Big Maxx heat exchanger cleaning

[zak77]

I recently noticed the exhaust from my heater smelled a little odd when i was outside so i started looking into it. I must say i've had this heater for about 10 years with no issues and no maintenance either. I found the lower tube not as hot as the others. Line pressure and manifold pressure were good and everything else not clogged/appeared fine. I then removed the inducer fan and found the lower tube with much more deposits than the other two. The steel "baffle" was removed and tube cleaned as far i could get. Any ideas why this 1 tube was clogging and other two were much cleaner?

 

[PoorUB]

Check the burner over well. Sooting up generally mean less air than fuel. Perhaps the nozzle is wrong, or the burner is dirty, it doesn't take much to screw them up. Dust or a spider nest is all it takes. Partially plugged venting? I assume it is running on LPG?

 

[fitter30]

Burning very rich thats why it's sooted up. Cleaning will make a big mess. A shop standard filter will blow soot right by it. Where old throw away clothes . Don't be surprise your skin will be black. If you pull the heater and take it outside can flush the tube with a garden hose. Soot turns into a oil like substance. Flue fan wheel might have to cleaned also.

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[danski0224]

Propane?

Looks like a fuel pressure issue.

This is why stuff needs to be checked with a combustion analyzer.

no issues

Ha. That's what you think. Just because it turns on, doesn't mean that it's working.

 

[PoorUB]

Propane?

Looks like a fuel pressure issue.

This is why stuff needs to be checked with a combustion analyzer.

Ha. That's what you think. Just because it turns on, doesn't mean that it's working.

We I did HVAC service we had installers like that. Hook it up and it runs, so we are done. Every furnace installation the installers did our service department went back and did the usual tests, gas pressure, temp rise, combustion analysis and of course it was all way off. About nine times out of ten we had to redo some of the venting and condensate lines too. Some guys don't understand gravity and that water runs down hill.

 

[American Locomotive]

I recently noticed the exhaust from my heater smelled a little odd when i was outside so i started looking into it. I must say i've had this heater for about 10 years with no issues and no maintenance either. I found the lower tube not as hot as the others. Line pressure and manifold pressure were good and everything else not clogged/appeared fine. I then removed the inducer fan and found the lower tube with much more deposits than the other two. The steel "baffle" was removed and tube cleaned as far i could get. Any ideas why this 1 tube was clogging and other two were much cleaner?

How did you verify that manifold pressure on the burner was good?

A natural gas/propane heater should *never* soot up like that unless the fuel pressure is way too high, or the air vents on the burners are restricted/incorrectly set.

 

[danski0224]

How did you verify that manifold pressure on the burner was good?

"It's working and looks ok to me".

 

[danski0224]

The steel "baffle" was removed and tube cleaned as far i could get.

Your going to have to pull that heat exchanger out and dip it in something to clean it.

Or, replace it.

 

[zak77]

Yes, LPG. And yes i figured it was running too rich which caused this issue so the question is why? I removed the inducer fan and cleaned that as well, which wasnt all that bad. I have not changed or touched anything in this heater since i purchased it new so it was setup for LPG prior to me getting it. I tested manifold pressure by removing the test port based on this video

. There was also some build up on a small screen for that burner, which was obviously cleaned after finding that. What's interesting to me is that if the manifold pressure was incorrect, why would only that 1 burner/tube be effected and not the others? Also keep in mind this heater in the garage and sees a fair amount of dust and other particulates with no filtering system in place. I am no HVAC tech so if the heater seems to be operating the same as when new, i wouldnt suspect a problem but i'm trying to learn why this happened, how to fix it and how to hopefully prevent it in the future.

 

[fitter30]

Yes, LPG. And yes i figured it was running too rich which caused this issue so the question is why? I removed the inducer fan and cleaned that as well, which wasnt all that bad. I have not changed or touched anything in this heater since i purchased it new so it was setup for LPG prior to me getting it. I tested manifold pressure by removing the test port based on this video

. There was also some build up on a small screen for that burner, which was obviously cleaned after finding that. What's interesting to me is that if the manifold pressure was incorrect, why would only that 1 burner/tube be effected and not the others? Also keep in mind this heater in the garage and sees a fair amount of dust and other particulates with no filtering system in place. I am no HVAC tech so if the heater seems to be operating the same as when new, i wouldnt suspect a problem but i'm trying to learn why this happened, how to fix it and how to hopefully prevent it in the future.

Could happen if a spider either built their web in the burner or orfice. Just have to see after its cleaned. How it burns.

 

[danski0224]

I know that people don't want to hear it, but there is no way to *LOOK* at the flame from an induced draft burner, and tell if it is OK or not. A problem is only noticeable when it is really bad, and probably at a point when it trips a safety.

 

[American Locomotive]

Yes, LPG. And yes i figured it was running too rich which caused this issue so the question is why? I removed the inducer fan and cleaned that as well, which wasnt all that bad. I have not changed or touched anything in this heater since i purchased it new so it was setup for LPG prior to me getting it. I tested manifold pressure by removing the test port based on this video

. There was also some build up on a small screen for that burner, which was obviously cleaned after finding that. What's interesting to me is that if the manifold pressure was incorrect, why would only that 1 burner/tube be effected and not the others? Also keep in mind this heater in the garage and sees a fair amount of dust and other particulates with no filtering system in place. I am no HVAC tech so if the heater seems to be operating the same as when new, i wouldnt suspect a problem but i'm trying to learn why this happened, how to fix it and how to hopefully prevent it in the future.

What tool did you use to check pressure? You have a manometer (or equivalent) that can read inches of water column? As others mentioned, it could be a cob web, spider, something in a gas jet or orifice.

You will need to clean that entire tube - you will need a very flexible brush.

 

[zak77]

Yes i used a manometer that read inches of water column. Once i get the new gaskets for the inducer fan and get it back together i will double check the settings to make sure they are still within spec and i will carefully clean the jets and manifold to make sure there's nothing blocking anything. Would anyone know where i could find a brush flexibale enough to fit in that tube? I tried searching all over and couldnt find anything that seemed flexible enough to make it past the first bend. Last thing i want is to get a brush stuck in the tube. The tube is about 1 1/8" ID.

 

[PoorUB]

I tried searching all over and couldnt find anything that seemed flexible enough to make it past the first bend. Last thing i want is to get a brush stuck in the tube. The tube is about 1 1/8" ID.

That might be a bit hard to find. You might be able to cut down a brush and fasten a couple light chains, fish the one chain through and grab the end of each chain and work it back and forth.

Another possibility it take the unit down, and pressure wash it out.

 

[zak77]

Just a follow up, everything is back working. I cleaned the lower tube the best i could with a flexible brush and vacuumed it out. I rechecked the line pressure and manifold pressure, which were good. What i'm thinking caused the problem in the first place is that the heater is close to where i have my miter saw and table saw, which got used a lot last fall, so the saw dust i was creating about 5-6' away was getting drawn into the heater, which seems to have affected mostly the lower tube. This also caused the screen for the burner to partially clog only making the situation worse. So, remember to clean those heaters regularly especially if they are exposed to lots of dust. I will be maintaining it more often than a decade at a time from now on.