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High vs low mass boilers

As you may already know nothing cheap about an system 2000 boiler, and yes there are some oil-saving benifits to them. And no they don't always have to have short in-efficient burn cycles, and you don't usually need buffering tanks to make them cycle longer. The system manager has a few dip switches that can help with the burn cycles, and adjust for different sized systems.

As for warranties these boilers are 25 year or lifetime. I can't think of many boilers with a 5 year heat exchanger warranty. Maybe the WMC condensing Ultra boiler, or a few others who have dared to make condensing boilers out of aluminum, but not many warranties that short.



  • MikeB34
    MikeB34 Member Posts: 155

    I know cast is best when it comes to boilers, but lately I have been seeing low mass steel boilers. How are these things? do they last? The warranty is only 5 years on the heat exchanger. I assume they are noisier, and need to be protected (p/s piping or bypass to preheat) I am starting to do more boilers and am loosing out to these jobs ($$$ mostly) they're a lot cheaper, but hey..you get what you pay ... right? can I get pros and cons from you excellent people?
    Mike B
  • Joe_13
    Joe_13 Member Posts: 201
    who said they're cheaper?

    I don't think low mass boilers are cheaper. Maybe when compared to Buderus and Viessman but these are more then any other boiler. You do have cast iron low mass: Slantfin, Biasi, Crown Freeport (Low water , not low mass!).
    Burnham, Thermo-dynamics and Laars have steel models that are not cheap and usually have 15 yr min warranties if not lifetime. Who only has a 5 year heat exchanger warranty?
    Are you talking gas models?

    Like you said, piping is critical and the low masses are not for all installations (gravity feed conversions). Buffer tanks usually are needed to prevent short cycling. That's why I like the reserve indirects for domestic hot water. Just adding a buffer tank for the heating zones turns your low mass back into a high mass. Many have also said that some of the low mass boilers are quieter since they are all wet leg and have water jackets that suround the fire box. Biasi and Crown Freeport are 3 pass designs that also muffle the sound.
  • MikeB34
    MikeB34 Member Posts: 155

    The manufacturer is New York Thermal in particular. Gas fired Steel boilers. I realize that there are very good low mass cast boilers. I am refering to these types in particular, They' re being quoted at 1/2 the price of what I use.
  • hot_rod
    hot_rod Member Posts: 22,266
    Application and care

    are the key to long life, I think. Keep the water inside treated with inhibitors, and keep the outside of the HX soot free and clean. Make sure the burner is adjusted correctly.

    The application is also very important. Multi zones and small loads can cause a low mass boiler to cycle a lot. This leads to inefficient burns and lot more component wear.

    I agree, a buffer tank, properly installed can provide long, hot burns, and provide a nice well insulated place to park BTUs until they are needed. Although the job cost goes up to supply and pipe one correctly.

    hot rod
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
  • Steve Ebels
    Steve Ebels Member Posts: 904
    High vs low

    My experience has been that there are few, I said few, as in almost no, applications that benefit from a low mass boiler. Look at what Hot Rod said, most of them wind up as high mass anyhow because of the addition of a buffer tank. Also look at Mark Eathertons post on the experimental model he's playing with. About the only time a low mass will save you some fuel $$$ is in the off season when making domestic hot water. Up here that's only two months of the year.

    We have an installation using a Munchkin in a 6" concrete slab with most of it on one zone. One of the remaining zones is a 20 x 22 office. When that zone was on by itself, the Munchie had the same burn time as the attention span of a 2 year old. We added a 30 gallon buffer to the system to calm it down. This was even piped primary/secondary with good flow through the boiler under all circumstances.

    As far as selling quality products, stick to your guns brother and stay with the better grade stuff. The hassle and pain of selling junk is not worth a sale. It comes back to haunt you until it finally dies.
  • MikeB34
    MikeB34 Member Posts: 155

    Thanks for the input everyone. I intend to keep using better stuff. We can now compare what is really done vs my offering.

This discussion has been closed.