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Are aluminum heat exchangers in MOD/CON doomed by bad PH levels?

D107
D107 Member Posts: 1,849
Thanks Darrell, Mark and the rest for some incredibly informative answers. With sealed combustion I'd think a drier in the boiler room wouldn't be a problem, but do the manufacturers' recommended clearances between drier exhaust vent and mod/con FAI seem to be adequate? That would also seem to be chemically laden air.

Also the installer I'm speaking to now won't do concentric vents. How much is either concentric or lateral mod-con venting known to result in exhaust air being sucked into FAI with whatever problems that may cause the HX fireside? I've heard some Wallies say as a precaution they extend the exhaust vent on a concentric out a few inches further to maintain proper separation. Of course with windy days, who knows...

Thanks,

David

Comments

  • tod_3
    tod_3 Member Posts: 3
    aluminum heat exchangers mod/con boilers

    Are aluminum heat exchangers in mod/con boilers doomed
    by bad system water PH levels? Aluminum exhangers seem
    to be failing in alarming rates. Any feedback out there
    on brands or circumstances?
  • MIke_Jonas
    MIke_Jonas Member Posts: 209
    A question for you

    Where is it reported that aluminum heat exchangers are failing at an alarming rate?

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  • tod_3
    tod_3 Member Posts: 3


    VIA THE FACT THAT MANUFACTURERS ARE NOW ALLOWING ONLY
    CERTAIN TYPES OF ALUMINUM APPROVED ANTI FREEZE TO
    BE USED IS A CLUE TO ME THAT SOMETHING IS UP! CRYO-TEK AL
    IS NOT ON THE LIST. DO WE HAVE TO EXTRACT CRYO TEK AL
    FROM ALL EXISITING SITUATIONS? OH MY!
  • MIke_Jonas
    MIke_Jonas Member Posts: 209
    chill, dude, chill

    Don't yell. Turn the caps lock off, please.

    Take a breath.

    Relax.

    Could you be a liitle more specific in regard to failures?

    Is there a service bulletion I may have missed from a particular manufacturer?

    Is there a specific problem your company is seeing?

    Warranty failures? Out of warranty failures? One specific model or size?

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  • tod_3
    tod_3 Member Posts: 3


    sorry, warranties cost money. I'd rather not mention
    manufacturers. The aluminum flaking and causing
    build up internally in heat exchangers and drains. Based
    on search of comments on the "the wall" more than one
    manufacturer may be experiencing this.
  • Mars_3
    Mars_3 Member Posts: 65
    Just my 2 cents.

    I am a pup at this, only been doing this for 15+ years but to my minds eye the use of alumunimn for a heat exchanger in a modulating condencing boiler is counter intuitive. the nature of the beast that we are talking about has to have a negative affect on the nature of the product. A wrong water chemestry on the inside of the heat exchanger and the corisive afects of the condensate would seem to me to be a bad idea. How many shops out there are going to check the water chemestry to see if it is bad for alumunimn. Case in point I have a contractor here in the denver metro area that has a in-floor heating system for the main floor and a GFA for the 2nd floor, in the winter months he needs humidity to keep his hardwood floors from seperating. he is on a well and in the course of five years we have instaled two diffrent types of steam humidifiers and have found that to this point they canot do what they need to do due to the water chemestry. Bear in mind that this guy has a $20,000.00 reverse osmosis carben filter set up for his water. The last steam cylinder that I replaced for this guy had so much build up on the elements that they were virtuly touching causing a short circut across the elements. It just is a case in point that the water chemestry in the area can have very bad affects on the equipment that is installed. For those of you that are intrested his well water has 3800 microsemens and after the filtraten the reading is 180 microseamens.
  • Steven Eayrs
    Steven Eayrs Member Posts: 33
    Great!

    Mars and Todd the pup both unload some news that there are massive problems with aluminum condensing boilers, yet can't name the brand, model or where these things are going bad at. Sounds like more of a hit and run crew.

    If theres problems I'm sure those of us that are installing these things would be seeing some of it. Obviously these guys aren't installing them.

    IF you got something real to bring up, and not just a bunch of bull, lets here it!!!
  • Tony_23
    Tony_23 Member Posts: 1,033
    C'mon

    Comments on The Wall does not a recall make ;)

    Properly treated water isn't that hard to attain.
  • scrook_3
    scrook_3 Member Posts: 66
    Antifreeze or condensate?

    Which side are you concerned about, fireside and condensate attack or waterside and antifreeze attack?
  • scrook_3
    scrook_3 Member Posts: 66
    Antifreeze or condensate?

    Which side are you concerned about, fireside and condensate attack or waterside and antifreeze attack?
  • Drew_2
    Drew_2 Member Posts: 158
    pH/Aluminum

    Tod & Mars

    I'll try to answer your questions with a little chemistry.

