Honeywell T8400C, T8401C User Manual

T8400C and T8401C

Electronic Thermostats

INSTALLATION INSTRUCTIONS

The T8400C and T8401C Thermostats provide single­stage, 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, or 9 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 Thermostat is
powered directly from the system transformer. Batteries
are not required because setpoints are held permanently
by non-volatile memory for all models.

All TRADELINE® models include a thermostat, wallplate
(for wiring and mounting thermostat) and owner’s guide.
The T8400C SUPER TRADELINE® model also includes
two decorator cover plates for covering wallmarks.

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.

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 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.

® U.S. Registered Trademark
Copyright © 2002 Honeywell • • All Rights Reserved

69- 1480- 1

T8400C AND T8401C ELECTRONIC THERMOSTATS

NO

NO

Fig. 1. Typical location of thermostat.

Mounting Decorator Cover Plate and Wallplate to Wall

IMPORTANT

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

NOTE: Only SUPER TRADELINE® models have the

cover plate.

Mount decorator cover plate (SUPER TRADELINE®
model only), wallplate, T8400C or T8401C, and the
screws provided (see Fig. 2) as follows:

1. Place the desired decorator cover plate and 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 decorator cover plate and 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.

YES

5 FEET

[1.5 METERS]

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

The T8400C Thermostat is powered through the heating/
cooling system controls and is adaptable to most 4-wire,
18 to 30 Vac heating-cooling systems.

The T8401C Thermostat is powered directly from the
system transformer and is adaptable to most 5-wire, 18
to 30 Vac heating-cooling systems. Refer to Fig. 5 and 6
for typical wiring hookups.

NO

M10308

5-3/4 IN. x 5-3/4 IN.
DECORATOR
COVER PLATE

1

WALL

WALL

ANCHORS (2)

2

Wiring

IMPORTANT

Use an 18-gauge maximum wire for wiring the
T8400C and T8401C 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 on the left
side of the terminals. See Fig. 3.

69-1480-1 2

1

3-7/8 IN. x 3-7/8 IN. DECORATOR COVER PLATE (SELECT MODELS).

2

DRILL 3/16 INCH HOLES (IF DRYWALL) OR 7/32 (PLASTER OR WOOD)
WHEN USING WALL ANCHORS.

Fig. 2. Mounting decorator cover plate

and wallplate to wall.

M11041C