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favorite electric on demand water heater?

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archibald tuttle
archibald tuttle Member Posts: 1,090
edited July 7 in Plumbing

I put in several Bosch units thinking that buying the brand name got me something. It did, lots of headaches. The flow switch is so sensitive in these things. Don't know if that is characteristic of the many brands where the footprint is so much smaller than gas on demand but to say i'm dissatisfied wouldn't do justice to dissatisfied.

first failure wasnot noticing that they said don't use pipe dope. who ever heard of that, or am i the last to know and everyone else is getting a good laugh? so the first time I had to disassemble and clean out the flow switch was my bad I guess. But I never have this problem on a gas takagi and the flow switch is much more facile and tempers the water while the bosch (3000C US9 40 amp nom.-32 amp measured) is strictly on-off. then a year later it started the same bull again and I had to dismember it (real PIA, be one thing if this needing regular cleaning and service and they made it easy). then a year after that again. now it's gone 3 years and started again with running hot, running on, vapor locking and kicking out the temperature reset. i'm ready to move on but not until i bad mouth the thing up one side and down the other.

it's discontinued, maybe they improved this with later design?

or what flavors do you like.

been very happy with this idea if not with this instantiation. It really doesn't draw more than a 40 gallon tank when you've used enough to trigger both elements and it's small and can locate near the load reducing waste to feed up to the fixture. And it keeps up with my modest flow shower. thoughts?

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  • Intplm.
    Intplm. Member Posts: 2,084
    edited July 7
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    Rinnai has been great. No issues. So far so good.

    Mad Dog_2
  • Larry Weingarten
    Larry Weingarten Member Posts: 3,389
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    Hi, Seisco made good units, but was bought by AO Smith in 2017. Not sure if Smith is using that technology now.🤔

    Yours, Larry

  • Intplm.
    Intplm. Member Posts: 2,084
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    Stiebel Eltron makes an all-electric that I have used for an entire house and performance superbly.

    With this type of water heater, they tend to need a lot of electricity. The whole house models can use up to three double pole breakers.

    My apologies as I misread the original post. (They all plug into the wall). I'm not sure that Rinnai makes an electric model. They make great products. Maybe a trip to their website will show an electric model. If they do have one I would surely go for it.

    Mad Dog_2
  • Jamie Hall
    Jamie Hall Member Posts: 23,655
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    There are really three distinct types of electric water heaters: tank type (including heat pump types), very small tanks suitable for a single lavatory or maybe, just maybe, a small kitchen sink, and instant on full flow types.

    Don't get them confused.

    If you want an instant on, point of use electric water heater suitable for a single bathroom group, which is sort of what I think you are after (it really isn't clear), they require dedicated wiring and circuit breakers; how large depends on just how big a unit you need. There are a number of makes and models of varying capacity out there. A nice small one for a single bathroom group — 2.5 gpm capacity — will require about 20 to 60 amps, 240 volts (two breakers).

    Small — up to 7 gallon tank — electric water heaters are also available, some of which can run on 15 or 20 amp 110 volt circuits. Not really suitable for a shower unless you take Navy style showers, but can do the job nicely for a half bath.

    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • GGross
    GGross Member Posts: 1,105
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    I have used the eemax units I believe they are a Rheem brand. They work well for what they are, its a lot of electricity to do a whole house, they have a pretty wide range. they always suggest a flow restrictor when comfort is concerned, or else you may exceed the flow rate and the water temp will drop.

    https://www.eemax.com/

  • PRR
    PRR Member Posts: 171
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    …what flavors do you like.

    Cheapest DUMB STORAGE electric WH in Lowe-Depot's fathers day flier. 40g, 60g, whatever.

    I recognize the potential in heat-pumps but not for our small needs. I recognize the advantage in on-demand designs but, especially on electric, over-over-insulation holds the heat-leakage down.

    I had a Rinaldi propane on-demand from the 1980s (no electricity except a piezo spark) and while the endless hot water is wonderful for flushing a frozen sewer, as it aged it was scalding worse and worse, and descaling is a chore which didn't solve anything. I asked my GAS guy and he said his customers went to electric storage and were happy. At our consumption we hardly noticed the increased electric bill, but the comfort was better right away. (Later I added a tempering mix-valve so I have lots of HOT water in storage but only slow-scalding at any tap.)