    First Tod;

    "Are aluminum heat exchangers in mod/con boilers doomed by bad system water PH levels? Aluminum exchangers seem to be failing in alarming rates. Any feedback out there on brands or circumstances?"

    Every metal can have problems with pH. Most have the problem with pH below 7 (acid). Aluminum doesn't like pH below 7 or above 9. Most manufacturers of boilers say between 7 and 8.5 . The reason manufacturers are listing different antifreezes than the ones in the past are because some of the AL antifreeze formulations were not holding up to the expected life seen with standard antifreezes of the past.
    Now Mars;
    "How many shops out there are going to check the water chemestry to see if it is bad for aluminum."

    You’re correct and that has been a problem for a long time. It's not just aluminum, its all metals.
    Not checking water for dissolved solids and pH is like using 3 in 1 oil as motor oil in you truck. Oil is oil, isn't it?

    I could go on for a long time about these issues and make your eyes cross, so I'll get off my soapbox and go grab another cup of coffee.


  • Rhomar Mike
    Rhomar Mike Member Posts: 11
    Glycol

    RhoGard Aluminum Safe Glycol is endorsed by most of the companies that manufacture boilers with aluminum heat exchangers.For more information our website. www.rhomarwater.com
  • D107
    D107 Member Posts: 1,849
    As homeowner

    who expects an estimate for a Buderus GB-142 next week, I was thinking that assuming a closed hydronic system and that a PH check is done, what's the problem? Does condensate attack the HX?

    According to a rhomar water test I did of the heating system water, hardness is 103ppm (a little more than desirable); chloride is 28ppm, a little high but will effect only stainless steel not aluminum. Suggestion was to run makeup water through a softener. They have had these boilers in Europe for quite a few years I understand; surely we would have seen reports by now of significant failures.

    Thanks,

    David

  • Dobber
    Dobber Member Posts: 91
    Treated Water

    David
    Check out Buderus site and download GB142 manual. They do not want water going through a softener. Great boiler choice. I have many in service. For the record I have replaced 3 stainless HX, No AL HX.

    Good Luck
    Dobber
    If you don't have time to do it right, what makes you think you have time to do it over?
  • Darrell_4
    Darrell_4 Member Posts: 79


    System side water chemistry is no big deal. A kit to test it with is easy to put together and you should be dropping pressure once a year to check the peripheral controls anyway. If you need antifreeze, use the stuff recommended and check it yearly at the annual check as per the manufacture's recommendation. And every boiler, regardless of manufacture or material is susceptible to system side chemistry problems.

    Fire side water/condensate chemistry is a different animal and cannot be balanced until it is out of the combustion chamber. The condensate does attack aluminum, and just about anything else it gets on. Don't let it run across your garage floor untreated and say goodbye to your Cast Iron floor drain. Following the manufacture's install guide to the letter seems to minimize the destruction of the metal by the condensate.

    Really guys, the system chemistry is no big deal. I see far more boilers destroyed by lack of annual comprehensive maintenance which every boiler manufacture says is required. If you owners aren't getting it done...you should. If you installers aren't going to do the maintenance because it isn't your gig, then you should recommend someone who does that for a living.
  • D107
    D107 Member Posts: 1,849
    Darrell just to clarify

    so you're saying that once the condensate is out of the combustion chamber, it is balanced by the filter (marble chips, etc. rendered to acceptable PH so that your drain system doesn't get eaten away. got that.

    But while it is in the combustion chamber it can attack the HX but if proper annual cleaning is done that mitigates the problem. I guess the question is have you installed these particular boilers or other aluminum hx boilers yourself given this fact?

    Thanks,

    David
  • Following the manufacture's install guide

    to the letter seems to minimize the destruction of the metal by the condensate

    and weil's rational behind their ultras is that the initial chemistry will affect the amt of inherent sediment, and if the chem is off/more sed, then there's more available sed to settle in the hx. and without annual flushing of the system and hx of sed, the sed will cause corrosion of the hx by destroying it's protective oxide layer
  • Mars_3
    Mars_3 Member Posts: 65
    Steve I am just saying that I would not be comfortable using one

    Thats all I am saying. As a desinger of these systems its my name and reputation on the line, and I am not ready to risk these at this point in time. If after some time they have a proven track record I may concider there aplication. That time has not yet come.
  • Mark Eatherton
    Mark Eatherton Member Posts: 5,853
    I can tell you this...

    I have yet to open an aluminum modcon that DIDN'T have its' trap COMPLETELY loaded with a silverish looking sludge (aluminum?)

    That indicates to me that there is a continuous degradation of the heat exchanger material on the fire side. According to the manufacturers, they are aware of this and have taken it into consideration in the design of the heat exchanger.

