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Hole in heat exchanger


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How safe is a furnace with a small hole in the heat exchanger? Rivet has deteriorated in 20 year old furnace. The flame is mostly blue with some orange tips. How safe is this with carbon monoxide detector present?

Livingston

Cedar Rapids Home Inspector

http://www.cedarrapidshomeinspectionllc.com/

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I wouldn't attach much importance to that carbon monoxide detector. One that would have the sensitivity to warn adequately would also annunciate in the presence of lots of other substances and result in a lot of nuisance alerts. People would simply turn it off. That's why they don't make them that sensitive, the technology to single out that particular gas and none other to the smallest concentrations that can sicken people just isn't here yet.

If the hole is only the size of a rivet, the amount of leakage multiplied by the amount of CO in that leakage leaves too little CO to be a worry.

20 years is a pretty good life for modern gas furnaces. I might write it up anyway as an excuse to recommend replacement.

Marc

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For my day job, I shut off and red tag (warning tag saying "DO NOT USE") any furnace with a cracked heat exchanger. Even if you only see one small crack/hole, there could be others.

I wouldn't recommend telling anyone that it's OK to use a furnace with a defective heat exchanger. While it usually wouldn't be a big deal, the perfect storm could happen.

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I'm with Marc,

It's a 20-year old gas furnace with a defect in the heat exchanger. They have an expected service life of 20 years. It's done what it was designed to do and lasted as long as it was designed to last. Time to get a new one.

ONE TEAM - ONE FIGHT!!!

Mike

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I wouldn't attach much importance to that carbon monoxide detector. One that would have the sensitivity to warn adequately would also annunciate in the presence of lots of other substances and result in a lot of nuisance alerts. People would simply turn it off. That's why they don't make them that sensitive, the technology to single out that particular gas and none other to the smallest concentrations that can sicken people just isn't here yet. . .

The technology has been around for a long time, it's just a matter of price point. My old Biosystems Toxilog from 1992 could do it easily. However, it cost $1,200 at the time and the modern equivalant probably costs more. No one wants to spend $1,200 on a CO alarm.

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  • 2 weeks later...

The other day I had a house that was a rental property and it had a 45 year old Rheem gas furnace. I took one look at that thing and thought, "Oh brotha!" The inspection was attended by the homeowner's property manager, who watched everything I did like a hawk and every so often walked off about 50 yards got on his cell phone. I asked the buyer's agent what was up with him - she explained that he was under instruction to monitor everything I did because the tenant was concerned about theft and damage to her property. The client was OK with it so I just did my thing.

Anyway, I got a new toy about a month ago; a bore scope/camera. Picked it up on sale at Harbor Freight for a little under $200. I'd been seeing the cheap non-camera $99 one for a couple of years but didn't get interested until they came out with an HD version.

So far, it's performing as I'd expected a less-than-$300 camera would perform - actually much better, and I think it's already paid for itself in terms of stuff discovered. This seemed like the perfect situation; 'cuz that old furnace, and a lot of other clues, told me the homeowner was pretty tight with a nickel and wasn't liable to believe anything I said about that furnace unless forced to do so.

I got out the scope and started from above through the draft hood. After just a couple of minutes I found a hole about a quarter inch in diameter and a broken button between two sections of exchanger in the right chamber. Each time, after I found the defect, I showed it to the client on-screen and then turned, looked at the watcher and motioned with my head for him to come over and take a look. He did so silently. The other two chambers were clean from above so I moved to the combustion chambers below. I didn't find anything in the right chamber or the center chamber but when I went into the left chamber it was all bright blue from intense heating and I knew I was going to probably find a crack. Sure enough, within a minute or two I found an obvious crack about two inches long.

After I showed the client, his realtor and the watcher that screen, I put the scope away, threw the breaker on and yelled inside to give Yung the OK to turn on the heat. As we waited for the furnace to come on, I told them, "Watch those three burners as they come on and then listen for the air handler to come on. When it does, you'll see some interesting stuff in those chambers with the cracked heat exchanger but that middle one will probably not change. The agent asked why, but before I had a chance to answer there was a click from the control valve and a second later the furnace came on with a whoosh. I pointed and said, "Just watch." The thing heated up for about two or three minutes and then, just as the impatient agent started to utter something, the blower kicked on and the flame was practically blown out in the left and right chambers and the center one stayed almost perfectly consistent. I turned and looked at the watcher. He had a grin from ear to ear. You could tell he was silently thinking, "Kewl Dude!"

A little while later he walked off to make another call on his cell. The client and agent took that opportunity to ask me whether I definitely thought that the furnace needed to be replaced. I said, "That furnace was designed to last about twenty years; it's now 45 years old and it has cracks in it. What do you think?" The agent then said, "I heard that a cracked heat exchanger could poison someone. Obviously this one hasn't done that." I told her, if it were a 19 year old gas furnace I would have told you to think of your furnace as Grandpa - Grandpa is in the nursing home under constant watch. Nobody knows when he'll expire but everyone knows that given the average life of men in his family it's not going to be very long now. "In the case of this one," I said, "you've got a zombie furnace. It died long ago but nobody knew it. Leaving that furnace in this home is like playing with fire - sooner or later, despite the fact it hasn't hurt anyone....yet, it's going to hurt someone. It needs to go."

Right about then the watcher walked over and caught the tail end of what I'd said. He spoke for the first time, "Don't worry about the furnace, the homeowner says you'll get a new one of your choosing." That's when I looked at the client and said, "If you don't remember anything else I've told you about this furnace, make sure when you start looking for the furnace of your choosing you use the words "Category Four," Can you remember that?" The client whipped out his smarty-pants phone and started thumbing the hell out of it and responded, "Category IV," you got it."

I can't help but think that if I hadn't had that little HD scope and been able to show them such a clear picture of those defects and been able to predict the outcome so clearly, based on those observed defects, that the homeowner probably would have been a whole lot more resistant to whatever I'd said in my report regardless of the age of the furnace.

So far, I'm not unhappy with my little HFT purchase, regardless of where it was made.

ONE TEAM - ONE FIGHT!!!

Mike

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