vent lengths of mod con boilers

It boils down to this:

The fan.

The controls that are dependent on that fan, to safely function.

The engineering capabilities of the manufacturer, given the restraints the marketing (a/k/a price "points")/bean counters demand.

And finally, what the contractor/installer is willing to settle for.

The fact that "the greatest boiler maker on earth" cannot and will not make their "premier" boiler vent over 20' may provide insight as to just how the relationship between engineering and marketing inter-act.

Simply stated: "Great marketing will overcome mediocre engineering every time; typically in a ratio of 2:1"

Bottom line, find a manufacturer who makes a product that meets your vent length requirement, and fawgettabowt Vitodens for this one. Make sure whatever you install, also has threads that are NPT, not "straight-cut."

Let us know how you make out, please.

coaxial Polypropylene

I beleive that coaxial Polypropylene is the pipe of the future here in the states. The discussions of not using PVC for venting has good arguments but when we look at the coaxial Polypropylene with a max vent temperature of 120c what can compare and give us the peace of mind on safety?

Vent length for Vitodens

I have a couple of questions about venting the Vitodens that Steve or others might be able to answer. The Viessmann sales rep has not been able to get an answer from Viessmann. The venting manual says that the maximum vent length for side-wall vents is 20' for all models while the maximum vertical vent length for the 11-44 is 33'. Although it includes diagrams for vertical venting that show that part of the 33' can be horizontal, it does not include guidlines for how much can be horizontal. One possibility for me is to go through the wall it will be mounted on with a ~9' horizontal run to a 90° upturn and go through heated garage space and through the roof an additional 16' for a total of 25'. Is this possible?

Another possiblility for me is to have a 10' run against the outside of the house, through a large overhang and out through the roof. Will this cause freezing of the condensate? Will insulation help?

Read the post above.

Does it not say what I have said over and over again?

"rumn8r" writes, "The Viessmann sales rep has not been able to get an answer from Viessmann." Blame the rep? Of course. Blame the confusing euro-speak installation instructions? Of course.

Better yet, blame me!

I suspect, Viessmann INTENTIONALLY uses vague and contradictory installation (especially with regard to venting) instructions, because it goes to their agenda of verticle marketing, and allows interpreted variations of those vagueries to be used against "non-member" installaters, if the customer has pre-bought Viessmann by virtue of the hyper-marketing they deploy.

It was PRECISELY that experience thet our client endured, (and we as installers did as well) in our most recent Viessmann debacle/install. Yet one more reason to use anything but a Viessmann boiler in our own experience.

Market limitations of the Vitodens 6-24 & 8-32

As a follow-up:

How much has the limited pump installed on the Vitodens 6-24 & 8-32 limited the use of the boiler. A larger pump that might increase the product cost by a hundred dollars or two would make the boiler usable in many applications that now requre a Low Loss Header, secondary pump, and power supply expansion board + the cost of installation of those items. That is quite costly.

My guess is that they could potentially double, tripple, or even more the market penetration if they had a larger pump as part of the boiler.

In my case my system would have worked with a pump that could put out about 8 GPM at 8 Ft head. That's not a very large pump. But I think a pump capable of 10 GPM at 10 ft head would have a lot more use - and still not be a very big pump.

The existing pump may be idealy designed for the boiler; why not chose a pump that would work for most systems by itself? Why increase the cost of an install?

Perry

Perry,

Loved your honest response and appraisel. I suggest Viessmann never supposed you would hook their boiler up directly to a heating system. It is implied by almost all mod-cons I am aware of that a P/S pumping array is "standard."

Given the relatively high Cv ratings of the boilers in THAT category, P/S IS the fundamental design premise.

As an ASHRAE member, I recall the topic of one meeting where the caveat that "proper engineering" suggests "over" engineering is as poor a choice as "under."

In America, we cater to conditions of homes ranging from 200 years old to ultra modern commerciual spaces. Leaving the boiler controls "off" the product in many cases is better engineering! That's because we apply boilers in a far more "custom" application than the Viessmann product line affords!

