Honeywell T8400B - User Manual

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Copyright © 2002 Honeywell • • All Rights Reserved
INSTALLATION INSTRUCTIONS
T8400B,C; T8401C
Electronic Thermostats
T8400B Thermostat provides single-stage, non-
programmable temperature control for 24V heat-only
applications. Heating cycle rate is selectable at 1, 3, 4,
5, 6, 9, or 12 cph. Temperature indication can be set for
°F or °C.
The T8400B Thermostat is powered through the heating
system controls.
The T8400C and T8401C 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, 6,
9, or 12 cph. Cooling cycle rate is fixed at 3 cph.
Temperature indication can be set for °F or °C.
The T8400C Thermostat is powered through the
heating/cooling system controls. The T8401C Thermo-
stat is powered directly from the system transformer.
Batteries are not required because setpoints are held
permanently by nonvolatile memory for all models.
All models include a thermostat, wallplate (for wiring
and mounting thermostat) and Owner’s Guide. Two
decorator cover plates (for covering wall marks) are
included for select models.
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. Dispose of properly.
Contact your local waste management authority
for instructions regarding recycling and the
proper disposal of an old control.
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
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 tempera-
ture. 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.
69-1494-1

Summary

INSTALLATION INSTRUCTIONS

INSTALLATION

General steps and precautions for installing the thermostat.

Location

Guidance on selecting the optimal installation location for the thermostat.

MERCURY NOTICE

Critical safety warning about disposing of old controls containing mercury.

Mounting Wallplate and Decorator Cover Plate (Select Models) to Wall

Detailed steps for mounting the wallplate and cover plate to the wall surface.

Wiring

T8400 B Wiring Diagrams

Wiring configurations for the T8400B thermostat in various systems.

T8400 C;T8401 C Wiring Diagrams

Wiring configurations for T8400C/T8401C in heating/cooling systems.

OPERATION

Mounting Thermostat to Wallplate

Steps for attaching the thermostat unit to the installed wallplate.

Setting FAN and SYSTEM Switches

How to configure fan and system mode settings on the thermostat.

FAN Switch Operation

Details on operating the fan switch and its modes (Auto, On).

SYSTEM Switch Settings

How to select system modes (Heat, Cool, Off).

Set Temperature Setpoint

Instructions for adjusting the desired temperature setpoint.

Setting °F;°C and Heat Cycle Rate

Guide to changing temperature units and heat cycle rate.

Optional System Checkout

Procedure for testing heating and cooling outputs.

CHECKOUT

Heating Checkout

Steps to verify proper operation of heating equipment.

Cooling Checkout

Steps to verify proper operation of cooling equipment.

Fan Checkout

Steps to verify proper operation of the fan.

Honeywell T8400B Specifications

General

Brand	Honeywell
Model	T8400B
Category	Thermostat
Language	English