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12 Volt Water Heater
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Barry Rietz



Joined: 21 Jun 2006
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City/Region: Sierra Vista
State or Province: AZ
PostPosted: Sun Oct 12, 2014 5:54 pm    Post subject: 12 Volt Water Heater Reply with quote

Has anyone tried this product?
http://www.greatlakesscuttlebutt.com/news/awesome-products/hot-water-on-the-go-for-outboard-boats/

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Sunbeam



Joined: 23 Feb 2012
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PostPosted: Sun Oct 12, 2014 6:10 pm    Post subject: Reply with quote

Of course one could look it up, but it's sort of funny that the article goes on (and on) for around ten paragraphs, and includes the sentence "The 12V Water Heater has a rapid heat up time producing hot water in less than an hour, and is highly efficient," and yet doesn't bother to mention how much it draws. Which is a pretty important piece of data.

That said, Whale tend to make quality products.

Edited to add: Of course I had to go look. And download the product datasheet to get past the "fluff" info. It draws 30 amps, and takes 40 minutes to heat to 104ºF and 80 minutes to heat to 140ºF (I didn't see mention of what temperature they presume your "plain" water is - perhaps there is a standard).
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Aurelia



Joined: 21 Aug 2009
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PostPosted: Sun Oct 12, 2014 6:15 pm    Post subject: Reply with quote

30 amps and I wish it was around when we had the 25. About time somebody did this right. Most consumers don't care how it works so long as it works. Skipping amp draw in a marketing/press release is not too surprising. I can see many more sport boats featuring a hot/cold shower on the swimstep soon.

Greg

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Sunbeam



Joined: 23 Feb 2012
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PostPosted: Sun Oct 12, 2014 6:25 pm    Post subject: Reply with quote

Aurelia wrote:
Skipping amp draw in a marketing/press release is not too surprising.


Oh fair enough. However then it was not on their many-tabbed web page for the product either. I had to download the data sheet. Not a problem, and I'm not in the market anyway, but I just found it curious, as it would seem to be a salient point (among others). Too, I have high expectations of Whale because they make great products. I've used their pumps for years and am a fan in general.


Last edited by Sunbeam on Sun Oct 12, 2014 6:26 pm; edited 1 time in total
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thataway



Joined: 02 Nov 2003
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PostPosted: Sun Oct 12, 2014 6:26 pm    Post subject: Reply with quote

The base temp was 60 degrees for the heat time. The 30 amps and 80 minutes means than the average group 24 battery would be depleted--and potentially damaged. With the Honda 90, the 16 amps alternator would take at least 2 1/2 to 3 hours to replace that amount of power---or running my Honda EU 1000 generator with 30 amp battery charger at fill tilt for 80 minutes. The box is 13" x 13" x 10" ; although smaller than the 6 gallon Atwood, the heater is still fairly good size.

Not going to buy one, but it is an interesting concept.

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journey on



Joined: 03 Mar 2005
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PostPosted: Sun Oct 12, 2014 7:17 pm    Post subject: Reply with quote

That's an interesting hot water heater. Let's look at what it does. And I'll summarize upfront: It's not for anybody with an outboard who doesn't want to run that motor for about 1 1/2 hr, just to supply the current needed. The best alternative is to use your portable generator if you're not plugged into the grid at the dock. 23 to 30 amps for over an hour is not going to come from any battery the C-Brats carry.

First there is a specific definition between heating water and energy used. For heating a liter of water 1 deg C, the energy required is 1000 calories, by definition. This is equal to ~1.2 kW_hr. Yes, definitions are in metric for even our world. The picture indicates the heater uses 300 watts, which at a nominal battery voltage of 13 vDC is 23 amps. Or 24 amp @ 12.5 VDC.

So, 3 gal is 11.3 liters and we can heat it 2 ways. First lets try using 300 watts to heat the water to 140 deg F (60 deg C) in 80 min, as the (blurry) picture indicates. Working through the arithmetic means that we start with 400 W_hr (300 W X 80/60 hr). Given that energy and an end point of 140 deg F, we have to start with water at 86 deg F. So, where do you get fresh water at that temperature? Probably at the equator, since we saw a max of 70 deg F while cruising in Washington this summer.

So, lets try starting with 70 deg F water and arriving at 140 deg F. If we want to do it in 80 min, that takes ~30 amps. Or if you want to hold the wattage to 300 watts (23 amps), it'll take over 100 min.

The ad is optimistic as any ad should be. Whale is a reputable company, but either there's something I missed or they dropped the ball on this one.

Boris
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Ray



Joined: 13 Dec 2011
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PostPosted: Sun Oct 12, 2014 7:47 pm    Post subject: Reply with quote

There's that pesky "physics" thing rearing its head again. Dangit! It just isn't going to happen.

