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electric wall hung water heaters

Larry Weingarten
Larry Weingarten Member Posts: 3,934
in THE MAIN WALL
...that electric heaters have energy factors in the low 90s. 100 is as high as one can go with resistance heating. Any tankless with computer control does have some standby loss. There are far greater gains to be found with drain heat recovery and modern hot water distribution systems. Rebuilding is the right time to put those sort of improvements in.

Yours, Larry
ps. Gary Klein has written three articles on hot water distribution systems that were in ASPEs journal "Plumbing Systems & Design".

Comments

  • BB_8
    BB_8 Member Posts: 2
    electric wall hung water heaters

    I was wondering if any of my heating brethren, could give me the low down on electric wall hung dhw heaters, do they really work as they say? what's the upsides and downsides to using this type of systems.any feed back on this subject would be most appreciated. thanks BB
  • singh
    singh Member Posts: 866
    not a problem

    First make sure you get a big enough heater for your family.
    A large heater may get you in the 5 gallons per min range. About
    two showers simultaneously. Yet, you will have to be tolerant with
    fixture usage. Like taking a bath and trying to wash clothes at the same time.
    Most cannot fill a tub at full flow, a tub dumps water in as fast as possible. You will have to throttle back a little, so tub may fill up slower but it will fill with all hot water. You will NEVER run out of hot water. Your electric bills will be lower than a 40 or 50 gal tank type electric. Maybe by half!
    If you have hard well water you will need a "scale stopper" cartridge .Or water sofner. Otherwise elements will cake with lime and performance reduced.
    Usually cheaper than gas tankless to install, but make sure you have the electrical capacity , they can use four seperate breakers.
    I have a Seisco, almost seven years now, paid for itself the first year. No problems. No regrets.

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  • Scott Gregg
    Scott Gregg Member Posts: 187
    Yes... but

    Here is the deal and I’ll try to keep this short...for now

    For "most" residential applications you will need a 120amp unit and may require an electrical upgrade. You will get about 4gpm at a 45* rise, which is enough for a two standard fixture load, not including tubs.

    The things to consider are these:

    Your incoming water temperature varies greatly from area to area, and well water is always colder than public. Typically I use a 60* rise when sizing a tankless. At this rise you are looking more like 2.5gpm total flow. Only enough for one fixture in most cases. I use this to make sure in the winter there will be an acceptable amount of hot water. If you are in the Deep South it is less of an issue. If you are up north it is more of one.

    If you are in the shower and another person operates a hot water fixture it is quite possible that you will get a surprise! Non of the electric tankless heaters (To my current knowledge) have the technology in them to control the flow rate of the heater to prevent temperature fluctuations due to flow rate changes. When the flow changes there is usually a period of time where the temperature fluctuates enough to upset the person in the shower.

    Also as stated you can “overshoot” the electric’s and have to throttle your flow manually so they can keep up in many cases. If not, you will get a temperature less than the setpoint.

    They can be less expensive due to no venting or gas line, however if you are going to require and electrical upgrade anyway, I suggest you get an LP tank and install a gas Noritz. (It can be installed outdoors also if you like and that should save you installation costs as well.)

    I expect we will see an electric tankless company step up with a unit that has better performance in the future and I for one am waiting for it! For now, I’ll stick with the gas. With a good quality gas unit all the other negatives go away. (Unlimited hot water, no overshooting, even temperatures.)

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  • singh
    singh Member Posts: 866
    possible

    but I have not had those experiences. I did not need an electrical upgrade. I have 150 amp service, but this was an all electric house, so I retired alot lot of baseboard heaters.
    No problem with someone in shower, unless washing clothes or filling tub at same time.
    I have well water 45* most of the year. I am experimenting with a heat exchanger feeding the tankless, getting the temp rise thru hydronic supply. Trick is to make that run most of the year, I am considering solar back-up also. Remember none of this is needed, I'm just running my own personal test. For seven years my tankless electric work fine, by itself, slight life style adaptation but nothing to get bothered over. If you are aware of this before, than it won't be a problem.
    I think Bosch has a better electric unit than Seisco.
    All of this depends on if you have gas in the house already, can venting be accomplished easily, electrical upgrades or not,family demands and peak load etc..

    So standard answer: IT DEPENDS!

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  • Uni R
    Uni R Member Posts: 663
    Not enough advantages...

    A tankless WH:

    - costs "many times" more (when sufficiently sized) but won't likely last "many times" longer than an electric tank WH (especially if the anode rods are properly maintained in the tank type heater)

    - has more complex controls that can fail as it ages

    - has difficulty with very low flows and very high flows

    - requires some serious added circuitry expenses

    - hammers the electric grid at peak usage hours

    - is useless in a power failure


    It's advantages are a smaller footprint and less standby losses, but any modern electric tank WH has ridiculously low standby losses to begin with. I wouldn't be surprised if an electric tankless doesn't have a similar minimal loss of efficiency by heating some air as it produces the hot water.

    If you don't need the space, I'd never recommend one.
  • BB_8
    BB_8 Member Posts: 2
    thanks

    Thanks for the input on this subject, once again my heating compardres have come to the rescue. that's why i love this business, you guy's are the best. BB
  • Brian (Tankless)
    Brian (Tankless) Member Posts: 340
    Hi Devan

    How do I find info on the Bosch electric tankless.

    Several years ago, Controlled Energy private labelled the Electric EeMax brand which were awful. I installed seven of them, and had to replace all with British "Powerstream's" or "Seisco's".

    Bosch now owns CEC, so I'm not sure what they sell.. maybe Steibel Eltron.

    Maybe I should just try CEC's website, eh? Duh.

    Back to Cameron, LA. tomorrow. You've never seen a town so devastated, except maybe what happened after the Tsunami.

    We are basically building a town from the ground up. There were NO utilities left intact, nothing. EVERY home & building within 30 miles is damaged or gone.

    Gov' Blanco finally showed up to survey the damage...six months after the fact. I don't think she'll be our next Gov'.

    I'll keep you guys posted later, with pictures, they're pretty bad.

    I'll be back next weekend, till then, take care out there.

    Brian, literally in Swampland.

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