Revealing the Easiest Method to Test Cracked Furnace Heat Exchanger

Stop Wasting Time! Verify a furnace heat exchanger for cracks in seconds! Professional HVAC Technician reveals trade secrets! Save Time! Protect Lives!
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#furnace #hvac #heatexchanger

[@danobrien3109]

This is a great tech tip for people. It also a very simple explanation of how the heat exchanger works . This could be easily explained to clients and then show them how you determine the defect. Nice work Mike.👍👍🇨🇦

[@UncleEarlHeatingAirCondition]

Interesting very. Enjoy your posts. Not to be a Hater Raider, truely. The true ways to verify a cracked heat exchanger or Combustion integrity issue (no certain order): A) To pull the heat exchanger and visibly check it. B) Use a mirror or camera to see it. C) Observe for main burner distortion when blower comes on. D) Use a Combustion Analyzer to check CO and O2 elevations when the blower comes on. Runs unit for at least 20-25 minutes with the Combustion compartment door on or closed. IF CO levels continually rises high and above 100 ppm "when blower comes on" and or O2 Levels are well above 7-9 percent "when blower on", then there is an issue with the heat exchanger or has been compromised. Thank you for continually sharing your knowledge and experiences.

[@PipeDoctor]

Yes, those are also proven methods.

[@xlostf8x348]

5 years of combustion analysis WHY did I not think of that. I'm gonna show my guys!

[@PipeDoctor]

A subscriber told me about this a couple weeks ago. Epic test

[@antoniosantiago2770]

Awesome test basically cycle the furnace so it can be hot then (sometimes cracks hide if furnace is not up to temp even with combustion test) t off the pressure switch and when fan comes on you'll catch that difference definitely a tool for the toolbox

[@kat2641]

I also watch my flame in the tubes if they change when the circulating fan comes on? Definitely a giveaway for more testing. ((if you’re not testing, you’re guessing.)) credit to pipe Dr!!!

[@summertop511]

Da hell this the easiest test. Just got my testo 310 back from recal for almost $500

[@scottvolage1752]

Protecting the health of the nation. Making the trades great again. Good Job Mike and Josh.

[@PipeDoctor]

Thank you

[@donaldclark1872]

Nice job Mikey Pipes as always!!! You have shared your knowledge on boilers with me for three years now.. I’m glad I could return the favor. Thank you!!

[@PipeDoctor]

That was you with this trick, wasn’t it??? ❤️

[@donaldclark1872]

It was me!!

[@John-m3z8r]

You need to put blower door on because your meter will read negative pressure from blower running being that close to blower

[@jrh86]

Thank you for sharing which was very interesting and explained with a pleasant demeanour.

[@PipeDoctor]

Glad you enjoyed it!

[@Jon-hx7pe]

when you do that test with the blower access panel off, you put the attic space under negative pressure, affecting the manometer reading. manometer reads pressure difference and has negative port. no substitute for a visual inspection imo

[@palamidi13]

We love you ,we are watching you from Greece!

[@PipeDoctor]

LOVE YOU TOO!!!!

[@MrBHVAC]

You can also take a long grille lighter, insert it into each burner, with and without the blower on. If the flame dances with the long lighter… there’s a crack/hole in that part of the exchanger

[@MrDmadness]

Read this after my identical comment. Jump r tog so blower comes on and do this. Yup.

[@abazism]

You mean insert the lighter and turn on the blower motor to see if the fame dance right ?

[@MrDmadness]

@@abazism yes. Its very obvious if you have a cracked exchanger

[@bruceorourke5432]

To me that's a sign of a good mechanic

[@PipeDoctor]

Agreed 👍

[@Mastamurph162]

Nice, i have a new way of checking besides trying to open the plenum or remove the blower😂 appreciate the knowledge mike you a G!

[@PipeDoctor]

Glad to help

[@barrykeller8019]

That small pressure difference on the manometer could also be caused by the suction of the blower fan right near the other open port of your differential measuring device. Be careful you may condemn every HX with a test like that.

[@denrayr]

You're both right. The meter is reporting the differential between the two ports as well as the absolute pressure on P2. You can see that during the blower test, the two numbers don't match which indicates the pressure in the attic changed, but the pressure in the exhaust path also changed.

[@denrayr]

This is a pretty neat test by the way.

[@antoniosantiago2770]

​@@denrayrT the two ports, great observation by the way

[@kangaroogod]

If the blower door was on I would buy it

[@Android_Warrior]

If that's the case then plug the other port.

