Check Gas Heat Units Frequently

After reading Tim McElwain’s letter to the editor about preseason checks [“Preseason Checks,” Nov. 19], I am glad that I am in AZ. We do not use a lot of heat here, but I cannot imagine letting a system go for five years before checking it out. A service check on a heating system is not only for operation but also for safety.

The checklist that he gave did not include what I consider to be one of the most important checks in it. That would be the heat exchanger inspection. With the dangerous possibilities that accompany the heat exchanger, I don’t see how you can let it go without checking it for that long. I have seen too many heat exchangers crack and allow carbon monoxide to leak into the home and some on fairly new equipment I have done service work for over 20 years, and I would never endanger someone’s life or my company’s reputation by that kind of negligence.

I don’t know how others feel about this issue, and he did say that people would find a hundred reasons to disagree with him, but this is my main reason. I hope that I am not the only one to feel this way.

Jerry Hanen, Operations Manager, Palmer’s Plumbing Service, Inc., Youngtown, AZ

McElwain’s Reply

My comments regarding John Hall’s article about preseason checks on heating systems [“Sears Service Deal Make a Good Impression,” Oct. 29] were not designed to be a comprehensive check of a heating system. Those checks I gave were designed to cover a one-hour quick check of a customer’s system.

It is also important to note that a thorough inspection (not just a visual) of a heat exchanger to determine a crack or hole cannot be done along with all of the rest of the checks in one hour. I’m curious to know how this individual is testing the heat exchanger.

There are two recommended methods in use today, the use of an infrared inspector camera and the “tracer gas technique.”

I would be surprised if everyone is doing that check on a preseason check. It is also a misconception that a cracked heat exchanger causes CO. Cracked heat exchangers do not cause CO. A cracked heat exchanger causes the gas and secondary air mix to be changed, typically making the mixture too lean; this would actually reduce CO. [Either]:

  • More air is pulled into the combustion chamber; or
  • More air is pushed into the chamber.
It is my experience that CO problems on hot air, hot water, steam systems, and also water heaters are caused primarily by insufficient air for combustion and operating the equipment in contaminated environments. The other cause is internal pressure changes in the building caused by exhaust fans, fireplaces, etc. In all cases, this usually causes recirculation of products of combustion (carbon dioxide), which in turn “quenches” the flame. The resultant CO can then be distributed very easily by the warm-air system because of its ducts entering into the living spaces, the blower door being loose, ducts not sealed properly, etc.

The cracked heat exchanger can, however, cause a change in flame stability. This will, in turn, cause the flame to impinge on the cooler heat exchanger surface. This will cause carbon deposits and eventually CO, usually accompanied by a pungent odor called aldehyde. Keep in mind that CO is odorless, colorless, and has no way of being detected without a CO tester.

It has been my 40 years of experience with gas systems that yearly inspections are not necessary. The utility I worked for had 100 service techs servicing all aspects of gas systems, giving full service. That company never offered maintenance contracts or preseason checks. We sold parts and service agreements only. During my 28 years with them and in my business since, I have had very little reason to recommend annual checks. I will stand my ground on this one. I will say, however, if you are going to do checks and charge the customer, then do a very thorough inspection.

Tim McElwain, President, Gas Appliance Service Training and Consulting, Riverside, RI

Publication date: 01/14/2002