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Thread: tankless water heater

  1. #1

    Default tankless water heater

    We are adding a master bathroom above garage space. Our current house has 2 full baths. The master bathroom will have a walk-in large shower with body sprays and shower head. We will not have a bath in the master edition. I am thinking toward the future in regard to hot water usage. We have 2 kids under five years old. We currently have a standard 40 gallon hot water heater for our hot water supply. I am considering having our plummer install a tankless heater to supply just the master bath edition. Is this overkill? Any helpful insight would be appreciated; brands, size etc...I have read a lot of "cons" when researching this subject. We live in the Minneapolis, Mn area if that helps.


    Thanks

  2. #2
    In the Trades Gary Swart's Avatar
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    The professionals that frequent this BBS have no good words for tankless water heaters. In my estimation, you would be better off installing either a second heater or a single large one that would give you the hot water capacity you need. You didn't indicate the heat source for the heater, but I would suggest if natural gas is available, that you use that. Gas heats much faster than electricity.

  3. #3
    Plumber/Gasfitter dubldare's Avatar
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    Rheem makes a few different versions of their 50 gallon natural gas heaters, one of which would work perfect for you. They are available in 40K, 50K and 60K btu models. A 50 gal/50K btu is virtually a direct replacement for a 40 gallon gas and makes quite a bit more hot water, the 50 gallon/60K btu is pretty much unstoppable in any residence.

    If you're on the east side of the river, you may be able to get a rebate from Xcel, depending on the model installed. Minnegasco offers no such rebate.

    I'm not a big fan of tankless heaters, yet. Maybe in a few years I'll change my mind. So far, I haven't been impressed.

  4. #4
    DIY Senior Member Cal's Avatar
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    Well not ALL the plumbers here dislike on-demand heaters. I have used several in just your application and gotten tremendous positive feed back.

    I only use the Rinnai , it is the best. You would really only want to do a tankless if you have gas. These are a great product but don't jump the gun,,do the reserch and find if others have used tankless in your area.
    GET A PRO who has expierience with tankless !!!

    Cal

  5. #5
    Plumbing Designer FloridaOrange's Avatar
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    I've spec'd several projects with tankless. Not always my first choice but under some circumstances they work real well. I'd say of those spec'd for tankless 80% of were smaller restaurantes; we also did large high end condos with them in conjunction with a 6 gal tank for recirculating. I like them and would definitely consider one when/if I ever do my house expansion.
    Matt
    Semi-professional plumbing designer
    Enjoying life in SW Florida

  6. #6
    Plumber Cass's Avatar
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    What is the water hardness in your area.

  7. #7
    Plumbing Designer FloridaOrange's Avatar
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    Quote Originally Posted by Cass
    What is the water hardness in your area.
    Is that for me or the original poster?
    Matt
    Semi-professional plumbing designer
    Enjoying life in SW Florida

  8. #8
    Plumber Cass's Avatar
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    Original poster

  9. #9

    Default Adding a storage tank

    Would it help to add a starage tank before the tankless to bring the water up to room temperature. In Cleveland the incoming water is 46 today.

  10. #10
    In the Trades Bob NH's Avatar
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    Default Tankless Probably Won't Meet Demand

    Original Post said:
    "The master bathroom will have a walk-in large shower with body sprays and shower head."

    Look at the Gallons Per Minute that your large shower with body sprays will demand, and compare that with any proposed tankless heater. Most tankless heaters will not do what you want.

    If your water in the winter is 40F as it is from many municipal supplies, then you need about 65F temperature rise for a shower.

    Now assume that you have a heater with 60,000 BTU OUTPUT to the water (not gas consumption). That will give you 15.38 #/minute = 1.85 GPM. That is NOT enough for your high demand shower system. In other words, it just wont meet your demand.

    You need to calculate the following:
    GPM for your shower x Minutes of shower x 0.75 = gallons used from your water heater, where the factor 0.75 is based on 130F heater temp and 40F feed water temp. That assumes NO OTHER DEMAND. I would add some margin by using a factor of 1.0 rather than 0.75.

    You probably want some hot water left over for others after you finish your shower. For a 10 minute shower at 5 GPM (why are you putting in such a nice shower if not to enjoy it), you should have at least a 50 gallon heater, and maybe an 80.

    If the shower is more than 30 ft from the water heater, you might want to add a small point-of-use tank heater nearby to reduce the delay in getting hot water. You probably need 3/4" copper to meet the shower demand.

  11. #11
    Master Plumber master plumber mark's Avatar
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    Talking tankless are junk

    you will be sorry,
    its just a matter of why and when...

    either when you realize it dont keep up with demand

    or when you need it serviced and its down for a month



    even the people that make them are not all that
    hot about them

    read this bradford white experiment report

    read between the lines and you can pretty much tell that
    they lean towards the tank type.....

    http://www.pmengineer.com/CDA/Articl...141364,00.html

  12. #12
    Master Plumber Dunbar Plumbing's Avatar
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    I just turned down a call today to install a tankless heater, happens about once or twice a month. I let the answering machine catch it since I'm sure they want a price and a free estimate. No can do. I always get shopped on the install of these.....most times they stick with tank type. There are some brave ones out there though. I can see the probability of these being installed in new construction...
    Read what the end of this sentence means.

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