Furnace Heat Exchanger Test Made Easy: Lennox Learning Solutions

[@attacknblack1984]

Can't believe I never thought of this in the 6 years I've been in the trade.

[@eeepeeep5206]

Wow, I can't express how much time this has saved me........Thank you so much !

[@JoseRodriguez-kx9gz]

I would think this wont catch small cracks. But its a great idea. I will put a known cracked heay echanger to test this method. Thanks. It can be a great method.

[@abdelmellouk7080]

Great Top to test the heat exchanger crack. It's a Very Smart Idea!!! Excellent job! Thanks again

[@abdelmellouk7080]

I meant great Helpful Tip

[@tyl8ter]

What about if you heat up the heat-exchanger first ( to a reasonably high temp) ...for expansion....then check with a match for a more reliable test?.....just curious

[@johncote2776]

interesting

[@actechformallyyomama746]

Heating up the heat exchanger is not recommended before testing. The hot metal will create a natural draft.

[@Kelvinbellrose]

What a helpful tip

[@davidestaab1]

I have found cracks in the heat exchangers that blow no air whatsoever just the starting of them. Sure this video is a great test but the hole or the crack would have to be pretty big to blow a match out. I’ve never in the decades that I’ve worked on furnaces and air conditioners I’ve come across a crack in the heat exchanger they could literally blow a match out. Most cracks are tiny but they can eventually irrupt into a massive gaping wound as you have there lol.

[@warbird101210]

Look for orange flame rather than blue aswell...

[@joemikhaiel3710]

Combustion analyzing tools and camera inspection of heat exchanger is the only way to tell the heat exchanger is cracked I use that method in the past on furnaces that the crack was too far up in the heat exchanger and did not blow the match off but still put out more than 30 ppm of CO into the house

[@hellbirdman]

At last a simple test for this problem. I have been carrying a 10-inch flexible lighter for the past 5 years to do just that. You can also take off the flue pipe off above the furnace and check it there provided it has an inducer and not a standing pilot light with only the fan on and a cool heat exchanger. You can also increase the static pressure by closing off some of the supply diffusers. It should be noted that if no flame wavering occurs, that then the furnace should be brought on and then observe that there is no flame wavering or roll out after a few moments of the fan running. Some cracks do not show up unless the heat exchanger steel starts expanding in the higher temperatures while it is running. Also, you should turn the blower on and off to be darn sure the flame wavers only when the fan is running with the blower door closed. This test does not count on standing pilot furnaces unless the heat exchanger is at ambient temperature.

[@92camaro100]

Thanks for that valuable information,IT will make every Tecks job alot easier .

[@deltat5775]

Sorry to disagree with you but this test will only work if you have a crack in the heat exchanger that is actually separated/offset. I have been certifying furnaces for over 20 years and Nate gas heating certified for 17. I have seen many cracks that have not yet opened that you would not lead enough air through to affect the flames or smoke from your match, kind of like a seam in the metal. You may say, "well if it's that tight it's not a problem". I can tell you this, I would never certify a furnace with a heat exchanger that has a visible defect. Could be the very next heat cycle when a fisher crack starts perpendicular to a hairline crack and starts curling back making a large opening. Personal experience tells me it only takes three months to go from a 2 inch closed hairline crack to a gaping hole a golf ball would fit through. (Early in my career, greenhorn mistake). I would not recommend using this test to verify condition or safety of a heat exchanger, it could definitely give you a false negative.

[@jstynon]

So how do you 100% certify that the furnace has no hairline cracks and is safe to operate.

[@marcoalvarez1276]

benzagon vanjoe the only way is to visually inspect it with cameras. I start off using the main limit hole and if I can't find anything there I pull the blower out and check the rest. On some of the c width furnaces, I'll lay on my side or back and check them.

