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Oil to Gas Boiler Upgrade - Which Boiler to Choose?

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BrennanU
BrennanU Member Posts: 8
in Gas Heating

Hi everyone,

I live in a 150 year old house that’s been heated for the last 50 years by a Crane 70-98 hot water boiler running on fuel oil. It’s been solid for decades, but I've had some troubles beginning last heating season.

I have the chance to connect to natural gas and I’m looking at gas boiler options. From what I’ve read, Weil-McLain seems to be one of the top brands.

Questions:

  1. Sizing the boiler:
    • Current unit is rated at 85,200 BTU/hr per the nameplate.
    • I’m not sure what nozzle is in it now, but used replacements laying around range from 0.65–0.85 GPH.
    • On the coldest days, it runs almost constantly, so it feels about right.
    • I did a Manual J years ago when installing mini-splits for cooling, and the heating load was ~50,000 BTU.
    • Any thoughts on how large of a unit I want? I'm guessing the 1970s era rated load is excluding the efficiency loss, so 65% of 85,200 = ~55k seems to line up about right.
  2. Combi unit for hot water?
    • Most combi units seem to start around 110,000 BTU (except AquaBalance 2 at 80k) which is considerably higher than my heating load.
    • Would a combi make sense for my load, or is that too big?
    • I know modulating units can throttle down, but it feels odd to run one at <50% on the coldest day.
  3. Model recommendations:
    • EcoTec 2 looks like the top-of-the-line option, but it’s pricey.
    • Is it worth the extra cost? I don’t mind paying more for quality if it makes sense.

Any advice or experience would be greatly appreciated!

Comments

  • EBEBRATT-Ed
    EBEBRATT-Ed Member Posts: 18,959

    Contractor is the most important thing. Lots of hacks around so beware. You could check Find a contractor on this site & post your location.

    The decision is a choice between a Condensing boiler or Combi and a standard CI boiler.

    Depends on what you have for heat emitters. Baseboard will not give you much better efficiency with a condensing boiler over a CI boiler. CI rads on the other hand are better with a condensing boiler.

    There are a lot of issues that have separated contractors into 2 camps. The CI camp and the condensing camp.

    CI lasts longer

    Almost anyone (within reason) can work on a CI boiler

    Less expensive install

    Requires service less often and parts are available and less expensive

    Condensing

    More efficient (but sometimes not as much as they claim)

    flame modulates (a nice thing)

    May require more service and is more "technical"

    Runs quiet

    Some MFGs change models frequently

    after 15ish years parts may be difficult to source,

    As far as sizing you can size to what your Manual J tells you. No need to add for domestic water.

    There are plenty of good people on this site that will comment from both camps so hang tight.

  • Steamhead
    Steamhead Member Posts: 18,099

    @BrennanU , where are you located? We might know someone who can help you……………

    All Steamed Up, Inc.
    Towson, MD, USA
    Steam, Vapor & Hot-Water Heating Specialists
    Oil & Gas Burner Service
    Consulting
  • hot_rod
    hot_rod Member Posts: 26,046

    combis will be around that 100,000 range so they can generate DHW at a 2 gpm or more flow

    If your incoming water drops below 50 degrees, I would go with a 120 or larger

    Combis and mod cons will have a 10-1 turndown. So the 100,000 boiler can run down to a 10,000 output. As such it will not be oversized in heating mode

    You would do a heat emitter assessment to see how low of a temperature you could run. Perhaps 80% of the heating season you are below design condition, and the boiler can run lower temperatures

    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream

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