[@throttlebottle5906]

the flue pipe is in front of the filter and it needs removed to change the filter. very likely they just left the flue and gas off for summer/multiple filter changes, figuring they'd put it back on when there was a no heat complaint. the blower compartment being open could cause pressure change enough via burner and flue openings to make the manometer read. test with the blower cover on, also it would be wise to block the flue hole, with the burner ports open then cover them individually and watch for pressure change. it's possible in some designs to have a very tiny pressure change due to leakage through fiber gasket material at burner and collector box end plates. you may have jumped the gate on that one, it's best to always back it up with visual inspections/proof.

[@kaceychapin2903]

St. Mike with another life saving technique.

[@PipeDoctor]

👍

[@DevinHVACInc]

Very nice troubleshooting. Learned something new on this channel.

[@PipeDoctor]

try to learn something new everyday

[@dburks1273]

Lol me too I learn new sh*t on his videos all the time.

[@joshhodges5688]

I have done that for years with 90% + furnace but never thought it would work on an 80% unit. I will have to give it a try.

[@acunlimited9683]

should also mention if you dont have a working man-o you can also check for flame influence by the blower turning on as well, but yes this is the prefered and safest way to check for a cracked H,E,. Mike has another great tip for the new guys

[@PipeDoctor]

Enjoy 😊

[@ApartmentMaintenancePro]

Great job explaining this, never knew you could do this with a manometer !

[@PipeDoctor]

Glad I could help

[@RC-Heli835]

Awesome test man! I haven't seen this version yet. I saw on another video this morning where a guy stuck a long lighter in each burner tube with the fan motor on only. The flame on the lighter stayed calm and steady in each tube and passed the test. So then for the purpose of the video he drilled a small hole in the heat exchanger and returned to the flame test. That tiny hole he drilled caused the flame to dance all over the place in the tube with the hole drilled.

[@PipeDoctor]

Very cool

[@giangnguyen8344]

Which video is that one? I'm trying to see if my heat exchanger has a crack. Thanks

[@xVizzeh]

This is a good idea however I think because you have the blower door off it could be affecting your test pulling the air from the port around the manometer, you should try putting the blower door on and covering your extra manometer port.

[@PipeDoctor]

possible, but unlikely.....wait for next weeks video.

[@stevedentremont9849]

I have never seen that done before and I love it totally makes sense. Great tip.

[@PipeDoctor]

👍

[@dexenationgracey1979]

I wish I knew that trick when I was starting out. I'll definitely use it on my next no heat call whenever working on older furnaces.

[@williamstrumfels3305]

would definitely like to see the same test on a few brand new furnaces ,to confirm diff between new / known good vs ones that test bad...its the scientific thing to do ...Dr Pipe Doctor

[@gaoutdoor4372]

Please post the result thanks

[@PipeDoctor]

watch in a couple days

[@denrayr]

I thought this test was interesting enough to test on my own ~10 year old 80%er. I got 0 change on the manometer indicating a good heat exchanger. The next test would be to pull the blower panel, but I didn't take it that far. I trust the results from the video.

[@dburks1273]

​@@PipeDoctorI'll be trying this method tomorrow Thanks. I'm a fan of yours bro keep the videos coming.

[@tillerdogg3232]

Great idea, I'll need to give it a try. Besides a combustion test I'll pull limit and drill a hole in the transition and put my cam in there.

[@jevianfe]

This is a great test, I’ll share this with the guys at work. Thank man!!!

[@measureQuick]

While what you are doing has some merit the test process is flawed in the fact that heat exchangers are not hermetically sealed. It's a great prescreening, but it is not definitive. So I am not saying don't do it, just go further. Section 4.5 of AHRI Guideline X on heat exchanger testing clearly states that a small amount of leakage can be normal. "Visually Inspect Heat Exchanger Disassemble the furnace until you can visually inspect all heat exchanger exterior surfaces. Any crack or hole that is big enough to affect combustion is visible to the naked eye. Do not use water, cameras, or smoking agents to check for leaks. Furnace heat exchangers joints are not hermetically sealed, so a small amount of leakage can occur. Replace the heat exchanger or the furnace if there are any splits, cracks or holes. Note: If the inspection described in Section 4.5 does not show holes, cracks or separated seams, further investigation is advised to determine the source of the CO contamination."

