Researching electric point-of-use water heaters
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    Researching electric point-of-use water heaters

    Original plan of having propane w/h (tank) in house addition bit the dust with venting problems. One alternative is an exterior, propane whole house on-demand unit. Pretty expensive and feel it's overkill for my needs - the normal bathing & laundry are in a completely separate part of the house. Only plumbing shared by sections of the house is that they're both supplied by a single well/pressure tank. Even the septics are separate.

    So now looking at an alternative of individual electric point-of-use for 3 areas. Seeing a lot of love/hate opinions. Problems that stand out to me are minimum flow to activate, maximum flow, maximum temp (avoid scalding), temp control, pressure variation vs temp (have well & pressure can vary 10-15 lb), and "cold water sandwich". Have enough electric to handle loads. Currently wiring in prep for drywall.

    1/2 bath (primary toilet for "living" section of house): Cannot use a mini-tank here because it would be very difficult to route TPR line. That leaves tankless. Doesn't look like the 110v versions perform well, so focusing on 220v. Most units sized for this usage seem to limit flow .5 to 1 gpm. Anyone use .5 for sink? Do you use 2 handle faucet or single to control temp? Does flow of water "feel" adequate? Do you have max temp limitation? Since temp highly dependant on rate of flow, in practice, does it "feel" normal to a visitor used to adjusting water temp by mixing cold & hot from a tank?

    3/4 bath (primarily for pool rinsing) + 1/2 bath (light usage): Looks like a min of 2 gpm needed here. Think tankless would be ok.

    kitchen/dining/outdoor kitchen: Looks like a min of 2 gpm here too. Kitchen has sink & d/w; dining also has sink & d/w; outdoor kitchen sink used occassionally. May have to worry about bacteria in pipe to outdoor sink because of not being used regularly - particularly in winter. Seldom get freezes here that last more than a few hours. Wonder if tankless alone will work or if need to add some sort of mini-tank/recirculation. Single or double handle faucets for sink temp control?

    Know would have to descale each unit 1 or 2 times each year. Plus have to deal with calcium. Our well water tastes very good, so don't want to filter cold.

    Appreciate thoughts.
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    coaltrain's Avatar
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    Just an option to think about -

    I remember you saying somewhere that you already have a lot of hot water storage (2-80 gallon water heaters?).

    You can plumb your hot water lines to this new section of the house with a return line and run a circulator pump. This would have hot water at each outlet constantly. Yeah, you would have some energy usage from heat loss and the circulator pump - just thought of it as an option. We specified commercial buildings with a system like this many times when the run was long. This way you had instant hot water at every outlet.
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    Official "Groovie" Dude
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    Diane my house is plumbed the way Coaltrain describes. Indirect boiler in the garage with a circulator and a loop to every hot water outlet in the house.

    I'm searching for my electric unit information so I'll post that in a bit.
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    Nope, I just have a 30 gal tank for the bedroom wing. Should replace it in the next year or so, but space will limit size. And there's a good 60-90 feet between existing tank and new plumbing. The way the attics are structured, would be nasty to pipe & insulate too.
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    Quote Originally Posted by coaltrain View Post
    Just an option to think about -

    You can plumb your hot water lines to this new section of the house with a return line and run a circulator pump. This would have hot water at each outlet constantly. Yeah, you would have some energy usage from heat loss and the circulator pump - just thought of it as an option. We specified commercial buildings with a system like this many times when the run was long. This way you had instant hot water at every outlet.
    I agree, I would run the additional lines to plumb all the hot water together.

    You might want to think about using PEX tubing to run the lines, it's real easy to work with. You'll need to invest in a specialized tool to attach the fittings, and here you have two choices; a crimper or a cincher. I have both and prefer the cincher.

    Here is what the cincher ring looks like.
    Click image for larger version. 

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    And here is the crimp style.
    Click image for larger version. 

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    You can buy the PEX tubing in rolls up to several hundred feet in length to minimize junctions. It's easy to cut, and it is bendable (radius depends on diameter).

    Our whole house is PEX, not one problem. I added a few new outdoor hose bibs a few years ago and the longest part of the project was finding where I had stored my tools and fittings.
    Last edited by rw580; 10-20-2017 at 08:55 AM. Reason: add close paren
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    Familiar with PEX - used it to make a DIY sewer cam. Since rough-in plumbing was done years ago, have all copper inside house addition. IF I end up with a "central" system for the house addition, I'm sure I'll be using PEX in the floor trusses for hot water distribution. I'm pretty firm that running hot from the existing tank is not an option.
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    Ok here is my electric unit.

    PowerStar AE-9.5 Electric Tankless Under Sink Water Heater https://www.amazon.com/dp/B000H5VJ0I..._3JF6zbS6J1BA2

    I have a single lever faucet and it doesn't require much on the hot side to get hot. I use it to wash hands, fill 5 gallon buckets, wash the dogs, and I've used it once for a shop shower with absolutely no issues. This is actually my second one of the same brand, because the first one froze on me due to a hole I didn't close off, but it was 10 years old and worked as good then as it did new. If you have any questions on this unit let me know and I'll see if I can answer them.

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    Thanks, pcabe5. Looks like it's a 2 gpm unit with .75 gpm min to activate. About the size I was looking at for 1/2 bath. Wonder if I'd be happy with any lower flow rate. Any problem with not turning water on "enough" to get unit activated when just washing hands?

    Bought this 4 gpm unit
    https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1
    last year to test for kit/din & 3/4 bath, but not 100% committed to using it in the house addition. Eventually want to have shower in the shop (out building).
    Last edited by dianedebuda; 10-20-2017 at 09:13 AM.
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    I have not had a problem with not turning it on enough. When I first installed the unit I played with it to see how much I needed to turn to activate the unit and IMO I don't have to have much flow to activate. In all honesty since it's a single lever, it's usually only turned to the activation point because that is plenty hot at full flow and can be quite hot if not using full flow.

    I have a similar unit to the one you link that I uses for my floor heat in my shop. Again, my opinion, is my smaller one heats faster and can be hotter than the bigger unit.

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    Quote Originally Posted by pcabe5 View Post
    since it's a single lever, it's usually only turned to the activation point because that is plenty hot at full flow and can be quite hot if not using full flow.
    Are you saying that you usually turn it on fully and that if it's only partially on, it gets really hot? Trying to visualize with my faucet levers that have a temp mix location left/right and you push back to increase water volume.
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