2 Stage Furnace Thermostat Wiring

How many thermostat wires needed for 2 stage stat. Thermostat wire is 18 gauge solid copper wire and over time it can become brittle.

This video is part of the heating and cooling series of training videos made to accompany my websites.

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2 stage furnace thermostat wiring. Im putting a new 2 stage variable speed furnace in my house and i want to upgrade the thermostat to a 2 stage one to better control it. My old thermostat has 4 wires connected to it with 2 extra ones unused in the wall. It will consist of three to eight wires of different colors including red white green yellow orange blue black etc.

It might be necessary to remove a cover over the control board to expose the wiring connections. This setup saves money by using only the outside heat pump unit when the temperatures are milder but ensures you have a warm house when the outside unit cant keep up with the cold temperatures. There are also thermostats that use a 2 wire dcv communications array.

Sometimes the wire could look good but it is broken. Locate where the wire bundle from the thermostat enters the furnace. For this extra stage you need to connect one additional wire to your furnace and your thermostat.

The most basic of systems such as an older heat only forced air gas furnace with a standing pilot light only need two wires for control. After a predetermined amount of time if it has not satisfied the temperature it kicks up to high until the temperature is satisfied. This one explains the 2 stage thermostat and how it is wired.

Basic checks two stage furnace air conditioner thermostat control problem you may also want to check the thermostat wire to make sure it is good especially at the terminations. Your thermostat calls for heat and the furnace kicks on low. A two stage furnace works like this.

Your current thermostat is designed to allow independent control of the outside heat pump and the inside auxiliary furnace two stage on the heat side. The entire bundle might be wrapped with a housing. They connect to a two wire thermostat generally a mechanical thermostat with a mercury filled ball connected to a coiled bi metal strip.