Need info on a Point of Use Electric tankless.

Discussion in 'Tankless Water Heater Forum' started by brianosaur, Jan 29, 2021.

  1. brianosaur

    brianosaur New Member

    Feb 24, 2009
    Selden, New York
    Remolded my bathroom last year. Turns out, as feared, the new shower head and shower valve uses too many GPM to keep up with my tankless oil fired boiler. Two or three minutes into a shower I lose the hot, or pretty much the "nice and hot".

    Pre-remodel I would just keep the pressure low and adjust hot & cold knobs separately to get away with a decent shower. We knew not to run the dishwasher or do laundry while showering. The new single lever thermostatic mixer doesn't let me dial in hot/cold pressure that well and the large rain 2.5 gpm head doesn't help the situation. If I switch to the hand held sprayer it will allow the boiler coil to catch up enough and I can get hot water all day long.

    (1.) I am uncertain what size TWH I would need to make up the additional temperature from a luke warm (leaning cold) shower.

    The size charts state geographic area based on ground water temps but since the water will be mostly/mildly pre-heated in my boiler would I need as large of a unit?

    Or should I run the cold line to the TWH and the hot output in parallel to the existing hot line to the shower, and get a standard size unit for my location & gpm need?

    Last edited: Jan 29, 2021
  2. fitter30

    fitter30 Well-Known Member

    Feb 2, 2020
    Retired service tech
    Peace valley missouri
    Last edited: Jan 30, 2021
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  4. Dana

    Dana In the trades

    Jan 14, 2009
    Electric tankless water heaters rarely deliver satisfactory performance at NY type water temps, especially in high flow applications like this. They're too restrictive, and underpowered for the job.

    By contrast an electric heat pump/hybrid water heater (tank) in lieu of your tankless coil would allow you to actually save money (even at Long Island type electricity rates) by turning down the low-limit to the boiler, and delivers great flow. And unlike a tankless it doesn't need wiring fat enough to pull the F-150 out of a ditch. When installed next to the boiler it "harvests" the standby loss heat from the boiler, putting it into the tank rather than leaving it in the boiler room to be lost, and during the summer it dehumidifies the boiler room, mitigating against "musty basement smell" issues. It costs a bit up front, but it uses about 1/3 the electricity of a plain old electric tank water heater or an electric tankless, and at L.I. electricity prices it pays for itself in short years.
  5. Aiman

    Aiman New Member

    Mar 22, 2021
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