[@PipeDoctor]

Thanks for sharing

[@joequalletjr.8328]

Thanks for sharing. Always learn something new in your videos!

[@PipeDoctor]

My pleasure!

[@dannykeane6565]

i think he will be a champ

[@PipeDoctor]

👍

[@Petty_nellguwop]

Omg never thought of this thank you! Definitely will be part of training

[@PipeDoctor]

You're so welcome!

[@barrykeller8019]

I like your channel and think you're a great tech, this test is useful. I also think that this test may show nothing. What if the crack was very close to burner openings, the air could enter and exit the HX without changing the pressure reading at all. As pointed out in other comments it's not sealed. To make the test better you could seal the vent connection which in this case the venting was already removed and seal the 3 burner openings using foil tape or if it's a hi-eff just seal the 2 pipes outside the same way. Now if air enters the HX it should show a positive reading on the manometer. You also mentioned in 1 of the comments that you are replacing the unit please do a follow up video and show the HX.

[@throttlebottle5906]

that should just be "one" test of the heat exchanger, others should be visual inspection inside and out as well as combustion analysis, watching the flame when indoor blower comes on and more.

[@kylewells6871]

Very clever st Mike. Nice job

[@migueldominguez7962]

I love the manometer testing . But I don’t understand the pressure difference with the numbers you came up with. Could you give a better explanation. Great job! Love the channel.

[@MrDmadness]

The inducer is connected to the exhaust side, the blower should not effect any pressures in that side as it is separated by the heat exchanger, so a reading from the combustion side with ablowr only running would indicate pressure change due to the blower ( but on the combustion side ) and so a crack

[@williamserver4332]

Great test

[@michaellupo3480]

Im not gonna lie i used to use my draft gauge same concept turn on the fan but this was for oil furnaces im gonna use this trick for gas great trick

[@PipeDoctor]

It works. 100%

[@gallowaylights]

Sweet trick!😊

[@PipeDoctor]

Sure is.

[@ronen10314]

Don’t know how reliable is that test. I would like a confirmation seeing a little vibration on the flame

[@PipeDoctor]

It’s more reliable and more accurate than a match like a handyman hack

[@Sesamestreet9080]

You can also back test this by having combustion analysis. Look at the oxygen and turn on the blower to see if oxygen rises. If it rises the heat exchanger is compromised

[@Jon-hx7pe]

can have perfect flames with a severely cracked heat exchanger - depends on where the cracks are. no substitute for a visual inspection.

[@Matts_Crafty]

lol @ handyman hack another clown phrase added to my dictionary well done Saint Mike hahhaaa love it!!!!@@PipeDoctor

[@Josh-px6xb]

I like this idea. A co worker told me about this about a year ago. In this case, I would be a little concerned about the blower sucking in air through the flue outlet back through the opening on the HX where the burners go through. But may be over thinking

[@rickdroesch5084]

Yeah with the blower door off and the flue pipe disconnected… I’m not buying it either lol.

[@chrisdevine5328]

Amazing tip, never thought of this. Im gonna start using this.

[@PipeDoctor]

:)

[@brianlutzak]

You should make a video next time you come across a bad HX comparing this test with a flame test to verify. Would be good to see.

[@PipeDoctor]

Great suggestion!

[@gman8962]

Aggree

[@demetriosa7646]

Ah St. Mike does it again. I wish you did more furnace videos but I know NY mostly steam boilers.

[@kcMan7938]

It was hard to tell from the video , but it looked like that vent pipe needed to be removed to access the space guard filter , and some forgot to reinstall it ?

[@compgb]

So 2 things/questions. Is it an up flow or down flow? (1) I see that the exhaust is routed through the blower compartment and that makes me feel like it is down flow. (2) It looks like the flue pipe has to be removed to access the Filter Cabinet to change the filter. I feel like someone removed it to change the filter and just never put it back or could not get it back on and just left it off.

[@rustyshakleford5230]

That is a smart trick. I would like to see what different size holes in the HE equate to pressure wise. Like how big if a hole does it take to get to .010" WC? Aint no way you are gonna meaure that woth an analog manometer.

[@PipeDoctor]

Wait and see

[@alirahal5900]

Great idea.

[@PipeDoctor]

Glad you think so!

