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Thread: Selecting a condensing gas boiler

  1. #1

    Default Selecting a condensing gas boiler

    Hi,

    Anyone have any advice for choosing a condensing gas boiler. I'm planning on replacing the ancient artifact in my basement, and I figure I'll let it make my domestic hot water too. I have a mix of hydronic radiators and in-floor radiant heat. Any brands stand out as a good choice or as something worth avoiding?

  2. #2
    DIY Senior Member CHH's Avatar
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    It's an interesting question. The real difference seems to be burner & heat exchanger design since the OEM gas valve and fan choices are so limited. The contractor folks I talked to weren't interested in selling anything without a stainless steel heat exchanger. After that the major consideration seemed to be price with the Munchkin winning that battle. There may be some good deals going with a Munchkin and SuperStor together since HTP makes both.

    Buderus has an edge on efficiency and may qualify for tax and/or utility credits/rebates. They are expensive though that might not be a major hurdle with the high gas prices you face in Brooklyn.

    Make sure your contractor is comfortable and experienced with the brand you're interested in. You don't want to be their "learning curve."

    Most folks seem to say stay away from coils for dometic hot water and use the sidearm tank.

  3. #3

    Default Condensing gas boiler

    Chh,
    Thank you for the reply.
    Yes, our gas prices are sky high, here in NYC, so effeciency is key. And I agree that a ss storage tank is the better solution for domestic hw.
    So is it your opinion that, in terms of durabililty and all, they're more or less the same? And is it easy to get replacement parts for a Buderus unit?

  4. #4
    Retired Defense Industry Engineer jadnashua's Avatar
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    I had a Buderus unit installed in January along with a SuperStor indirect. Hope I don't ever need parts, but the US distributor is about 15-miles away from my house, so, if the worst happens, I can go knock on their door (they're in Londonderry, NH). As the modulating burner calls for less heat, it gets more efficient, and at the max output, it gets 94.5% (it takes 95% to get the tax credit, and last I looked the smallest unit that could do that was around 200K BTU; things might have changed). If you get the outside reset, it adjusts the boiler based on the need which increases the comfort level.
    Jim DeBruycker
    Important note - I'm not a pro
    Retired Defense Industry Engineer; Schluter 2.5-day Workshop Completed 2013, 2014

  5. #5
    DIY Senior Member CHH's Avatar
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    Quote Originally Posted by BrooklynJon View Post
    Chh,
    Thank you for the reply.
    Yes, our gas prices are sky high, here in NYC, so effeciency is key. And I agree that a ss storage tank is the better solution for domestic hw.
    So is it your opinion that, in terms of durabililty and all, they're more or less the same? And is it easy to get replacement parts for a Buderus unit?
    They all seem to use either the Honeywell or Dungs modulating gas valve. I have no idea about any internal acceptance testing or failure rates. From OEM advertising I think that they use standard blowers. HTP uses a standard burner controller. So other than acceptance testing and final QC they are all going to be pretty much the same in terms of blowers and gas valves.

    The real difference is in the burner/heat exchanger and packaging. HTP prorates it's heat exchanger warranty and I think that other manufacturer's do also but it's worth checking.

    I'm not working with these things every day so I just have a snapshot from doing my pre-purchase research. The stainless steel heat exchangers seem to take thermal shocks as well as can be expected but some of the cast iron heat exchangers have problems with cracking. I didn't like the idea of gaskets and "built-up" heat exchangers so I looked for a welded unit on the wet side of things.

    In the end I suspect the high end mod cons with stainless steel heat exchangers are all similar. Picking one is sort of like pick a Ford or Chevy or Audi (since you asked about Buderus parts :-)).

    Installation is important since incorrect venting will shutdown any of the units. Following the manual and attention to detail is critical. On my system the darn Taco pump flanges had paint "runs" in the gasket grooves that had to be removed or the gaskets wouldn't have sealed. Basically it's up to your installer to fix all the manufacturers' QC problems on every item in the system. Pick an installer who is experienced with the brand you choose. Maybe get Grumpy to come down for the install since he seems to like boilers.

  6. #6

    Default

    Thanks. Any experience with the Viessmann Vitodens 200?

  7. #7
    Retired Defense Industry Engineer jadnashua's Avatar
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    When I was looking at them, I got a quote on that...it was 2x the cost of the Buderus. Now, I will admit that the Viessman was not spec'ed exactly the same - it was more sophisticated, but not 2x worth. Their US office is in, I think, Connecticut.
    Jim DeBruycker
    Important note - I'm not a pro
    Retired Defense Industry Engineer; Schluter 2.5-day Workshop Completed 2013, 2014

  8. #8
    In the Trades mattbee24's Avatar
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    We have had great luck with Triangle tube condensing boilers. They also make their own indirect fired water heaters. The boiler has a stainless heat exchanger and the water heaters have a stainless liner.

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