I propose the Viessmann is over-engineered on a few points, and grossly underengineered in others. I suggest over, or under, engineered products are inferior. The former because over-engineering wastes money and generally makes things more complicated than necessary, and under-engineering result in quality compromises.

Unlike most, I want my cake, and to eat it. I find most American boilers, be they 1 HP mod-cons or 500 HP Clever Brooks to be more aligned with "spot on" engineering far more frequently than anything out of europe. Buderus being the lone excpetion out of Europe, so far.

Not in mine either

And it should be in the venting manual. (hint to Viessmann)

I got that info from the Viessmann rep a year or so ago when I ran into the same situation on a job. It's also covered in their training classes IIRC.

Hear Hear!

The Vitodens is a neat piece of engineering and the compromises that were made reflect the markets it's most often found in. The EU has 400MM inhabitants and is 97%+ hydronic heated. The US has 300MM inhabitants, and 7% hydronic heating systems.

As a rule, product engineering usually attempts to cover the largest markets, not the niches. EU systems, by and large, have TRVs on every radiator, very few circulators, and a lot of house mass to play with (stone homes combined with standing/hanging rads). Thus, these systems can play with wide ΔTs and low flow.

US homes, for the most part, are wooden construction, relatively low mass, and some of the emitter choices are very low mass as well (baseboard, hydro-air, etc.) Thus, flow rates needs can be much higher to deliver the required number of BTUs as the house temperature roller-coasters up and down. In a high mass-home, the rise and fall in temperature will be much more gradual.

The variable-speed pump built into some Vitodens' reflects the energy-efficiency aims of Viessmann, IMO. When a US lab compared the Vitodens to its competition, it had a 8x lower power consumption annually than the likes of an Ultra, for example. Using a variable-speed circulator is a large part of that equation.

That circulator (and the required power supply) undoubtedly add $$$ to the cost of a Vitodens. Having more circulators to choose from would be nice, but it could also defeat the ΔT the controller seems to be looking for. Never mind the legal raminifications of trying to get a boiler with multiple pump options certified via the myriad of federal, state, and local agencies.

I'm with you though on the point that the Vitodens is beautifully engineered to do what it is supposed to. Plus, once you pipe a bypass as Brad suggests (back into the supply header upstream of the pump, not the return), the extra pumps needed to run US systems on the other side of a LLH will no longer have a negative impact on the energy efficiency of the boiler.

As for the vents, these boilers reflect the trend in the EU to put these sorts of boilers under the roof in new construction. Who says a boiler has to be in the cellar, particularly if it runs on gas?

Does it not

trouble you that the "best engineered boiler in the world," can't even get the basic installation instructions down properly?

Doesn't part of the basic equation of good engineering begin with good documentation?

I rest my case!

I found the "basic installation instructions" both comprehensive and quite adequate. With regards to venting I found it rather obvious that horizontal and vertical were different.

With horizontal, it was "keep it short". With vertical it was "keep it vertical as much as possible up to 33' equivalent length".

My only real beef with the instructions and technical data (at least provided in the US) is that systems with a single, directly connected heating circuit (e.g. no low-loss header) were described only by exclusion. I still consider such to be the TRUE method envisioned by the Vitodens engineers with everything else an efficiency concession (no matter how slight) to their original vision.

BTW, I could have used vertical venting in my application in a big old 2 1/2 story home with the boiler in the basement. Problem was that I'd already used some otherwise "wasted" space next to the chimney in my master suite closet to house a little cube refrigerator and tiny high-faucet sink to fill the gallon water jug.

Ken

Ahhh.... I studied the manuals for a half dozen boilers (and still have them) when looking at boiler options for my house. Some I downloaded from the internet - others I emailed the companies and they sent me one (with their sales literature). I even got Viessman to mail me stuff in addition to what I downloaded from their site (and I have the general access password to get to all the manuals and technical information).

