Honeywell t8424d Installation Instructions Manual

Page 1

Multistage Thermostat

The T8424 Thermostat provides electronic control of single-zone, multistage heating and cooling systems. First and second stage cooling cycle rates are fixed at 3 cph. Heating cycle rate is selectable. Temperature indication can be set for °F or °C.

The T8424 Thermostat is powered from the system transformer. Batteries are not required because setpoints are held permanently by non-volatile memory.

The T8424 includes a thermostat, wallplate (for wiring and mounting thermostat) and owner ’s guide.

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.

Contact your local waste management authority for instructions regarding recycling and the proper disposal of an old control containing mercury in a sealed tube.

If you have questions, call Honeywell Inc. at 1-800-468-1502.

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.

T8424D Electronic

INSTALLATION INSTRUCTIONS

CAUTION

Electrical Shock or Equipment Damage Hazard. Can shock individuals or short equipment circuitry.

Disconnect power supply before installation.

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: — 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.

This thermostat is a precision instrument and was carefully adjusted at the factory. Handle it carefully.

Mounting Wallplate to Wall

IMPORTANT

Level only for appearance. The thermostat functions normally even when not level.

Mount wallplate, T8424 and 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 decorator cover plate, then through the wallplate entrance hole.

3. Select the two mounting holes that best fit the application.

4. Fasten the wallplate to the wall using the anchors and screws provided.

5. After wiring the wallplate, plug the hole to prevent drafts from affecting the thermostat; see Wiring section.

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T8424D ELECTRONIC MULTISTAGE THERMOSTAT

Wiring

WALL

MOUNTING SCREWS (2)

WHEN USING WALL ANCHORS, DRILL 3/16 INCH HOLES FOR DRYWALL, 7/32 INCH HOLES FOR PLASTER OR WOOD.

WALL ANCHORS (2)

WALLPLATE

Fig. 2. Mounting wallplate to wall.

YES

5 FEET

[1.5 METERS]

Fig. 1. Typical location of thermostat.

The T8424 Thermostat is powered through the system transformer and is adaptable to most 24 Vac multistage heating-cooling systems. Refer to Fig. 5 for typical wiring hookups.

KEEP WIRING IN SHADED AREA

M12202A

M11338

IMPORTANT

Use an 18-gauge maximum wire for wiring the T8424 Thermostat.

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. 3.

The shape of the terminals permits insertion of straight or wraparound wiring connections; either method is acceptable. See Fig. 4.

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MOUNTING SCREW HOLE

WIRING ENTRANCE HOLE

Fig. 3. Restrict wiring to shaded area.

MOUNTING SCREW HOLE

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T8424D ELECTRONIC MULTISTAGE THERMOSTAT

TERMINAL SCREW

FOR STRAIGHT INSERTION STRIP 5/16 IN. (8 MM)

FOR WRAPAROUND STRIP 7/16 IN. (11 MM)

M20212

Fig. 4. Wiring connections.

T8424

L1 (HOT)

Fig. 5. Typical hookup of T8424 in two-stage heat and

two-stage cool system with manual changeover.

24V

POWER SUPPLY. PROVIDE DISCONNECT MEANS AND

OVERLOAD PROTECTION AS REQUIRED.

STAGE-TWO HEATING

STAGE-ONE HEATING

1ST STAGE COOLING

FAN RELAY

2ND STAGE COOLING

M20213

DASHED LINES INDICATE TABS ON BACK OF THERMOSTAT

YSTEM

Cool O

ff Heat

ENGAGE TABS AT TOP OF THERMOSTAT WITH SLOTS ON MOUNTING PLATE.

Cool Off Heat

PRESS LOWER EDGE OF

CASE TO LATCH.

Fig. 6. Mounting thermostat wallplate.

M14677

Mounting Thermostat to Wallplate

1. Engage the tabs at the top of the thermostat and wallplate.

2. Swing down the thermostat and press the lower edge of the thermostat onto the wallplate to latch. See Fig. 6.

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. 7.

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.

SYSTEM Switch

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.

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T8424D ELECTRONIC MULTISTAGE THERMOSTAT

TEMPERATURE DISPLAY

INCREASE SETTING

DECREASE SETTING

FAN

Auto On

SYSTEM

FAN SWITCH

SYSTEM SWITCH

Fig. 7. Digital display and system

switches (FAN and SYSTEM).

l O

ff H

M14678

Set Temperature Setpoint

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

37°C).

