Prepare for installation

CT87A,B,J ROUND® THERMOSTAT

1.Carefully unpack your new thermostat; rough handling may affect its accuracy. Save your receipt and identify the following parts:

•CT87 Thermostat

•Screws: two 1-in. sheet metal screws, two 1/2-in. binding head screws, and two 1/4-in. round head screws

•Wallplate (CT87A) or subbase (CT87B, CT87J)

•Cover ring (select models only). Necessary if installing on an outlet box. Optional if installing directly on the wall; can be used to hide wall marks.

•These Installation Instructions and the Installation Quick Guide.

•Wiring labels

2.Gather these tools:

Required Tools			Optional Tools

•	Flat blade	• Hand or power drill with 1/16-in. drill bit
•	screwdriver	•	Wire cutter/stripper or sharp knife
•	Spirit level	•	Pencil

Remove the old thermostat

1.Turn off power to the heating/cooling system at the main fuse/circuit breaker panel.

2.Remove the cover of your old thermostat. You may need to unscrew the cover if it is locked on.

3.Locate the heat anticipator adjustment scale and lever on the old thermostat (Fig. 1).

Fig. 1. Mercury switch location.

MERCURY

SWITCH

OLD THERMOSTAT

ANTICIPATOR

SCALE

LEVER
TYPICAL LOCATION OF A
MERCURY SWITCH IN
A THERMOSTAT	M20206

In the box below, record the number that the adjustment lever points to. This is the current (amp) rating of your heating system.

Current setting:

If you cannot find the heat anticipator setting on the old thermostat, you can use a standard setting for your type of system when you reach Step 8 of this installation.

4.Unscrew and remove the old thermostat wallplate from the wall, but do not disconnect the wires.

69-0274-6

CT87A specifications

The Honeywell CT87A is a well-regarded thermostatic control unit designed for residential and light commercial HVAC applications. Specifically known for its reliable performance and user-friendly interface, the CT87A promotes energy efficiency while ensuring a comfortable indoor environment. This model is often referred to as the "Round" thermostat, with its distinctive circular design making it a recognizable fixture in homes.

One of the main features of the CT87A is its straightforward mechanical operation. Utilizing a bimetallic strip, it provides accurate temperature readings and control without the need for complex programming. This simplicity is a significant advantage for users who prefer a manual approach over digital displays and smart technologies. The CT87A comes with an easy-to-read temperature scale, allowing users to adjust the setting effortlessly to their desired comfort level.

In terms of technology, the CT87A functions purely on mechanical principles, making it highly durable over time. The thermostat operates on a 24-volt system, which is standard in many residential heating and cooling units. It is capable of controlling both heating and cooling systems, providing versatility for year-round use. Additionally, it allows for compatibility with a variety of HVAC equipment, making it an ideal choice for homeowners looking to upgrade their system without extensive modifications.

A notable characteristic of the Honeywell CT87A is its ability to deliver consistent performance with minimal power consumption. This contributes to energy savings, making it an environmentally-friendly choice for conscientious consumers. The conventional design does not rely on batteries or complicated electrical systems, reducing maintenance costs and the risk of failure.

Furthermore, the CT87A includes a built-in anticipator that helps to prevent temperature swings, enhancing user comfort. This feature enables the thermostat to adjust its operation slightly ahead of actual heating or cooling demands, ensuring that the desired room temperature is reached more efficiently.

In summary, the Honeywell CT87A thermostat combines reliable mechanical operation, energy efficiency, and ease of use, making it an excellent choice for those who appreciate simplicity and performance in temperature control. Its time-tested design, coupled with essential features, places it among the favorites for homeowners seeking a balance between functionality and comfort. Whether for a heating or cooling system, the CT87A consistently meets the demands of everyday use, ensuring a pleasant living environment.