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How Much Do You Disassemble?


hausdok
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Hi All,

Had a situation yesterday where a client shot me an email to tell me that when he'd finally gotten around to getting the 14-year old furnace on the house he bought serviced, as I'd recommended, that "as soon as the technician opened up the furnace he found a crack in the heat exchanger."

I drove over there last night thinking that as soon as I took the cover off that unit that there would be a crack visible. There wasn't. I looked and looked but couldn't see a crack.

"Where's the crack," I asked the client. "Behind there," he said, pointing to the bakelite plate behind which I'd find the limit switch if I were to open up the unit.

"Well, that explains it," I answered, "I'm only doing a visual inspection on these furnaces and I wouldn't have removed that component to look inside. Other than to remove the cover, about the only thing that I ever remove is the heat shield, if there is one, so that I can get a better look into the combustion chambers."

Just to see what kind of crack he was talking about, I pulled the switch to look behind it. There, right at the edge of one of those dimples in the exchanger elements, was a crack. Not a wide crack, mind you, but one that I could feel with the tip of my finger and see. the sides of the crack were slightly offset from one another. It seemed odd to me that a service tech would have pulled that - it's almost like the guy knew what he'd find.

Thinking about that crack afterward, I had the sneaky suspicion that if anyone stuck the rubber handle of a screwdriver through that opening and jammed it sideways a little bit that they might have been able to cause that crack; but, not seeing any tool marks anywhere I knew I didn't have a prayer in hell of proving that. Wish I'd asked the client if he'd been there when the HVAC guy pulled that switch though.

I reassembled the furnace and explained to him that, not excusing the fact that there is a crack, I thought the furnace company might be overstating their case. Then I explained to him what I'd heard from Ellis Pracht, The Heat Exchanger Expert; that allegedly about 95% of all furnaces have cracked heat exchangers, that the HVAC industry knows it, and that folks aren't too concerned with it because, when the system is running and the fan is on, that the exchanger is under positive pressure, and, if the flame is adjusted to a good 10 to 1 combustion ratio that there is practically no CO being produced and that it was unlikely that it would get into the air of the house unless there was a serious flue obstruction.

He told me up front that he doesn't intend to replace just the exchanger as recommended by the tech because it costs about half of what a new furnace would costs; so, if he must he'll install a new furnace. I explained that the new furnace was the way to go but if he opted not to do that right away for some reason he should at least get the HVAC guys back in to check the air/fuel ratios on the furnace to ensure it's burning cleanly and install a couple of really sensitive CO detectors.

OK, that's what happened, but the question isn't about the recommendation I made to him - which I'm kind of uncomfortable about - or even about the crack - it's about how far any of you go to look inside one of these heat exchangers.

Below this switch/sensor there is a narrow metal shield. Even with a one of Jim's long strips of mirror, I doubt that anyone could have seen the sensor or the crack above it; I would have had to use a See Snake or something similar to get up into the area where that switch is, or done what Pracht is always talking about, pull the plenum on top and looks straight down into the unit or pull the air handler blower from underneath, shinny into that return plenum and look up into the furnace with a flashlight. Or I could do what that particular HVAC tech did and pull that limit switch and look through that 1-1/2-inch wide by 2-1/2-inch long hole.

Most of that, with the exception of pulling a heat shield off and using mirrors to look up into the heat exchanger is not how I'd been taught to inspect these things and now I'm wondering if a lot of guys pull these sensors.

What say you all?

ONE TEAM - ONE FIGHT!!!

Mike

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I experienced a similar situation a few years ago.

The HVAC tech removed the sensor and was able to see inside and found a crack. The tech was hired by the buyer before the inspection contingency expired.

Even if the crack was discovered long after closing, I would be 100% confident of my position and prepared to defend it. After all, it's spelled out pretty clearly in my inspection agreement the heat exchangers aren't covered.

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Mike,

I have never disassembled a furnace to get a "better" look at the heat exchanger. I always crank up the thermostat, check the flame pattern(both with the blower on/off) and almost always recommend a cleaning and maintenance call by a qualifed HVAC contractor. I find that most homeowners, just don't have their furnaces serviced, as is recommended.

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I do exactly what you do, Mike, and would have handled the situation similarly. With one major exception. What you wrote about cracks and pressure differentials is spot on, but I think you made a mistake telling the guy it was okay to operate the furnace knowing the heat exchanger was cracked.

