Central Boiler Heat Exchanger Maintenance

Classic Edge 750 Vertical Heat Exchanger

Maintenance is Not Sexy!

Say it ain’t so.  Upon reflection, it seems to me that be it in the workplace, or in life, the steady Eddy gets little credit.  When things work, or go according to plan, well, of course that’s what we expected.  When things fail however, the fixer gets all credit, a big pat on the back, and is called in the next time there is a failure.  It’s even less glamorous in this life; because I have no one but myself to blame in the event of failure, and then I have to fix it, too.

Vertical Heat Exchanger Maintenance

Let’s just say that I did not do much.  Okay, it’s true.  I don’t know what I was thinking.  I know better.  And so, upon start-up this year, the boiler simply could not keep the water temperature much above 155°F.  The set-point is 185°F, and the normal operating range is 175°F to 185°F.  Fortunately, one of the viewers of the YouTube video I made of the start-up, “Central Boiler Classic Edge 750 Start-up Year 2,” emailed me and discreetly offered that “it looks to me like your water jacket/smoke exit is almost plugged.”  Hmmmm.  Thank you Bud F. of Ettrick WI for the sage advice!

Accessing the Vertical Heat Exchanger for Maintenance

Access to the heat exchanger is made through the firebox.  Which is to say that you have to get IN the firebox to access the vertical heat exchanger for maintenance.  Of course this meant that the boiler was shut down and allowed to cool before maintenance was possible.  Then, all of the unburned wood and ash from the firebox was removed.

Ash removed from firebox

I’m told that in later iterations of this design Central Boiler has provided access from the outside, at the rear of the boiler, but of course that does me no good.  There is a heat shield at the back of the firebox, that basically extends from the bypass door to the floor of the firebox, secured by six cap nuts, with 5/16-18 threads.

Central Boiler Classic Edge 750 Vertical Heat Exchanger Heat Shield

Bypass door open, at top, Central Boiler Classic Edge 750 Vertical Heat Exchanger Heat Shield, below

To remove the nuts, you need a wire brush, to clean-up the nuts a bit, and a 9/16 inch socket to remove them.  The heat shield is in two pieces, one set above the other.  Once the heat shield is removed, you need again the wire brush, and a 1/2 inch deep socket to remove the nuts securing the covers, also two, but side-by-side in this case.  Removal of the heat shields and covers was suprisingly uneventful.

Having completed these two steps, I was confronted by the complete mess I had made of the vertical heat exchanger, which you can see at left in the photo collage atop this post.  It’s a wonder it was able to keep a fire going at all.

Cleaning the Central Boiler Classic Edge 750 Vertical Heat Exchanger

Central Boiler publishes animations and videos of the cleaning process on their website, of course animations and videos of the work being described while looking at a pristine, never seen fire, heat exchanger, is a lot less intimidating than what I faced.  Tools are important.  And fortunately the special tools I needed were provided with the furnace by Central Boiler:

  • the Wonderbar, basically a flat pry bar, about 15 inches in length
  • a Hoe; heavy duty, with a long handle, about 6+ feet
  • the all-important “cleaning rod,” also 6+ feet in length
  • and stamina
Central Boiler maintenance tools provided with every new furnace

Central Boiler provided special tools

The cleaning rod was especially useful, as it allowed me to clean between the heat exchanger “fins” while standing outside, at the door opening to the firebox.  There is also some access to the bottom of the vertical heat exchanger through the “Reaction Chamber,” this section is again cleaned using the “cleaning rod.”  It took me about 5 hours start to finish.

Lesson Learned: Do the Maintenance!

How many times do I need to suffer this sort of consequence.  You’d think I’d have learned by now.  And you might have noticed in the photo collage at the top of the post, in the right image, some chains hanging between the “fins.”  Those are to be used frequently, weekly is specified, to remove still-loose ash from the vertical heat exchanger, before the mess develops.  Interesting note, you actually have to USE the chain cleaner to gain the benefit. #whodathunkit

Vertical Heat Exchanger Maintenance Done

The Central Boiler is cookin’!  Reaction Chamber temps of over 1,300°F are seen.  Burns hot and fast, very efficiently.  No problem maintaining comfortable temps in the home.

All the best, and kind regards,

John (more About Us)

6 replies
  1. Chris
    Chris says:

    Have you cleaned the side channels out yet? Are they easy to get out? I’m about to clean the channels but was hoping for some advise before i do so. Thanks

    • John Newell
      John Newell says:

      I’m sorry I cannot help with that, I have yet to need to clean out the side channels.

  2. Rob Kufalk
    Rob Kufalk says:

    John, you are being way to kind in your details on maintenence. I am in my 3rd year with the 750 classic edge, I have had to clean the rear heat exchanger tubes 4 times. It is truly a pain in the ***. This has not been my only issue though. What is more irritating is the face full of smoke you get loading wood. I have had many phone calls to the company about my issues.
    My stove is clean, including the side channels and the elbows directing the airflow into channels are cleaned, I get my wood from an Amish saw mill, it test in the low 20% moisure range. The wood I cut myself is store in a shed and not used until it is down in the same moisture range. This version of the stove I believe was a hurried experiment to get product to market without adequate testing.
    It can be a good stove if you have the time to do a maintenance ritual. The problem comes when you don’t continue the ritual

    • John Newell
      John Newell says:

      Hi Rob, thanks for your comments. I’m not providing a “review” per se, rather a record of my experience. Since I’ve been using the chains daily I’ve had no problem with the heat exchanger. I only burn hardwoods because that’s all I have on my property. After I open the bypass I do wait a couple of seconds before opening the door, and I don’t put my face in the opening; no doubt about it smoke rolls out of the door. I’ve not had to clean the side channels; I have cleaned the air supply elbows. As for wood, I’ve burned green in the past for sure, but I avoid it completely now. I do not check moisture content. Thanks again Rob.

  3. Mark Madden
    Mark Madden says:

    Thanks for posting I have a 550 model that I have to clean the heat exchanger ,this my 3rd year and never cleaned, furnace is a mess,not looking forward to crawling in fire box as I am a good sized guy!

    • John Newell
      John Newell says:

      Hi Mark. It is a pain, I’ll say that. Subsequent models, I’m not sure of the year or serial number break, the vertical heat exchanger is accessible from the back of the furnace. For you and I it’s through the firebox. Using the chain cleaner regularly and often is important, only a bit less so if you’re burning only hardwoods like me. Good luck, and thanks for commenting. — John

Comments are closed.