[@FixthisCD]

That's cool. I thought you were going to supply 120v externally to the inducer motor and then turn the fan on to see if there was a difference

[@bruceorourke5432]

That's a good way to check it I've never seen that in all the years that I've been doing it I only seen the Kraken exchange when the with that way when the pressure switch wouldn't make how to put a t in to make sure it wasn't the switch

[@PipeDoctor]

Yup 👍

[@DC-do8vd]

This test could be used as a starting point, but I definitely would not rely on that test alone. There are many reasons besides a faulty heat exchanger that could produce those results. First off, a heat exchanger is not completely hermetically sealed, so it is possible the blower could ever so slightly infiltrate the heat exchanger. Secondly, it could also be an inexpensive faulty inducer or Heat exchanger gasket. And finally, it could just be the natural draft flowing through the heat exchanger from the intake to the exhaust. If you suspect a faulty heat exchanger you should monitor your flames for any disturbances, perform a combustion analysis and monitor your oxygen and excess air readings followed by a good visual inspection.

[@PipeDoctor]

Yeah, you think the HX isn’t sealed from the gas manifold to the inducer? Wow. Just stop. Leave the keyboard alone.

[@DC-do8vd]

@@PipeDoctor Of course it is, but as I have experienced and been taught from factory training is that a heat exchanger is not 100% hermetically sealed. I have been doing this for over 20 years and I can tell you that your test is not 100% accurate. That said, I will not leave my keyboard alone so others can read my replies and make their own educated decisions.

[@dwaynemcallister7231]

I suspect that for many HVAC repairmen they make more $ swapping the complete furnace out, so if they can say it's bad with a simple test they will look no further.@@DC-do8vd

[@Clamjammer]

Do this little test and also do a combustion analysis and let’s see what the analyzer reads for excess o2

[@davedube1148]

I was going to ask why the previous technician would disconnect the exhaust pipe but maybe it was to alert the next technician that there was a problem with the system?

[@PipeDoctor]

maybe, homeowner claims to know nothing. deposit on new system on the books.

[@lolopete]

Another fine howdy do.

[@PipeDoctor]

👋

[@RC-Heli835]

Did you end up replacing the entire furnace or just the heat exchanger? I figure the outer shell of a furnace would last a life time or two! Like dropping a fresh engine in a 1920's car you could run the body forever. With fresh parts you could run it 500 years maybe? Easier to get a new one than swap a motor though to be sure.

[@PipeDoctor]

Entire furnace

[@RC-Heli835]

@@PipeDoctor Did you ever see the cracked heat exchanger or just scrap it man? I'm fixing to try the test on my old 88 furnace. All I have is a vacuum gauge that I use on engines but it should work. The thing has never set off a carbone monoxide alarm in the house but there is a lot of rust in the flue and in front of the burner tubes.

[@woodystokes1543]

Very good job 😊

[@PipeDoctor]

Thank you! Cheers!

[@swimbikeruntoday]

Great video. I have seen draft inducer assemblies replaced with a less than perfect application of the 3M rubber tape for the gasket (slight gaps in the tape but 98% sealed). Could this not also cause a reading with the blower activated? Basically, could this leak be coming from a less than perfect gasket between the inducer and the heat exchanger?

[@bruceorourke5432]

Is that if that door was open or closed when he tested that heat exchanger would not make a difference because you have a full opening and you're pulling off the ceiling there or the crawl space or whatever he was in so it would just be like having a closed door

[@PipeDoctor]

Makes no difference. We are measuring pressure.

[@engrpiman]

if you that test in a functional system i assume you get zero? would be interested to see what the variance is 0.04 is small

[@RockoRocko-rz7kx]

Ya i agree id like to see that done on a brand new furnace out of the box as were talking about a fraction of a water column

[@PipeDoctor]

You doubt the test?

[@RockoRocko-rz7kx]

@@PipeDoctor Kinda just because if their was holes or cracks i think you would have got a huge pressure differential not just fractions of a water column. Especially as the fan was running through the heat exchanger. Next time i do a new install id like to try your tip though. No disrespect i do value your education and skills especially in hydronics.

[@MrDmadness]

​@@PipeDoctorI would not trust that low of a reading exclusively. Jump r to g and use a long lighter or match as a confirmation is my method after this test. You can do both in under 10 mins and then you KNOW for sure. I also use a single port manometer for the pressure switch test your showed here as it has no external influence... respectfully.

