Honeywell T8400C1099 Thermostat User Manual

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T8400C1099, T8401C1031

Electronic Thermostats

INSTALLATION INSTRUCTIONS

The T8400 and T8401 Thermostats provide single-stage,

non-programmable temperature control for 24V heating-

cooling systems with manual changeover from heat to

cool. Heating cycle rate is selectable at 1, 3, 4, 5, 6, 9, or

CAUTION

Electrical Shock or Equipment Damage

Hazard.

2 cph. Cooling cycle rate is fixed at 3 cph. Temperature

indication can be set for °F or °C.

Can shock individuals or short equipment

circuitry.

Disconnect power supply before installation.

The T8400 Thermostat is powered through the heating/

cooling system controls. The T8401 requires a common

wire for operation. Batteries are not required because

setpoints are held permanently by non-volatile memory.

Location

Install the thermostat about 5 ft (1.5m) above the floor in

an area with good air circulation at average temperature.

See Fig. 1. Do not install the thermostat where it can be

affected by:

The T8400 and T8401 models include a thermostat,

wallplate (for wiring and mounting thermostat) and

owner’s guide.

—

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 such as an outside wall

behind the thermostat.

MERCURY NOTICE

If this control is replacing a control that contains

mercury in a sealed tube, do not place your old

control in the trash.

This thermostat is a precision instrument and was

carefully adjusted at the factory. Handle it carefully.

Contact your local waste management authority

for instructions regarding recycling and the

proper disposal of an old control containing

mercury in a sealed tube.

Mounting Wallplate to Wall

IMPORTANT

Level only for appearance. The thermostat func-

tions normally even when not level.

INSTALLATION

Mount the T8400 and T8401 with the screws provided

(

see Fig. 2) as follows:

1. Place the wallplate at the desired location on the

wall.

2. Pull the thermostat wire through the entrance hole

on the wallplate.

3. Fasten the wallplate to the wall using the anchors

and screws provided.

4. After wiring the wallplate, plug the hole to prevent

drafts from affecting the thermostat; see Wiring

section.

When Installing this Product…

Read these instructions carefully. Failure to follow

them could damage the product or cause a hazard-

ous condition.

Check the ratings given in the instructions and on

the product to make sure the product is suitable for

your application.

Installer must be a trained, experienced service

technician.

After installation is complete, check out product

operation as provided in these instructions.

U.S. Registered Trademark

9-1484-2

T8400C1099, T8401C1031 ELECTRONIC THERMOSTATS

YES

FEET

[

1.5 METERS]

M11338

Fig. 1. Typical location of thermostat.

Wiring

WALL

ANCHORS (2)

IMPORTANT

Use an 18-gauge maximum wire to wire the

T8400 and T8401 Thermostats.

All wiring must comply with local electrical codes and

ordinances. Disconnect the power supply to prevent

electrical shock or equipment damage.

NOTE: To ensure proper mounting of thermostat,

restrict all wiring to the shaded area. See Fig. 4.

The shape of the terminals permits insertion of straight or

wraparound wiring connections; either method is

acceptable. See Fig. 5.

MOUNTING

SCREWS (2)

WALLPLATE

WHEN USING WALL ANCHORS, DRILL 3/16 INCH

HOLES FOR DRYWALL, 7/32 INCH HOLES FOR

Refer to Fig. 6 through 10 for typical wiring hookups.

PLASTER OR WOOD.

M12202A

Fig. 2. Mounting wallplate to wall.

Setting Fan Operation (Fuel) Switch

The fan operation (fuel) switch is preset at the factory in

the F position. See Fig. 3. This is the correct setting for

most systems. If this system is an electric heat system,

set the switch to the E position. The E setting allows the

fan to turn on immediately with the heating or cooling

equipment in a system where the G terminal is

connected.

FAN OPERATION (FUEL) SWITCH

M12580

Fig. 3. Fan operation (fuel) switch.

