How To Install A Gas Furnace On Your Own?

All residences across the United States need a furnace to warm themselves in chilly nights. Calling a HVAC professional is of course, the beaten way to get a furnace installed in your house. But it can be done by oneself at home too. And the bonus is money that you are going to save on installation. Here is a guide to installing a furnace in the house.

Size of the unit

In the HVAC industry size in be all and end all. Buying a big furnace will not give you more heat. Similarly, an undersized furnace will not help. The usual process that is followed by most companies is taking the climatic condition, the square footage of the home, the size of the furnace and its efficiency into account. A house located in moderate climate would need at least 25 to 30 Btu of heat per square feet. Going by this standard, a mid-sized home of 2,000 square feet would need approximately 50,000 to 60,000 Btu to heat it properly. If the efficiency of the furnace is towards the lower side, say 80 percent, this would require a 60,000- to 72,000-Btu furnace. With a high-efficiency furnace operating at 95 percent, the home only need a 52,500- to 63,000-Btu furnace.

Deciding the place

First of all decide the side from which the return air duct will connect to your furnace, whether it will be attached to any of the sides or bottom of the unit. In most units you will find a mark that designates an opening of the right size. It only needs to be cut. Now place the unit in the desired place. Ensure that the unit stands on rubber isolation pads so that there is no vibrating or jerky sound during operation. If you are going to place the furnace in the basement, then make sure that it is at least four inches above the floor. In case it is going to be housed in the attic, then there should be a secondary drainage pan under the unit.

The condensate drain

Also decide the side, in which the condensate drain will exist. The drain should be fixed so that it is at a level with unit, but sloped slightly towards the exit. Once you connect the condensate drain, run a pipe to a drain location. This should be a 3/4 inch PVC pipe.

Connecting with the ducts

After you have finished placing the unit, it is time to connect it with the ducts that will convey the hot air to rooms. Once you make the connections seal them with with a metal foil tape or a duct sealant.

Connect the vent pipes

Most high efficiency furnaces have their inlets and exhausts made of PVC. Once you connect the vents, glue the joints properly. The pipes should be sloped back to the furnace at 1/4 inch per 4 feet. This is to facilitate good venting.

Linking the gas supply with the unit

Now comes the most vital part of the installation. The pipe that will bring fuel to the unit has to be connected to it. You will find a shutoff valve installed outside the unit. You should install drip leg here, before connecting the gas pipe. A drip leg is a sediment trap that can be called a capped off section of gas line. This is installed in such a way that it traps debris or moisture in the gas and allows pure gas to reach the furnace. The drip leg is installed with a tee that has a capped nipple sticking out the bottom. The gas would come at the top and central part of the tee would move towards the furnace. After installing the gas piping, ensure there are no gas leaks. You can spray a gas leak detector solution on the connections and watch for bubbles. If they are formed then there is leakage.

Make the electric connections

A furnace typically has a low voltage (24v) and line voltage (120v) connections. The line voltage wires would run from the furnace junction box to a disconnect switch within three feet of the unit. Check for polarity at the connection. A new unit would be polar sensitive.

The low voltage wires run from the furnace control board to the air conditioner and/or the thermostat. This is how the connections should happen-

• R terminal on furnace board connected to R terminal on thermostat
• W terminal on furnace board connected to W terminal on thermostat
• G terminal on furnace board connected to G terminal on
• C terminal on furnace board connected to C terminal on thermostat
• Y terminal on furnace board connected to the Y terminal on the thermostat


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