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Boiler/HW tank help

kevin Member Posts: 420
of hot water...kind of a farce that he is concerned about high eff. at that much "waste" of water. If you need that much demand you need that much bang to power it.You are still modulating it a bit to get a more "matched" system load/output.try the 140 M and a tandem of 80 gallon indirects piped in paralell and/or use a sparco mixing valve to boost your output. If you have the room try to boost your output more w/ a gfx heat x-changer in the drain line. See ME post above... Also contact HTproducts to see if they have some info for you...I assume you were going to use a superstor ultra. good luck...kpc


  • scottDP
    scottDP Member Posts: 2
    reccomendations for boiler/tank combo

    I have a client who has chosen to heat his floor with radiant heat. We also want to heat his hot water inderectly from the boiler. The house is in a warmer climate (santa cruz CA) and the heating load is low. It is about 1500 sq ft. As I have only installed a couple of radiant systems, I sent the plans out to have a radiant system designed for the house. The system that was spec'ed out was a condensing Munchkin variable output boiler with a min output btu of 27K and a maximum output of 80K. A 45 gallon storage tank was also specified. Ok, everything is great. However, when the customer went out to pick out shower valves, he chooses two shower valves for the master bath which have multiple heads on them (Ondine ESS System). One shower in the master bath has 6 body sprays , 1 shower head, and one giant sunflower head. The other shower in the master bath has 3 body sprays, one handshower and one shower head. I should also add that there is another multiple head shower system in the guest bath that will be used occasionally.
    I should note that there is a solar HW preheating tank before the HW storage tank, but I am not including this in my calculations since there will be times during the year that the solar system will not be functional.
    I know that my current system will not keep up with the hot water demand. I figured that if the client keeps his water savers in and the water is limited to 2.5 GPM , then both showers in the master bath going at once will create a demand of 32GPM. As a guesstimate, I figure about a 1/3 of that water will be from the HW tank (depending on what temp we store it at). So that creates an approximate deamand of 10GPM of HW, which would have to be maintained for about 1/2 hr (a long shower. I know I can get a bigger boiler, but then I am ruining the efficiency of the heating system. I also know I can get a 116 gal storage tank, but I'm not sure if that will be big enough to outlast the demand...
    Does anyone have software of a formula to help get some hard numbers for the size of the boiler/storage tank I need for this job? I am begining to lean towards a separate high efficiency/high BTU HW heater..... All replies and suggestions will be appreciated.
  • Wayco Wayne_2
    Wayco Wayne_2 Member Posts: 2,479
    Use a

    tankless after the water heater. That way if it's cloudy for the solar and he uses up the storsge in the indirect, the tankless can make up the difference at the outlet end. If all is working OK he gets his high eff with the solar and the indirect and backs it up with the tankless.

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  • Nate Perkins
    Nate Perkins Member Posts: 8

    Don't guess this one.
    Contact shower mfg and get accurate flow information for each shower. Then calc proportion of hot water needed.
    Likely will need to contact indirect mfg and get their recomendation for boiler input vs first hour hot water production.

    1/3-2/3 mix of hot and cold water would require very high hot water storage temps. Better check that out.

  • Since a lot of energy is going toward heating water for the shower, would it not pay to install a GFX drain heat recovery system(www.gfxtechnology.com)?

    It sounds to me like this would be the perfect application for one, but don't take my word for it, I'm just a concrete guy. Ask Mark Eatherton, he gave me the information and is familiar with them.
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