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condensing boiler?

Steve Ebels_3
Steve Ebels_3 Member Posts: 1,291
Having installed more than a few condensers on BB systems, I have to say that unless your BB is severely undersized, a M/C boiler is THE WAY TO GO. The theory that you have to have 180* water in baseboard in order to heat at all is just plain wrong. The modulating temperature available in nearly all M/C boilers works wonderfully with baseboard or any other type of radiation that I have run across. I use Munchkin, Prestige and Viessmann boilers, all of which are stainless steel. The Munchkin, Viessmann 100 series and even the Prestige are very reasonable in price. The Prestige would probably be a nearly perfect match if you have a typical BB system due to its low pressure drop and integral circulator. (15-58 Grundfos)

In every single instance where we have taken out a cast iron boiler and replaced it with a condensing version, the owners fuel consumption has dropped 25-40%. The payback is there right now and will only get better as fuel prices inevitably rise.


  • Michael J. Brennan
    Michael J. Brennan Member Posts: 29
    condensing boiler?

    Hey guys, looking for some opions, i am going to install a new weil mclain sealed combustion hot water boiler w/an indirect fired hot water heater and 3 baseboard zones, is it worth it to install a condensing boiler or a regular hot water boiler? there will not be any low temp zones on this install, and the budget is kinda tight, I know the price of the weil mclain Ultra is almost double the price of a weil mclain CG's model, but would it make sense to use the ultra? the venting with the ultra looks to be a bit more straight forward with using 3" pvc pipe as opposed to using stainless steel.. Also if i go with the ultra model would i still have to use primary/secondary pumping even though I will not have any low temp zones on this application, thanks for the input guys...
  • Mitch_4
    Mitch_4 Member Posts: 955
    a couple thoughts

    I do mostly forced air, but here are a couple things I present (in a nutshell) when looking at boiler replacements.

    1- CI boilers are cheaper, ut have a limited temperature range of operation. (above 140° H2O usually), require protection piping in some form, and have a lower efficiency.

    2- ModCon boilers are more expensive, but are more efficient, and can handle lower water temperatures. Many incorporate outdoor reset, and lower both the the water temperature, and gas consumption saving money. (baseboard even at 120° water will emit heat). When in a multi zone system, the modulating input as various zones demand / are satified can save even more

    3- A mid line choice can be a condensing NON modulating boiler with outdoor reset. Condensing tchnology benefits, and savinbgs at lower water temperatures with a simpler control strategy resulting in a lower cost boiler. With the right size boiler and reset curve, you can still obtain substantial savings.

    All the above assume proper installation and sizing by a knowledgable pro. I use the Olsen boilers in Canada (Dunkirk / Utica's in the USA) primarily because I have used Olsen for 20+ years for furnaces, but secondly because the condensing boilers (both Modulating and non modulktaing) do not require protection piping, and I can design for wider delta T. #3 scenario is the most common for me as there are few boiler in my area, and fewer of them with multiple zones. They get a high efficiency boiler, simple controls, and substantial savings (some over 55% from the old boiler withour modulating)

    Get some pro's in, and ask questions, listen to the answers, and if you don't know...post it here..you will get an earful one way or the other.

    Whatever you decide to do, make sure the installer knows what he is doing..saving money on the install, and not reap long term savings is bass ackwards..like taking a high % short term loan to invest in a modest return long term investment strategy. Spend a few more $$ upfront so you can save over the long run...you will be more than amply repaid by having it done properly.

  • Uni R_2
    Uni R_2 Member Posts: 589
    Get the modulating condensing boiler...

    Way more comfort in the shoulder seasons, way way way better efficiency in the shoulder seasons, way better efficiency all winter - probably 30% better.