[@kens.3729]

Carrier Model I had for 20+ years had to be partially dismantled to Check the Heat Exchanger Annually. Owner of HVAC Co. Required if because of Dangers. 👍🙏

[@PipeDoctor]

That sucks

[@chasingcapsaicin]

I will present you a personally hand made borosilicate water column metric scale. If passing through NY that is

[@PipeDoctor]

:)

[@MrDmadness]

Respectfully disagree. Imo the easy way is jump r to g and then use a long stem lighter or match and test every burner port, if one causes the flame to dance then its cracked. This test you show is a good test but you gotta cap the other port on the differential meter or use a single port manometer

[@AmericanFarmerHVAC2024]

The ol long match trick works too.

[@PipeDoctor]

This is more accurate

[@AmericanFarmerHVAC2024]

@@PipeDoctor I don't understand why someone would disconnect the flue though. I always pull the w wire or something else some joe schmo homeowner or landlord won't be able to figure out.

[@Matts_Crafty]

Yeah I keep 12" match sticks in my tool bag right next to the duct tape lol@@PipeDoctor

[@ericmilburn9841]

With the blower door off and flue pipe not attached that isn't an efficient way to test, especially when the flue runs through the blower cabinet. Enjoyed the video never the less and this method may work it in other applications.

[@hozerhvac4406]

Great now all the new guys are gonna condemn so many heat exchangers lol

[@dannykeane6565]

Soul Zilla

[@PipeDoctor]

Ha

[@bruceorourke5432]

To verify that works all you have to do is drill a hole in the plumber and take a carbon dioxide test I'm going to try that a few times over this winter

[@PipeDoctor]

Wait and see

[@Keegeth]

Can someone please explain to me what a common wire really is? Sounds crazy but I’ve been in the trade for 4 years and I still don’t fully understand what a Common really is. Is it some type of neutral wire?

[@realSamAndrew]

There are several youtube videos that cover just this topic. Do a search. At least one is from HVAC School I think.

[@PipeDoctor]

@Keegeth - you are correct. The common is exactly like a NEUTRAL. Having just 24 volts on R don't do nothing unless something is there for that return back. It functions just like GROUND. Look at a main panel. The white wires and greens all end up in the same place (i know not really, but on a 24 volt circuit it does.)

[@sweetcaroline7679]

👍

[@PipeDoctor]

👍

[@markschocken7059]

👍👍

[@PipeDoctor]

👍

[@scottmaz4063]

What no log lighting match 😂

[@PipeDoctor]

Nope

[@tooflybeatz4097]

👍🏿

[@PipeDoctor]

Thanks

[@elleondejuda4681]

Do the fan running and the matches proof test. But wait , why change the whole unit when you can just put a new heat exchanger for a lot less of $$$ People don’t have a pocket full of money let them decide , give them New unit cost is $. 5 k This is old new heat exchanger is $800 ? But , is old , you could still use this for a few more years bla bla bla

[@HonchHeado]

I wonder if he d/c flu explaining to them if they turn it on they will die? Cos just turning off gas obviously customers know how to turn that back on ive had that happen when they didn't want to pay for repair and then they tried to blame me for it exploding even after putting lock out tags which they took off, that didn't go far 😂

[@MrDmadness]

I always clip a wire to ensure they cannot get it operating

[@scottmaz4063]

So your the 2nd opinion guy and 1st guy was right. Sell them a new one mikey.

[@PipeDoctor]

Installing a Bosch Dual Fuel next week.

[@HVACRverse]

Omg 🤦🏼‍♂️ that is not how you are supposed to perform that test. You missed 3 steps you. Please don't teach this I wanna see the compromised part of the heat exchanger

[@PipeDoctor]

Don't be a hater cause I posted about this first. It works. Facts. Go away

[@SuperComfee]

why use a manometer to test? waste of time. there are better methods.

[@bachphi1]

DONT LISTEN TO THIS CRAB! He did not not show the actual cracked, meaning NO PROOF. Give me a break. Look at the his title "EASIEST", well is it practical? who has the meter to do this kind of test? Is it still easiest?

[@harryschrysan3183]

Sorry, but you are a moron. Every hvac technician should have a digital manometer. If you are a DIY guy then either leave to the professionals or suck it up and buy yourself a manometer.

[@MrDmadness]

Literally ANY professional has a manometer, it's a good test but imo not a full test

[@zacharypalczynski8450]

This test does work……if the the blower compartment is Completely sealed from inducer deck, there still will be slight pressure difference from power negative pressure from blower and blower compartment and pulling pressure from burner entry 🤙🏼🫡 fuxkn love ya Mikey pipes !