Honeywell T8400C Product Data
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Honeywell T8400C Product Data

Electronic thermostats
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See also: Owner's Manual , Instruction and Installation Manual

APPLICATION

The T8400C and T8401C Standard Electronic Thermostats
provide single-stage, non-programmable temperature control
for 24V heating-cooling systems with manual changeover
from heat to cool.
The T8424C Electronic Multistage Thermostat provides two-
stage heat and one-stage cool control.
The T8424D Electronic Multistage Thermostat provides two-
stage heat and two-stage cool control.
® U.S. Registered Trademark
Copyright © 2001 Honeywell • All Rights Reserved
T8400C, T8401C and T8424C,D
Electronic Thermostats
T8400C and
T8401C
T8424C,D

FEATURES

• Attractive styling complements any decor to the
homeowner's delight.
• Ease-of-use means fewer homeowner questions and
increased homeowner satisfaction.
• Large display for quick easy readability.
• Conveniently sized 3-1/2 x 3-1/2 thermostat with
optional decorator cover plates (3-7/8 in. x 3-7/8 in. and
5-3/4 in. x 5-3/4 in.) makes it easy to install in a variety
of locations.
• Keys are located for easy access.
• Fan and system switches are located on the lower
edge to eliminate accidental setting changes.
• Easy installation, setup and self-test saves time and
increases installer productivity.
• Manual changeover from heat to cool eliminates
unexpected system operation.
• °F or °C temperature display for added model
flexibility.
• Selectable heating cycle rate (1, 3, 4, 5, 6 or 9, 12 cph)
for a variety of applications which reduces the amount
of inventory.
• Cooling cycle rate is fixed (3 cph), the standard setting
for compressors, for speedy installation.
• Setpoints are permanently held in memory (no
batteries used) and retained during power outages for
increased installer and homeowner convenience.
• Power stealing and hard wired models available for
virtually all equipment and application needs including
gravity or radiating systems, hydronic heat,
condensing gas furnaces, gas or oil forced air and
electric heat.
Application ........................................................................
Features ...........................................................................
Specifications ...................................................................
Ordering Information ........................................................
Installation ........................................................................
Settings and Adjustments .................................................
Operation .......................................................................... 10
Checkout .......................................................................... 12
Troubleshooting ................................................................ 13
PRODUCT DATA
Contents
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68- 0180-3

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Summary of Contents for Honeywell T8400C

  • Page 1: Table Of Contents

    APPLICATION • Cooling cycle rate is fixed (3 cph), the standard setting for compressors, for speedy installation. The T8400C and T8401C Standard Electronic Thermostats provide single-stage, non-programmable temperature control • Setpoints are permanently held in memory (no batteries used) and retained during power outages for for 24V heating-cooling systems with manual changeover increased installer and homeowner convenience.

  • Page 2: Specifications

    3-7/8 in. and 5-3/4 in x 5-3/4 in.), and owner’s guide. Steam, gravity Power: Hydronic heat, condensing T8400C: 24 Vac nominal, 18 to 30 Vac, 50/60 Hz. gas furnaces T8401C: 24 Vac nominal, 18 to 30 Vac, 50/60 Hz. T8424C,D: 24 Vac nominal, 18 to 30 Vac, 50/60 Hz.

  • Page 3: Installation

    T8400C, T8401C AND T8424C,D ELECTRONIC THERMOSTATS THERMOSTAT WALLPLATE THERMOSTAT AND WALLPLATE 2-7/8 (78) 3-1/2 (89) 1-3/16 (55) 2-1/2 (64) 1-1/2 (37) 2-7/8 3-1/2 (78) (89) Room SYSTEM Cool Off Heat Auto On M10283A Fig. 1. T8400/T8401 Thermostat dimensions in in. (mm).
  • Page 4 ANCHORS (2) covering wall marks). Mount decorator cover plate (SUPER TRADELINE® model only), wallplate, T8400C, T8401C or T8424C,D, and the screws provided (see Fig. 4 or 5) as follows: 1. Place the desired decorator cover plate and the wall- plate at the desired location on the wall.
  • Page 5 T8400C, T8401C AND T8424C,D ELECTRONIC THERMOSTATS WALL KEEP WIRING IN WALL SHADED AREA ANCHORS (2) MOUNTING WALLPLATE SCREWS (2) WHEN USING WALL ANCHORS, DRILL 3/16 INCH HOLES FOR DRYWALL, 7/32 INCH HOLES FOR PLASTER OR WOOD. M12202A Fig. 5. Mounting the T8424 wallplate to wall.
  • Page 6 Fig. 11. T8400C/T8401C heat-cool wiring diagram in oil heating/electric cooling system. Oil primary has its own transformer. M20212 Fig. 9. T8424 wiring connections. The T8400C Thermostats steal power through the heating T8424 and cooling system controls and are adaptable to most 4-wire, STAGE-ONE HEATING 18 to 30 Vac heating-cooling systems.
  • Page 7 USE ONE R8239 FOR EVERY FOUR ZONES. MOTOR M10285A Fig. 13. T8400C/T8401C heat only wiring diagram for controlling incompatible or 3-wire zone valves or dampers. Heating equipment is operated by end switch on the zone valve or motor, or by thermostat in master zone. T8400C, T8401C...

  • Page 8: Settings And Adjustments

    T8400C, T8401C AND T8424C,D ELECTRONIC THERMOSTATS SETTINGS AND ADJUSTMENTS 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 Setting Fan and System Switches the thermostat onto the wallplate to latch.
  • Page 9 T8400C, T8401C AND T8424C,D ELECTRONIC THERMOSTATS most systems). When using an electric To set the °F/°C indication and heat cycle rate: heat thermostat, the fan starts and stops 1. If the room temperature is displayed with the heating equipment. in °F, set the temperature setpoint to Slide the switch in the bottom left corner of the thermostat to 52°F.

  • Page 10: Operation

    The shown, but CC varies by model. This informa- T8400C Thermostat requires only 2.5 mA of load current (1/32 tion is for factory use only. of previous models) when the heating or cooling is on. When M18420 14.

  • Page 11: Wiring

    Refer to the maps in the Operation You can save energy with the T8400C, T8401C and section for typical energy savings. T8424C,D Thermostats in the heating mode by lowering the temperature setting 5°F (3°C) to 10°F (5°C) at night and...

  • Page 12: Checkout

    3. Press the key to raise the temperature setting above the room temperature. Cooling system should shut A minimum off-timer in the T8400C, T8401C and T8424C,D down. assures that the cooling compressor does not come on again for at least five minutes after it turns off. The minimum-off timer is triggered when the compressor turns off and when the system switch is changed.

  • Page 13: Troubleshooting

    T8400C, T8401C AND T8424C,D ELECTRONIC THERMOSTATS TROUBLESHOOTING Refer to Fig. 21 for the proper troubleshooting procedure. SYMPTOM POSSIBLE CAUSE ACTION HEATING OR COOLING EQUIPMENT • CHECK THAT C TERMINAL IS CONNECTED TO NO AC POWER TO THERMOSTAT. WON'T OPERATE. THE SYSTEM TRANSFORMER.
  • Page 14 68-0180-3...
  • Page 15 68-0180-3...
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This manual is also suitable for:

T8424cT8424dT8401c

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