[@deltat5775]

benzagon vanjoe , I do the same as Marco. You could perform the match test proposed by Jose as a first check and it would tell you if there is a large opening in the heat exchanger, in which case I would not bother with a visual inspection, the heat exchanger or furnace needs to be replaced for safety. However, If the match doesn’t Flickr it doesn’t mean there is no crack. So, if there is no match Flickr you still have to do a visual inspection with whatever means you have, I use a 3 foot long inspection camera with high definition, also pull blower and inspect from under, on furnaces that will allow. American guess association American gas association states first there must be no visible defects when inspecting heat exchangers. This is very difficult and sometimes impossible to visualize on certain types of heat exchangers without completely removing and/or disassembling the heat exchanger, which in my 25 years of experience have never found a customer that is willing to pay what it would cost to do so. Most are not too difficult to look at, from the top or the blower or through the exchanger burner and takes or through the limit switch faceplate penetration. My normal routine consists of preliminary check of burner deviation with blower on then a visual check and finally a carbon monoxide test in the Plenum and surrounding area. That is when I am certifying a heat exchanger is safe for operation

[@JustPlumDucky]

@@deltat5775 What video inspection camera do you use?

[@SombraLocs]

Great test!

[@KM-gf8oy]

Excellent video!! Being able to tell if you Really have a cracked heat exchanger and not just a technician telling you that it is cracked is a wonderful thing. Some companies will try to tell you the heat exchanger is cracked in order to sell you a new $8000 unit. I just did this test after a technician told me he saw "soot" and that means there is a leak. The flame barely moved in all 3 cells. It did move just a little. I’m convinced that I don’t have serious leak. I wanted to see if the small movement of the flame was cause by a leak or just the drafts around the furnace with the blower running. So I did another test: With the blower running but still not the heat, I lit the match (I actually used a fireplace lighter) and held it to the side, but not inside a cell. The flamed moved around a little just due to the drafts. Then I placed the flame inside the cell and compared the motion of the flame. It moved, but no more than it did in the 1st test. So there is no more airflow from the fan that just from drafts around the unit. That tells me there is no serious leak!!! This video saved me a lot of money. Thank you!!

[@KM-gf8oy]

@@HVAClearning I will have a HVAC tech come out but now I understand more. Thanks

[@daveYena-st8kz]

What type of burners?: The gun type that shoots fire into the exchanger? Or long tubes with slots? If the latter, if tubes start rotting, and disintegrating, the flame can go from blue to yellow. The yellow can cause soot due to poor combustion? You also can clean burner tubes stlest better with a long wire brush like for ridding out boiler tubes. This can help clear the slots and then you can see if you improved the flames more uniformly You want to see a dual looking blue flame that might show say a 1" cone of blue just above the burner tubes. And then blue flame above the cones. These type furnaces you can better tell at least a bad exchanger issue by starting furnace and carefully watching the flames before the blower comes on. Then, when the blower comes on, see if any of the flames start to dance. If it does, you have a bad exchanger. I once found a newer type condensing furnace where a chunk came out of the primary exchanger and could visually see it easily.

[@1abeltv]

great tip (:, I enjoy watching your instructional videos, Jose De La Portilla.

[@chewykarma]

Bloody brilliant. Sure beats tearing everything apart. Thanks.

[@evankeefer5321]

I would still do that anyway mate. Clean the burners

[@MMGJ10]

Awesome! I suspect I might have this issue and this makes it very easy to check. Thanks

[@dddddd2100]

I bought a box of long reach matches, they are heavy duty and are harder to blow out, doing the same test with one of these the flame on the match was normal on 2 burners but the 3rd and last burner the match flame was dancing and was even burning on the match upside down due to the air from the fan blowing thru the cracked heat exchanger.

[@thomasharmon7800]

I just had a Goodman furnace I had to change the heat exchanger out the flame was rolling out just a little bit I had to do some research on it and found out it was bad I took the furnace out and look down in it and you could see a massive crack in it big enough you could put five pencils down in it

[@Pskawt]

That’s awesome! 🙏 do you guys ever repair heat exchangers? It’s against our code

[@tyebundlez8262]

I gotta run this by grayfurnaceman he never mentioned this and he’s the pope of furnaces lol

[@mrofnocnon]

Actually he is not.

[@david-m-creations799]

What did grayfurnaceman say?

[@ethelryan257]

@@mrofnocnon Actually, he is. Just 'cause you got shortchanged below the belt....

