Furnace Inspection Process

Originally Posted By: dmacy
This post was automatically imported from our archived forum.

I would like to receive some advice on the process other inspectors are using when doing a conventional forced warm air furnace inspection.

1)Do you take off the heat shield?
2)Do you use a mirror? I can never see anything with a mirror
3)What about a heat spray or smoke in the heat exchanger.
4) Do you test for CO? If you do what instrument are you using?
5) If you are using a CO & combustion analyzer could you explain your inspecting techniques.
6) How much time to you spend on the furnace inspection?

Also when Inspecting a mid or high efficiency unit. How does your inspection differ?

Thank you

Originally Posted By: cbottger
This post was automatically imported from our archived forum.


According to the standards of practice for the state that I inspect in does not require an HI to remove anymore panels on the furnace than a normal homeowner would remove. I have removed the heat shields on some furnaces but do not make a practice of doing so.

I check the blower compartment and blower wheel for lint accumulation and try to determine if the past owner has been reliable with the filter changing. I look for a nice blue flame and check the bottom of the burner barrel compartment for rust build up that has fallen from the burner side of the heat exchanger. I do use a mirror with an retractable extension on the handle and yes they do not allow you to see much of the exchanger.

I riley very heavy on a UEI 70 CO meter that I have re-calibrated by the factory every year. I check for CO at the nearest supply register from the furnace plenum.

I check the wiring to ensure that it is not to close to the burners and has been damaged from excessive heat. I ensure that the roll out safety switch is in place on furnaces that are installed with them. The combination high limit and fan switch should have the on/off cycle checked to ensure the fan is activating where it is set to come on and cycles off at the set temperature on the switch. The newer furnaces have the fan come on and off with time determined by a solid state board and is not adjustable as the older fan switches are. The inexperienced HI can be tricked very easy by this switch. I have found more of these switches than I can count that were cycling on the limit switch rather than the fan switch. When the limit switch opens as it should in the area of 200 degrees it will kill the gas to the burner and as soon as the switch cools from the fan the burner will re-ignite and start the whole process again. The furnace should cycle with the thermostat not the limit switch. Keep in mind with these furnaces regardless of the type newer or older cleanliness is next to godliness, switches and or solid state boards have their life expectancy decreased tremendously with dirt. If the furnace is located in an enclosed closet I ensure that there is proper combustion air provide for the burner. I check for dirty legs in the gas supply line and shut off valves near the the furnace outside of the furnace cabinet. Keep in mind dirty legs should not be installed on gas lines that are exposed to freezing temperatures as moisture can accumulate in this dirty leg and rupture then we all know what happens next. I do not think you have to worry much about that in Florida or South Texas.

I also check the pilot light aluminum line where it connects to the control valve as I find a tremendous amount of small gas leaks on this line I use the old standard liquid dish soap (Dawn) in a spray bottle.These checks requires no more than 15 minutes.

Hope this helps somewhat.

Don't argue with an idiot someone watching may not be able to tell the difference.