Did Your Home Inspector REALLY Inspect Your Furnace?

Over the past thirty one years of watching home inspectors perform home inspections I have come to the conclusion that not all inspectors are created equal. Most do an outstanding job yet many seem not to be very well trained. Unfortunately, the buyers assume they are getting a complete home inspection with every inspector.

One potentially very expensive area for your inspector to be inadequately trained is when the heating system is being inspected. Most inspectors use a flashlight and mirror to inspect the visible portion of the heat exchanger. Some even go to the bother of removing the blower unit so they can see a larger portion of the heat exchanger. But even this procedure allows visual inspection of less than 50% of the heat exchanger (according to heating contractors I have spoken to.). Note: if the heat exchanger is cracked and it is later determined that you need a new furnace, your financial exposure will be around $3,000. And, no, your inspector can not be held liable for the furnace replacement expense. - The agreement you sign when you hire them states that they can only be held liable for damages up to the amount you paid them to do the home inspection.

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Many home inspectors and even HVAC heating contractors go a step further to test the heat exchanger. They use an inert gas test to verify the condition of the heat exchanger. This gas test can detect large cracks in the furnace heat exchanger, but then again, this type of test has missed cracks in exchangers so many times that many HVAC contractors no longer rely on inert gas tests to determine the health of a furnace. Most home inspectors do not offer this type of test. Most simply rely on a gas detector called a Tiff 8800. This little red tester should never be used to determine if a heat exchanger is cracked. It just is not sensitive enough to do much more than find leaking natural gas from the supply piping to the furnace. I have personally seen HVAC contractors test a furnace with a known cracked heat exchanger with one of these inexpensive devices with no detection of the carbon monoxide leak.

I recently called ten HVAC contractors to learn more about how they determine if a heat exchanger is cracked. The general consensus of my investigation was that a highly sensitive tester must be used. The follow manufactures of gas testers can test particles of carbon monoxide down to one part-per-10,000. (However, NOT all of these manufactures units specifically test for carbon monoxide.) You need to specifically ask if the tester they use tests for carbon monoxide gas – the totally odorless type of gas that can kill you while you sleep.

1. Bacharach

2. Flied Piece

3. Testo

4. Snifit

There may be other brands of sensitive test equipment out there. Just be sure that your home inspector uses testing machine that can detect carbon monoxide particles of one-per-ten thousand or it is likely that you really will not know if the furnace you are about to buy is safe.

My understanding is that outside air can have three or four parts-per-ten thousand and that a furnace has a cracked exchanger when the levels go as high as around 30 parts-per-ten thousand. Be sure your home inspector also allows the furnace to run for at least 20 minutes before testing the air coming out of a floor vent. It often takes that long for the metal in an exchanger to expand to allow carbon monoxide gas to leak out into the air you will be breathing.

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If your future furnace is properly tested and it is determined to have a cracked heat exchanger, you might as well expect the seller to pay for a new furnace. It is a lot less expensive for you to catch the problem before you become the property owner.