Alaska recommendation for boiler?

Discussion in 'Boiler Forum' started by Tory, Sep 9, 2019.

  1. Tory

    Tory New Member

    Joined:
    Sep 6, 2019
    Location:
    Chugiak, AK
    We're looking to replace and improve our heating/water heating situation somewhat soon.

    We're in Chugiak, AK (99567) just north of Anchorage, in a 2-story house, about 1800 sq ft. Home is 1996 construction (2x6, decent windows) currently served by WM 80% 70K boiler and separate 50K/50gal WH of the same vintage. All NG.

    I don't know how much life the WH has left, and we'd like to replace the system before re-roofing (coming sooner rather than later.) We'll exhaust through the utility room wall and won't use the vertical venting (saves one roof penetration and hopefully we'll insulate that cavity to add a little comfort in a cold bedroom corner.)

    The original boiler is close to right-sized but I don't know why they installed a stand-alone WH and not an indirect. I'm putting our heatload at about 40K (maybe a bit under.) I can't do a very accurate fuel consumption calculation, as the gas splits after the meter to serve a 30K Modine in a detached garage.

    I may have gone about this backwards (some advice says to pick the installer first) but I think I'm down to HTP or Lochinvar as my top choices - I know the UFT 80 gets recommended often, or a Lochinvar Knight, WHB 085 (convince me to go o55?) Either would be paired with their company's 40 indirect WH. 30 gal may be enough - there are only two of us and no abnormal hot water needs.

    This should be a pretty easy install, 2 heating zones (66' and 40' of fin-tube baseboard.) Comfort, efficiency, and reliability are our top priorities.

    Know any good HTP or Lochinvar installers in the Anchorage area? Or a different suggestion?
     
  2. Dana

    Dana In the trades

    Joined:
    Jan 14, 2009
    Location:
    01609
    There's no reason to down-size to the WHB-055, especially since you're also supporting an indirect. The smaller burner would make for longer recovery times on the indirect almost as slow as a standalone water heater, whereas the WHB-085 or UFT-080W can out-run a continuous 2 gpm shower (=~70,000 BTU/hr at a temperature rise of 70F from the incoming water to the shower head) , and will have recovered before you have your pants on after showering, or maybe even before you reach for the towel.

    There are other boilers that fill the bill, and local support is usually more important than the boiler manufacturer. A key feature to keep in mind in selecting the boiler is that with the shortest zone being 40' it's good to have a minimum firing rate output of not too much more than 40' x 200 BTU/hr= 8000 BTU/hr to be able to run it in condensing mode without excessive cycling. A boiler that only modulates down to 20,000 BTU/hr is going to be prone to cycling, and may take a lot of tweaking (or a higher water temperature) to keep it from efficiency robbing short-cycling.

    The indirect should be sized for the biggest tub you need to fill. A 30 might be a tad skimpy unless you set the storage temp high, but a 40 shouldn't be any problem as long as you don't have a big soaker-tub to deal with.
     
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  4. Tory

    Tory New Member

    Joined:
    Sep 6, 2019
    Location:
    Chugiak, AK
    Thanks Dana,

    I've been doing my homework, and thought I was on the right track.

    I know you often recommend the UFT. Are there others that you like? And is the Knight to UFT an "apple-apples" comparison?
     
  5. Dana

    Dana In the trades

    Joined:
    Jan 14, 2009
    Location:
    01609
    The WHB-085 to UFT-080W is almost apples-to-apples. The burner sized and modulation ranges are similar. Lochinvar voids the warranty if you pump direct rather than primary/secondary whereas HTP advertizes "no primary/secondary needed" for the UFTs. The UFT has about 3.1 gallons of water mass to work with compared to the WHT-085's 2.2 gallons. There are more parameters to tweak in the setup with the WHB.

    The Lochinvar Noble NKB080N fire tube boiler is similar, but also simpler/cheaper, but only 1.2 gallons. But since it modulates down to 8300 BTU/hr-in, 8000 BTU/hr-out it can still run at 95% efficiency without short-cycling on a 40 foot baseboard zone (that's 200 BTU/hr per foot, which would balance at average water temp of a bit less than 120F.)

    Navien's NCB-80 also modulates down to 7600 BTU/hr out, which works fine at condensing temps with a 40' stick of fin-tube as the smallest zone. But since it's a higher pumping head low mass water tube type heat exchanger it absolutely needs to be plumbed primary/secondary on most multi-zoned systems.

    I tend to recommend the UFT since it's relatively inexpensive, and has a bit more design forgiveness/flexibility than some other boilers. In my case I'm only an hour away from HTP's headquarters, and local support is good. YMMV. Local installer & distributor support can be important.
     
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