question about a tankless heater?

Discussion in 'Plumbing Forum, Professional & DIY Advice, Tips & ' started by LivDoug, Jan 26, 2006.

  1. LivDoug

    LivDoug New Member

    Messages:
    3
    I am considering going with a tankless water heater for my home. It would be natural gas.

    The one I am considering getting is made by bosch, the 250sx. And the only real question I have is that it says .8gpm minimum flow...is that low enough for a sink to activate it? I am not sure how fast .8gpm is?
    Last edited: Jan 26, 2006
  2. Bob NH

    Bob NH In the Trades

    Messages:
    3,317
    Location:
    New Hampshire
    If it fills your 1 pint measuring cup in 9 seconds or less, or 1 quart in 18 seconds, you are ok.

    I gallon = 8 pints.
  3. LivDoug

    LivDoug New Member

    Messages:
    3
    ill have to check that, thank you.

    does anyone have any comment on weither tankless would be right for my situiation? I know it is a touchy subject from what I have read, but I have to ask, because every situiation is different :confused:

    I am having my bathroom remodled, and my new shower will flow a max of 5gpm @ 60psi. And being disabled, a typical shower for myself will last about 20 minutes. And I also have a whirlpool tub going in there.

    I am somewhat concerned about going tanked or tankless...which would be better?

    For the ammount of hot water I will need I will prob need 2 tanks in series, or a tankless. I have been told that both are questionable. The tankless I am considering is the Bosch 250sx, which I think would deliver what I need ok...would be close, I think, since I live in central NY...where out temperatures get pretty low quite often.

    But then even if I go with the tanked in series...I currently have one 40gal that if only 3 years old, and am considering adding a 50gal in series with it, but am wondering if that will allow myself, and my wife each enough hot water for a shower(since as I stated it takes me a good 20 minutes in there)?

    I could really use some good opinions on what people think would be better for this situiation.
  4. Bob NH

    Bob NH In the Trades

    Messages:
    3,317
    Location:
    New Hampshire
    If your water is supplied from a lake as many municipal systems are, it can get down to around 35 to 38 F in the winter. If you want a 105 F shower the temperature rise will be 70 F which corresponds to 4.2 GPM in the table at the Bosch site.

    If you have a 50 gallon heater in series with the 40 gallon heater, and you operate them at 140 F, they will deliver 135 gallons when 45 gallons of 35 F water is mixed with the 140 F water to deliver 105 F water to your shower. The two heaters in series would also benefit from the recovery rate of both burners so you would get another 20 gallons or so of hot water while taking your 20 minute shower.

    An interesting point on the "series water heater" idea would be putting the tankless heater on the inlet of the tank heater and have it come on only if the flow exceeded the "on" setting for two minutes or some similar period of time. That way it would not be coming on every time someone washed their hands or filled the teakettle. That is something that I might engineer for myself but you probably won't find a plumber to recommend it.

    Another thought on the minimum flow requirement: If the lavatory faucet is opened for mixed flow the hot water component might not exceed the 0.8 GPM minimum to actuate the flow switch.
  5. steve from Turlock

    steve from Turlock New Member

    Messages:
    2
    tankless?

    bosch heaters,tankless need lots of gas flow what size pipe does your house have. I charge a lot to install a tankless hot water heater, at least twice as much as a covential one.
  6. dubldare

    dubldare Plumber/Gasfitter

    Messages:
    286
    Location:
    MN/ND
    You would be much better served by installing another heater (the same as your existing one) in parallel to your current heater.

    If done right, they are unstoppable.

    It would also be a lot cheaper, and not someone's "science project" that you'd have to worry about fixing in the future.
  7. GoingTankless

    GoingTankless Plumber

    Messages:
    14
    Location:
    NJ
    tankless help

    There are many tankless to choose from. Bosch has very good customer service and will help you with finding an installer in your area. Installing a tankless heater is not for your DIY'ers. There are many factors to consider before installing one.
    If you choose to install a Tankless heater just make sure its done by a qualified installer. They will give you everything your looking for.

    Good luck.www.boschhotater.com
  8. hj

    hj Moderator & Master Plumber Staff Member

    Messages:
    26,309
    Location:
    Cave Creek, Arizona
    heaters

    The key words in the suggestion about parallel is "done right". Done wrong and you will never realize the full potential of the two tanks, and "done right" also means that both tanks have to be identical. The cannot be a 30 gallon and a 50 gallon, nor can one be a Sears, and the other one from Lowes, or a conventional one with a self cleaning model. In series every drop of water used has to pass through both tanks and thus is subjected to the heat from both burners. If you run out of hot water with this system, there is no way any other installation could have given any more hot water.
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