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 .

INDICATOR

ROOM TEMPERATURE

Room

Set

SETPOINT TEMPERATURE

To set temperature setpoint:

1. Select Heat or Cool by sliding the SYSTEM switch in the lower right corner of the thermostat to the desired mode. See Fig. 7.

2. To display the temperature setpoint on the digital display, press either the ▲ or ▼ key once. The temperature setpoint is displayed for approximately five seconds as the indicator points to Set and flashes.

M14679

4. To decrease the temperature setpoint press the ▼

key. Each press changes the setpoint one degree; press and hold to change the setpoint several degrees.

M14682

Setting °F/°C Indication and Heat Cycle Rate

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

heat cycle rate, all seven steps must be completed.

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

1. If the temperature is displayed in °F, set the temperature setpoint to 52°F. If the room temperature is displayed in °C, set the temperature setpoint to 11° C.

M14683

2. 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 displayed.

M14686

OPTIONAL SYSTEM CHECKOUT

When in steps 2 and 3 only, the 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.

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

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

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

turns it off; if coo l is off, ▼ turns it on.

▼

key can be used to

M14684

M14680

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.

M14681

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M14685

NOTE: In Optional System Checkout for multistage

models, pressing the ▼ key turns on the first stage output. (The second press of the ▼ key turns on the second stage output.)

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

▲ 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.

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T8424D ELECTRONIC MULTISTAGE THERMOSTAT

3. Press the ▲ key. Factory information is displayed.

A typical example is shown, but information displayed varies by model. This information is for factory use only.

M14687

4. Press the ▲ key again to display °C or °F.

M14688

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

M14689

NOTE: Steps 6-9 apply only to T8424 Thermostats.

6. Press ▲ to display number of cooling stages.

7. Press ▼ to change number of cooling stages.

M20208

M20207

8. Press ▲ to display number of heat stages.

M20209

9. Press ▼ to change number of heat stages.

11. Press the ▲ key to display algorithm configuration

default.

M18419

12. Press the ▲ key again to change algorithm to C1

or C3.

C1 = Standard algorithm. C3 = Aggressive algorithm (can cause

13. Press the ▲ key again. Current configuration (CC)

overshooting).

is displayed. A typical example is shown, but CC varies by model. (This information is for factory use only.)

M18420

Table 1. Heating Cycle Rates for Stage-Two Heating.

System Cycles Per Hour

Steam, gravity 1

Hydronic heat, condensing gas

furnace

Special applications

4,5

Gas or oil forced air (default) 6

Electric heat 9

Special applications

High efficiency furnace.

Refer to equipment manufacturer’s instructions.

14. Press the ▲ key to save all changes, exit installer

setup mode and return to normal operation.

NOTE: After exiting installer setup mode, change the

setpoint to the desired room temperature.

M20210

10. Press the ▲ key to display the heat cycle rate of 1,

3, 4, 5, 6, 9, or 12. (If the T8424 is set for two heat stages, both stages operate at the selected cycle rate.) If the desired cycle is d isplayed, press the ▲ key to exit the installer setup mode. To change the heat cycle rate, press the ▼ key to scroll between 1, 3, 4, 5, 6, 9, or 12. Stop scrolling when the desired rate is displayed. See Table 1 for the cycle rate options and the corresponding system equipment.

M18500

CHECKOUT

Heating

1. Slide the SYSTEM switch to Heat and the FAN switch to Auto.

2. Press and hold the ▲ key to raise the temperature setting several degrees above the room temperature. 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.

3. Press the ▼ key to lower the temperature setting below the room temperature. Heating equipment should stop.

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Cooling

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.

• For compressor protection, during power interruption and on initial startup, the T8424 Thermostat goes into a 5 minute delay. During this delay the cooling icon, a snowflake ❄, flashes.

1. Slide the SYSTEM switch to Cool and the FAN switch to Auto.

2. 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 cooling equipment.

3. Press the ▲ key to raise the temperature setting

above the room temperature. Cooling system should shut down.

NOTE: To bypass the 5 minute delay, see the Optional

System Checkout section.

Fan

1. Slide the SYSTEM switch to Off and the FAN switch to On. The fan should run continuously.

2. 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 equipment 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.

Make certain all equipment responds properly to the thermostat.

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