There is no comparison - the Vitodens manuals are in a class by themselves. To say that they miss a tiny bit here and there... is an indication of where Viessmann did wrong -- compared to what you consider the "better and right engineered" US boilers is laughable... Based on your previous arguments I know that you believe that The American boiler Companies supply only what the American market needs - and only what the American heating installer needs. Obviously, not only the top notch professionals (many represented on this site) but the average ones and even the lower ones can easily install those American boilers correctly - with often scant instructions and technical information. Heck, these boilers are so easy to install that half the questions asked or situations on this site (over and over again) - must be the work of shills... Either that or you read a different forum than I do.

Are you implying that the great Instruction and Technical manuals from Viessmann - in your opinion - another example of Viessmann "over" engineering their product?


Perry

Chimney

You can vent either material in an abandoned chimney.

So how do you vent through uninsulated attic space?

Had I known

you you would be challenged by the word "obtuse," I would have saved you $2.00.

I am not ashamed of waiving the flag. And Mark; that would be the American flag, just for the record.

Had Viessmann made a condensing oil boiler in te BTU range necessary for my load, they would have had a horse in the race.

The boiler I used to heat my home was engineered so well, there is no thread issue; merely four 3/4" pairs/sets of high and low temp female copper connections. I stuck a piece of 3/4" M copper tube in each, and took off from there.

At least this euro maker actually demonstrated some semblence of competent engineering, unlike the brand you seem so transfixed by!

I know. I know. Now you'll have to look up another $2.00 word.

Plus...

... there are a number of beautiful technical aids at our disposal these days... phones, fax machines, digital cameras, and computers! So many ways to get in touch with technical support, paint a picture, get some straight answers.

As for the completeness of manuals, remember all the trouble that Ron Jr. went through for installing a drop header on a steam boiler? How explicit does a manual have to be in its assumptions about the knowledge of the installer/inspector?

AL Boiler HX degradation in Europe & US Mfr's Limitations

Constantin:

Months ago when researching boiler options I spend a good number of hours researching Aluminium block HX's in Boilers. What I found was interesting - and enough to tell me that I did not want to retrofit one into my existing system.

Because I did not answer all the questions I had - I planned on someday finishing the research - and due to other items of more importance at the time - did not post what I had found.

To find information on the European experience where they have been used for about 15 years I constructed a search to look over there - and then paged through 20, 30, 40 (or so) google pages to find comments and information on the experience in Europe with Aluminium block HXs - and then intended to construct searches off of the results, but only did a few of those searches.

Unfortunately I do not have a list of all the sites I visited. But here is one that I can recover - a review by a commercial boiler installer (plumber) in England of a SS mod/con (Keston 25).

www.dooyoo.co.uk/archive-house-garden/keston-celsius-25-modulating-domestic-condensing-boiler/433028/

Because websites have a tendency to disapear I am attaching the complete review, and note the following statement:

"Keston have wisely chosen stainless steel as the material for the boiler heat exchanger. I always advise customers to insist on this material when choosing a condensing boiler. Aluminium heat exchangers have a tendency to rot away with time and leave a slimy mess for the service engineer. Keston guarantee the heat exchanger for five years."

I also found several other post (or reviews) from boiler installers or service technitions that reflect the degradation of Aluminium block HXs and the mess they leave in the system. I cannot recover those post at this time and am not going to try to reconstruct my search.

I do note that it seems that warrantee practices in Europe (and for boilers) in general are much different than common US practice - so don't be put off by the 5 year warrantee statement.

However, the impression I was left with after doing my search... Installation of Aluminum block HXs on existing systems with iron (or steel) piping and radiation was where most of the problems occured. Aluminium radiators were available and recommended for new installations where Aluminium block boilers were going to be used. I was curious if Aluminium fittings were also available such that you could construct a system purely from Aluminium (or galvanically compatible materials) - which would eliminate one of the most obvous problems with using Aluminium and Iron or steel in the same system (and I'm not sure how Aluminium and Copper react). However, I did not get that far in my searching.