[@warbird101210]

I never trusted the pope....way better peeps on youtube than him....rookie.....

[@beieber4life]

Hahaha, great comment man. And I’ll be honest, this method makes 100% sense

[@yurizhivago4848]

One method I use is to put a AC stick thermometer (that we use to stick in ducts) in the area of the rollout switch and just barely above and behind the front end of the burners. Multi-tester with a temp probe will also work. Run it for 5 mins and watch the temp. Should be around 70-90F as the air flowing across it is room temp air plus a bit of heat from the burners. If it is cracked then usually after 5 mins (or sooner) the crack opens and then air enters the exchanger and causes the flames to get pushed back out the front ( rollout ) and you will quickly see the temp rise to up to 300-350 F or whatever the switch is set for.

[@chrismaddox15]

Really great method. Thanks for sharing.

[@borninspainv]

This is cool to know. I'm not a tradesman but I've watched plenty of HVAC videos over the past few weeks and man have I learned and retained alot

[@jptrainor]

I did this simple test. I didn't need the flame. I could easily feel the blower air exiting out of the same, single, burner cell where I had already observed roll out. It was the nail the coffin for my furnace. Thanks!

[@hvacservicementor]

Unfortunately, this test will only be effective when the crack or hole is substantial. In that case, the blower would also be blowing combustion products and flame out while the furnace is firing. The vast majority of cracks that exist will never be indicated by this test.

[@cgeorge6786]

So it won't detect insubstantial leaks?

[@adamradley4407]

@@cgeorge6786 no it won't. Let's say you have a hairline fracture at a seam. Those typically only open when the heat exchanger is hot. No amount of external pressure will work it's way in. Generally, in my experience, this test is only valid when the crack has been there for a while. Doing a visual inspection yearly is what will find the cracks before they become a health issue for the occupants. Remember to check the back of the secondary also. That seam/gasket can start to leak condensate.

[@derekddurbin]

I sold two furnaces today off cracked heat exchangers one was a 90% furnace and had 968 ppm I pulled the limit and stuck camera in found two rings laying on top of the secondary $$$$$

[@mhnaali5551]

What about a bbq lighter

[@TheOne-ofMany]

Wow. Super easy. Glad I found this video. I am sure it wouldn't be a problem, but I'm going to use a flexible grill lighter just to make sure the top of the match does fall off in the exchanger.

[@justinpeck5021]

A visual inspection with a good combustion analysis is the best way to find out what's up .... and a manometer test at the outlet side of the valve , wouldn't hurt to back up your findings ... but an interesting trick I would say ....

[@thebenholmes]

Yup. While this is a cool, nothing beats using the right instrumentation.

[@billcowhig5739]

What would you expect the manometer to tell you in this case?

[@joemikhaiel3710]

I agree that method is totally baloney it may work sometimes but if the cracked his way up in the heat exchanger away from the opening it will not put the match out bad advice

[@AmericanFarmerHVAC2024]

Some cracks won't show up on the combustion test, major ones yes.

[@WillieMakeit]

Great job

[@dsd-downshiftdave8056]

You got to be kidding me lighting a match around a gas line!!! How about just doing a Combustion analysis

[@insightvideo6136]

Fantastic video. Thank you!

[@tagetes1442]

You might want to explain the process of turning the blower fan on without both the flame and the exhaust fan engaged.

[@stevenoliger2763]

I think many thermostats have a "fan only" mode. If not, you would have to check your control board for an appropriate switch or jumper setting.

[@happycamper2877]

You fail to tell us how to turn on furnace fan without heat or how to start the blower motor under the burners so we can make the test ...Without that info the video has no value...SORRY

[@fosterhensleycm8378]

Been testing this way for years, recommend disconnecting flue connector.

[@dddddd2100]

Although some people disagree with this method, I think it is a great way to test for a cracked heat exchanger, I have a 3 burner furnace and one of the burners would flicker, sputter with a loud noise (or whatever terminology you want to use) when the blower fan kicked on. otherwise the flame was calm before the fan was running. I did the match test just like you showed here and the match flame was good on 2 of the burners but was dancing and blew out on the same burner that had the flame flickering. Thanks for the Video.

