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Product Application
This thermostat provides electronic control of 24 VAC single-stage and multi-stage
heating and cooling systems, or 750 mV heating systems.
System Types
(up to 2 heat/2 cool)
• Gas, oil, or electric heat with air
conditioning
• Warm air, hot water, high-efficiency
furnaces, heat pumps, steam, gravity
• Heat only — two-wire systems,
power to open and close zone
valves (Series 20), and normally-
open zone valves
• Heat only with fan
• Cool only
• 750 mV heating systems
Power Options
• Battery power only
• Common wire only
• Common wire with battery backup
Changeover Options
• Selectable manual or
auto-changeover modes
System Settings
• Heat, Off, Cool,Auto, Em Heat
Fan Settings
• Auto, On
Must be installed by a trained, experienced technician
• Read these instructions carefully. Failure to follow these instructions can
damage the product or cause a hazardous condition.
• Check the ratings in this booklet to verify that this product is suitable for your
application (see page 17).
• Always test for proper operation after installation (see page 13).
CAUTION: ELECTRICAL HAZARD
Can cause electrical shock or equipment damage. Disconnect power before
beginning installation.
MERCURY NOTICE
If this product is replacing a control that contains mercury in a sealed tube, do not
place the old control in the trash. Contact your local waste management authority for
instructions regarding recycling and proper disposal.
Install the thermostat about 5 feet (1.5m) above the floor in an area
with good air circulation at average temperature.
Do not install in locations where the thermostat can be affected by:
• Drafts or dead spots behind doors and in corners
• Hot or cold air from ducts
• Sunlight or radiant heat from appliances
• Concealed pipes or chimneys
• Unheated/uncooled areas such as an outside wall behind the thermostat
NO
NO
NO
® U.S. Registered Trademark. Patents pending.
Copyright © 2005 Honeywell International Inc. All rights reserved.
IInnssttaallllaattiioonn
Pre-installation checklist ................2
Wallplate installation ......................3
Wiring..............................................4
Wiring diagrams ..............................5
Power options ..............................10
Thermostat mounting ..................10
SSeettuupp aanndd tteessttiinngg
Installer setup................................11
Installer system test ......................13
Explanation of features ................14
AAppppeennddiicceess
Quick reference to controls..........15
Quick reference to display............15
Battery replacement......................15
In case of difficulty ......................16
Accessories/replacement parts ....17
Specifications ................................17
Table of contents
Installation tips