Heating a water tank at 12V is just not practical no matter how many different ways you carve up the thermodynamics problem.

If you don't have a diesel with a heat exchanger, then the next best 'anchored' solution is an EU2000 plugged into your shore power outlet for 20min.

Well, except for the sunshower or garden sprayer, of course......
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Sunbeam



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PostPosted: Sun Oct 12, 2014 8:09 pm    Post subject: Reply with quote

Ray wrote:
There's that pesky "physics" thing rearing its head again. Dangit!

Don't you hate that?

Ray wrote:
Well, except for the sunshower or garden sprayer, of course......


That's what I use (garden sprayer) along with a tea kettle when necessary to sort out the water temperature; but I can totally understand why some people would like a "regular" water heater.
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Lost Petrel



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PostPosted: Sun Oct 12, 2014 9:03 pm    Post subject: Reply with quote

Quote:
That's what I use (garden sprayer)


Yep, the only energy this took was hoisting it up on the roof


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Sunbeam



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PostPosted: Sun Oct 12, 2014 9:11 pm    Post subject: Reply with quote

Although I don't need a water heater, I clearly *could* use one of those arches. They look handy for all manner of things Thumbs Up Plus I could get the anchor light out of my eyes (shines through hatch in the V-berth) (I did order a little black shield for it, but how much nicer to have it completely away/aft and get my reasonably dark sky back).
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Aurelia



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PostPosted: Sun Oct 12, 2014 9:14 pm    Post subject: Reply with quote

Seems like the folks from many other places have made heating water in modest quantities with DC power work well for years. This is the type of sink I am considering for Ari and I think would be suitable for the way lots of C-dorys are used. They normally are designed/installed to only run when the engine is running.

http://www.tealwash.com/product-tag/motor-vehicles/

http://www.eberspacher.com/products/handwash.html

file:///C:/Users/Greg/Downloads/handwash_brochure_ebuk_22385.pdf

Unfortunately, there is not a single source of them in this country because everyone is brainwashed by our complicate-the-heck-out-of-it approach to appliances.

Some C-dorys do carry enough power on board to take a 30AH+ draw. I do it every time I charge our Torqeedo battery from below about 30% using 12v and it works quite well. Instead of adding a brick of a generator, a person could add another battery and possibly not need the generator at all.

Seems to work for many in other places where physics follows the same rules. Couldn't resist the counterpoint. Sometimes good enough gets overlooked in a sea of bigger/better.

Greg
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cmetzenberg



Joined: 04 Jan 2014
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PostPosted: Sun Oct 12, 2014 9:33 pm    Post subject: Reply with quote

I haven't done any research on this at all but, has anyone looked into gas/diesel water heaters and the viability of their application aboard a small boat?
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cmetzenberg



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PostPosted: Sun Oct 12, 2014 9:43 pm    Post subject: Reply with quote

I've always thought it would be cool to be able to have a way of pouring hot water into the water heater's tank on Kanaloa. Then i could fab up something like this but a bit less redneck.

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journey on



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PostPosted: Sun Oct 12, 2014 9:50 pm    Post subject: Reply with quote

Greg/Aurelia,

I'm interested in recharging your Torqueedo battery. You mentioned that it takes 30 A from a 12 V battery. How long does it take? ! hr? More, less?

Looking at those heating units, they're intended for hand washing. They use 10 amps at 13.5 VDC (135 W) to raise the water temp to ~110 deg F, and it's certainly smaller than 3 gal. So, yes it's just the temperature difference and how much water against the available power. And the Teal unit only runs when the engine/generator does.

And, yes a Group 27 battery has a 90 A-H capacity. So you could run a fully charged battery down to 50% and then recharge it. I'm just not sure that I'd want to do that on a regular basis. Journey On's Honda 150 has a 40 amp generator and it cost $12,000. A Honda 2000 costs $1000, so I'd rather use that.

Boris

One makes their own choices and they'll all work out.

Boris
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Aurelia



Joined: 21 Aug 2009
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PostPosted: Sun Oct 12, 2014 10:08 pm    Post subject: Reply with quote

The Victron says it takes 16-34 amp hours to charge so far (depending on how much we discharged it) and we usually do it overnight while anchored so far. It is not a fast charger and runs at a few amps for many hours. We have a 220AH house bank and so far we have not really needed even 50% of that. We like having the extra margin. I also would not run an outboard for charging instead of a generator, We tend to motor somewhere even if we come back to the same spot for the night so we get pretty reliable charging from that outboard while running around for sightseeing for fishing. Even at low speeds it charges at over 10amps (older Honda). I am sure we are not the only ones that move around regularly. A sport boat that is always running would be in good shape.

The Tealwash unit has a 20amp draw. And they do offer a non-sensed unit for heating when the engine is not running. That was the model I was looking at for us but in the Handiwash size.

Greg
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