One year old Williamson-Thermoflo heat exchanger failure
Yesterday I did a maintenance call on a one year old Williamson-Thermoflo oil fired furnace. When the time came to do the combustion analysis I found the O2% in the flue pipe increasing significantly when the blower comes on. I shut off the oil burner and allowed the fan and limit control to run the blower until the heat exchanger cooled off. Then I measured draft in the flue pipe with everything off. When I manually started the blower the draft in the flue pipe went from -.01 to -.04".
Williamson-Thermoflo requires pictures of the heat exchanger failure so I stripped the jacket off the furnace and found the top of the heat exchanger bulging on all three visible sides and I found several large cracks in the back of the heat exchanger.
My problem is the tech support guy I spoke said they aren't going to warranty the heat exchanger because the chimney is an exterior masonry chimney (cinderblock with a 8"x8" terracotta liner) and the heat exchanger failed due to a "cold chimney" and back drafts. My draft measurements were within their specifications of -.02 to -.035". The burner flame retention head and combustion chamber showed no signs of overheating.
Does anyone else think this is BS? The chimney was in good condition. Even if it was in poor condition, a heat exchanger should last more than a year!
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My problem is the tech support guy I spoke said they aren't going to warranty the heat exchanger because the chimney is an exterior masonry chimney (cinderblock with a 8"x8" terracotta liner) and the heat exchanger failed due to a "cold chimney" and back drafts.
Are those requirements listed in the IOM?
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Unfortunately I didn't have the manual on site. I'm sure my boss is going to look into it. I've worked on hundreds if not thousands of oil burning furnaces and boilers with the exact same chimney. My chimney at my house is identical to it. I've never once experienced any issues associated with down drafts due to a "cold chimney". The stack temperature was well over 400⁰. The draft was within specifications. I don't think the chimney was a problem whatsoever.
Airflow on the other hand....that was likely the culprit. Homeowner was using an extremely restrictive 1" filter, and it was filthy. The evaporator coil was really dirty. But the manufacturer didn't even ask me about that. They were super quick to blame the chimney, without even seeing the pictures of the heat exchanger and furnace. I'll post the pictures here when I get a chance.
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Take it up the chain.
Ive read a few manuals and do not recall that requirement. Minimum, maximum sizes yes. Not in exterior chimneys?
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Sounds like BS fight them.
Sounds like something went way wrong the HX failing in one year is awful. I wonder what the temp rise was?
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@SuperTech said:
Airflow on the other hand....that was likely the culprit. Homeowner was using an extremely restrictive 1" filter. The evaporator coil was really dirty. But the manufacturer didn't even ask me about that.
I'm not a heating pro, just homeowner/engineer. But I had to troubleshoot an overheating gas furnace at my church last year, and airflow was indeed the culprit. Installers had installed an undersized return plenum that increased the static pressure far above mfr's spec, choking airflow and causing repeated shutdowns due to overheating.
My question for your situation is, why didn't the customer's furnace shut down on thermal overheat protection? Our church furnaces, standard Carrier models, all have temperature sensors on the heated air side of the HX that will shut them down when the sensed air temp gets too high. This is supposed to prevent damage to the HX in just such a low-flow condition. So why didn't your customer's furnace shut down to prevent those overheats? Faulty sensor?
If you can prove the temp sensor is faulty, then maybe you have a shot at warranty remedy.
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From damage description sounds like classic overheat. I'm betting with JESMED1 on high limit failure.
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These oil furnaces have an old fashioned fan and limit operating control that cycles the blower and oil burner on and off as the furnace heats up. It's much different than the safety high limit switch on a gas furnace. That's another reason why I called BS on his "cold chimney" theory.
I didn't run the furnace long enough to get a good temperature rise measurement. As soon as I saw the combustion issue I shut it off because I was concerned about the furnace being unsafe to operate.
I should have measured TESP.
I'm not the business owner or the homeowner but I am still pissed off and disappointed with Williamson-Thermoflo/Weil McLain for not supporting their products. I've seen dozens of Thermopride oil furnaces operate in much worse conditions with poor airflow and draft and they operate flawlessly for 20, 30 even 40 years.
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Knowing TESP would help prove your theory, but it would also probably undermine your case against the mfr.
In the case of our church furnace, mfr's max spec TESP was 0.5" WC. When I measured the actual TESP, it was 1.4, and almost half of that was due solely to the HVAC contractor's undersized return plenum.
I assume your customer's furnace also has a max TESP spec from the mfr, and if your measurement exceeds that, I assume the mfr would simply blame the TESP, and understandably so, as they have no control over it. In my case the furnace mfr had no control over the HVAC contractor's bad duct sizing.
Not saying you don't have a right to be disappointed, just observing that confirming low airflow with a high TESP may not help your case with the mfr.
But it does seem odd that they wouldn't have a better design for limiting high temps at the HX. The gas furnaces have one very simple high limit temp sensor, and I don't see why they couldn't do the same thing in an oil furnace.
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Does this look like the effects of a "cold chimney"? I would expect a cracked flame retention head or warped/melted oil pump coupling if the chimney was back drafting.
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The high limit is to keep it from starting a fire, it isn't to keep it from damaging the hx over time if it is improperly installed and has repeated high limit shutdowns.
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If the high limit failed to shut off the burner, then the cause of the heat exchanger failure is the manufacturer's failed high limit. I would look at the High Limit to see if there is a problem with it. That part whould be covered by the warranty and therefore the HX failure that was a result of the warranty covered failed limit. I would avoid anything related to poor duct design. I wouldn't even look for that condition.
