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Tankless questions

Wayco Wayne_2
Wayco Wayne_2 Member Posts: 2,479
in THE MAIN WALL
I am looking at a job for onw or 2 tankless water heaters. It's 2 locker rooms with 8 showers heads in it. That's 16 in total for those of us who are math challenged. :) How many should I use at what capacity? Should I use a recirc line? What brands are the best? Thanks for any help you can give me. WW

Comments

  • CMadatMe
    CMadatMe Member Posts: 3,086
    Sizing

    What's the incoming water temp in the dead of winter? What gpm sized heads are there? Are there lav faucets also? How many showers running at the same time?



    32gpm x 70 degree rise x 500 = 1,120,000 btus needed for both.

    16gpm x 70 x 500 = 560,000 btu's for each.



    Based on just 2gpm shower heads. The number of units is up to you.

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  • Andyk
    Andyk Member Posts: 13
    Tankless

    I would take a good look at the Eternal. I have attached the link below.



    http://eternalwaterheater.com/

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  • EricAune
    EricAune Member Posts: 432
    Check this out

    http://calc.rinnai.us/



    As always, this is just a guide.  Check with your local rep for assistance.  I have been very happy with the results from Rinnai.  Maybe this will help, maybe not.

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  • bob eck
    bob eck Member Posts: 930
    tankless

    take a look at noritz tankless gas water heaters. http://noritz.com/professionals/products/flow_rate_reference/

    if you use units over 199,000 btu input the units will need to be ASME units.

    noritz has ASME units over 199,000 btu input but they also have units that are 199,000 btu input and you would need 5 to 6 units look at models NCC199 condensing PVC vented & NC199 stainless steel vented. look at using ALSONS 1.6 GPM shower heads.

    http://alsons.com/water-saving/water-amplifying_shower_heads/Default.aspx
  • Mark Eatherton
    Mark Eatherton Member Posts: 5,858
    Chris....

    Your assumption (X 500) is that the shower heads will ALL be on for a full hour?



    What are the chances of THAT actually occurring?



    The national average shower duration time is less than 10 minutes per shower. (actually 7.5 minutes)



    So the real time load is based on the actual number of bodies being washed, NOT the number of shower heads in the stalls. It is also dictated by the number of people showering at the same time.



    If it were me, I'd spec a good modcon with a reverse indirect. Just need to figure out how big they both need to be.





    ME

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  • CMadatMe
    CMadatMe Member Posts: 3,086
    Never Know What Goes

    On in the gym locker room...:) I could see a steady half hour maybe more depending on the gym use. That's a question that needs to be asked..



    Your right on with the mod/con and indirect. Just quoted a job where there where two  80 Gal 160,000 btus wtr htrs taking care of 36 apts. One's a leaker. Commerical htr costs are out of this world. My solution to them.

    One Vitodens 200 WB2B-105 w/a 120 Gal Vitocell Dual Coil SS tank. Price difference is minimal when talking gas savings and replacment cost in another 6 years when one leaks again... This will actually give them a better recovery then the 2 tanks sitting there now... 

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  • icesailor
    icesailor Member Posts: 7,265
    Thermostatic Mixer:

    You better check and see if the shower heads are fed through a pressure balance thermostatic mixer like  Leonard or Powers. You can get into a real problem if you don't plan to have 130 degree or 140 degree water going into the valve.

    If they are anti-scald protected, this is what you may find.
  • Jean-David Beyer
    Jean-David Beyer Member Posts: 2,666
    Which kind of mixer do you mean?

    I have a mixer that is two staged. The first stage is a pressure balancer; the second stage takes the pressure-balanced hot and cold water and runs it through a thermostatic mixer. The pressure balancer operates quickly, but takes no account of the water temperature. The thermostatic stage operates somewhat slower, but notices temperature of the output and thus compensates for changes in input temperature.



    I have experienced mixer valves that are pressure-only, and they do not hold temperature very well unless the hot and cold water supply remain at the same temperatures, and the output flow rate is not changed. On mine, changing the flow rate does not make much difference unless it is set below 1/2 gallon per minute, where the accuracy drops noticably. This is documented in the data sheet.



    Are you talking about pressure balancer only valves, those with both pressure and temperature stages, or temperature stage only ones?
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