Anything wacky that happens after you say that to him . . . anything at all, and he's gonna bleat, "But the inspector dude said it was okay to run the heater."

The only way to get a really good look at a heat exchanger is to slide the squirrel cage out and stick your head inside the furnace. I can't imagine anyone does that during the normal course of an inspection.

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Mike,

I have never disassembled a furnace to get a "better" look at the heat exchanger. I always crank up the thermostat, check the flame pattern(both with the blower on/off) and almost always recommend a cleaning and maintenance call by a qualifed HVAC contractor. I find that most homeowners, just don't have their furnaces serviced, as is recommended.

I remove the front cover and watch the flame action when the unit is running. I also remove the blower compartment door and filter. I think removal of any other components is outside our scope. I clearly note in my default comment about the furnace's operation that only the front access cover was removed and internal components, heat exchangers, return/duct sizing, etc. is outside the scope. I also note that the unit was only operated using normal operation controls (ie, thermostat).

Even if we can see the the heat exchanger (on older models), we can probably only see a very little part of it. Telling the client 'no cracks were visible' only gives part of the story. Recommend a thorough clean/service of the system if no service records are present from the past 12 months.

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I never remove any parts except access panels designed to be removed for inspection or service. That does not include removing parts, ANY parts. There is no way anyone can use a mirror, SeeSnake, or any other tool to do a full inspection of the heat exchanger without total disassembly. We perform a limited inspection, not an technically exhaustive specialized inspection. The tech in your case either got lucky, knew from experience where to find a crack on that particular furnace (unlikely) or caused the damage in order to sell a new furnace (not unheard of).

We have to know our limits and keep our clients informed of the limitations.

I keep thinking I want to include the "I'm not Superman and I can't see through walls..." line in my contract. I do sometimes mention it verbally and it seems to get the point across.

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The only way to get a really good look at a heat exchanger is to slide the squirrel cage out and stick your head inside the furnace.

Agreed, but I bet this particular crack wouldn't be visible doing that.

The tech's I work with agree with Ellis; pretty much every heat exchanger has a crack, and if it doesn't, it will tomorrow. Lots of brand new heat exchangers have cracks.

I don't pull the sensor plate.

The guy got lucky, and you got unlucky.

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The only way to get a really good look at a heat exchanger is to slide the squirrel cage out and stick your head inside the furnace.

Agreed, but I bet this particular crack wouldn't be visible doing that.

The tech's I work with agree with Ellis; pretty much every heat exchanger has a crack, and if it doesn't, it will tomorrow. Lots of brand new heat exchangers have cracks.

I don't pull the sensor plate.

The guy got lucky, and you got unlucky.

Maybe not, but maybe. The guy who taught me, and with whom I've pulled several blowers, does a visual from below, then stays in place while someone shines a flashlight into the individual chambers. If the crack is in the upper portion of the exchanger, you can often see the light-beam leakage.

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I think Kurt is spot on. This is a numbers game, and nobody bats 1.000. If you inspect enough houses, sooner or later you're going to have one of those conversations. That's why it's so important to explain the limits of what we do unmistakably clearly.

We can't know everything and we can't see everything. We have to learn as much as we can; make sure we see as much as we can; and make sure our clients know what they're getting from us and what they're not.

Then, you go home, eat a nice dinner, sleep soundly, and do it again the following day.

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I haven't looked at a heating system yet that hasn't needed service. The only thing I do that hasn't been mentioned yet, during the heating season I try to make mental notes of how many times I hear the system run. Not a specific count mind you, but a general idea. If I only notice the system running once, or if it runs more than 3 or 4 times during the course of an inspection, I know there is something not quite right with it. Beyond that, if the furnace fires while I'm inspecting something else close to it, I'll stop and do the furnace while it is running, then go back to what I was doing. I don't have to worry about resetting T-stats that way.