  • archibald tuttle
    archibald tuttle Member Posts: 1,090
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    @Jamie Hall

    i thought "on demand" is the way to say flow heater, but I guess if you want hot water when you want it, it is always on demand in a sense but there is no storage.

    already have a bosch US-9 40 amp flow heater. i'm disgusted with the flow control. constant problems. never had any issue with the flow controls on any takagi on-demand gas. I have ones that are 20 years in and never had a hiccup. i've had this friggin bosch broke down 4 times and it wants another in 5 years (well it breaks down and then i have to break it down, if you will)

    I can see that Bosch has changed their design and seem to provide a different kind of temperature control that appears to suggest that the newer models are not strictly on-off but vary amperage/load according to flow. that is a nice feature which the virtually failproof (in my experience with maybe 2 dozen installed) takagi's have had since i started using them. but what i care about more is that I don't have to service the damn flow switch time after time after time, or if the small form factor creates more likelihood of failure that serviced access is more modular.

    so i am looking for recommendations for an "instant" or "on demand" or "flow" style water heater 40 amp electric that folks have had success with. that is the minimum nominal amperage i've found can handle a shower.

  • archibald tuttle
    archibald tuttle Member Posts: 1,090
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    @PRR I have never had a performance problem with the propane or natural gas on demand units, scale or no scale. I understand the idea of scale problems and impact on temperature delivery related to flow, but I have never had this happen in 20 years of installing those. color me perplexed, maybe, but i'm a believer.

    I don't disagree that insulation on a tank style electric helps keep loss down , but they cost twice as much as on demands and the small form factor means i can locate the electric on-demand 4 feet from the demand meaning i get less loss in pipes. i've been happy with this setup except for the finicky flow switch on the bosch i bought. i just didn't expect that aspect to perform so poorly after never having a prob lem with the gas units.


  • Mad Dog_2
    Mad Dog_2 Member Posts: 7,250
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    Stiebel Eltron hands down. Just be prepared to feed it with MEGA power and amperage that they call for. In many cases, they are practical for a bathroom 🚻 or cottage. To supply multiple hot water fixtures, adequately, the work, cost & feasibility electrically speaking is cost-prohibitive OR the building simply doesn't have the amperage coming in off the pole or in the panel. Mad 🐕 Dog

    PC7060Intplm.
  • Jamie Hall
    Jamie Hall Member Posts: 23,655
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    40 amps at 240 volts is a smidge less than 1 gpm at a 70 degree rise (note there is a typo in my previous comment — 2.5 gpm requires 50 to 60 amps, not 20 to 60, and I didn't mention that it depends on the temperature rise as well).

    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • Larry Weingarten
    Larry Weingarten Member Posts: 3,389
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    Hi @archibald tuttle , What are the loads you're trying to meet? I'd supply a tub or shower differently than I'd supply a lav sink. 🤔

    Yours, Larry

  • archibald tuttle
    archibald tuttle Member Posts: 1,090
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    @Jamie Hall @Larry Weingarteni worked it out emperically that 40 amp 240V models will satisfy me for a shower. (albeit the models are 40 amp breaker required but are actually like 7.3 to 7.5 kilowatts or operating at just over 30 amps depending on voltage.) then it meets the needs of all the smaller loads excepting whether it s able to actively vary current either gradually or in steps. the one I have now, you can set it high or low but it is just plain vanilla on and off, 1 or 0 according to flow.

    I notice that Stiebel Eltron in that size (7.3 kw i think) is back ordered for 2 months at least my common supplier. various comments on its page suggest load matching which I presume means that it does not have self varying current supply based on flow. it does look like the new bosch's may have such a feature although i'm gunshy after the last version.

  • mattmia2
    mattmia2 Member Posts: 9,962
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    On/Off is probably controlled with a flow switch and modulation is probably controlled by a supply water temp sensor. Since the entering water will vary in temp, the outlet temp tells you far more than flow ever would.

  • mattmia2
    mattmia2 Member Posts: 9,962
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    Side note, have you contacted Bosch? Perhaps they have a design change that can be retrofitted to your model that is more reliable or at least can be service more easily.