Aluminium block boilers only represented about 2% of the 2004 and 2005 European market and were not growing in market share. Cast Iron or steel boilers dominate (my memory was 70-80%), with SS boilers next. My memory is also that SS boilers were growing in market share.

When I saw the web literature for the first Aluminium boiler I jotted down 4 or 5 engineering questions or issues that I had on the material being used in a boiler. While 1 or 2 of them were answered by further research - the others were not; and the "degrading and sliming up the system" comments from Europe largly fall into line with some of my initial questions.

If you look at the limitations that the US Manufactures have imposed you can see that they are aware of the issue (but are not overtly telling people). My general take after reading up on the issue this summer was that to ensure an Aluminium block HX would work:

First, you have test the system and chemically treat as necessary (anticorrosin additives seem to be highly recommended).

Second, you have to annually test the system and then chemically treat to get the system to where it needs to be chemically.

Third, they exclude warranty coverage for any Aluminium HX degradation caused by the system not maintained with proper chemistry. An example:

Wells McLain Ultra 80 warranty:

"This warranty does not cover boilers operated with combustion air contaminated externally by chemical vapors or with improper fuel additives, or with water/ system conditions which may have caused heat exchanger failure."

It seems that other companies have adopted some kind of wording about "chemistry" into their warranties when talking about Aluminum block HX's (although they may have just added it into their general warrantee). Companies that offer lifetime warranties for cast iron only offer limited life warranties for Aluminium.


So my question is: How many people or heating contractors are actually going to properely test and chemically treat their boiler water up front when the boiler is new. Only the best. Many heating contractors in the US will not do it (they've never had to do that in the past).

How many people are going to properely annually test and adjust their system chemistry.... My guess is only a few. Even the best heating contractors - those who understand and are willing to do it - are limited by people who do not want to pay an annual service call.

How many boiler companies will pay for a degraded Aluminium block HX after it degrads due to improper system chemisty... (seeing how every company that I have checked on specifically exclude this from their warrantee). Zip.

Who is going to pay to clean up a "slimed up" system?

Lets look at a common example of Aluminium in a HX. An automotive radiator. Why do you need a routing cooling system flush and refill (every several years). Not because the antifreeze goes bad - but because the additives (anti-corrosion) get used up and go bad. Ever see a radiator or Aluminium head that has run for several years beyond the life of the additives. This is the biggest cause for sale of new radiators... Heads usually are OK only because they have more material to loose; but I know of cases where the head had to be replaced as well.

So that is what I know.

This portion of this thread started largly becaus Ken has a saying that marketing overcomes poor engineering. I agree.

If you hear that an Aluminium HX transfers heat better than SS (steel, or Cast Iron). That is marketing, not engineering. It is true that for the same thickness that Aluminium transmits heat faster than the other materials. The problem with the way the statment has been used is the cast aluminium block HXs are much thicker - as such, a thin SS based tubed HX transferes heat better.

If you hear that Aluminium is highly corrosion resistant. That is marketing, not engineering. Only in the right environment is an Aluminium corrosion resistant. Given the warnings about improper chemistry and oxygen from make-up water and non-barriered PEX, and the experiences in Europe where some of these have been installed long enough for the problems to start to appear... you've got to wonder how they can claim this with a straight face. That is marketing.

There is only one reason that Aluminium block HXs are being used. They are cheaper to Mfr than SS ones. round SS tubes have limits on heat transfer due to geometry, and odd shaped tubes cost more to Mfr yet. A very nice thin SS casting would outpreform the Aluminium block HXs - but would be expensive to produce because you can only get the thinness and details needed with a lost wax process casting.

Now my guess is that an Aluminium block boiler installed on a new system that does not have any Iron in it (and are Aluminium fittings available) will probably do well.

I doubt that they have a long life as a retrofit into an iron piped and radiator system - unless a lot of chemical monitoring or treatment is done.

Perry