    Also, VIessmann USE to have an aluminum block heat exchanger in their lower end appliance. According to a very knowledgeable person inside of V, they took it out of their line up due to the dissolving HXer. It didn't comply with Viessmann's motus operandi of longevity.

    If you chose to use an aluminum block boiler, you have to be aware that it will eventually (who knows how long) hole through, requiring eventual replacement. But as has been discussed on this board ad nauseum, who WANTS to hang on to an appliance for longer than 10 or 12 years? TIme and technology changes. I suspect that 10 years from now NO ONE will be producing a mod con boiler. Can you say hydrogen fuel cell?

    FWIW, I no longer deal in aluminum boilers for all the above reasons. If you chose to do so, its your decision. Just be prepared, and prepare your customers, for the eventualities.

    And who knows what ugliness is going to raise its head in the stainless steel mod con arena. We've already seen pictures of HXers that have died different deaths, most of them associated with salt failures...

    It's a crap shoot. Pick your poison carefully.

    JMHO

    ME
    It's not so much a case of "You got what you paid for", as it is a matter of "You DIDN'T get what you DIDN'T pay for, and you're NOT going to get what you thought you were in the way of comfort". Borrowed from Heatboy.
  • hot_rod
    hot_rod Member Posts: 21,853
    all metals

    have a tolerance level. Even stainless steel does. Which is why there are so many different grades manufactured. The same grade of ss used for the water side, may not be the best for the fire side. Check with the OWF manufacturers as they have struggled with a choice of stainless that works well for fire and water chemistry.

    The issue with aluminum, perhaps... is the corrossion from the fire side caused by the stuff they blend into natural gas these days. From what I am hearing is more fireside corrosion and pin holes were caused in areas where they use, or have switched to, imported natural gas, or started blending imported gas with domestic gas. Not all gasses, like water, glycol, paint, food, etc are created equal.

    The AL boilers I check seem to fill the clear plastic condensate trap with gunk. That has to be from the fire side condensate, not the water quality.

    The stainless boiler that are failing could be related to the air they inhale. i know for a fact one that is located alongside a major interstate pass inhales all the road ice melt chemicals the use now a days. I lived there! SS doesn't go well with chlorides, they tell me. That road spray also went after the metal roof and ABC seamless metal siding on the building. Even killed many of the hardy cedar bushes in the yard as the experimented with various chemicals for ice melt.

    I agree the water side chemistry is fairly easy to check and maintain, knowing and controlling what comes out of you gas pipe from the utility is a bit more of a challange. It takes some special talent and equipment to anayze what is "in" natural gas. I guess it's not so natural after all :) And if it changes based on utility suppliers the testing would need to be on-going.

    hr
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
  • ME

    thanks again for a mo better balanced reality
  • scrook_3
    scrook_3 Member Posts: 66
    sulfur?

    Higher sulfur in the some NG supplies (as in #2 oil) perhaps?

    Re: chlorides, they are tough on many otherwise highly corrosion resistant stainless steels and can cause corrosion at high stress points, in crevices, and/or pitting on surfaces. Exotic highly alloyed grades are available that survive chlorides better.
  • Darrell_4
    Darrell_4 Member Posts: 79


    I do not do installs...maintenance and service is my thing. I do take care of a number of boilers of different construction, different theories, different manufacture and different installers. I have done many installs prior to this phase of my life.

    1. Proper install cannot be over stated. All the high efficiency in the world is a waste of time and money if the install doesn't support the technology.

    2. Proper maintenance cannot be overstated. We often got away with not seeing a simple CI boiler for years...or so we thought. But, the anecdotal facts are clear that the newer boilers, of whatever material or manufacture must be seen at least yearly and probably twice yearly.

    3. Some materials are more susceptible to degradation under chemical attack than others. Aluminum seems to not like the condensate as well as stainless steel. Most of the failures of stainless steel seem to be related to heat stress and chemical laden combustion air. Heat stress is often the product of improperly sized or controlled boilers. Chemically laden combustion air is a tough one because we may simply not be aware of the airborne chemicals. Most of the failures of the Aluminum are related to condensate erosion...and so far there is no way of preventing it. Some manufacture's predict a longer life cycle simply by having thicker castings. A CI boiler, improperly installed, controlled and oversized will condensate and fall apart pretty shortly too.

    4. Proper Installer education and Owner education cannot be over-stated. The days of thirty year old boilers appear to be gone...and much of my time is spent educating owners of new equipment on topics like life cycle, maintenance cycle and voided warranties that the installer should have covered with his client before he ever cashed their check. I see lots of unhappy owners due to mis-information, over-stated expectations and cash and run contracting.

    I am not down on mod-con boilers. I am unhappy with manufactures that force their product onto the market place without sufficient research just to satisfy the high efficiency desires and claims of the market place.
  • Darrell_4
    Darrell_4 Member Posts: 79


    Yes...the dryer vent is chemically laden...and also full of particulate lint.