69-1484-2

T8400C1099, T8401C1031 ELECTRONIC THERMOSTATS

KEEP WIRING IN

SHADED AREA

COOLING

CONTACTOR

FAN

RELAY

HEATING

PRIMARY

CONTROL

(HOT)

24V

POWER SUPPLY. PROVIDE DISCONNECT MEANS AND

OVERLOAD PROTECTION AS REQUIRED.

FACTORY INSTALLED JUMPER.

M13275

Fig. 6. Typical hookup of T8400C1099 in heat-cool

system with single transformer.

MOUNTING

SCREW HOLE

WIRING ENTRANCE

HOLE

MOUNTING

SCREW HOLE

FAN

RELAY

COOL

DAMPER

HEAT

DAMPER

COMPRESSOR

CONTACTOR

HEAT

RELAY

(HOT)

HOT)

(

M16432

COOLING

TRANSFORMER

HEATING

TRANSFORMER

POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD

PROTECTION AS REQUIRED.

Fig. 4. Restrict wiring to shaded area

T8400C1099 shown).

(

REMOVE RC TO R JUMPER WHEN INSTALLED ON A TWO TRANSFORMER

SYSTEM.

FOR STRAIGHT INSERTION

STRIP 5/16 IN. (8 MM)

TERMINAL

SCREW

CAN BE USED FOR CHANGEOVER VALVE ON SINGLE-STAGE HEAT

PUMP SYSTEMS.

FOR WRAPAROUND

STRIP 7/16 IN. (11 MM)

POWER TO R TERMINAL IS REQUIRED WHEN THE SYSTEM SWITCH IS IN

THE OFF POSITION.

M12562A

Fig. 7. Typical hookup of T8400C1099 in heat-cool

system with two transformers.

HEAT

CHANGEOVER

COOL

CHANGEOVER

FAN

RELAY

HOT)

COMPRESSOR

(

24V

M13274

TRANSFORMER

POWER SUPPLY. PROVIDE DISCONNECT MEANS

AND OVERLOAD PROTECTION AS REQUIRED.

Fig. 5. Wiring connections

T8400C1099 shown).

(

CAN BE USED FOR CHANGEOVER VALVE ON

SINGLE-STAGE HEAT PUMP SYSTEMS.

FACTORY INSTALLED JUMPER.

FIELD INSTALLED JUMPER.

M20880

Fig. 8. Typical hookup of T8400C1099 in single-stage

heat pump systems.

69-1484-2

T8400C1099, T8401C1031 ELECTRONIC THERMOSTATS

DASHED LINES INDICATE TABS

ON BACK OF THERMOSTAT

HEAT

COOL

FAN

RELAY

(HOT)

24V

Auto On

FAN

TRANSFORMER

POWER SUPPLY. PROVIDE DISCONNECT MEANS

AND OVERLOAD PROTECTION AS REQUIRED.

Cool O

SYS Tf fE MH eat

M20881

Fig. 9. Typical hookup of T8401C1031 in heat-cool

system.

ENGAGE TABS AT TOP OF THERMOSTAT

WITH SLOTS ON MOUNTING PLATE.

HEAT

CHANGEOVER

COOL

CHANGEOVER

FAN

RELAY

HOT)

COMPRESSOR

FAN

uto On

(

24V

TRANSFORMER

Cool Off Heat

SYSTEM

POWER SUPPLY. PROVIDE DISCONNECT MEANS

AND OVERLOAD PROTECTION AS REQUIRED.

CAN BE USED FOR CHANGEOVER VALVE ON

SINGLE-STAGE HEAT PUMP SYSTEMS.

FIELD INSTALLED JUMPER.

M20882

Fig. 10. Typical hookup of T8401C1031 in single-

stage heat pump system.

PRESS LOWER EDGE OF

CASE TO LATCH.

M14677

Fig. 11. Mounting thermostat wallplate.

Mounting Thermostat to Wallplate

Engage the tabs at the top of the thermostat and

wallplate.

