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Thread: Battery Backup for Tankless Water Heater

  1. #1
    DIY Junior Member BrianC's Avatar
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    Default Battery Backup for Tankless Water Heater

    I'm thinking about replacing a failing 50gal gas water heater with a tankless unit. The problem is that my house experiences frequent power outages, sometimes days at a time. So far we have been able to weather the outages because the tank heater still provided hot water. If I switch to a tankless unit, that benefit goes away. I've seen an ad online for something called the Hugo battery backup for tankless heaters http://hugo-powersupply.com/ . It looks like it will do the trick. However, the only thing I can find about it seems to have been written by the guy trying to sell them. Has anyone here used these devices, and what was your experience with them? Are there any other alternatives I should be considering? (I realize that sticking with a tank unit or installing a generator are options)


    Thanks,
    Brian

  2. #2
    Test, Don't Guess! cacher_chick's Avatar
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    You would need to know how much power the heater needs to determine what size backup unit is required. Watts or Amps.

  3. #3
    DIY Junior Member BrianC's Avatar
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    It's listed as 97 watts for normal use and 120 watts for anti-frost protection. I'm looking at a Rinnai RL94i.

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    Test, Don't Guess! cacher_chick's Avatar
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    The most simple and economical solution would be a couple of automotive or Gel batteries and a power inverter. This is essentially what the Hugo unit is, minus the electronics to automatically switch it over.
    The amount of runtime is dependent on the size and number of batteries used.

    I'm assuming you have city water supply. If you are on a private well you are going to need a generator, which eliminates the need for a backup unit.

  5. #5
    Master Plumber master plumber mark's Avatar
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    Cool Knock yourself out

    Quote Originally Posted by BrianC View Post
    I'm thinking about replacing a failing 50gal gas water heater with a tankless unit. The problem is that my house experiences frequent power outages, sometimes days at a time. So far we have been able to weather the outages because the tank heater still provided hot water. If I switch to a tankless unit, that benefit goes away. I've seen an ad online for something called the Hugo battery backup for tankless heaters http://hugo-powersupply.com/ . It looks like it will do the trick. However, the only thing I can find about it seems to have been written by the guy trying to sell them. Has anyone here used these devices, and what was your experience with them? Are there any other alternatives I should be considering? (I realize that sticking with a tank unit or installing a generator are options)


    Thanks,
    Brian

    You would have to be nuts to go to all this trouble
    ....you have never had a problem with the 50 gallon
    gas heater you presently have... it has worked through the worst power outages...
    why in the world would you want to play with fire like this and probably spend 5 times more over a common tank type heater????

    I am seriously trying to understand the reason... please explain what you think
    you are going to gain here???

    read this link http://weilhammerplumbing.com/houseofhorrors/
    Last edited by master plumber mark; 02-10-2013 at 08:32 PM. Reason: blow me with passion

  6. #6
    Retired Defense Industry Engineer jadnashua's Avatar
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    120W at 12vdc is 10A. That will run a typical car battery flat in less than a day easily should it ever need the frost protection, and that might happen if you lost power for an extended time. If you want a longer time, you need lots more batteries. This can get quite expensive, and with a big battery farm, you have to worry about H2 gas when charging them up, not counting the space they require. THen, you must consider that no voltage conversion is 100%, and to get that 10A, you may need 11A draw or so. By far, the least expensive is to just rely on a tank for both the upfront costs and running costs assuming you have a reasonably efficient WH. A tankless also requires (typically) annual demineralization of the heat exchanger to maintain good operation, so it's not a set and forget item. Considering the upfront costs (you may need to upgrade your gas lines and maybe meter), and the other factors, it's not something I'd consider. For bang for the buck, a tank is your better bet.
    Jim DeBruycker
    Important note - I'm not a pro
    Retired Defense Industry Engineer; Schluter 2.5-day Workshop Completed 2013, 2014

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    Forum Admin, Expert Plumber Terry's Avatar
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    A big reason for going tankless is not having to worry about running out when it's your turn for the shower.
    They don't need much power for the back up battery. It's a small cost to pay for that.

    Mark is right about the old style tanks being more simple, but if you're the one paying the rent, and the water's gone when it's your turn, then that part isn't going to matter.

    By the way, my GF has a tankless unit, and I'm kind of liking it.

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