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Munchkin heat exchanger problems

tim smithtim smith Member Posts: 2,226
heat exchanger quite closely on one of the failed ones. I would definately say it is the fireside. Caused by pitting from the iron deposits I think. When we clean the Munchies you find that their is corrosion under the iron build up on the heat x. It gets kinda rough on surface of stainless where the iron deposit adheres to the metal. My first failure was I think over a year ago and was only in for 2 or so years. It had failed on the inside of condensate collector pan, looked like again where iron deposits were sitting on stainless pan and corroded out through under small coffee ground deposit. I feel the grade of stainless, (I am not a metallurgist) is the main problem. Just a guess but I think a good pot shot. Also it's design allows for debris to sit in bottom of heat x and then gets moist from condensate formation and I think exacerbates corrosion. My nickels worth, Tim


  • mr bullmr bull Member Posts: 15
    Munchkin heat exchanger failures

    This week I was called out alot due to our cold weather. I have 2 Munchkin boilers with failed heat exchangers, water pouring out of the condensate with the autofill on. Anyone eles running across heat exchanger problems with Munchkin.
  • mr bullmr bull Member Posts: 15
    Munchkin heat exchanger failures

    This week I was called out alot due to our cold weather. I have 2 Munchkin boilers with failed heat exchangers, water pouring out of the condensate with the autofill on. Anyone eles running across heat exchanger problems with Munchkin.
  • PerryPerry Member Posts: 141
    I would like to know where exactly they failed. Also pictures

    Back in 2006 when I was looking at which boiler to buy... My engineering background and experience said to stay away from the Munchkin boiler HX as I felt that I could tell you exactly where and how they would fail (and did not see them as a long life design).

    I'd be really curious to find out how these failed - even to the point that I'd love to have a failed HX in my hands for analysis.

    If you do not know... I went with the Vitodens.

  • Jim PompettiJim Pompetti Member Posts: 549
    This year

    I was only called on one leaker , after inspection I found the clamp that holds the venting was loose.

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  • tim smithtim smith Member Posts: 2,226
    I have had 2 failed ones, one on pressure side and one

    on corroded out condensate pan at bottom!! Tim
  • TimSTimS Member Posts: 82
    ya some but not the boiler fault

    I seen several every year I'd say only a couple did not know what caused the failure but all the rest are obvious its always water quality problems, make up water running cause of a leak often the relief valve leaking and never gets fixed correctly = SCALED HX . Used to see installation issues on retrofits no P/S piping . Also nonbarrier tube w/ iron pumps and other iron components = failed heat exchanger . No service done, neglect, is considered ABUSE . Rentals or restaurants are common abusers .
    Technically these things void your warranty !! Its not the boiler fault!
  • PerryPerry Member Posts: 141
    Failed HX due to Iron pump/pipe?

    Also nonbarrier tube w/ iron pumps and other iron components = failed heat exchanger.

    Really, what causes that? There should not be any galvanic issue between iron (or steel) and the SS HX. I can't think of a single reason you would need a barrier tube. Also, what material would you make the barrier tube from?

  • TimSTimS Member Posts: 82
    thats one trend i have seen

    is when there is poly or potable pex or sch 80 or 1/4" black rubber vacuum tube in the system. When used for infloor and supply returns water quality is poor muddy brown any iron in system is very rusty and some of this will plug a HX tube or cavitate HX tubes like sandblasting inside the HX if over pumped .
    IF you must use this type of boiler you have protect it : best choice is to isolate the boiler from the system with a heat exchanger next option may be bronze pumps, and no iron any where in system use only copper and brass and a dirt seperator on inlet of boiler and use oxygen scavengers, corosion inhibiters, glycol and maintain inhibiters annually thats what I try to do .
    The I&O manuals are very specific on water quality and piping materials and maintenance.
    Personally I shut off OR disconnect make up water instead use either a large floor mount expansion tank and/or a glycol auto feeder pump for premix solution for makeup.
  • Wayco WayneWayco Wayne Member Posts: 2,467
    I have a leaker

    and I can't find where the water is coming from. I've checked the usual suspects. The condensate drain connection on the back of the HX, the header O rings, the tp valve connection. I've cleaned the HX and flushed it. I don't want to tear into it too much since it's cold outside and I don't want to disable it. The boiler itself was a generous donation by HTP to replace a Voyager that had to be replaced several times due to the problem with the top of the HX on that product. I'm afraid this customer is out of warranty time. It's making me look bad to a very good customer. WW