In the meantime, you need to get the customer's heat back on. Order the HX and Limit control using a credit card. That way you have recourse with the credit card to file a charge back to Williamson or the wholesaler.
w
Edward Young Retired
After you make that expensive repair and you still have the same problem, What will you check next?
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Where is it actually compromised? Looks like there was a bad weld or seam or something that came apart, doesn't look like it got anywhere near melting temps. The colors will tell you how hot the steel got.
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In my picture of the back of the heat exchanger you can see several large cracks in the center where the heat exchanger obviously overheated. All three visible sides of the box shaped parts of the heat exchanger are bulging out in the middle.
I agree that the limit control needs to be tested and temperature rise measurements need to be done.
Thankfully this furnace was installed on a dual fuel heat pump system.
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That things that look like scratches are actually cracks?
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@mattmia2 yes. What appears to be scratches are actually cracks. I could stick my fingernail into those "scratches"and I could feel they were pretty deep. I'm sure once the furnace is hot and the metal expands some of those cracks open up enough to cause the results of what I saw when performing the combustion analysis.
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I agree that a bad chimney or lack of draft usually shows up as a coked-up nozzle, burned retention head or blast tube, melted coupling, soot on the floor around the burner and soot-stained electrodes.
Don't assume that the MFGs are always right or know what they are doing because they don't.
Some of you may recall an Adams oil fired furnace I installed about 7 years ago that I posted about.
The HX was NG on the initial start up because the factory "forgot" to weld a steel plate in the hX.
Another time it was a Miller oil fired furnace for a trailer, again brand new with a bad spot in one of the welds.
Williamson at the very least should cover the cost of and supply a new HX.
It's only going to cost them $200 or so + shipping
Lawsuits cost more than that.
I would make them eat it.
I would also tell the supply house to put pressure on Williamson or they will lose your business.
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if it is Duel Fuel inspect the evaporator drain pan and coil as well.
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That picture is part of the heat exchanger cover? The picture with the lovely rainbow?
Sorry. That is really wildly overheated. The only way you can get those lovely colours is to get the temperature in the heat exchanger up to near glowing.
And the only way to do that is woefully inadequate air flow through the heat exchanger.
Now why didn't an overtemp control trip, assuming there is one? Again, poor airflow — it may well have tripped eventually, but long after that poor thing was cooked.
The draught or lack of it in the chimney has nothing to do with it.
Now… why poor airflow? Hard to say. Severely undersized ductwork? Clogged filters? Was the fan even running?
I might add that you are fortunate that whatever shut it down did — you weren't all that far from a fire.
Br. Jamie, osb
Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England0 -
or did the fan/limit get stuck and never advance enough to even turn the fan on?
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What's the chamber look like?
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I'm going back there for my second job of the day. I'll measure temperature rise and get more pictures.
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Is that impingement?
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nothing wron with burner or chamber.
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I went back to this furnace today. First thing I did was measure TESP with just the fan running. I measured 0.53". It was better than I expected. Pressure drop through the evaporator coil was low.
Then I went to measure temperature rise. The burner is equipped with a Carlin 70200 primary control and I noticed the burner was running for 5 minutes before the fan and limit control brought the blower on! So I drilled a hole in the jacket to measure temperature next to the fan and limit helix . The "fan on" setting on the fan and limit control was factory set for 110⁰. The blower didn't come on until the limit control was at 150⁰ and my thermometer was measuring 170⁰. After 13 minutes of operation my temperature rise was 63⁰.,
At this point I was satisfied that a defective fan and limit control was the reason for the heat exchanger failure. I repeated my test and recorded a video of the malfunction. I called the Williamson-Thermoflo tech support agent and informed him of my findings.
He continued to insist that the chimney was the problem and on top of that he said he never, ever saw a heat exchanger fail where the cracks are in my picture. He said he would need to see my a piece of paper go through the cracks or pictures of open holes before he could confirm that the heat exchanger has failed. He said the fan and limit control malfunction could not cause that. I insisted that my combustion analysis and pictures prove the heat exchanger failed.
Fortunately the good folks at the warranty department at Williamson-Thermoflo have provided my company a written confirmation that the warranty claim has been approved at this point.
Despite the way they insisted that a "cold chimney" was the culprit the installation instructions did not state that the furnace can't be installed on an exterior masonry chimney.
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it’s good there covering it.
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so the stop was at 110 but the dial passed it and went to 150 before it turned the fan on?
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Good that they finally stepped up.
We see on this forum that the quality of some installs is terrible (not you @SuperTech )
so I can understand the MFGs providing some pushback but You @SuperTech have the testing and documentation to back up your claim.
Good job
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@mattmia2 yes the stop was at 110 but the blower didn't come on until the dial was at 150, I was measuring 170⁰ right next to the helix of the fan and limit control.
I can certainly understand the manufacturers push back and I know voiding warranty claims helps their profit margins. But this particular tech support guy at Williamson-Thermoflo who I will not be naming, he really needs a better "go to" BS reason for denying claims. I still find it ridiculous that he would blame the failure of a one year old heat exchanger on the furnace being connected to a very common chimney installation, without even seeing any pictures of anything.
They probably get a lot techs calling them who don't have the tools and the knowledge to be able test every aspect of the way the furnace is running. Unfortunately too many techs don't perform combustion analysis and measure draft, static pressure and temperature rise
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@SuperTech said:
"Unfortunately too many techs don't perform combustion analysis and measure draft, static pressure and temperature rise."
The guys who installed our church furnace with a new undersized return and a TESP almost 3x mfr's spec limit sure didn't. 🙄
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I can see how it happens on gas, I don't see how you can do it on oil.
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