
Recycling Notice
This control contains mercury in a sealed tube. Do not
place control in the trash at the end of its useful life.
If this control is replacing a control that contains mer-
cury in a sealed tube, do not place your old control in the
trash.
Contact your local waste management authority for
instructions regarding recycling and the proper disposal of
this control, or of an old control containing mercury in a
sealed tube.
If you have questions, call Honeywell Inc. at 1-800468-1502.
Installation
WHEN INSTALLING THIS PRODUCT…
1. Read these instructions carefully. Failure to follow
them could damage the product or cause a hazardous
condition.
2. Check the ratings given in the instructions and on
the product to make sure the product is suitable for your
application.
3. Installer must be a trained experienced service
technician.
4. After installation is complete, check out product operation as provided in these instructions.
CAUTION
1. Disconnect power supply to prevent electrical
shock or equipment damage.
2. Run wires as close as possible to the subbase.
To prevent interference with the thermostat
linkage, keep wire length to a minimum. Push
excess wire back into the hole and plug hole
to prevent drafts from affecting thermostat
operation.
3. Do not overtighten thermostat captive
mounting screws because damage to subbase
threads may result.
4. Do not short across coil terminals on relay;
this may burn out the heat anticipator.
LOCATION
Locate thermostat about 5 ft [1.5m] above the floor in an
area with good air circulation at average temperature. Do
not mount the thermostat where it may be affected by:
— drafts, or dead spots behind doors and in corners.
— hot or cold air from ducts.
— radiant heat from the sun or appliances.
— concealed pipes and chimneys.
— unheated (uncooled) areas behind the thermostat.
Run wires from the heating, cooling or heating-cooling
equipment to the new thermostat location.
The number of wires required to connect this thermostat
to the heating, cooling or heating-cooling equipment depends on how the thermostat is powered—by the 24 Vac or
battery, or through the control system. Refer to the Typical
Wiring Diagrams section to determine the number of wires
required for your application.
UNPACK THERMOSTAT
Handle your new thermostat carefully; rough handling
may interfere with its accuracy. Before unpacking, refer to
Fig. 1.
Remove and discard the shipping wrap.
IMPORTANT: Save package of screws and instructions
for the homeowner.
Fig. 1—Unpack thermostat.
THERMOSTAT
COVER
80
70
60
12
9
50
3
6
THERMOSTAT
BASE
CAPTIVE
MOUNTING
SCREWS
LIFT
COVER
M1518
Remove the thermostat cover by lifting from the bottom.
Set aside cover until needed later.
Carefully remove the material protecting the mercury
switch bulb.
Loosen two captive mounting screws and separate the
wallplate (if provided) from the back of the thermostat base.
MOUNT WALLPLATE OR SUBBASE
Wall Mounting (See Fig. 2)
Hold the wallplate or subbase in position on the wall.
See Fig. 2.
Mark holes on the wall for anchors. Use the spirit level
to make sure the wallplate or subbase is level.
Drill 3/16 in. holes and gently tap the anchors into the
holes until flush with the wall.
Pull wires through the large wiring hole in the wallplate
or subbase.
Loosely fasten the wallplate or subbase to the wall with
the three screws. Do not tighten the screws completely.
Carefully level the wallplate or subbase and firmly
tighten the screws. See Fig. 3.
Outlet Box Mounting (See Fig. 4)
Use a horizontally mounted outlet box if possible. If a
vertical outlet box is used, mount the wallplate or subbase
on a 193121A (beige) or 202689A (white) Cover Plate
Assembly (ordered separately). Follow the instructions
provided with the cover plate assembly.
Align wallplate or subbase mounting holes on the outlet
box and loosely fasten with two screws.
Carefully level the wallplate or subbase and firmly
tighten the screws. See Fig. 3.
69-0750—1 2
Fig. 2—Mounting wallplate or subbase to wall.
3 SCREW HOLES
WITH PLASTIC
ANCHORS
HEATING-ONLY
WALLPLATE
O
B
R
W
G
FAN
HEATING/COOLING SUBBASE
Fig. 3—Leveling methods
for wallplate or subbase.
Y
AUTO OFF
HEATON
COOL
PLUMB
BOB OR
WEIGHT
PLUMB
LINE
M1552A
FAN
O
R
G
AUTO OFF
Fig. 4—Mounting wallplate or subbase on horizontal outlet box.
3 SCREW HOLES
WITH PLASTIC
ANCHORS
SPIRIT LEVEL
B
W
Y
COOL
HEATON
M857
M1555
EXISTING
HORIZONTAL
OUTLET BOX
FAN
O
B
R
W
G
Y
AUTO OFF
HEATON
HEATING/
COOLING
SUBBASE
COOL
M1553A
VERTICAL
OUTLET
BOX
NOT INCLUDED WITH UNIT.
1
ACCESSORY PARTS AVAILABLE.
2
EXISTING
HORIZONTAL
OUTLET BOX
R
W
HEATING-ONLY
WALLPLATE
M856A
1
2
SUBBASE OR
WALLPLATE
ADAPTER
RING
MOUNTING
SCREWS (2)
COVER
PLATE
2
R
G
O
B
W
Y
M1554A
3 69-0750—1
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