[@dddddd2100]

I bought a box of long reach matches, they are heavy duty and are harder to blow out, doing the same test with one of these the flame on the match was normal on 2 burners but the 3rd and last burner the match flame was dancing and was even burning on the match upside down due to the air from the fan blowing thru the cracked heat exchanger.

[@april464]

Thank you for sharing this valuable information!

[@bretth1760]

Combustion analysis! You'd get high oxygen reading in this example, best method if you have the tool.

[@jgabriel1625]

combustion flue analysis is the last thing you wanna do. theres plenty of simple method like this one, or visual, smoke etc. just because you get high oxygen reading doesnt mean you got cracked heat exchanger

[@jgabriel1625]

having a tool not necessarily a best method. it can fail or out of calibration. best use your own sense

[@lachcik5084]

i see it alot when the flames light up it comes back

[@kevinroach9380]

I have s roll out switch that keeps popping out and shutting off the gas flow, what could be the problem?

[@kendallcrampton5544]

Infiltration of air into the exchange, carrier, Bryant, and Payne are known for their secondarys clogging and causing this to happen. Or you could simply have something impinging the flame, this could be a simple as dust or a spider web stuck in the burner itself.

[@darryls8066]

Sigh I guess that I have killed enough time researching. I have a 5 Year old Package 5 ton Dual Fuel IHybrid 2 stage. The flame rollout safety switch trips after a long runtime on high fire (2nd stage) I have checked everything else cleaned burners - checked gas pressures - checked for correct orfice size and just now even put a tach on the inducer fan to make sure it speeds up on 2nd stage. It passes the match test but it has to have a crack that opens apparently once the heat exchanger tubes are hot. The flame roll out safety switch has 320f marked on it. A temp probe at the safety switch area indicates approx 200F on 1st stage low fire but I get approx 300f on 2nd stage high fire after about 5 to 10 minutes run time which tells me it will exceed that 320f there and trip the safety. Getting my resolve together to pull the top of this monstrosity to get a visual on the HX. It does have a lifetime HX warranty so that is some motivation I guess Hahah

[@mrofnocnon]

What you just tested could equally have been a failed vestibule plate gasket and not a heat exchanger failure. I you are going to be doing furnace videos then be more specific. G1

[@seanolson4648]

Thanks!!! Great idea 👍

[@jvirg]

Non registration needed 20 year heat exchanger warranty is what it says on my paper I got with my furnace. How that works if it breaks down. I don't know. It doesn't says how to make a claim.

[@THEODINOFFICIAL]

You sir are short simple and straight to the point bout time someone makes a quick video with the info I needed!!!! Liked and subscribed

[@senginc]

I just tried this on my Goodman 12 yr old high efficiency unit in the basement. I have had a few rollout switch trips in the last 2 yrs. With flame off, blower on, all 4 burners push the match flame out towards me a little. I tried this on my 2nd floor Goodman 12 yr old high efficiency unit and the flames were steady (this furnace has been used very little). The flames on the basement unit when running are smooth with no indication of instability. I checked gas pressure with my manometer and it was in spec. I have ordered an Ultra Low CO monitor (Kidde Model KN-COU-B) that will display down to 10 ppm. I hope that it will confirm if I have a CO problem. This spring I will remove the heat exchanger for a thorough inspection. - - - Any other suggestions or tips ?

[@THEODINOFFICIAL]

What’s a rollout switch flipped and how do you turn back on?

[@adamradley4407]

@@THEODINOFFICIAL a roll out switch is a safety device that monitors heat I the burner box. They are manual resets only, small vutton on them, as they I dicate a serious issue with the furnace. If you have a roll out switch tripped call a reputable hvac company to check it out and prepare yourself for bad new. It could be just debris near an orifice but it could be a faulty heat exchanger get also.

[@jenkinssthomson8879]

Brilliant!!

[@zackelkins5655]

Can you tell me why a heat exchanger would need to be replaced in a 7 year old Lennox SLP98 series and how long it would take to replace one?

