Honeywell B Installation Guide

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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:

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).

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.

• Flat blade 

screwdriver

• Spirit level

• Hand or power drill with 1/16-in. drill bit

• Wire cutter/stripper or sharp knife

• Pencil

M20206

MERCURY
SWITCH

OLD THERMOSTAT
ANTICIPATOR 
SCALE

LEVER