Before you can install a new thermostat, you need to remove your old one. If you need to remove a Honeywell thermostat, the process is relatively easy. Before you start pulling off the old thermostat, make note of the wiring to help when you install the replacement.
Basic Thermostat Wiring
Thermostat wiring consists of low-voltage wires that are powered by the furnace circuit. The wires correspond to different parts of your HVAC system, so they need to be connected correctly when you install your new thermostat.
Thermostat wiring is color-coded using industry standards:
- White: Heating system.
- Yellow: Compressor.
- Green: Fan.
- Orange: Heat pump (if you have one).
- Red (C):
24 VAC transformer for the cooling system.
- Red (H): 24 VAC transformer for the heating system.
- Blue: Common or "C" wire.
Preparing for Thermostat Removal
Before you do any work with your Honeywell thermostat, shut off the circuit breaker for the entire HVAC system. Verify that it's turned off to prevent shocks when you reach the wires.
If you have an old thermostat, it might have a glass vial of mercury inside it. Handle these thermostats with care to avoid breaking the glass vial. Don't toss the thermostat in the trash because the mercury vial could break and contaminate the environment. Check with your local waste management company to find a location to dispose of the thermostat and to ensure you comply with state regulations. The Thermostat Recycling Corporation can help you find a location to recycle the mercury thermostat.
Removing the Honeywell Thermostat Cover
The visible portion of the Honeywell thermostat needs to come off the wall to reveal the wiring and bracket. On most models, you can simply pull the thermostat straight away from the wall. Pull firmly, being careful not to rip the base off the wall at the same time. Some thermostats might have a button or latch that you need to press to release the cover.
Removing this cover should reveal the wires and terminals. However, if you don't see the wires, look for a plate that might be screwed into place that you can remove with a screwdriver.
Marking the Thermostat Wires
Reconnecting the wires correctly for your new thermostat is necessary to get the system to work correctly. Take a photo of the wiring system before you disconnect anything to make the wiring step of the installation easier. Then, place a small piece of painters' tape on each wire labeled with the corresponding terminal where it connects. When you install the new thermostat, you have an easy guide to help you reconnect the wires.
Removing the Wires and Bracket
Carefully disconnect the wires so you can finish removing the thermostat. They're often held in place by a screw, so you'll need a screwdriver to remove them. Others use push-in terminals with a release button that you engage using a small screwdriver, ballpoint pen, or similar object. Be careful not to pull the labels off the wires.
Unscrew the wall plate that remains, as your new thermostat will come with its own bracket. Make any repairs to the wall, such as removing old anchors, patching holes, and touching up paint, especially if your new thermostat is a different size than the old one.
Shelley Frost combines her love of DIY and writing in her freelance career. She has first-hand experience with tiling, painting, refinishing hardwood floors, installing lighting, roofing and many other home improvement projects. She keeps her DIY skills fresh with regular projects around the house and extensive writing work on the topic.