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  • Convotherm 4, Bottom Burner – Gas Burner technicians.

    guest created 2 years ago 1 Member · 17 Posts
  • guest

    October 17, 2017 at 12:00 am

    Convotherm 4 Unit, had an error code last night, Igniter had rubbed against aluminum foil, was shorting out to oven chassis. Go to replace the igniter and this is what I find.




    I’ve worked on the former model of this oven many times, I’ve had threads gall, studs break off and welded new ones on and had to do the works on these units but this, I’ve never seen anything like this before

    I’m not talking about the missing stud, I am talking about the cracks in the metal and the melted parts of the ignition module and combustion blower. The stud came off today as it was galled when I tried to loosen the nut.

    I am sure I can TIG it back together, tack it to the oven chassis and make it flat, weld on a new stud and replace the gasket and its all good but it’s starting to get a little odd with all the problems I am having with this “new” oven.

    Anybody seen this before?

  • ectofix

    October 17, 2017 at 4:49 pm

    olivero, what size oven is that?

  • olivero

    October 17, 2017 at 4:53 pm
  • olivero

    October 17, 2017 at 8:42 pm

    Well, I am certainly happy I am not the only one with this problem……. Did it happen with one burner or both? My top one looks totally fine.


    I can weld a stud on it from the side I am looking at it, I would prefer to do it where I drill a hole and just drop it in but it can definetley still be done.


    I find it very interesting that these problems are coming up (referring to all the stuff I’ve had happen already), makes me think somebody missed something in their testing phase. I will have to see what Cleveland says about it as I am not too keen in spending $2-3K on replacing all of these things just “because” There has to be some reason for this other than “tough shit” especially since I was a very good boy for the last 2 years and kept my hands out of the oven and let the certified tech do all the work and now this happens.


    I actually didn’t have THAT list with pictures, that definetley is easier to navigate, thank you.


    I went to take a look at it again after you mentioned the heat exchanger, figured I might as well remove it now and make sure I am not missing anything.



    That’s what the heat exchanger looks like the side that mounts to the inside of the unit.

  • fixbear

    October 17, 2017 at 8:53 pm

    I have no doubt that you can weld the crack and replace the stud.  But, how do you get the flange back true so that it will hold a seal?  Flame erosion has removed a lot of metal there. All this looks like it started with flange warp-age and a small gasket leak.


    As for the galled studs,  I wonder what alloy they are using for them.  What never seize are they using for assembly./

  • ectofix

    October 18, 2017 at 5:38 am

    WOW!  Those cracks are obviously far worse when looking from the inside of the oven with the exchanger removed. The rusty discoloration at 1 to 3 o’clock appears to be where flame might’ve actually leeched into the cooking compartment.


    So, I’m guessing this is a spritzer oven?  If so, makes me think there was some warpage due to the hot heat exchanger getting quenched by cold water sprayed on it.  But…I don’t know.  I don’t have any spritzer-type ovens, and don’t want any.


    In my situation (on my Rational), the oven’s wall didn’t have any cracks.  Just the heat exchanger.

  • ectofix

    October 18, 2017 at 5:39 am

    I had that same meltdown occur numerous times on our Rational 202 (same size as yours).  More about that in a second…


    About that broken stud:  It’s spot-welded to the heat exchanger flange, so you’d need to remove the heat exchanger from inside the oven to weld on a new stud.

    However, you should consider probably just replacing the heat exchanger and all ITS gaskets along with all those gas burner components you’re going to replace due to the meltdown.  I’d also replace the metal mesh burner.  So, pretty much everything for that particular heat exchanger all the way back to the gas supply feeding it.


    NOW.  In my case, I dealt with numerous meltdowns of that ridiculously plastic burner blower/air-gas mixer…and the plastic shroud housing it all.  Initially I’d related it to an electrical connection problem not energizing the burner blower when it should and possibly causing backflash of the gas.  INDEED I DID find that the wire harness (in Rationals) supplying that blower was fragile – ultimately causing the wire strands to abrade within the plugs down to a final strand, then result in failure of the motor to operate.


    HOWEVER…after chasing my @$$ addressing those issues and replacing several burner assemblies in a six week period, I was at wit’s end and asked my boss to call in Rational’s authorized service company.

