Another life saved?

John R. Hall

You be the judge:

http://www.achrnews.com/CDA/ArticleInformation/RegionalNews_Item/1,6084,127756-South,00.html

jerry scharf_2

how common are furnace HX cracks

I'm asking this because of a recent experience. I was helping a friend change out a furnace (less than 10 years old,) and I decided to look at the HX carefully. There were 4 cracks that were at least an inch long, but none had spread very wide. These cracks were on the bottom of the tubes, and the only way to see them was to list the unit and remove the bottom. I doubt you could have seen them with an inspection mirror because of their location and accessability, and the unit had been serviced within the last year.

There was not a CO problem with the furnace, (I was helping to learn more about CO testing) but I found this disquieting to say the least.

What are your thoughts and experiences on finding hidden HX cracks on systems that otherwise look fine?

thanks,
jerry

Rudy

Changes in readings when the blower activates

When I was regularly running service, my experience was that watching for a change in the O2 reading when the blower came on was a good way to check for the soundness of a HX. If it went up more than 1/2 of a percent, I was pretty certain there was a problem.

Usually if the CO reading went up (when the blower came on), the crack was pretty substantial and there was obvious changes in the flame, you know, like flame chasing me across the basement!!

I've even seen the CO go down when the blower came on... but a change in any of the analyzer readings when the blower activates calls for a 'closer look'.

Glenn Harrison_2

It's very common to have cracks in HX's

it however is very uncommon to have those cracks cause immediate problems. However, you don't want to take the chance that they will grow and cause eventual problems.

As Rudy said, a combustion analyzer can be very helpfull in finding those hidden cracks.

I personally feel the best way is a thourough inspection, including pulling the HX (easier said then done on many units). But even this is no guarantee, as there maybe a seam that looks fine, until the HX is heated up, then the seam opens up and starts leaking.