    If you got a Prestige you could skip the primary secondary and minimize the electrical consumption for heat. You also wouldn't need to treat the water in all cases like with would with the Ultra. I'm very pleased with mine.
  • ALH_4
    ALH_4 Member Posts: 1,790
    Heat Loss

    You dont mention the heat loss of the structure. Bumping up to a mod/con might make sense if the heat loss is high enough. The cutoff will depend on many factors. As you burn more fuel, efficiency gains buy you more. It's the dichotomy of conservation and efficiency in terms of economics. For example, if your heat loss is 40,000 btu/h at design, a mod/con may not make financial sense.

    Also, from what I have seen, sealed combustion cast iron boilers are relatively high priced among cast iron boilers. Something like a Triangle Tube Prestige may not be that much more than the sealed combustion cast iron boiler.
  • Michael J. Brennan
    Michael J. Brennan Member Posts: 29

    my heat loss for the structure is 54,000 btu's, chimney is being removed, and would like to go with a indirect fired water heater, along with the baseboard....
  • Michael J. Brennan
    Michael J. Brennan Member Posts: 29

    looking to atay away from stainless steel, the job is on Long Island and the water here can attack the stainless steel, thats the reason i am lookin to go with weil mclain, and their indirects can handle this water alot better, a tech from weil mclain told me that Long Island is the one place where they have had problems with their indirects in the past, so they came out with a better linded tank, im looking to give them a shot, i have always used burnham in the past... thanks for your help guys, anymore input would be great
  • Louis_3
    Louis_3 Member Posts: 2

    I'm in the market for a boiler after just finishing my install; Is the supply and return on the Vitoden 100 at 3/4" suffient for 3 zones? the Munchkin and Prestige are 1 1/4 and 1.

    will the supply of 3 zones with 3/4 tubing and 85' high output BB be OK. I was thinking of using zone valves but am not sure of the circulator size.
  • Glenn Sossin_2
    Glenn Sossin_2 Member Posts: 592
    Am I missing something here ?

    The indirect from Weil McClain is the same as Phase III, it's a stainless tank. Are you referring to well water as opposed to city water ??

    Are you thinking, or do you have experience that suggests the aluminum block of the Ultra WeilMclain boiler is going fare better than a stainless steel heat exchanger such as that from a Prestige or Viesmann mod con in the LI climate??

    Don't know, but I would think the opposite would be true.

  • Ted_9
    Ted_9 Member Posts: 1,718

    Are there any piping diagrams that came with the Vitodens 100? I would ask the Viessmann rep. or Viessmann for proper piping.

  • mod con

    mike check out a munchkin t80 the t50 is hard pressed for hot water production ,i've done a few ultras and found the munchkin a little easier to install and i prefer stainless steel ,i personally have a wall hung 80 and it has been good to me i have slant fin 30 and run a max temp of 145 and it works wonderfully,as for bang for your bucks munchkin is probalby the best value since most mod con are quite a bit more then the munchkin but i my opion they all use simalar burner design with differnt controllers and reset options ,as for fuel comsumption mod cons are true fuel savers when it comes to gas useage and sooner or later all will be embracing them and outdoor reset as time goes on and fuel cost rise peace and good luck clammy
  • Bfliqezs
    Bfliqezs Member Posts: 4
    Weil Mclain Ultra

    I second Steve's comments. We replaced a 80's-era boiler with a Weil Mclain Ultra 155 in an 1800's home that had a lot of upgrades, including an additional in-floor radiant loop to two existing baseboard zones. The old construction and renovations made precise heat loss calculations difficult; for example, the walls were uninsulated, but much heavier construction than new houses. Also, the old wood siding had been left in place and covered-over with styrofoam-backed vinyl-coated aluminum siding. Try to calculate that R-factor!

    Anyway, modulating boilers allow you to reasonably oversize the boiler by estimating the worst-case scenario.

    As an engineer, condensing systems just plain make sense in any cold climate - it's a no-brainer.

    The bottom line is that our gas bills have decreased by 30-40%, once you correct for average monthly temperature differences. Again, this is hard to do given the radically different winters we've had (in Ohio) lately - thus the large error range in my estimated gas savings. But even on the conservative side, 30% savings is huge at current fuel prices. We saved $100's in the first winter alone.

This discussion has been closed.