Summer is coming to an end. Pretty soon the furnace will stay on. This is a good time to do a thorough inspection of your furnace to make sure that it will function properly in winter. Inspections should be performed annually and there are some key areas to pay attention to.


Your filter is responsible for catching all of all the duct, dirt, and allergens in your home. It is located between the furnace and the return ductwork at the furnace. When the air coming back into the furnace blows across the filter, the fiberglass and nylon fibers catch the foreign materials keeping your air clean. Like all filters, they have to be replaced every so often, in this case, every 3-6 months depending on pets, kids, and number of occupants. When replacing filters, make sure that you insert the filter the correct way. You will see an arrow on the filter. This goes in the direction of the air flow, which is toward the furnace.

Blower Motor

The blower motor is what distributes the warm air from the furnace to your house. To test, make sure the furnace is running and remove the protective cover at the bottom of the furnace. The furnace will shut down at this point. The will be a depression switch on the upper right hand corner. Push it, and the furnace will turn back on. Watch the blower motor for about 2 minutes. Listen for any unusual noises or grinding, rubbing noises. These are all signs that the blower motor is starting reach the end of it’s usefulness and may need to be replaced. If you have these suspicions, call your HVAC professional for a second opinion. Tell them the actions you took for testing over the phone first. Sometimes they can tell over the phone if he motor should be replaced and you can avoid a trip charge.

Heat Exchanger

The heat exchanger is usually not visible through the site glass of your furnace, but the burners should be able to give you clues a to the condition o the heat exchanger. When the furnace is on, look for soot or dirt on the burners. This is a sign that your filters have not been changed regularly enough ad the particles that re getting through are being burned and settle on the heat exchanger and burners. The burner flames should be completely blue. A blue flame is the hottest flame that can be produced, so it makes sense that your burners emitting a blue flame would also be the most efficient. It is common to see a little string of orange and yellow flames at the top of a blue flame, but if the flames from your burners are yellow and orange, you need to have the burners calibrated by an HVAC technician. If you see rust of any kind on the burners, you should have you HVAC technician perform a thorough cleaning of your furnace.

Condensate Lines

The average furnace produces between 6 and 10 gallons of water per day during the heating season. This is caused by the large temperature swings in the heat exchanger. A plastic tube (condensate line) runs from the heat exchanger and out of the furnace, usually to a floor drain. Make sure that the hose is free of obstructions and that water flows freely from down the condensate line. Testing this can take up to 20 minutes or so. If no water comes out of the hose, you have a clog somewhere along the hose. Call your HVAC Technician to unclog or replace the condensate line.

If you have a humidifier unit to as part of your furnace heating system, there will also be a condensate line for this as well. Take the cover off and make sure the filter is clean. If not, discard and put in a new filter that matches the brand and model number of your humidification unit. These condensate lines get clogged easily. To test, use a Pyrex measuring cup and pour water down the condensate tube. The water should flow freely to the drain. If it does not, remove the condensate line from the bottom of the humidification unit and take it outside. Either blow out the tube with and air compressor, or with a garden hose. Then re-attach.

Make sure you put the cover back on the humidification unit after inspection. This is tied directly to your supply ductwork.


Depending on the efficiency of your furnace, you will either have PVC piping that exhausts the combustion gases outside, or a metal pipe that exhausts combustion gases out of a chimney. Either on is acceptable, but they have to be installed properly.

PVC These pipes are the intake and exhaust for high efficiency furnaces. The burner fires into the heat exchanger and the gases travel down through the sealed heat exchanger by being pulled through the heat exchanger by an induced draft fan. This fan then blows the exhaust gases out of the house. The PVC pipe that goes out of your house should be supported every 3 feet on the ceiling and have a negative slope back toward the furnace for drainage of condensation. There should be a condensate catch at the bottom of the pipe at the furnace with a condensate line attached to it for proper drainage. Use the methods of condensate line inspection you used for the humidification unit to test this component.

The pipe should be free of cracks or leaks and should also be sealed at the point of existing to the exterior. Use can foam sealant at the exit point if not properly sealed.

Metal Pipe 

Metal pipes are typical of natural draft and other non-high efficiency furnaces. The metal will be very hot to the touch and should not have any combustibles within 12″ of it included PVC, wiring, or any storage materials that can melt, char, or com bust. Make sure that it does not leak exhaust fumes as these chimneys carry a large amount of exhaust out of the house. No supports are needed as metal pipes are rigid enough to carry their own weight.


If you do not have a programmable thermostat, you should consider purchasing one. A $30 investment and about 30 minutes of time will lead to about 10-15% in energy savings. Programmable thermostats are much more accurate at temperature reading and have several setbacks and programmable variation to decrease your energy usage when you are at work or out of the house.

One thing to check with programmable thermostats is to change the batteries every year without exception. False temperature readings and programming malfunction can occur if your thermostat is not kept up to date. Some thermostats do not require batteries. The battery compartment, if you have one, is located behind the thermostat. You will see a tab on the sides or the top and bottom. Depress the tabs and the face of the thermostat pops off. Change the batteries, and pop the face back on.

Going through this process every year will help you to prevent furnace failure during the heating season, which can be very expensive and also hard on your house.

Furnace Inspection