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Water heaters certified for space heating use? Boilerpro

Boilerpro_5 Member Posts: 407
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  • Boilerpro_5
    Boilerpro_5 Member Posts: 407
    Who makes them?

    I have a number of very small load jobs that have radiant floor in only portions of a home to provide improved comfort over the forced air system and need a low cost heat source. I understand there are some units certified for space heating use and would like to here your experiences.


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  • Timco
    Timco Member Posts: 3,040

    Not sure as to actual rating for heat...some better WH's have side taps for heating use. As I understand it, so long as you leave the T&P valve provided with the unit installed, and add a 30# relief, you are good. I use 6-gal electrics to warm kitchen floors & smaller areas. Works great with wirsbo joist trac plates.

    Just a guy running some pipes.
  • hr
    hr Member Posts: 6,106
    Certified by whom?

    that's the tricky part. Typically water heaters are listed under ANSI, whereas boilers (most :)have ASME listings.

    So if the AHJ insists on a ASME H stamp that leaves most residential sized WHs out of the question.

    Bradford White seems to be able to sell those Combi 2 dual use heaters in all the States. They do qualify as a double walled HX and seem to be accepted in Michigan and the Seattle area where double walled is a must.

    I've also seen some Lochinvar tanks with stickers indicating approved for hydronic heating applications.

    HTP has been selling the dual use Voyager for 10 years or more as a HW and hydronic appliance.

    Again I'm not sure who approves it?

    As far as a basic plain HW tank as a hydronic only heat source, I've done it for years without any AHJ's refusing the job. I feel they are plenty safe, much higher pressure rating then a boiler and 3 T&P safeties.

    I think the word boiler needs to disapper from the hydronics scene. It's old world terminology intended to cover appliances that boil water for steam.

    Perhaps a new class "Hydronic Appliances" is needed?

    hot rod

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  • Al Letellier_9
    Al Letellier_9 Member Posts: 929
    water heaters

    To me a water heater is a water heater and a boiler is a boiler but Boch has told me that their units are approved for use as a heat source for small radiant applications. Check with the manufacturer first.
  • Which gas water heaters have spill and rollout switches?

    Or vent dampers, for that matter. Manufacturers of heating appliances can't get around those laws. I think I wouldn't want to find myself in court defending against an accidental death caused by my installation of a heating appliance that is a residential water heater (that is designed to only run minutes per day), and my system has it run more than half of each day, installed only to be less expensive to install than my competitions quote....

    Are redundant gas valves required where you install heating equipment? How about an operating control AND a high limit? Are low water cut offs required where you are?

    I'm only concerned for your safety, and for your customer's.

  • Kal Row
    Kal Row Member Posts: 1,520
    attached pdf has worked for me...

    we use "boiler" for "closed-loop", lower pressures and higher continuous temps and smaller temp differences, and "water-heater" for "open-loop", higher pressures and lower continuous temps and larger temp differences – but these distinctions are by no means locked in stone – especially with modern modulating condensing boilers

    water-heaters are also treated to handle the steady stream of oxygenated and chlorinated domestic water – the Lochinvar “armor” water heater for eg, uses a different grade stainless in it’s heat exchanger than the almost identical Lochinvar “knight” boiler and you pay apx 10% more for that

    am waiting for the Russians to start decommissioning their all titanium typhoon class subs so we can make boilers out them cheap – those things are huge – about the size of a
    WW II aircraft carrier complete with swimming pool, and with the rubber coating, were really quiet, but we found them from space anyway simply by the amount of ocean water they displaced – actually curved the ocean surface and could be picked up by phased array radar
  • Boilerpro_5
    Boilerpro_5 Member Posts: 407
    Noel, my point exactly....

    I don't want to be installing something that is unsafe or unapproved. Even if there were a problem completely unrelated to the heater, the field day lawyers could have would be outrageous.
    That said, I am looking for something that can at least be competitive with the flood of small radiant jobs that are using a cheap domestic water heater. I am not talking anything even big enough for an instantaneous unit, but just a simple tank unit.


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  • I think we are talking about....

    the difference between a "listed heating appliance" and an "unlisted heating appliance". A different set of codes applies to unlisted heating appliances.

  • hr
    hr Member Posts: 6,106
    It doesn't exist Boilerpro

    at least to my knowledge in a gas or oil fired device. The word "cheap" isn't synonymous with many radiant heat sources, that are safe, legal, listed, and attorney proof ;) Although you need to define "cheap"

    Small areas can work nicely with electric boilers. I've done a bunch of 7,000 btu and under loads with that Laing combo pump heater EHR2. It has UL and SA listings at least.

    Thermolec has a nice line of modulating electric boilers.

    Watts Radiant has some electric systems listed for under floor retro fits as well as above. Even staple up to wood, I'm told?

    hot rod

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This discussion has been closed.