Marketing with a local Realtor Saturday and she told me this interesting story. She used a somewhat local inspector once, and once only, followed him around and it came time for the HVAC inspection. From what she said, he tried to impress her with spraying water into the HVAC as it was running to check for a cracked heat exchanger. He stated, look at the flames, you have a crack. She wanted my opinion and I stated as to not hearing of that before. Her impression was he was trying to impress her with his vast knowledge.
My question, is this common practice to check the heat exchanger in this fashion? Don’t want to make a judgment until I have the skinny on this.
New one on me. I have never heard of it, and I sure as heck would not try it. I can hear the Attorney Ask and what standardization is that spray water into the heat exchanger adapted from, and what training have you had to spray water into a lit furnace?
[size=3]Types of Heat Exchanger Tests
There are three basic types of heat exchangers: clamshell, Serpentine, and tubular. This article is going to focus solely on the clamshell because it is most commonly found on the older models (typically installed before 1990) and is still in use today. The Serpentine & tubular exchangers are common on a portion of the newer furnaces (mid '80’s - today) and different tests should be applied to these. Leak Test: **
** For the clamshell heat exchanger, the most accurate test is the leak test. **This test involves spraying the outside of the heat exchanger with a water-surfactant solution and then looking on the inside to see if it has leaked through. **If it has, anyone conducting this test is 100% certain a crack exists. This test will find 95%+ of all cracks in the clamshell heat exchangers. Visual Inspection:
For a clamshell heat exchanger, a visual only inspection is the most ineffective test. Some companies try to fool you by informing you they use “state-of-the-art” video camera systems to look for cracks. What they are admitting is they do not have proper training to inspect your heat exchanger. Using the expensive camera or mirrors, these companies will only find about 10% of the actual cracks. Why will they fail to find most of the cracks? Most furnaces at this stage of their lives have rust or soot buildup on the inside of the heat exchanger preventing anybody from seeing the cracks. Couple this with the fact that CO gas can seep through cracks not visible by the human eye and you can see their shortcomings. CO Gas Test:
If conducted alone, the CO gas test is another test where the HVAC company is admitting to you that they do not have proper training to inspect heat exchangers. This test has nothing to do with inspecting the condition of the metal of the heat exchanger. This test consists of boring a small hole above the plenum and inserting a carbon monoxide detector. The only useful information this test tells you is if the furnace is currently blowing carbon monoxide gas throughout the home. If they fail to let the furnace run long enough, the crack may not widen to allow the CO gas to leak out. Also, conditions have to be just right for CO gas to be produced. Unless the flame is burning inefficiently and is finding its way through the crack at that specific time when the test is conducted, their CO detector may never register any levels. If a crack is found using this test, chances are a crack existed in this furnace for almost 2 years! That is a long time to chance the safety of the occupants of the home!!! Smoke Test:
This test consists of setting smoke canisters inside the heat exchanger and seeing if the smoke leaks to the outside. Most companies that were conducting the smoke test in the past have graduated up to the leak test for the clamshells. The main reasons are the leak test is faster, has a higher probability of finding a crack, and does not set off the smoke detectors. One of the downsides to the smoke test, as with the CO Gas test, is if the heat exchanger is not warmed up enough, the test may not find the crack.
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I hope some HVAC guys will comment but I agree that it would be well beyond the scope of a “visual” Home Inspection.
I use a CO detector but the problem is you can have a cracked heat exchanger and still measure little CO in the exhaust stream if the burner is adjusted correctly.
Let’s hear from the HVAC guys on the board and see how they test heat exchangers.
Absolutely not this guy had not a clue as to what he was doing.
I personally use a Co detector as a HI. Is it fool proof NO but is the best source available to a HI as no disassembly is required. Some HI’s like to totally disclaim a heat exchanger as not being visible and this is true. I still perform a Co test and record the result better than a sharp jab in the eye with a pointed stick???
No argument here but keep in mind some home owners service their furnace every year and the rust at the bottom of the chamber has been removed and does not always give the appearance of its age. Any time a furnace has exceeded 20 years of life its just a roll of the dice as to when failure will occur. I am not a gambler and a furnace is not a piece of equipment that should be operated to failure You may wake up dead. I have found many furnaces with cracked heat exchangers using the Co tester and if I can save just one life its worth every minute I spend checking.
Spraying water into a hot heat exchanger will CAUSE a crack in the heat exchanger!
So, I guess he was correct!
For a home inspector; if you turn on the furnace (while looking into the burner ports) and wait for the indoor fan to come on. If the flame changes in any of the ports, you may have a leak. Outside of this, you are acting outside the scope of home inspection as it is going beyond “visual”.
Heat exchanger inspection/certification should not be attempted by HI’s as the liability is “way out there” and there is no sure way of testing heat exchangers 100%.
So ifI sub contract a local heat and air man to do my inspection’s ,and he finds a problem.Should he then not be the one to fix the problem? i know that if remodel repairs are needed my husband and i cannot bid on the repair work for 1 year after the inspection.I am curious how ethical this would be?I also really wondered if the clients need to know I sub that part out.Then if they call that same furnace man to fix any problems we reported then they would be hiring him.Would it be OK for him to do this work?
The homeowner should be able to hire anyone they want to. It is separate from your inspection and should be a business agreement and contract between those two parties. If they ask you anything about it that is exactly what I would tell them.
I always used a very bright light and a mirror or the smoke test myself however I’ve heard of other techs using the water spray method.
The metal heat exchangers are made of won’t crack from spraying water on it unless it’s made of cast iron.
Like was said there really is no 100% sure way to guarantee “no cracks” without completely dismantling a furnace but with a thoroughly executed inspection we can be reasonably sure it’s OK.
Many people think furnaces produce CO like an automobile exhaust does when in fact a properly burning furnace only produces CO2.
I’ve seen furnaces that have operated with cracked heat exchangers for years with no CO ever entering the duct work or living space BUT the potential of a very dangerious condition was still there because they could have started producing CO at the drop of a hat.
Anyway, CO is not necessarily a sign of a cracked heat exchanger and a cracked heat exchanger is not necessarily a sign of CO being present.