Swing down the thermostat and press the lower

edge of the thermostat onto the wallplate to latch.

See Fig. 11.

OPERATION

Setting FAN and SYSTEM Switches

Fan and system settings are controlled manually by

using the switches located at the bottom of the

thermostat case. See Fig. 12.

FAN Switch

Fan switch settings are:

On: The fan runs continuously. Use for improved air

circulation and air quality.

Auto: Normal setting for most homes. In cooling, the

fan starts and stops with the cooling equipment. In

heating, the fan is controlled directly by the heating

equipment and may start a few minutes after the

heating equipment turns on (on most systems).

When using an electric heat thermostat, the fan

starts and stops with the heating equipment.

Slide the FAN switch in the bottom left corner of the

thermostat to select the desired fan setting.

69-1484-2

T8400C1099, T8401C1031 ELECTRONIC THERMOSTATS

SYSTEM Switch

3. To increase the temperature setpoint press the ▼

key. Each press changes the setpoint one degree;

press and hold to change the setpoint several

degrees.

System switch settings control thermostat operation as

follows:

Cool: The thermostat controls the cooling system.

Off: Both heating and cooling are off.

Heat: The thermostat controls the heating system.

Slide the SYSTEM switch in the bottom right corner of

the thermostat to select the desired system setting.

M14681

To decrease the temperature setpoint press the ▼

key. Each press changes the setpoint one degree;

press and hold to change the setpoint several

degrees.

TEMPERATURE DISPLAY

INCREASE SETTING

DECREASE SETTING

M14682

Setting °F/°C Indication and Heat Cycle Rate

NOTE: To save changes to the °F/°C indication, the

heat cycle rate and the C3/C1 temperature

control, tap the ▼ key until exiting the installer

setup.

to On

To set the °F/°C indication, the heat cycle rate and the

C3/C1 temperature control:

SYSTEM

Cool Off Heat

1. If the temperature is displayed in °F, set the tem-

perature setpoint to 52°F. If the room temperature

is displayed in °C, set the temperature setpoint to

FAN SWITCH

M14678

SYSTEM SWITCH

11°C.

Fig. 12. Digital display and system

switches (FAN and SYSTEM).

M14683

Set Temperature Setpoint

OPTIONAL SYSTEM CHECKOUT

NOTE: Temperature setpoint range is 40° to 99°F (5° to

7°C).

When in steps 2 and 3 only, the ▼key can be used to

turn heat or cool outputs on and off. Change the

SYSTEM switch setting to test heat or cool outputs. No

action takes place If the system switch is in the Off

position.

The temperature setpoint and the room temperature are

shown separately on the digital display. The ▼indicator

points to Set when the temperature setpoint is displayed

and to Room when the room temperature is displayed.

Examples:System setting at HEAT: If heat is on, the ▼

key turns it off; if heat is off, ▼turns it on.

INDICATOR

ROOM TEMPERATURE

Set

Room

M14684

SETPOINT TEMPERATURE

M14679

System setting at COOL: If cool is on, ▼key

turns it off; if cool is off, ▼turns it on.

To set temperature setpoint:

Select Heat or Cool by sliding the SYSTEM switch

in the lower right corner of the thermostat to the

desired mode. See Fig. 12.

To display the temperature setpoint on the digital

display, press either the ▼ or ▼key once. The tem-

perature setpoint is displayed for approximately

five seconds as the indicator points to Set and

flashes.

M14685

Press the ▼▼keys simultaneously for more than

one second to light all segments on display and to

enter installer setup mode. When the keys are

released, a two-digit software revision code is dis-

played.

M14680

M14686

69-1484-2

T8400C1099, T8401C1031 ELECTRONIC THERMOSTATS

NOTE: In installer setup mode only, each press of the

Table 1. Heating Cycle Rates.