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  • tim smithtim smith Member Posts: 2,226
    Wayne, we pulled the heat exchanger, took about an hour and

    looked on the underside, pinholes in the drain pan leaking out. 5 or six of them. Easy to pull and check. Tim
  • Leo GLeo G Member Posts: 11

    I had 3 of them at the beginning of 08. Our NG is very dirty here, so a lot of build up, including iron/rust. Seems the iron attaches itself to the SSHX and breaks it down. At least this is what I was told as to the problems. All had pinhole leaks, PITA!

    Leo G
  • PlumdogPlumdog Member Posts: 873
    I seen it

    I've seen monster corrosion happening in systems with non-barrier tube. Pump housings full of rust, impellers ground down to a nub, inside of zone valves caked with crust, the little balls breaking off at the stem and getting lodged in the outlet, pipes nearly closed off with rust, iron air scoops with holes rusted thru the side, air tanks rusted thru at the neck. Unbelievable what a little oxygen can do in the presence of water.
  • troytroy Member Posts: 109
    leaking Munchkins

    I've had three. Tiny pin hole leaks in the HX tubes, All boilers were cleaned annually. Analyzed each year and No rubber ever has been installed on my jobs. Every system had barrier pex. During the annual clean it looks like a spider web when a flashlight is shone into the HX. The leaks were so small still that the water just ran down the condensate drain.
  • mr bullmr bull Member Posts: 15

    Thanks for all the comments on this problem. Both systems I encounted had Wirsbo heatpex tubing, supplyed with city treated water. I did not find any major signs of rusty water or trashed cast iron parts. Its hard to explain to a good customer why there new boiler needs to be replaced.
    I'm hoping Munchkin will be fail on some sort of Warranty.
    Good luck out there!! Merry Christmas.
    Mr Bull.
  • PerryPerry Member Posts: 141
    Responses to various issues:


    OK, lets break this down to the issues you identify (or the issues I think you identify).

    1) Use of non-oxygen barrier tubing... I understand how oxygen would cause problems in a system with iron in it - and even how oxygen could cause problems directly to the HX. However, if you do not use any form of plastic pipe/tubing (as in my case) or use adequate oxygen barrier pex I do not see why there would be a problem.

    Obviously - if oxygen is allowed in an iron based system (such as my 50+ year old monoflow T system) - you would get a lot of red rust that would indeed potentially plug the HX (especially any HX with tight passages).

    2) Dirty water in the system. You should adequately flush the system prior to boiler installation. Again, it is obvious that if you have a lot of gunk in the system and do not flush it that it could plug up a boiler with tight passages.

    3) Plugging of the HX from gunk in the system (from either points 1 or 2). Of course, if you have or create gunk in the system you can plug the HX. That could create a hot spot in the HX and lead to any of several attacks.

    3) Use of various chemicals. I saw nothing in the manual about that... and I don't think it is needed for all cases (or even for many cases. I don't understand the need for glycol in any but a few systems). A little O2 scavenger perhaps on initial system fill.

    Note that this is different than system flush and cleaning of new soldered piping.

    4) Excess makeup water... A leak is a problem for multiple reasons (hard water, oxygen, chlorine, etc); I like your large expansion tank idea. If the system needs more than a bit after bleeding then there is a leak somewhere.

    5) Excess water velocity (sandblasting - overpumped). SS is the most velocity errosion resistant material in any of the systems. You would need to have a velocity well over 10 ft/s (and I think 20 Ft/s) to have problems here - even with entrained particulates. I don't see how you are going to get those velocities in any home heating system. The pressure drop through the HX would be huge - and I doubt there is a home heating system pump that could do it.

    I guess all I see as real possibilities here are related to gunk in the system either from inadequate flushing of the old system, the use of non-oxygen barrier pipe or tubing, and leaks bringing in a constant supply of makeup water (hard water deposits, O2, etc).