[@mattdaddy_888]

Cracked heat exchanger it's simple really flame rollout.

[@roykinder4134]

Slick, a common sense test that anyone can run in a few minutes. Thanks!

[@maggief1095]

How can I buy a flame stick like the one that was used for testing in this video?

[@AmericanFarmerHVAC2024]

This is on a Lennox furnace? I thought they never crack? 🤔

[@marks6663]

what if the crack is on the top above the cell? The blower air from the bottom is not going to go down.

[@harassingphonesolicitors7788]

Suspected mine might be cracked as it over 20yrs and a goodman heater Did the test and its fine Wow i cant believe this thing keeps going

[@gregj7002]

Is this test performed when the furnace is shut down, or do you run the fan while doing the test?

[@cskye6529]

OK so mine flickers in the second cell and a little in the 4th. Match didn't go out. 2004 80% Carrier mounted upside down - downflow (so the second cell would be similar to the 3rd in this). Looks similar to this. What now?

[@cskye6529]

@@HVAClearning No flame roll out or distortion.

[@l.crossjr]

Can the cell be blocked while the new furnace ships?

[@ehroberts1853]

Thank you. Very genius basic way before going to far!!!

[@frankvonfrauner]

Also a very quick and effective method for testing for a gas leak

[@YOUZTUBE2000]

frankvonfrauner 😳🙈

[@scottmitchell1893]

If you don’t smell the mercaptan before you do this I doubt you will find a leak

[@The.Lone.Wolf.]

So very helpful

[@JustPlumDucky]

Would this work on a downflow-type mobile home furnace?

[@FearlessFoundation]

Super helpful. Nice trick.

[@supabiscuit]

I learned from this. Thanks

[@colonelradec5956]

thats brilliant lol wow.

[@fredmeebley]

Does this method show cracks better than just lighting the furnace and watching the flame as the blower kicks on. If it put your match out, wouldn't it also blow the burner flame all over the place?

[@Kilinngthemkings]

this is the way I found my crack, of all 4 flames, one was violently splattering all over the hole.

[@theLeftHandedDog]

I tried running this test but there was a pretty strong flow of air coming towards me, seemingly from behind the row of igniter tubes, and all across them. I was able to stick my match into the near ends of the tube openings, but the ends near the exchanger were blocked by a sheet of metal. I tried the near end, and my match somehow stayed lit for the first two but went out on the middle one. I didn't even bother trying the other two; the moving air was too strong. (mine has five). I'm going to check if my exhaust PVC is blocked, tomorrow. I figure that's the only thing that could cause the air to blow back like that, but I don't understand how. Another thing that puzzles me is that the last time I had a cracked exchanger, the exhaust gases stank so much our neighbors complained. I should have checked it again, this time, but I wasn't even thinking about the exchanger. I was counting on a $20 solution, not a $6,000 solution. If anybody reads this tonight (Jan 21 2022) and has any ideas, please respond.

[@THEODINOFFICIAL]

I just started getting a burning dust smell out of nowhere and went to look... and I have a lot of orange pops in the flames but can’t tell if it’s blowout...... also the entire face of the rail is lit not just where the exchangers are not sure if that’s normal... so basically there’s a flame that runs completely across the rail in the front plus flames going into the holes

[@coheedmonstar33]

what ended up happening? lol

[@boby115]

We have been using this test for decades at the gas utility in St Louis, Missouri. Just an FYI, birthday candles work a lot better and if you purchase the right brand the wax will roll down toward your holder & won't drip a bit.

[@mikemccloskey1991]

What are the right brand of B-day candles?

[@boby115]

@@mikemccloskey1991 , sorry I've been out of the game for 2 and 1/2 years ( retired after 35 years). I just remember they were reduced drip ( they just keep you from leaving an ounce or two of wax in the bottom of a heat exchanger).

[@mikemccloskey1991]

@@boby115 ok, thank you sir!

[@vladseb2009]

Awesome!

[@toolemanful]

what are the names of the different furnace heat exchangers

[@toolemanful]

Lennox Learning Solutions thank you for the feed back!! Im in havac school and just trying to get the information all in lol

[@killer350dz]

I’ll take this lesson, seems like a good idea to me 🙂👍🏻

[@raulrobles2961]

Im new to the field so what would be a sign for a tech to check if there is a crack in the first place.

