Methods of Certifying a furnace
It is unfortunate that in the HVAC industry there is really no formal ruling as to how a “Clean & Certification” is defined or its procedures. Each contractor takes a little different approach based on what they deem a clean and certification should be and or the limitations of their test equipment. More likely it is the technicians lack of training and understanding of combustion basics that limits him.
It is generally excepted that there is some level of cleaning involved as well as a basic check of the safety components and associated equipment (i.e. combustion runs, disconnect switch, gas line, etc.). Finally there is one or more tests done to verify that there is not a leaking or damaged heat exchanger. At the end of the clean and certification process the contractor may have a list of suggested repairs or replacements.
Colorado Residential customers can expect to pay anywhere from $125.00-$250.00 for a true Clean and Certification (depending on methods used). However, in most cases a certification is only required for the sale of a home and is not part of a yearly tune-up or preventative maintenance program. Normally an adequate cleaning and inspection is all that is necessary for a basic yearly maintenance. A “tune up”, which this article does not address, is usually a more involved process and in most cases, results in additional or separate costs.
Many contractors only clean some of the furnace with a shop vac. Additionally they rely on a single test method to inspect the heat exchanger. Make sure that your certification shows evidence of both the integrity of the heat exchanger and provides actual data detailing the combustion efficiency of the unit. In English this means the potential home buyer will be satisfied that the furnace is both safe and operating as well as the day the furnace was installed. Remember that this should only be done by a qualified technician that carries a current “Heat Exchanger Expert” certification. Ask your technician to provide these credentials so that you may rest assured that your furnace is in good hands.
This Article represents only a fraction of the different kinds of methods that are in use today. In 1986 The American Gas Association (AGA) printed a “Fact Sheet” that explained that the gas tracer method was the most reliable testing procedure.”
This test is still in wide use today and even requested by many home inspection companies. While the gas tracer procedure is effective on tubular exchangers it should be noted that these tests by the AGA are nearly 30 years old. Since then much research and development has been accomplished in this area. We have found this test to be unreliable on serpentine and clam shell heat exchangers because more often than not it will give a false positive to a crack. If the test is not administered carefully the leakage from the test itself will lead the tester to believe that there is a crack when one may not even exist.
Another common method is to run the furnace to full operating temperature and then place a digital carbon monoxide detector above the furnace into the air stream. This is to check for CO in the breathing air. This test is a good test to be used in other diagnostics and to help narrow down a possible leak in the home but is not a sufficient test for a “Certification”. In our experience this test will only catch about 10 out of 100 furnaces with cracks. In these cases the measured CO was hardly even noticeable and could have been misinterpreted to only be the + or – 3 ppm of a typical variance in the detector itself. Additionally the measured CO is highly diluted. So it is a challenge to accurately measure the actual ppm in the breathing air. Besides even if the contractor was to measure up to 9ppm (+/- 3ppm) in a workplace, it could still be thought to be “safe” and therefore not reported. This furnace could then be deemed “Certified” by the technician performing this method.
(9ppm is an 8 hr. acceptable maximum according to Occupational Health and Safety Act (OSHA)
In most cases a cracked heat exchanger will not result in CO leaking into the breathing air but Oxygen (O2) be forced into the heat exchanger, through the crack, by the positive pressure circulatory blower wheel. The potential of CO in the breathing air as a direct result of a cracked heat exchanger exists, but is rarely ever the case. The more likely cause of CO in the breathing air will be caused by a problem in the venting system or may be coming from another source altogether
There many unlicensed and untrained technicians in Colorado who do not have the first clue how to test a heat exchanger or provide a detailed combustion analysis. There are different test procedures for the different types of heat exchanger. For example a hydro (water based formula) solution sprayed on a natural draft “clam shell” style heat exchanger is an excellent way to find a breach or crack. However the AHRI strictly condemns this method, ( 2009 (Guideline X) “Guideline for Induced Draft Furnace Heat Exchanger Inspection”.) for use on a induced draft furnace. This is because the majority of induced draft furnaces do not have “clam shell” style heat exchangers and if this test is used it will ALWAYS show a leak even on a brand new heat exchanger.
While there are no real clear laws governing this practice in Colorado there are some highly respected sources who are providing guidelines to the HVAC community. The American heating and refrigeration institute (AHRI), Bachrach, inc (founding member of the Green Mechanical Council), The ecso institute, COSA, and many others, offer hundreds of years worth of training and experience on these test methods and the value of understanding the combustion process.
Square One’s approach is to use as many methods necessary to ensure a safe and comfortable environment for our valuable customers and to set a standard for technicians across Colorado. Our target range for acceptable CO in a customer’s home is 0.00ppm. Our technicians run full combustion analysis before and after they clean and certifiy each furnace so as to provide actual tangible data to our clients. Our clients can see the improvements that our techs made during the cleaning process. This data is also recorded and filed for our customer’s so that we can track the performance of their equipment from year to year and to raise our odds at finding a safety issue BEFORE it ever becomes dangerous. If an unsafe situation is found we can provide the diagnostic camera views as well as a printed data, directly from our instruments, and computer software that show the measured failure(s). Our techs will then advise you on the best course of action to take with that information and in most cases they are capable of making the repairs at that time.
It is important to remember that furnaces over 13 years old are not always certifiable. We have learned that the average expected lifespan of a gas fired furnace in Colorado is approximately 7 years so many companies will not certify anything beyond 13 years old. This short lifespan is directly due to improper furnace installation and lack of professional maintenance. While 13 year limitation is not a law, many contractors are justifiably concerned that the liability is just too high. A failure on the furnace or a breach in a heat exchanger is a serious problem and precious lives hang on a technician’s decision. Most people do not maintain their equipment on a regular basis. So the safeties, heat exchangers and the years worth of inadequately maintained equipment make for a liability nightmare. We understand that receiving bad news about your furnace is troublesome but your safety is by far our number one concern.
Recent Tweets