    Is that a good summation. For the most part - I don't think these items explains why these HXs are failing due to pitting as reported elsewhere. Please see my follow-up down below as I address the pitting issue and my concerns there.

  • PerryPerry Member Posts: 141
    Plausable Failure Mechanisms

    There are so many post with usable information that I cannot respond to them all and make sense.

    I am trying to figure this out from an Engineering Failure Analysis perspective.

    For starters - if you have sludge in the system, leaks with a lot of hard makeup water (water scale), or non-oxygen barrier system - and plug up the HX then the problem is obvious. Pluggage of a boiler HX creates hot spots. The hot spots are subject to a variety of attacks that occur due to the higher temperatures.

    While you can say that these failures are not the boilers fault... I don't quite buy that either. From an good engineering perspective Boilers should be designed to handle most normal situations they will see in use; and home heating boilers are not industrial boilers where system water chemistry and other factors are well controlled. The old boilers handled most of these problems without failing (except for a lot of O2) - I cannot see why a new boiler would not be expected to be designed to handle these issues. To me - this is poor design, and perhaps someone will sue over it someday and win (I think it would be hard to defend against that claim).

    Also, if exposed to the right chemicals SS can indeed rust - and look just like carbon steel rusting. In this case the HX would just rust away. No pits, no cracks. I consider it plausible that with the "wrong" dirty natural gas that you might be able to induce a normal steel rusting process - but not the failures as described.

    What concerns me is the reports of pitting and very fine spider webs - I've seen spider web cracking before.

    The explanations of how the Iron particles attack the SS is not something I recognize at all - and does not sound plausible either.

    300 Series SS is known to pit and to crack under certain conditions. Most common is a chloride based attack - although there are some other compounds that will do the same thing.

    Now add a small sludge or scale layer on the waterside of the tube which causes the tube temperatures to go up and the chloride attack rates go up exponentially (if it is chloride).

    Note that when you look at the Munchkin Installation manual and look at all the things and areas to avoid near the boiler or where the fresh air comes from (swimming pool - laundry - garage - etc); that is because of chlorinated product use (the product list is rather distinct).

    Now perhaps it is something else (it is not iron particles) - and I'd sure love to get one (or several) of these failed HXs for personal examination (and to cut apart and do a look see). Depending on what I see... it may be worthwhile to do some lab work on it (that would cost money); but a lot can be ruled in or out with a good visual inspection.

    A question I have is does these problems originate from the fireside - or the tube side; or both depending on failure mechanism?

    Second best would be some high resolution pictures of the spider webs and the pits.


    One other suggestion that I posted several years ago without much response.

    When installing a mod/con boiler: Install a inline carbon filter on the make-up system. That will kill the chlorine going into the fill water. It is so simple to do - and you do wish to minimize chlorine and related chemical exposure. A particulate filter is not a bad idea either. Make sure your inlet air is fresh air free from any likely chlorinated product use in the area.

    I also note that Viessmann Vitodens manuals does not have all the same warnings as the Munchkin manual. I am not sure why, as I don't believe the Titanium stabilization has a lot of effect on the chloride sensitivity of the metal. However, it certainly has a lot to do with improving the capabilities of the 316 alloy to handle various natural gas trace elements and temperature effects. If these leakage/pitting problems are generally originating from the fireside then the Titanium stabilized 316 may be the solution (but I still worry about chloride attack even there).

    Edited to add:

    Also, 439 SS is generally immune from Chloride Stress Corrosion Cracking - but not Chloride Pitting.

    I have not seen any HXs built from material I would consider likely immune from these problems. On thinking about it I believe I know why - something for me to ask my favorite tube metallurgist about (who works for the largest US Mfr of SS HX tubing)

    Also, what material is the drip pans made of. That would help me figure out the mechanism.

  • PerryPerry Member Posts: 141
    Thanks for the Info Tim... Now the question is how to prevent it

    Under-deposit corrosion is the general classification of that phenomena. What is the corrodant is not clear at all at this point (it is not iron - the iron deposit is the end-result of the corrosion). Not all deposits have under-deposit corrosion going on.

