Honeywell T8424D User Manual

PRODUCT DATA
® U.S. Registered Trademark
Copyright © 2001 Honeywell • All Rights Reserved
68- 0180- 3
T8400C, T8401C and T8424C,D
Electronic Thermostats
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.
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.
T8400C and
T8401C
T8424C,D
Contents
Application ........................................................................ 1
Features ........................................................................... 1
Specifications ................................................................... 2
Ordering Information ........................................................ 2
Installation ........................................................................ 3
Settings and Adjustments ................................................. 8
Operation .......................................................................... 10
Checkout .......................................................................... 12
Troubleshooting ................................................................ 13

Honeywell T8424D Specifications

General

Display	Backlit LCD
Power Source	24V AC
Voltage	24 Vac
Stages of Heating	1
Stages of Cooling	1
Mounting	Wall mount
Type	Digital
Compatibility	Heat/Cool
Maximum Load	1.5A
Warranty	1 Year
Temperature Range	40°F to 90°F (4°C to 32°C)

Summary

Features

Application

Specifications

Electrical Ratings

Details voltage, current, and inrush ratings for heating, cooling, and fan operations.

Temperature Adjustment

Explains how to adjust setpoints using keys and the temperature setting range.

Cycle Rates

Details selectable heating and fixed cooling cycle rates for various system types.

Dimensions

Refers to figures illustrating the physical dimensions of the thermostats.

Ordering Information

Installation

General Installation Notes

Provides essential precautions and steps for safe and effective product installation.

Mercury Notice

Instructs on proper disposal of old mercury-containing controls.

Location

Guidelines for selecting an optimal thermostat installation location.

Mounting Wallplate

Instructions for mounting the wallplate and optional decorator cover plates to the wall.

Wiring

Detailed instructions and diagrams for wiring the thermostat to HVAC systems.

Mounting Thermostat to Wallplate

Step-by-step guide on how to attach the thermostat to its wallplate.

Settings and Adjustments

Setting Fan and System Switches

Explains how to configure fan and system mode switches.

Set Temperature Setpoint

Guide on how to adjust the desired temperature setpoint.

Setting °F/°C Indication and Heat Cycle Rate

Instructions for setting temperature display units and heating cycle rates.

Operation

Zero Droop Performance

Explains the thermostat's precise temperature control and comfort benefits.

Power Stealing

Details how the T8400C model draws power from the system.

Energy Savings

Provides tips on how to save energy by adjusting temperature settings.

Sequence of Operations

Describes the thermostat's response to different fan and system settings.

Checkout

Troubleshooting