[@alpena2835]

Cool telescoping wand dude! Lol!

[@monroekunz1331]

First thing start furnace do co test in exhaust most furnaces under 20 ppm if cracked will be cosiderable higher 100 ppm with clean burners pretty much guarantee bad heat exchanger

[@deepblu39]

I tried using the thermostat to turn fan on and heat off, didn't turn on....is there another simple way to just turn fan on?

[@jaydd73]

I typically just close the gas valve near the furnace, and turn the system on as normal to call for heat. (Note: I'm not a technician or certified or anything but am very handy and have fixed plenty of hvac systems.)

[@The.Lone.Wolf.]

Jump R & G on the board

[@stephenburns3262]

Wrong but close after you set the smoke detectors off and the old lady tells about the matches

[@justwhatever6680]

Perfect!

[@natehicks8939]

Excellent technical advice!

[@mattmacurdy8020]

Grand!

[@bushcraftchip]

Awesome. Tip. I'll keep that one in my mental toolbox for shiggity...

[@garydiane1577]

Very clever. That makes me wonder... how does CO get into your house’s heat ducts with a cracked exchanger when the blower is actually pushing air out?

[@tier3rd375]

The blower is pushing the flame out of the burner and its combustion products as well. It's even worse if the hole is facing the supply plenum because the blower won't be pushing air out of the exchanger and may not cause the flame rollout switch to trip.

[@scottmitchell1893]

@@tier3rd375 If that was the case, do you think you’d still be able to see the flame dance around if doing this test?

[@tier3rd375]

You may notice the flame behaving differently. I don't exactly know what to expect if the hole is facing the supply plenum. Normally you should not see any change in the flame when the blower starts up and if you notice one, even a subtle difference, it might be worth getting it investigated.

[@scottmitchell1893]

Thank you

[@letterwriting]

just run the furnace and see if the flame dances or rolls out once the blower comes on

[@billcowhig5739]

Greyfurnaceman (?) has an excellent short video that shows how effective that can be. Visializes “flame rollout” pretty well.

[@cskye6529]

Mine doesn't do this though but the match flame flickers in the third exchanger cell from the right.

[@lastar3557]

Great tip, thank you from the San Jose Bay Area

[@hvacrjunky6119]

Great tip, thanks!😎

[@davidstewart4149]

What about the fourth one?

[@blitzblutz]

Love it! So simple!

[@rusticsurviving2606]

Will this work with a Ducane package unit where the burners are on the top and the induced draft motor is on the bottom? thank you

[@kencalder1826]

Wow...Thanks for this great Tip how to test for a cracked exchanger, it is so simple to perform. Recently I have had to reset the rollout switch, but on visual inspection I don't see any flame rollout ?

[@girohead]

This is brilliant, I trust it more than the camera, they still lie, 'can't you see it?'....

[@donnierobertson3088]

Great job and video like always

[@bobgallo2178]

Smoke pen works just as well.

[@garyduran1]

Great video.. my inducer fan comes on when there is no call for heat. it comes on then off a few times in a five minute period. When I do call for heat everything works fine and efficient. Can you help me figure out why? Thank you.

[@193CRAZY]

With my little experience in the field but broad knowledge in da books, I would check the thermostat.

[@blackishpariah]

This is a common circuit board issue. You have a relay on the board that is most likely damaged.

[@tl3614]

Good idea but Not a accurate test for checking if a heat exchanger has failed.

[@DJRBush12]

Which wires would I need to jump to get the blower running

[@roberts1159]

If you are talking about the air handler blower then jumper between red and green. Red is hot and green is fan, provided thermostat was wired typically.

[@ramblinman7153]

Just turn on the fan at the thermostat or jumper G and R.

[@mty252]

great video thank you

[@joebickers893]

Brilliant, thanks 😁

[@jamesholder5725]

G40?

[@user-dx7gh8qi4o]

Damn, thats good

[@kelvinlyons3401]

thank you..