    I've been thinking of starting a new thread on if Mod/Cons can be expected to last long term where I will discuss the possible failure modes in more detail and the differences in design and construction that may help eliminate the problems (including material choices).

    I've been thinking all night on the issue (and mentally designing a concept for a mod/con boiler HX to address all the issues in my head).

    This will take some time to write though.
  • rogGoarfsoonyrogGoarfsoony Member Posts: 8
    Munchkin Issues

    I have no dog in this fight. I have noticed that Munchkin boilers get a fair amount of press (both good and not so good) on the Wall and the few other heating related sites I frequent.

    To my uneducated eye, the Munchkin looks to be a fairly well engineered and thought out American product. What seems to happen is that a great idea has to be converted into a marketable product. In that process, materials have to be carefully chosen to make an affordable, profitable item.

    I don't know how the munchkin stacks up to it's competition. With proper maintainance, I'd like to think that one could get a couple of decades out of it. Is this wishfull thinking? If so, why?

    I saw a short segment inside the Munchkin factory on a cable show. I was impressed with the state of the art facilities. The owner came across to me as being passionate about his company and products.

    That being said, do the professionals who install and maitain this unit feel that the producer has made a somewhat flawed product? If so, it behooves the professional to personally contact the Munchkin factory brass with thier concerns and observations. The ball is then in Munchkins court.
  • Leo GLeo G Member Posts: 87

    interesting stuff Perry. I think that if chlorides are the problem, then maybe living by the ocean could be a factor that should be warned about. I remember getting a Harden Brass tub filler years ago, that had a warranty limitation, "if installed within 5 miles of the ocean, this warranty is void" Maybe they were on to something, eh?

    Leo G
  • DerheatmeisterDerheatmeister Member Posts: 950
    Well Engineered?

    Do not think so...

    If you take the potential combustion efficiency's of a Modcon boiler and based it on Setpoint not outdoor reset(ODR) then i do not see a " fairly well engineered and thought out American product."

    That is like taking a Ferrari engine and installing it into a Snow cat/ which point one will have to "Play with the Clutch" to even get it to move..

    Or: Taking an Mercedes engine,installing it into a Yugo and then go Rock crawling/4X4 with it..

    And yes i do think that Heat transfer products has made a flawed product and stated this to them on many occasions..

    The only "Improvement's" that i have seen over the years are that they now are based on ODR and they installed Hasps on the Plastic covers..Wow

    Too many issues and not the right forum/place to mention all of the "Problems" associated with this boiler and it's design..
  • tim smithtim smith Member Posts: 2,226
    As I have stated numerous times, I think the Triangle tube

    Prestige heat x is the best design out there. Maybe not quite as good of SS as in a Viessmann but its vertical fire tube design does help to wash down build up and keep debris from sitting on surfaces of heat x to cause corrosion. Very simple design and after 3 yrs of no cleaning, they look almost dead clear. Little deposits around top of tube sheet but minimal. My take on it anyway. Merry christmas all, Tim
  • TimSTimS Member Posts: 82
    agreed responses

    notes 1,2,3,3,4 I agree. 5) I am stating the possiblity as told to me by my rep for this I am torn, is it possible? I have not cut apart any HX's to know if it cavitated . cavitation happens elsewhere like copperfin boiler tubes and dhw recirc systems , why not in a small passage ss hx?

    All the leaking hx's I have seen been failures on the water side most for obvious reasons but I have read here opinions differ from mine (leaks caused from fire side of HX) I wonder if the water side was overlooked. My eyes are now opened to this possibility but I dont comprehend how the fireside of HX is the cause of leaks.

    The use of glycol seems to be a habit/personal preferences for some installers.
  • TimSTimS Member Posts: 82

    Interesting description. Is the webbing thru out the combustion chamber or just on the target wall and refractory surfaces?
  • Steve EbelsSteve Ebels Member Posts: 1,287
    For those of us with insomnia

    Here's some recommended reading on stainless steels.
  • PerryPerry Member Posts: 141
    But you missed...


    You are only scratching the surface.

    If you want to understand what can go wrong with these alloys... look at the technical information for some of the other alloys.

    I direct your attention to AL 29-4C.