Tom

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John,

I agree with you, it's not the best recommendation; but, early in this gig and long before I'd met Pracht, I'd looked into a 24-year old gas furnace one day and saw a hole in the back of the heat exchanger that was about the size of a 50-cent piece. I straightened up, declared that there was a hole in the heat exchanger and that the furnace was a CO hazard and told my client that it needed to be replaced. This was one of those inspections where the listing agent "was just passing by" halfway through the inspection and was standing nearby in the basement talking to the selling agent. When he heard me declare that the furnace was a CO hazard, he come over to us and said, "That's nuts; that furnace was just serviced. If there were a hole in the heat exchanger these folks would be dead right now." I just handed him the flashlight and said, "See for yourself, back wall of the second chamber from the left." He bent down, took a look, stifled a curse, handed me the flashlight and said that he was calling the tech that had serviced the furnace right away. Then he got on his cell and went outside.

After he went outside, we all could hear him ranting on the phone at the HVAC firm, even down in the basement. A few minutes later, he came back inside and said to me, "The furnace company says that there is nothing to worry about as long as there is a proper 10 to 1 combustion ratio and a clear flue. Did you know that and measure the combustion ratio?" I responded, "Yeah, I know about the 10:1 ratio deal but nope, I'm not going to measure the exhaust gas. I'm not a furnace tech, I'm a home inspector. I did test the exhaust and got acceptable readings, but there's no way you'll convince me that a hole the size of a Kennedy half dollar in the back of a furnace that's 4 years beyond it's expected service life, that wasn't there when it was manufactured, is acceptable. You might be able to convince them though (motioning to the clients who were standing there listening)."

He realized that I wasn't listening to "the code" that he was sending so he turned it on the selling agent whose transmitter picked it up right away. I went back to what I was doing but glanced at the clients and gave them a roll of my eyes as if to say, "What a maroon; can you believe this dildo?" They got it, within ten seconds of the selling agent trying to retransmit the code to them, the husband cut him off and said, "Hey, this is why we hired this guy. The furnace is obviously shot. If the seller isn't willing to replace this furnace when we've offered more than the asking price for this house, he can try selling it to the next person because we won't be buying it."

I just continued on with what I was doing. They stood in there arguing for at least five more minutes before the couple caught up to me, the selling agent in tow and the listing agent having left.

That hole was big enough that you'd expect that all of us standing there would have been overcome by CO poisoning but we weren't. After that job, I've always felt like I was splitting hairs when I found small cracks in heat exchangers and wrote them up. I write 'em up anyway; after all, they allegedly weren't there when the furnaces were made,...or were they?

Everyone,

Thanks All for your responses. I was pretty sure that I wasn't doing anything differently than most other inspectors and I was right. The client trusts me (I've done four inspections for his family), so it was pretty much up to me to fess up if I'd screwed up. He listened to my explanation and agreed that there was no way I could have known about the crack. I also explained that, per the terms of the contract, heat exchanger cracks aren't covered, but that I'd rather refund his fee, if it would ease his pain, than to have a customer that's unhappy with my service.

He said that he had no expectation that I should bear responsibility for it when he contacted me, but that he did want me to know about it, because it seemed like such a simple thing to do - remove two screws to look behind that switch (...and it is, I'm thinking about adopting it as part of my procedure) - and he wasn't sure if I'd done that or not. He'd remembered me taking something off the furnace in his Dad's house (the heat shield) but couldn't remember what it was. He said that he knew I'd accept responsibility and do the right thing if I'd messed up, so he refused the refund, saying that he trusts me and accepts my explanation. He and I are solid.

I was pretty confident that you guys would spank me pretty hard if I'd screwed up. If I had, I'd be mailing him a check to cover the cost of a new furnace right now, regardless of the terms of the contract.

You guys are what makes TIJ such a great resource. Thanks for being part of the TIJ family.

ONE TEAM - ONE FIGHT!!!

Mike

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I agree with most posts, that finding that crack would have been outside the scope of the home inspection. I emphasize both verbally and in the written report how important it is to have an HVAC contractor perform an additional inspection and service to maintain prior to closing. I explain/document the potential for a cracked heat exhanger. That has always served me well.

I do find it frustrating to make a call ( bad heat exchanger, bad roof, etc) to only have a technician, contractor, etc fully bless it, as the one did in your example of the 50 cent piece hole in the exchanger. Then to turn around and have another technician condemn something not "readily visible" and not any where near the magnitude of the previous example. Some of these contractors are eager to throw the home inspector under the bus, while they are "making a sale".

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Mike,

I probably play defense more often than is necessary, but like me, I'm sure you take heat for all kinds of dopey stuff, whether real or imagined. So . . . I typically err on the side of wimpy.

