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Which would you choose: Viessmann Vitodens 200-W vs. IBC SL G3 Boiler?

Ames Member Posts: 3
Can I get folks opinion on two boilers that we’re trying to decide between?
  • Viessmann Vitodens 200-W, B2HE-85
  • IBC SL 10-85 G3
Up front costs and finding a good installer are not an issue (cost difference b/t the two boilers is not significant enough to sway the decision and the installer we plan on working with is very experienced with both product lines).

Which boiler would you choose when it comes to efficiency, reliability and longevity? Are std service costs/needs substantially different between the two?

In case it’s relevant, the boiler will service a single zone radiant heating system in a single story 1960’s home in the SF Bay Area and will also be connected to a ~ 55 gallon indirect.

Thanks in advance for any input!


  • Hot_water_fan
    Hot_water_fan Member Posts: 118
    What's your heat loss and how does that compare to your installed radiation? Do you have AC?
  • Ames
    Ames Member Posts: 3
    Hi there

    - No AC
    - The existing boiler is a 28+ year old non condensing unit, i.e. Hydrotherm 100k
    - The installed radiation is 3/8” copper piping in a concrete slab - it was installed when the house was built in 1964 so it's not super efficient (no insulation, etc). I don’t know the length of the tubing or much in the way of the design specs for what was installed.
    - I did do a heat load calculation based on our historical usage data (following the guide here I was not able to separate out gas usage for the water heater and the boiler, but even with both in play, our heat load was ~28k for the coldest month last winter
    - Total square footage is 1759

    The installer will do heat loss calculations before install…Happy to upsize if the data warrants it but I actually think we could do with a smaller sized boiler. However, 85k is the smallest size both companies offer.

    I'm new to all this so apologize if this isn't answering your question well enough - just let me know if there's other info that I can provide and I'll send it over if I can.

    Do you have a preference b/t Viessmann and IBC based on that?

    Thanks so much

  • Hot_water_fan
    Hot_water_fan Member Posts: 118
    That's the exact article I would have pointed you to!
    Can you share how many therms you used last year? I'm guessing around 1100 or so.
    There's absolutely no need to upsize at all. Frankly, there's no need for the installer to do the heat loss, you have a more accurate one (fuel usage based) in hand.
    You checked some important boxes off: you're using radiant floor and your heat loss is low so you'll be able to condense the whole winter (ie using low temp water). That'll put your floor temp around 80 degrees on the coldest day of the year.
    There's a tradeoff here: you'll probably be able to use a condensing boiler with no issue and either will probably be just fine. However, you live in a mild climate with a low heat loss, so energy savings will be low (in therms, not %). You'll have to decide if the dollar savings are worth the cost difference between a condensing boiler and the existing one. If environmental impacts are also important to you, then there's more to this decision, in which case:

    Is AC in the future for you? That would significantly change things.
  • Ames
    Ames Member Posts: 3
    Oh my lord are you spot on - therms used last year = 1109.

    I wish AC was an option but the house is post and beam construction so it's not an easy addition (and not currently in the budget).

    And yes you're right re: cost savings (or there being very little) - I ran the numbers a few weeks ago and there is no ROI over the lifespan of the equipment. Frankly, I'd consider a more efficient atmospheric boiler than what we currently have given longevity and lower cost, but there are quite a few requirements re: new appliance efficiency in this area that limit that (I have been curious about the GV90+ but I haven't found anyone local that installs them given the restrictions).

    We do need to replace the existing boiler in the next year or two so I figured we'd just go ahead and do it now before there's a serious issue. Wish there was an ROI but for now, I'm just hoping we choose one that ends up being really reliable and as efficient as possible.

  • Hot_water_fan
    Hot_water_fan Member Posts: 118
    Gotcha - if AC was in the cards, a heat pump would be the best heating option by far with the mild temperatures and dual heating/cooling capability. However, hard to do 100% ducted with post and beam, so you'd be looking at ductless/maybe small ducted combinations/maybe electric resistance for the smallest rooms.

    If the installer is experienced with both boilers, it's probably a coin flip.
  • kcopp
    kcopp Member Posts: 3,771
    IBC SL... great boiler. Control is wonderful. I have many in.