    The guy who showed up apparently had better eyes than I…had spyed a crack in the heat exchanger…and even pointed at it to show me.

    I really never saw it (the crack), didn’t question it.  After all, whatever he decided to replace was good for a 30 day labor/90 day parts warranty.  If what he did lasted through those periods, then it would’ve far surpassed my bumbling through replacing melted plastic  burner components every couple of weeks.


    SO…he replaced EVERYTHING I’ve advised you to do.  I shouldn’t say this (for fear of hexing my oven) – BUT…I haven’t had any similar problems with that oven for nearly two years.


    As to WHY this only happened on my one-and-only 202G…I don’t know.


    Anyway, I hope this helps.  Although I’m sure you have it, here’s a copy of their part list.  The heat exchangers are on pages 33 & 34:


  • fixbear

    October 18, 2017 at 8:06 am

    Got to appreciate the power of expansion contraction with high heat over time.  How old is this oven?  Great pictures olivero.

  • olivero

    October 18, 2017 at 8:54 am

    Yeah, it seems pretty bad whatever happened, still trying to get word from Cleveland on it.


    It does definetley look like the flame leeched into the interior has that carbonized look, getting everything flat and even shouldn’t be too difficult, some padding, fine grit grinding, polishing and we should be there. I won’t do a thing until Cleveland gives their OK though, not comitting that much to this oven.


    From what I see, there are no cracks in the heat exchanger which I thought was kind of interesting, if the sprizter was to blame I would expect the cracks to be there but then again who knows. If the stainless got heavily carbonized and some of the chrome got carbonized, it could make the metal much more brittle and it would eliminate the benefit of “flexibility” in stainless which is also what causes galling. I have seen it on copper pipe before as well, it seems to be the “soft” metals that do it.


    Oven’s barely 2 years old. It’s kind of ridiculous.

  • fixbear

    October 18, 2017 at 10:31 am

    f it’s only 2 years old,  I’d be looking at flame shaping, mixture, venting and  calibration.  The marks show that the gasket failure was light on set in that blow out area. And you had blue flame coming out.  Determining why it was a light set  is probably gone. A small particle near a stud or a manufacturing warpage of the flange is all it takes.

  • olivero

    October 18, 2017 at 11:41 am

    More High Def



    The burners were calibrated about 6 months after we got the oven due to constant error codes on ignition and messed up igniters and so forth.


    I spoke to Cleveland, after a bit of arguing they agreed to cover the parts, new heat exchanger, ignition mod, combustion blower and all new gaskets. About 3.5 K worth of parts, and then add the overnight into it.


    Now they are going back and forth on welding it up or not, i mean there is not much choice, it’s gotta be done or the whole thing replaced. Seems pretty simple to me, I just need it from them.

  • ryantruck9

    October 18, 2017 at 12:18 pm

    great pictures!

    the factory may be concerned about liability with a welding repair. I would think reliability as well trying to keep it all flush.

    maybe they come up with plates to cover cracks?

    I just cant see a factory signing off on the welding, unless they were doing it. and they would never do it.

    but being a 20.20 it would be hard to just replace the oven.

    A mini sure but floor model ?


    I find that the burners are gassed so high and the restrictions they have in their heat exchangers really cause a potential

    for failure. be it blown exchangers or combustion leaks or even back flaming into the burner “sock”.

    thankfully the ignition module is normally one of the first things to melt so its fairly obvious when there is a leak


    I have never found anti seize on any heat exchanger studs from the factory, only units serviced by a technician familiar with these studs breaking.


    when asking tech support if the nuts were standard or metric thread was told either will work….. 

    this was several years ago however.

  • olivero

    October 18, 2017 at 12:51 pm

    ryantruck9 wrote:


    when asking tech support if the nuts were standard or metric thread was told either will work….. 

    this was several years ago however.


    Haha, gotta love that “either will work”.


    I believe it though, its all metric though all german parts, they even use torx or however its spelled screws which I don’t see too often.


    Their former model seemed to be a bit less “German” in terms of their esoteric things.


    It’s rolling forward but they did agree to let me weld it, just making sure its nice and clear that they are authorizing me. They don’t have to sign off on anything, I am not charging them for it I am doing it since they are paying 3.5 K for parts and add overnight to that then I’ll gladly do my part to get the oven fixed.