    I note that they have changed marketing strategies and I have attached both the old (October 2000) and the new (July 2007) tech data sheets.

    In the old brochure they specifically discuss furnace/boiler related uses. In the new brochure they target the condenser tube market (and acknowledges the existence of Sea-Cure - but does not present any comparison test results between AL 39-4C and Sea-Cure: Sea-Cure virtually owns this market). I also note that there is more tons of metal in a single power plant condenser than in all the home furnaces & boilers built in the last decade; so if they can sell one condenser tube set they are way ahead on total metal sales for the alloy.

    There are also other factors to consider - and I will touch on them in my larger writeup. But this gives you a primer on some of the issues (as well as some really great information).

    Enjoy - and I hope you find the information useful:
  • tim smithtim smith Member Posts: 2,226
    I was sitting here trying to read those data sheets but I kept

    hitting the escape key with my forehead as I nodded off. :o
  • Dan HaraburdaDan Haraburda Member Posts: 2
    Munhkin E14 and F14 Errors

    Munchkin T80M - I am getting E14 and F14 errors. The faults occur when the motor is not supposed to be running. There are two scenarios when the fault occurs:

    First: No call for heat. The combustion motor runs at 1450-1500 RPMs when there is no call heat. After about a minute it shuts off.

    Second: Water temp has reached 180, combustion has shutoff waiting for the water temp to reach 159. Once again the combustion motor runs for a while then shuts off with a E14 error. The E14 changes to F14. Upon resetting F14, combustion will go a through another cycle if the water temp is less than 159.

    The point is: There would be no issue if the motor would shut off when it is supposed to. Is this a motor problem or a controller problem? or?
  • PerryPerry Member Posts: 11
    Please post this as a separat thread


    You will get more attention - and the right attention if you repost this as a separate thread - and ask for no more postings in this one.

  • TimcoTimco Member Posts: 2,813

    wouldn't a good dirt separator solve the issue of rust & gunk plugging a HX with small passages? I always use at least a y strainer on converted gravity & other old dirt sep's catch rust?

    Working on steam and hot-water systems isn't rocket's actually much harder.
  • PerryPerry Member Posts: 11
    How fine is your strainer?

    Given how tight I think these passageways are - I think you should probably filter at the 10 - 15 micron range if you are going to prevent sludge from building up in the corners (and even then it might still build up).

    That's a lot finer than a Y strainer.

    But yes, you could install such a strainer and filter.

  • RolandRoland Member Posts: 7
    Munchkin Issues

    Derheatmeister, Thanks for your response to my post. I was within one or two rph's (totally NOT P.C.) of having a Munchkin installed in my home but, changed my mind due to financial issues.

    Do you think ALL presently manufactured Mod/Con boilers for home/light industrial use are in need of re-engineering?

    Are Mod/Con boilers essentially expensive, short-lived devices?

    In your estimation, what are the weak spots in current Mod/Con boiler design? You don't need to mention specific manufacturers or models.

    Why don't we hear about these issues from Europe where Mod/Cons have been used for some time now?
  • DerheatmeisterDerheatmeister Member Posts: 950
    \"Whipping Post\"

    As i do not want to offend any one Manufacture in "Public" anymore and have gotten lots of negative feedback for my real world first hand experience's with Poorly designed Premature and pre launched Modcon boilers

    I rather "Talk" to you directly!

    I think that time will tell which manufactures are serious and have an great R&D/Support on the products before they "Push them out the Doors" and i do not have to fight about it anymore.!!

    As we say in Germany: Wer andern die Wahrheit Geigt, Dem schl
  • RolandRoland Member Posts: 7
    Munchkin Issues

    "A man is accepted into a church for what he believes and he is turned out for what he knows." Samuel Clemens......

  • hot rodhot rod Member Posts: 7,003
    a good dirt separator

    can remove down to 5 microns without risking any flow restriction. Here is an example of one brand with an explanation as to how they differ from Y strainers.

    Dirt separators should be included in all mod con conversions, especially old iron system conversions.

    Bob "hot rod" Rohr
    trainer for Caleffi NA
    The magic is in hydronics, and hydronics is in me
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