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Need Help On A Heating System/Water Heater

 Do I have infloor radiant heating in the basement and under the main floor level. Its a 2000sq foot with approximately 2,000 feet of infloor heating 1/2" pex thats spaced about every 8"-10". I live in Northern MN and I plan on only running the in floor heating half the year through winter. Also I need a water heating unit for the 2 bathrooms and 1 kitchen. Would a combi unit, boiler and tankless water heater, or boiler with reservoir tank be best? Plan on running propane and use a circulator pump for constant hot water. Whats your best advice and combinations/models?

Comments

  • Jamie HallJamie Hall Member Posts: 12,947
    Before looking at what sort of boiler -- and water heater -- to consider, a quick but critical question: has a Manual J heat loss been done on the building, and can the radiant floor meet the heating requirement?
    Br. Jamie, osb

    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England.

    Hoffman Equipped System (all original except boiler), Weil-Mclain 580, 2.75 gph Carlin, Vapourstat 0.5 -- 6.0 ounces per square inch
  • hot_rodhot_rod Member Posts: 13,500
    WAG under a 60K heat load.
    The smallest combis are around 110K to give adequate 2.5 gpm hot water. A 110K locked at 50% might match the heat load nicely. if it is one or two zones, short cycling would not be an issue.
    I'm a believer and user of combis, not everyone agrees :)
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    The magic is in hydronics, and hydronics is in me
  • KamikazeGandhiKamikazeGandhi Member Posts: 3
    No a heatloss has never been done but winter is coming in a couple months and I can't wait to do one unless you can do it in the summer? It should be able to do the requirements, the house is very insulated. If I got a combi unit would be using it 6 months a year just for heating drinking water be very damaging for the machine? There's roughly 6 loops ranging from 300-350 feet. How long have you had your combi and any issues? Also at 2.5gpm be enough to run 2 showers at once if it happens?
  • psb75psb75 Member Posts: 220
    You can definitely do or have done, a comprehensive heat-loss even in the summer. Look at the one that SlantFin offers on line. Or hire someone to do a Manual J. Hard potable water CAN be problematic for an on-demand water heater, incl. the plate exchanger in a combi boiler. The heat exchanger should be acid flushed accordingly. Your in-floor heating loops are "a bit" longer than is recommended. It is better to keep them UNDER 300' in length. So you might want to be careful in balancing them well with valves and flow-meters on the system. 2.5 gpm is NOT enough flow for two showers at once. If you definitely want this ability, you will have to size the combi boiler according to domestic hot water demands. Not the best approach.
  • hot_rodhot_rod Member Posts: 13,500

    No a heatloss has never been done but winter is coming in a couple months and I can't wait to do one unless you can do it in the summer? It should be able to do the requirements, the house is very insulated. If I got a combi unit would be using it 6 months a year just for heating drinking water be very damaging for the machine? There's roughly 6 loops ranging from 300-350 feet. How long have you had your combi and any issues? Also at 2.5gpm be enough to run 2 showers at once if it happens?

    I have had a combi in my mother in laws, now our home for 15 years, a Laars mascot. It is on a water softener, I have never had to delime the HX. In fact I only cleaned the inside of the boiler twice in 15 years!
    I also have a Lochinvar Cadet 120 Combi in my shop it is about 7 years old, de limed once on hard water.
    Replacing the Mascot is a 110 Nobel, probably 5 years old, delimed once.

    It really depends on how hard your water is and how many gallon go thru the HX, as far as a delime schedule.

    In your area with cold incoming water, I would say 2 gpm is possible, maybe more if you are on a well with 50° incoming water. Output is typically rated at a 77° temperature rise. typical shower head is 1.5 gpm.

    A 150K may be a better for if you need more dhw capacity. It can be derated for the heating side also.

    I suspect the combi manufacturers know the loads will be lopsided, so they give you the ability to lower the output, ramp delay, anti cycle, and other features, depending on brand and model.

    Thermodynamically speaking the boiler locked on low fire , low temperature could be most efficient operation mode. As you are exposing a large surface area to a small burner output so a lot of surface area to condense. I think Viessmann did some studies on the concept.
    Most boilers now require a yearly clean and check. With proper purge valves, the delime is a quick task, it could be done at the same time the boiler burner is removed and cleaned, connect the delime kit and plug it in.
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    The magic is in hydronics, and hydronics is in me
  • Alan (California Radiant) ForbesAlan (California Radiant) Forbes Member Posts: 2,358
    edited July 31
    We just installed two of the Lochinvar Noble combi's. They were the 150,000 BTU models, sized to provide plenty of domestic hot water for 1 bathroom/1 kitchen units. We limited the heating side to 50% with their "Max. Rate Limiting" feature to reduce short cycling, a very nice feature. I also like their "Pre-Heat" option which keeps the boiler water hot to shorten DHW delivery time. First heard about them from hot rod.



    Personally, I would use the 150,000 BTU model on a 2-bathroom residence with water saver shower heads.

    I never used to like combis because they weren't reliable. Now, with so many improved models, I'm all in and we use them often.
    Often wrong, never in doubt.

    Click here to learn more about this contractor.
  • KamikazeGandhiKamikazeGandhi Member Posts: 3
    Any recommendations on some name brands of combis? Debqting on checking out the local menards or possibly Amazon? Do I need supply tanks or anything to go with combis? Also should I get one with a recirculation pump installed or use a separate pump?
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