Furnace installation is an involved procedure and one that many people prefer to leave to professionals. In fact, in some states a new furnace has to be put in by a qualified HVAC contractor because of permit requirements. Where it is allowed, however, it is a job you can undertake yourself, although it’s something that needs two people involved in order to complete a successful installation.
What You Need:
Step 1 - Removing the Old Furnace
- New furnace
- Sheet metal screws
- Duct tape
- Utility knife
- Safety gloves
Before undertaking a new furnace installation, you will need to take out the old one. To start, switch off the gas or oil supply to the furnace. There will be valve on the supply pipe that will allow you to do this. For additional safety, you should also turn off the gas supply to the house. Make sure the area is well-ventilated as some gas will escape when you remove the furnace.
A furnace also needs electricity to function. If your furnace plugs into an outlet, simply remove it from the socket. If the furnace is hard-wired into the wall, turn the circuit off at the breaker. Remove the cover plate and unscrew the wire nuts before freeing the wires.
Now, you need to remove the old ductwork for the hot air delivery and the cold air return from the plenum. To do this, slice through the duct tape holding the ductwork in place and remove it carefully, wearing safety gloves as you do so (the sheet metal is extremely sharp). The furnace will be held in place with bolts. Remove these and the old furnace can be removed. Be warned that this is a job that will require at least two people.
Step 2 - Connecting the Furnace
The new furnace will need to be unpacked. When it’s positioned where you want it, the furnace needs to be leveled in all directions using the level and adding solid shims where necessary. Your furnace will come with the hardware needed to secure it in place. Now the furnace installation can begin.
Use the ductwork that’s already in place for hot air delivery and cold air return, adding more if you need to establish a better fitting length, and secure it to the existing ductwork by drilling holes and using sheet metal screws. Secure the ductwork to the new furnace with duct tape.
It’s now time to reconnect the electricity. If the furnace plugs in, that’s very simple. For hard wiring, connect the hot wire (which will be red or black), neutral (white) and ground (green) wires to the correct terminals, using the wire nuts you already have. Turn the circuit back on at the breaker box. Following the manufacturer’s instructions, turn on the fan to check the electricity is operating properly.
You will need to connect the fuel supply pipe to the new furnace installation. If you're using gas, put a little soapy water around the fitting. Once you have a tight fit, open the valve for the gas or oil (with gas you will have to turn back on at the house main valve). Inspect for leaks. An oil leak will be immediately visible. With gas, you should notice the smell and a leak will make the soapy water on the fitting bubble.
Step 3 - Turn On the Furnace
To complete the furnace installation, you’ll need to light the pilot. Turn the gas control knob (indicated in your manual) and hold it down. Some furnaces use an electronic ignition for the gas. Others are lit manually. Wait until you smell gas then light the pilot with a match or lighter. Keep the knob pressed down for another minute then release. The pilot flame should stay lit.
To finish, turn up the thermostat to check the furnace is operating properly.