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Thread: Need boiler replacement advice

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    DIY Junior Member nhboilerguy's Avatar
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    Default Need boiler replacement advice

    I currently need to replace my boiler/ tankless dhw system and I am looking for some advice from professionals. A little info to help with any questions about my requirements. I live about 20 miles inland from the seacoast area of New Hampshire so winters are cold but not not very often below zero, maybe only 10 days a year. My house is about a 1600 sf cape, 25 years old and a factory built Epoch with six inch exterior walls and heavy gauge vinyl siding with a full wrap of tyvek underneath. Well insulated all around. My current heating/ dhw system is a heatmaker plus 100 in 84 out and has served me well despite its reputation. The lower coil has started leaking over and it over pressurizes and blows off and sometimes goes off on high limit.
    I have gotten quotes from good local contractors and have 3 apparently good choices in brands. All full modulating, condensing wall hung units. A Rinnai E110C with attached dhw, a Triangle Tube Prestige solo 110 with a Superstor Ultra stainless steel indirect fired SSU-45 for dhw and a Viessmann Vitodens 100-W with combi plus kit for dhw. After reading all the brochures and specs and doing a little online searching I think that I like the Viessmann the best. The Rinnai has a copper nickel secondary plate exchanger which worries me in a condensing unit due to corrosion. I like the Triangle Tubes heat exchanger design but would really like to not have the big water tank. I just wanted some input and thoughts about pros and cons before making the final decision.

  2. #2
    In the trades Dana's Avatar
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    Quote Originally Posted by nhboilerguy View Post
    I currently need to replace my boiler/ tankless dhw system and I am looking for some advice from professionals. A little info to help with any questions about my requirements. I live about 20 miles inland from the seacoast area of New Hampshire so winters are cold but not not very often below zero, maybe only 10 days a year. My house is about a 1600 sf cape, 25 years old and a factory built Epoch with six inch exterior walls and heavy gauge vinyl siding with a full wrap of tyvek underneath. Well insulated all around. My current heating/ dhw system is a heatmaker plus 100 in 84 out and has served me well despite its reputation. The lower coil has started leaking over and it over pressurizes and blows off and sometimes goes off on high limit.
    I have gotten quotes from good local contractors and have 3 apparently good choices in brands. All full modulating, condensing wall hung units. A Rinnai E110C with attached dhw, a Triangle Tube Prestige solo 110 with a Superstor Ultra stainless steel indirect fired SSU-45 for dhw and a Viessmann Vitodens 100-W with combi plus kit for dhw. After reading all the brochures and specs and doing a little online searching I think that I like the Viessmann the best. The Rinnai has a copper nickel secondary plate exchanger which worries me in a condensing unit due to corrosion. I like the Triangle Tubes heat exchanger design but would really like to not have the big water tank. I just wanted some input and thoughts about pros and cons before making the final decision.
    These boilers are all at LEAST 2x oversized for your design day heat load, (probably more than 3x oversized) and you'd get better efficiency & comfort out of something sized more appropriately for your heat load!

    If you have a recent gas bill that gives an average outdoor temp (or exact billing dates and a zip code to be able to look up degree-day data) it's fairly straightforward to determine an upper bound on your heat load at your 99% outside design temperature working backward from fuel use per heating degree day, and the 84% nameplate efficiency of the existing boiler.

    As long as your house has glass in the windows and doors that closed it's unlikely that your heat load at 0F or even -5F is anywhere near 50,000BTU/hr, and it's very likely to be half-that, and below the minimum-firing rate of a Vitodens 100 or Solo 110. If you think we're going into another ice age and need to be covered for a cold snap of -150F these boilers might make sense, but I'm guessing that's a temp not seen in coastal NH in the past 10,000 years.

    The type and size of your heat emitters/radiation, and the number of zones also factor in to what makes sense. There are many mod-con boilers in the 50-60KBTU/hr range that modulate down to under 20K, but you may have a heat load more appropriate to a tank hot water solution like a condensing Vertex or something.

    The fuel use numbers will tell the biggest part of the story, so let's have 'em! But measuring up the radiation (per zone, if multi-zoned) will also be an important factor for getting it right.

  3. #3
    Retired Defense Industry Engineer jadnashua's Avatar
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    You might also consider Buderus whose US headquarters is near you in Londonderry. I looked at both the Viessman and the Buderus (and a couple others), and I felt the Buderus was a better buy. Mine's now about 5-years old. It replaced an old Trianco Heatmaker II. My heating bills went down considerably. A decent indirect is much nicer than the make as you go in our weather where the incoming cold water can be quite cold.
    Jim DeBruycker
    Important note - I'm not a pro
    Retired Defense Industry Engineer; Schluter 2.5-day Workshop Completed 2013, 2014

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    Master Hot Water Mpls,MN BadgerBoilerMN's Avatar
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    A proper Manual J heat load and yours is a likely candidate for a combi-water heater as Dana suggests. It is not the appliance but the correct application and installation that really matters. "Reputation" is about people, not things...

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    DIY Junior Member nhboilerguy's Avatar
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    Well guys, I have been busy trying to get some local advise about good contractors. I had a neighbor suggest a guy he's been using at work and at home for years. As we were looking at my old equipment and talking about the options he started asking questions. My neighbor heard water dripping, which was the pressure relief valve dripping into the bucket behind the boiler. This was caused by the pinhole leak in the lower coil I was told by the service tech for the gas company. The contractor was quick to ask me, is that why I'm replacing the boiler? Because if so, I was lead down the wrong path. He immediately checked the expansion tank and found it was water logged. This was the cause of the pressure valve always going off. I shut down the auto fill valve a week ago and no more over pressure problems. I will be replacing the expansion tank as soon as the weather warms up enough to shut down the heat for a few hours. I plan on replacing the auto fill valve at the same time as it may be leaking by now from constantly opening. I still need to think about doing something with my 25 year old boiler, but now more on my terms and I know who I'll be calling to do the job. As you say, BadgerBoiler MN, reputation is about people for sure. 4 other companies came out to quote me on a boiler and not one asked any questions about what the system was doing that made me think I had a bad lower coil. Bad call for them.

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    In the trades Dana's Avatar
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    Sometimes the problems are obvious to the trained eye, eh?

    Just be sure to run the load calculations before springing for the replacement. Having too much boiler becomes a design & function problem far more often than a solution for anything. The comfort of knowing that you're covered down to an outside temp last seen 10,000 years ago isn't really worth much.

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    In the Trades mtcummins's Avatar
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    Not to direct you away from this great site, but you might want to go have a look/post a quarry The Wall over at HeatingHelp dot com. Those guys are heating specialists that in general can't stand all the shortcuts taken by many in the industry (not doing a proper load calculation, for one), and they have a pretty good network of good contractors, some of which might service your area.

  8. #8
    Master Hot Water Mpls,MN BadgerBoilerMN's Avatar
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    Ya, Dana and I are just chopped liver...heheheeee

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    DIY Junior Member nhboilerguy's Avatar
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    Thanks guys for all the help.

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