Having said that, I've never--not even once--heard of anyone succumbing to CO poisoning due to a cracked heat exchanger.

The only CO incident that made news in my area during the past few years occurred because birds had nested in a water heater flue-pipe. The flue gases spilled out into the house and sent an entire family to the emergency room.

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Mike, clearly pulling the high limit sensor is well beyond the standards. There should be no expectation on the part of the customer that you'd find that crack.

Having said that, I'll admit that I thought this was my own personal secret inspection technique for Carrier-design furnaces. I've been doing it for some time with great success.

If you want to attempt this technique is it absolutely necessary to SHUT THE POWER to the furnace before you begin. If you don't you can short out the leads to the switch and blow a fuse in the circuit board. This can ruin your whole day. Also, when you're done, TURN THE POWER BACK ON or that can ruin your whole day too.

- Jim Katen, Oregon

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Mike, clearly pulling the high limit sensor is well beyond the standards. There should be no expectation on the part of the customer that you'd find that crack.

Having said that, I'll admit that I thought this was my own personal secret inspection technique for Carrier-design furnaces. I've been doing it for some time with great success.

If you want to attempt this technique is it absolutely necessary to SHUT THE POWER to the furnace before you begin. If you don't you can short out the leads to the switch and blow a fuse in the circuit board. This can ruin your whole day. Also, when you're done, TURN THE POWER BACK ON or that can ruin your whole day too.

- Jim Katen, Oregon

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Pretty darn slick........I've always wondered what was behind that sucker.

That said, if that teeny crack was on any of the other several dozen dimples, you'd never see it. Is there something that makes it crack right there by the sensor more than anywhere else?

That's where they crack, though. They stamp that dimple in and it fatigues the metal. The tech I've worked with has shown me dozens of those, and they're always on the dimple edge.

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. . . Pretty darn slick........I've always wondered what was behind that sucker.

That said, if that teeny crack was on any of the other several dozen dimples, you'd never see it. Is there something that makes it crack right there by the sensor more than anywhere else?

Don't know. I can, however, see several of the dimples from that little opening and the one near the opening seems to crack the most often. I think it's because it gets hottest there. The limit switch has a little metal shroud over it that slows down the air flow in this region. That might mean that the heat exchanger gets hotter in that particular spot -- just a theory.

- Jim Katen, Oregon

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Reasonable theory....it might also be that the engineers know that's the hottest area, so that's where they place the sensor.

Either, way, next time I see one, I'm pulling it and looking. You just shut off power at the unit, right?

I shut it off at the breaker and test for power at the unit to be sure.

I loosen the lower screw that holds the backing plate on and remove the top one. (Later I'll use the screw that I only loosened as a register to hold the sucker back in place.)

Very slowy and carefully slip the switch out and place it one one side. Be especially careful of the gasket material; you don't want to loose it. There will probably also be a metal baffle above the switch, held on by a third screw. Carefully remove that. Don't drop it down between the heat exchanger sections.

Then use your fancy girly-man LED flashlight to peek inside. You should be able to see about a half dozen of the dimples if you crane your head around & use a small mirror too. But the most obvious cracks will be right there in the front where you can easily see them and feel them.

It works best with the Carrier 80% designs including Bryant, Payne & Day & Night.

Don't even bother with the Rheem/Ruud furnaces, they have those tubular exchangers and you can't see a damn thing.

- Jim Katen, Oregon

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Slight drift, but since Jim is feeling professorial. . .

I once blew a three-amp fuse replacing a thermostat for a friend, because lots of Carrier thermostats have "common" wires, whereas most others don't and I screwed up somehow. I inadvertently touched a couple of wires together (no clue which) and blew the fuse.

I've never understood the reasoning behind having the extra wire. Any clue?

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Slight drift, but since Jim is feeling professorial. . .

I once blew a three-amp fuse replacing a thermostat for a friend, because lots of Carrier thermostats have "common" wires, whereas most others don't and I screwed up somehow. I inadvertently touched a couple of wires together (no clue which) and blew the fuse.

I've never understood the reasoning behind having the extra wire. Any clue?

I'm afraid I have no idea. But I think that the common wire thing has less to do with Carrier than it has to do with the functions of the thermostat.

- Jim Katen, Oregon

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