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Question posted by jojwillen on December 31st, 2017

Replacement. .?

I have a Honeywell T8400C 1099 thermostat. Will this replace it without a lot of wiring changes.Or can you recommend a direct replacement?Thank you very muc

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Answer #1: Posted by katcoco13 on January 11th, 2018 3:03 PM

katcoco13

Member since:
January 11th, 2018

Points: 90

90
points

most likely it will replace with little to no changes in your wiring but its always best to confirm with your electrician as they will be able to accurately direct you in proceeding with this process

Related Honeywell T8400C Manual Pages

Owner's Manual - Page 1

Set Room FAN Auto On SYSTEM Cool Off Heat M18535 Em Ht Aux Ht Set Room Electronic Thermostat OWNER'S GUIDE FAN Auto On SYSTEM Cool Off Heat Em.Ht. M18539 1 69-1490 69-1490

Owner's Manual - Page 2

... to use. Over 100 years of Honeywell engineering expertise went into the making of your temperature settings are not required because your new thermostat! You can easily read the current ...room temperature at a glance. • No need for you with a more comfortable and convenient living environment. • Simple and easy to change...

Owner's Manual - Page 3

... on . Settings Setting FAN and SYSTEM Switches Fan and system settings are controlled by using FAN and SYSTEM switches located on the bottom of the thermostat case.

Owner's Manual - Page 7

... temperature setting, press the ▲ key. When in the heating mode, lowering the temperature at night or during the day can lower your energy costs. Changing Temperature Setting 1. When in the cooling mode, raising the temperature before you leave for work or school also lowers your energy costs. Set Room M18443...

Owner's Manual - Page 8

...If you like saving energy, but would like your thermostat to automatically change the temperature setting, you choose and your home, ...where you live, the number of energy saving periods you might want to consider purchasing the Honeywell Chronotherm® Programmable Thermostat. Energy Savings You can save energy with this thermostat...

Owner's Manual - Page 9

... 18% 19 TO 22% 23 TO 33% COOL * YOUR SAVINGS DEPENDS ON HOME SIZE AND ACTUAL HEAT LOSS OR GAIN, GEOGRAPHIC LOCATION, FREQUENCY OF TEMPERATURES CHANGE, AND RANGE IN DEGREES OF...

Owner's Manual - Page 10

...• Check that the SYSTEM switch on . Heating or cooling does not come on the thermostat is below 50°F (10°C). Troubleshooting Guide CAUTION To avoid possible equipment damage, do not...outside temperature is set to Heat or Cool. • Check the system fuse or circuit breaker and replace or reset if necessary. • Check for air movement at the register. • Check power...

Owner's Manual - Page 11

If you have questions concerning this thermostat, call Honeywell Customer Assistance at 1-800-468-1502, Monday-Friday, 7:00 am-5:30 pm, Central time. For service, contact your local heating and cooling contractor: 11 69-1490

Owner's Manual - Page 12

Registered Trademark 69-1490 J.H. 9-00 6ww9w-1.h4o9ne0ywell.com/yourhome 12 Honeywell Limited-Honeywell Limitée 1985 Douglas Drive North 35 Dynamic Drive Golden Valley, MN 55422 Scarborough, Ontario M1V 4Z9 Copyright © 2000 Honeywell All Rights Reserved ® U.S. Automation and Control Solutions Honeywell International Inc.

Installation Instructions - Page 1

...T8400C SUPER TRADELINE® model also includes two decorator cover plates for wiring and mounting thermostat) and owner's guide. T8400C and T8401C Electronic Thermostats INSTALLATION INSTRUCTIONS The T8400C and T8401C Thermostats... This thermostat is replacing a control that contains mercury in a sealed tube, do not place your old control in corners. - The T8400C Thermostat is ...

Installation Instructions - Page 2

...-cooling systems. The T8401C Thermostat is powered directly from affecting the thermostat; After wiring the wallplate, plug the hole to the wall using the anchors and screws provided. 5. x 5-3/4 IN. DECORATOR COVER PLATE WALL 1 2 WALL ANCHORS (2) Wiring IMPORTANT Use an 18-gauge maximum wire for appearance. T8400C AND T8401C ELECTRONIC THERMOSTATS YES NO NO 5 FEET [1.5 METERS...

Installation Instructions - Page 3

... and SYSTEM Switches Fan and system settings are : On: The fan runs continuously. Wiring connections. Swing down the thermostat and press the lower edge of the thermostat onto the wallplate to Wallplate 1. Restrict wiring to shaded area. T8400C AND T8401C ELECTRONIC THERMOSTATS KEEP WIRING IN SHADED AREA ALTERNATE MOUNTING SCREW HOLE W Y G R C MOUNTING SCREW HOLE ALTERNATE MOUNTING...

Installation Instructions - Page 4

...No action takes place If the system switch is displayed . Heat: The thermostat controls the heating system. Each press changes the setpoint one second to light all seven steps must be used to turn... display, press either the s or t key once. T8400C AND T8401C ELECTRONIC THERMOSTATS Slide the FAN switch in the bottom left corner of the thermostat to select the desired system setting.

Installation Instructions - Page 5

.... Press the s key. Press the t key to change the setpoint to raise the temperature setting above the room ...thermostat. Refer to Auto. 2. Press the s key again. Heating Cycle Rates. Slide the SYSTEM switch to Cool and the FAN switch to manufacturer's recommendations. 1. A typical example is displayed, press the s key to On. T8400C AND T8401C ELECTRONIC THERMOSTATS...

Installation Instructions - Page 6

Automation and Control Solutions Honeywell Honeywell Limited-Honeywell Limitée 1985 Douglas Drive North 35 Dynamic Drive Golden Valley, MN 55422 Scarborough, Ontario M1V 4Z9 69-1480-1 G.H. Rev. 2-02 www.honeywell.com/yourhome