Type of Wire
A thermostat wire size is 18 gauge and can come with 10 or more wires. Once you determine the number of wires needed for your HVAC system, it’s a good idea to add two spares to give you more flexibility in the future. Most HVAC systems require 5 or more wires if both heating and cooling are involved.
Each wire matters, so make sure to talk to your certified technician. A c-wire, for example, can monitor the indoor and outdoor temperatures as well as other climate features.
Relocating Your Replacement
If you’re relocating your thermostat or installing a new one, its home should be as comfortable as yours. Thermostats should be installed on interior walls because exterior walls are cooler in the winter and warmer in the summer, which can affect your thermostat readings. The best spot for a central forced air system is close to a central return grill.
You’ll want to install your thermostat and its wiring in a place where it can avoid:
Drafts from doors and windows
Heat or steam from bathrooms
Heat from other appliances
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