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Video:How to Fix a Gas Furnace: Thermostat Problems

with Erick Noack

A properly functioning thermostat is necessary for a gas furnace to heat your home, but you can run into a number of problems with a thermostat. Here is a video detailing some thermostat problems that might mess with your gas furnace.See Transcript

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Transcript:How to Fix a Gas Furnace: Thermostat Problems

Hi, my name is Erick Noack. I'm an HVAC technician for ABC Plumbing, Heating, Cooling, and Electric. And we're here for About.com. Today I'm going to show you things to look for if you're having problems with your thermostat.

Possible Thermostat Issues

The first thing to look for is to make sure the display is in the thermostat like you normally see. The other thing is look and see if there's an icon that's looking for a battery. If you see an icon in the display asking for a battery, you need to follow your manufacturer's instructions and replace the battery with an appropriate size. If you see no display here at all, then you want to check the power to the furnace. This particular thermostat has a sealed battery in it, and it's not replaceable. Another thing you might notice is erratic furnace operation. Either short cycling, coming on and off very quickly, not enough heat coming into the home, too much heat coming into the home. All of these things could be due to poor thermostat operation.

Types of Thermostats

So there's three basic types of thermostats. There's a millivolt thermostat, a line voltage thermostat, and a low voltage thermostat. Line voltage thermostats are typically used in commercial applications in a warehouse or a large space with a hanging heater. Millivolt thermostats are typically used in a non-powered situation like a pool heater or a jacuzzi heater possibly. Low voltage thermostats are the most commonly used thermostat used in a residential application. They have to be matched to the system based on the type of furnace that's used and the capacity and capability of that furnace.

Identifying Thermostat Type

When you're attempting to identify the type of thermostat you've got, one way to find out what it is is to remove the thermostat and check out the wiring in the back. In this case, it's got very small, low voltage wires, so we know this is a low voltage thermostat. If you're going to remove this thermostat and take it to the home store for a match, you want to make sure you know where those wires went so you can get them in the right place on the new one. Like most electronic devices these days, thermostats are pretty solid state.

Replacing Thermostat

If you've checked the battery, you've checked the power, and it's still not operating properly, it's likely that you're just going to have to replace your thermostat. It's important to understand how your thermostat operates when it's normal, when everything is right. If you're familiar with the proper operation of your equipment, then it's going to make it easier if you notice something acting unusually and you can call for a proper diagnosis.

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