    You would be correct. You will need to weld it pad the thin area and weld it down. Let me know if there is anything else.”


    That was the last email. 

  • olivero

    October 18, 2017 at 5:35 pm

    Well, they did end up sending all new parts. Heat exchanger should arrive in a couple of weeks, for now I welded a new stud on the existing one and will be welding closed those cracks and flattening it out and whatnot later tonight. Tomorrow morning I should have all new gaskets, ignition module and combustion blower.


    All in a days work.

  • ectofix

    October 18, 2017 at 6:10 pm

    olivero wrote:


    Their former model seemed to be a bit less “German” in terms of their esoteric things.


    I think Cleveland built those less “German” Convotherms right here in the U.S. only up until a few years ago.


    Around that time when I was oven-shopping oven for our Executive Chef (another story), I”d conversed with Cleveland about their Convotherm ovens and was told that their production would soon to move back to Germany.  That information was soon amplified by the separation of the their two names shortly thereafter.  As recently as three years ago, you could go to Cleveland Range’s website to find Convotherm ovens emblazoned all over it.  They were Cleveland Convotherm ovens…a Cleveland product.

    NOW – there’s nothing on Cleveland’s website about combi-ovens AT ALL.  For Convotherm ovens, you must go to THEIR website.


    Need I say that they’re BOTH Enodis, uh Manitow…ummm…I mean Welbilt companies?



    Probably not necessary for me to say that “they don’t make things like they used” but I said that to point out that – indeed, THEY DON’T!


    Your Convotherm’s 4’s predecessor, a Cleveland Convotherm OGS 20.20 (built in the U.S.) was a different animal.

    Granted, its technology is dated now, but consider THIS:

    • The OGS 20.20 weighed 970 lbs.
    • The C4eT 20.20 GS weighs 791 lbs.

    So the newer oven that does exactly the same thing as the the old one is nearly 200 lbs. lighter.  Where did that 200 lbs go?


    Well, the newer oven is 10″ narrower and a 4″ loss in depth.  Mostly that’s just less cabinet space for functional components and insulation.  The cooking compartment is the same.  Otherwise, thinner metal ALL around.  That being due to newer manufacturing techniques that relies on metallic strength from folds and bends rather than the brute strength of thicker metals.


    That fact was right in my face when I did THIS project last year:



    When I tore down that oven to its last bolt, rivet, etc. – I’d discovered that the ENTIRETY of its structural integrity…relied entirely on strategic attachments to the COOKING COMPARTMENT.  The cooking compartment was the foundation. NOT the base frame – nor the exterior cabinet.

    Much like a cardboard box – without its contents,  it was as if you could jump on it and it would collapse.


    Along with the cooking compartment’s strength (from its curves, recesses and welds), all OTHER metal piece’s strength was bolstered merely by MORE folds, bends and angles.

    I don’t think a single metal panel or piece in it exceeded 18 guage in thickness.

  • fixbear

    October 19, 2017 at 8:01 am

    Olivero,  How about sectioning out a circle?  That way you could make a machined piece to weld in instead of trying to weld cracks that will eventually re-crack and making it level and true thickness would be easier.

  • olivero

    October 19, 2017 at 1:17 pm



    I whole heartedly agree with you, when we bought the OGS it was in 2009 or so, its been sitting for 3 years or so before they moved in and it got used by that time, the software was already outdated which led to a fatal error that resulted in the oven going out the door and the Convotherm coming in.


    The convotherm 4 unit has smaller burners and less BTU’s than the OGS. So all that weight and honking goodness went out along with the performance, very dissapointing. Now this, this was just about the 3rd last straw I’ve had with Cleveland on their combi’s it just shows it was not built right and it wasn’t properly tested.




    We thought about that but figured that for now, this will have to do. The plan is to get rid of these units and switch over to Alto Shaam, they have a much better support group and 24/7 tech support which is a good enough reason for me with all the problems we went through on these 2, I would have expected much more support from Cleveland on it.


    Here are the after shots.



    Both sides.


    It went pretty smooth, took a while but we got it done and parts showed up this morning, put everything in with gaskets and all, turned it on, no visible heat leaks and I ran my finger around the flange and I don’t feel any heat escaping so it looks like we are good.

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