System Cycles Per Hour

Steam, gravity

▼

key momentarily displays 01. Each press of

the ▼key momentarily displays 02. When the

keys are released, these two-digit codes are no

longer displayed.

Hydronic heat, condensing gas

furnace^a

Press the ▼ key. Factory information is displayed.

A typical example is shown, but information dis-

played varies by model. This information is for fac-

tory use only.

Gas or oil forced air

Electric heat

_S_p_e_c_i_a_l_a_p_p_l_i_c_a_t_i_o_n_sb

4, 5, 12

High efficiency furnace.

Refer to equipment manufacturer’s instructions.

M14687

Press the ▼ key again to display °C or °F.

0. Press the ▼ key to save all changes, exit installer

setup mode and return to normal operation.

NOTE: After exiting installer setup mode, slide the

System switch to the desired position and

change the setpoint to the desired room

temperature.

M14688

Press the ▼key to change the °C or °F indication.

CHECKOUT

M14689

Press the ▼ key to display the heat cycle rate of 1,

, 4, 5, 6, 9, or 12. To change the heat cycle rate,

press the ▼key to scroll between 1, 3, 4, 5, 6, 9, or

2. Stop scrolling when the desired rate is dis-

Heating

Slide the SYSTEM switch to Heat and the FAN

switch to Auto.

played. See Table 1 for the cycle rate options and

the corresponding system equipment.

Press and hold the ▼ key to raise the temperature

setting several degrees above the room tempera-

ture. After approximately ten seconds, the heating

equipment should start. In conventional systems,

the system turns on the fan through the use of a

time delay relay or through a limit control. When

using an electric heat thermostat, the fan starts

immediately.

M14690

Press the ▼ key to display heating/cooling temper-

ature control default..

Press the ▼key to lower the temperature setting

below the room temperature. Heating equipment

should stop.

M18419A

Cooling

Press the ▼key again to change heating/cooling

temperature control to C1 or C3.

C1 = Standard heating/cooling temperature

control.

C3 = Aggressive heating/cooling temperature

control (can cause room temperature to

overshoot the setpoint).

CAUTION

Low Temperature Hazard.

Operating at too low of an outdoor

temperature may cause compressor damage.

Do not operate cooling if outdoor temperature is

below 50°F (10°C). Refer to manufacturer’s

recommendations.

Press the ▼ key again. Factory information (varies

by model) is shown.

•

For compressor protection, during power

interruption and on initial startup, the T8400

and T8401 Thermostats go into a five-minute

delay. During this delay, the cooling icon (a

snowflake ▼) flashes.

M18420

Slide the SYSTEM switch to Cool and the FAN

switch to Auto.

Press the ▼ key to lower the temperature setting

several degrees below the room temperature. After

approximately five minutes, the cooling equipment

should start. The fan starts and stops with the cool-

ing equipment.

69-1484-2

T8400C1099, T8401C1031 ELECTRONIC THERMOSTATS

Press the ▼ key to raise the temperature setting

above the room temperature. Cooling system

should shut down.

Fan

Slide the SYSTEM switch to Off and the FAN

switch to On. The fan should run continuously.

Slide the FAN switch to Auto. In heating, the fan is

controlled directly by the heating equipment and

may start a few minutes after the heating equip-

ment turns on (on most systems). When using an

electric heat thermostat, the fan starts and stops

with the heating equipment. In cooling, the fan

starts and stops with the cooling equipment.

NOTE: To bypass the five-minute delay, see the

Optional System Checkout section.

Be sure all equipment responds correctly to the

thermostat.

69-1484-2

T8400C1099, T8401C1031 ELECTRONIC THERMOSTATS

Automation and Control Solutions

Honeywell

985 Douglas Drive North

Golden Valley, MN 55422

Honeywell Limited-Honeywell Limitée

35 Dynamic Drive

Scarborough, Ontario

M1V 4Z9

69-1484-2 G.H. Rev. 11-02

Printed in Mexico

www.honeywell.com/yourhome

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