On the Condensing Boilers in Hydronic Systems Discussion Board…

Expert instructor Roy Collver discusses construction materials and manufacturers of condensing boiler machines.

Student 1:

Roy, great videos and a ton of great information! Thanks a million! I have a couple of comments and questions. Stainless steel is very strong on the galvanic charts, but have you looked at the thermal conductivity of stainless steel versus other materials of construction? I know why we prefer stainless, but when comparing the thermal conductivity of stainless vs. a material like copper or even aluminum, it makes much more sense to use those materials. With aluminum I have understood (and this weeks videos summed up what I thought and taught me more) the downsides and can see why one would want to use an alternative. But, what do you think about hybrid boilers using copper primary heat exchangers and maybe a stainless secondary? I have seen some of the efficiencies of these boilers and they are some of the best overall. Manufacturers like RBI, Camus and Thermal Solutions have some really neat concepts and they can utilize the heat transfer coefficients of copper to make more efficient boilers using less metal… remember the Lochinvar Intelli-Fin that had a copper primary and a coated copper secondary. Additionally, you reference the Hydrotherm KN boiler, which is cast iron. I am a rep here in MN and one of the many lines we rep is the Mestek family of products. The Hydrotherm has been a workhorse for us and we sell hundreds a year. Interestingly enough, it is just a cast iron boiler, no different then those that have been made for years, with one exception: they put the burner on the top vs. the bottom. This way, any condensate that would develop on the heat exchanger or the pins would be blown off during the post purge cycle. We have several that are pushing the ten year mark that are still in operation (commercial, primarily) and we have not had one failure due to condensation. Thanks again, and I am really enjoying this!

Roy Collver:

Thanks for the good words Joe. Yes, stainless steel isn’t the best for thermal conductivity, but it can stand up to most of the nasty fire side and water side corrosion better than most metals. Aluminum is the best conductor, but has to be in a very pH neutral environment. The hybrid boiler approach is interesting, and a good compromise, especially in larger boilers where you are trying to minimize size. They should do very well provided the interface between the two materials is handled properly (durable gaskets, dielectric separation, etc.).

Thanks for the information on the KN boilers. Mestek is a good company, and I know they would have done their homework (especially in light of the Hydropulse disasters of yore). A combustion chamber post purge to drive moisture out makes sense. Cast-iron is not bad at corrosion resistance, but hates acidic environments, as does copper.

As for Viessmann – they are really in a class of their own when it comes to R&D, but then it is a Family run business, and they can look past the next quarterly dividend and develop longer term projects.

Too bad most North American companies have shareholders weighing them down with constant demands for cash. R&D departments have had budgets cut too deep. Just look at how everyone has jumped on the AIC bandwagon rather than come up with a made in America solution. We have all of that metal working expertise in our automotive, aerospace and marine industries and we can’t develop an affordable condensing boiler heat exchanger? Of course we can. There was my rant for the week – how was it?

Student 2:

Question (1) are there special considerations (piping, controls, valving) when combining condensing boilers with conventional boilers on commercial, institutional scale?

Question (2) can you offer a list of condensing boiler manufacturers for large commercial, industrial projects? (ie. Viessmann)

Roy Collver:

1 – Yes, there are many special considerations in combining condensing boilers with conventional – but it works really well if it is done right. Normally you would be looking at primary / secondary piping to isolate high system flow rates from the boilers and provide each boiler with its own optimal flow. Then it is all about control strategies.

2 – I would suggest you look at the AHRI ratings for larger boiler for an idea of who is making large commercial. Certainly Viessmann would be one of my first choices here in BC, and there are others, but as I have always advised – you need to find an acceptable product that has strong representation in your area so that you can get adequate support and advice. Unfortunately, many of the traditional large boiler manufacturers have been reluctant or slow to dive into the R&D necessary to develop reliable products. I will get back to you with a list, but I am hard pressed to recommend anyone other than Viessmann right now – just no track record out there for many of the contenders (or a bad track record).

Enroll in Roy’s Condensing Boilers in Hydronic Systems and spend 6 weeks optimizing your system designs and control strategies to take full advantage of the energy savings and comfort benefits boilers have to offer.

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About Roy Collver – President, OTBC Inc

Hydronics Specialist / Educator, Class 1 Gas-Fitter and Illustrator, Roy has applied his creative force and problem solving abilities toward the improvement of hydronics in North America for over 35 years. His varied experience at the very cutting edge of new development in hydronics has allowed him to apply his unique knowledge and skill set toward becoming a premier “translator” of new technology to a traditionally conservative and slow-to-change Industry. His training is up-to-date, comprehensive, and entertaining. After ten years at the top level of his trade “on the tools,” Roy worked closely with many eminent design and application engineers on new and innovative products—from initial concept to final production and marketing. Working in the very “inner sanctums” of these most progressive companies; he was a key partner in helping them design and bring to market, many game-changing hydronics products. He produced many outstanding training programs along with the technical and promotional materials needed to explain the effective application of these new products in the real world.

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