    I would rather see all of the sealed combustion equipment vent vertically out the roof and draw combustion air from the roof as well.

    Frost is not an issue. Cross contamination from other sources is not an issues except on some commercial building where the roof is also the equipment platform for cooling and ventilation and tec.

    Plant fuzz, dog/cat hair, dryer lint, leaves, dust, fertilizer, cooking exhaust, lawn mower gasoline, frost and moisture all are potential issues for sealed combustion equipment.
  • Leo G_103
    Leo G_103 Member Posts: 34
    coming down the pike,

    actually, Bosch's new condensing tankless heater is already using it, is a copper/stainless combo. Copper on the interior wall of the tube, wrapped by stainless. Could be a very interesting combo eh?

    Leo G
  • hot_rod
    hot_rod Member Posts: 21,853
    dryer lint, or dust

    will find it's way into the inducer motor, circuit board, etc. My Lochinvar Knight is in the laundry room and it does get a small coating of dust on those compoponents. Especially the rear end of the inducer motor, which contains some electronics.

    Sealed combustion seals the combustion chamber, not the othert components.

    The Knight does have the combustion air coupled to the inducer, not into the case like some other brands. The brands with air being pulled into the case are more sensitive to "dirty" room air.

    hr

    hr
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
  • Hollywood
    Hollywood Member Posts: 4


    would love to know where your information comes from.
    heat exchanges failing at an alarming rate?
    To date have not seen ONE of ours fail like you have stated. I do work for a manufacturer of a mod/con alu ex.
    would like to see something that could back up such a harsh statement.
  • I was told

    in the mid 90s, when we were installing the near condensing weil mclain gold units,during the failed ultra vent and plex vent debockle. We were told that we had to replace the vent with AL 294C. At first my rep tried to tell me I had to do it to protect myself! Yea right, because every lawyers dream is to take my old plumbers truck and my mortgaged home. Soon enough the boiler manufacturers started a replacement program where they dictated how much they would pay on a job to job basis, which I refused to take part in. But during this transition time I had ask several manufacturers why we couldnt use aluminum tubing or pipe. I was told that aluminum would never be able to withstand the ravages of flue gas condensation. This seemed a little odd to me since we were installing aluminum liners by the hundreds on subcontract from the local gas utility. At that time aluminum liners were not in long enough to really make a sound decision as to their longevity. We know now they last a very short time! Then came the new modcons and they were stainless and we knew stainless would hold up because we had installed many hydropulse units that had quite a few years on by that time with very little trouble with the exchangers. Then came the aluminum modcons, I just have to shake my head and laugh anymore. I guess its like they say, if we dont learn from history then we are bound to repeat it.
  • Mark Eatherton
    Mark Eatherton Member Posts: 5,853
    So, Hollywood....

    Welcome to the fray.

    How many years experience does the Bob Cat have?

    How much parent material sloughs off of the heat exchanger per year?

    How long does your company expect the heat exchanger to last?

    How much research did your company do prior to applying aluminum to it's product? Did they go to Europe to look at the Al heat exchangers that had been in operation over there for a long time?

    Just curious, based on what I've seen in the field...

    ME
    It's not so much a case of "You got what you paid for", as it is a matter of "You DIDN'T get what you DIDN'T pay for, and you're NOT going to get what you thought you were in the way of comfort". Borrowed from Heatboy.
  • D107
    D107 Member Posts: 1,849
    Bottom line

    Seems that the main concern is the HX. If one buys a mod con today installs and maintains it to the letter but in 15 years the HX is shot, what relative percentage to replacing the entire boiler will replacing the HX be? Maybe it's not that big a deal. (I'm supposed to change my timing belet on my car every 60K miles and a long list of other things get changed over 15 years, likely including the car itself.)

    David
  • Darrell_4
    Darrell_4 Member Posts: 79


    I did one...

    The manufacture decided tp not warrant the HX...after it was put in on apromise of warranty. I had to strip all the sensors, fittings, and perripherals stuff and refit them to the new HX. The manufacture does not cover labor in the warranty.

    A new boiler, just like the old one would have been four union, six wire nuts, and a couple of hose clamps. Done and fun.

    In this particular case a whole new boiler would have been cheaper because of labor.
  • D107
    D107 Member Posts: 1,849
    thanks for the feedback

    well so much for my optimism there. One more try: is it possible to design or are some modcons already designed with an easily replaceable HX or is that just inherently unlikely given the interconnections you mention?

    Thanks,

    David
  • Hollywood
    Hollywood Member Posts: 4


    the Bobcat by Slant Fin Corp.
    the HX could be replaced in about an hour.
    Very service friendly. Yes alot of R&D was performed.
    Before mass production was done 5 years worth. Check it out on there web site. 1 inch water ways.
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