12 Volt DC Water Heater?
gold
Pat you can forget 12 volt for heating water . uses way to much energy
you might want to look int an instant hot water heater run on propane.
this would be practicle and effecient
P.Bennett
In article <327809...@li.net>, Pat Long <pl...@li.net> writes...
>My sailboat has a hot water tank that can be heated by running the
>engine or plugging into dockside AC. I'm installing a wind generator
>with a regulator with a divert function when my batteries are fully
>charged. I would like to use the excess power generated to heat water.
>Hot showers sure are nice & I've got a water maker installed. Is there a
>12 volt DC water heater element on the market I can install? Any other
>ideas?
It takes a _lot_ of electricity to generate useful heat. (see the current
thread re 12V hair dryer, and a recent thread on a 12V coffee maker).
The 120V element in your heater is probably rated at least 1000 watts - this
will draw 10 amps at 120 V. An aequivalent 12 Volt element would draw 100
Amps!!!
Therefore, I doubt very much if you would find a 12 V heater element.
Peter Bennett VE7CEI | Vessels shall be deemed to be in sight
Internet: ben...@triumf.ca | of one another only when one can be
Packet: ve7cei@ve7kit.#vanc.bc.ca | observed visually from the other
TRIUMF, Vancouver, B.C., Canada | ColRegs 3(k)
GPS and NMEA info and programs: ftp://sundae.triumf.ca/pub/peter/index.html
or: ftp://ftp-i2.informatik.rwth-aachen.de/pub/arnd/GPS/peter/index.html
or: http://vancouver-webpages.com/peter/index.html
Pat Long
Larry Butler
Pat Long <pl...@li.net> wrote:
Let's see, the water heater has a 1500 watt element in it....If we
could get one for 12V it would draw 1500/12=125 amps at 12v. Does
your windcharger put out 125 amps? 1500 watts isn't much heating
water...a good home water heater draws about 4000-8000watts at 240VAC.
It's not practical for solar or wind to heat water. Got any place to
put a solar water heating panel? They work great!
Larry kn...@mindspring.com
Charleston, SC
Miles and miles of waterways - unspoiled by condos!
Come Sea!
P.Bennett
In article <55aj1g$s...@camel2.mindspring.com>, gha...@pipeline.com writes...
>>My sailboat has a hot water tank that can be heated by running the
>>engine or plugging into dockside AC. I'm installing a wind generator
>>with a regulator with a divert function when my batteries are fully
>>charged. I would like to use the excess power generated to heat water.
>>Hot showers sure are nice & I've got a water maker installed. Is there a
>>12 volt DC water heater element on the market I can install? Any other
>>ideas?
>
>coil - should be plenty of resistance to provide a good load. I might
>measure the resistance (V = I*R, W = I*V = V*V/R) to see what you
>can expect. Anyone in agreement?
No.
A 1200 watt 120V heating element will have a resistance of 12 ohms. At 12
volts, this same element will only draw 1 amp, and consume 12 watts - not
enough for any useful heating.
It takes a _lot_ of electricity to generate useful heat, (see the recent
threads re 12V hair dryer and coffee pot), so it is not practical to run a
water heater - you would need 50 to 100 amps at 12 volts to make a useful
quantity of hot water.
gha...@pipeline.com
Sean Holland
In a previous article, pl...@li.net (Pat Long) says:
>My sailboat has a hot water tank that can be heated by running the
>engine or plugging into dockside AC. I'm installing a wind generator
>with a regulator with a divert function when my batteries are fully
>charged. I would like to use the excess power generated to heat water.
>Hot showers sure are nice & I've got a water maker installed. Is there a
>12 volt DC water heater element on the market I can install? Any other
>ideas?
>
Installing a 12 vdc heating element, will certainly eliminate any excess
power. Your stove and a stove and or a Sun Shower might be a more
efficient means to accomplish the warm shower. 73.
--
Sean F. Holland
S/V Spindrift NP2AU
au...@lafn.org
Dennie McKee
Do you know a source for such a propane water heater?
--
Dennie McKee dmc...@infogo.com
106 S. Haley St. Phone 501-574-2513
E. Camden, AR 71701 Fax 501-574-2513
http://www.infogo.com/~dmckee/
Ken Eitenmiller
Pat Long wrote:
>
> My sailboat has a hot water tank that can be heated by running the
> engine or plugging into dockside AC. I'm installing a wind generator
> with a regulator with a divert function when my batteries are fully
> charged. I would like to use the excess power generated to heat water.
> Hot showers sure are nice & I've got a water maker installed. Is there a
> 12 volt DC water heater element on the market I can install? Any other
> ideas?
There are replacement elements available for water heaters appropriate
for 12 volts. A good source is your local camping store. They are used
in motorhomes. They normally draw about 30 amps and will heat a 6 gal
water heater in about 1 hour. You can proportion the time; ie 10 amps
will take 3 hours etc.
The problem is that you will have to give up your 115 volt element
because most water heaters only have a boss for one element. To get the
115 volt element to work off of your generator you need to step up its
voltage with a simple inverter that can be constructed from about 20$
worth of parts from Radio Shack (if you need help, send me an e-mail).
P=VI P=I*IR P=V*V/R V=IR I=V/R P=V*V/R
R=V*V/P=115*115/1500=13225/1500=8.8 OHMS
LETS SAY YOU WANT TO USE 10 AMPS FROM EITHER YOUR GENERATOR OR YOUR
BATTERY(THIS IS WHAT I USE. WARM NOT HOTHOT AFTER A COUPLE OF HRS).
THEN: P=12VOLTS FRON GEN * 10AMPS = 120 WATTS VOLTAGE FROM INVERTER =
SQUARE ROOT OF 120*8.8 = 32VOLTS
Jere Lull
>My sailboat has a hot water tank that can be heated by running the
>engine or plugging into dockside AC.
Most arrangements like that are heated by the engine cooling water
flowing through a coil in the hot water tank. Requires a freshwater
cooled engine, of course. (or so I'm told...) Nice way to use heat that
would otherwise be wasted.
Jere Lull
Xan-a-Deux
'73 Tanzer 28 #4
out of Georgetown, MD
Rod Mc Innis
Ken Eitenmiller (kg...@ix.netcom.com) wrote:
: There are replacement elements available for water heaters appropriate
: for 12 volts. A good source is your local camping store. They are used
: in motorhomes. They normally draw about 30 amps and will heat a 6 gal
: water heater in about 1 hour.
That would be quite impossible.
The accepted definition of a BTU is the amount of heat required to
raise one pound of water one degree F.
Water weighs 8.3 pounds per gallon. Thus, that 6 gallon water tank
would be holding 49.8 pounds of water.
If you started at "room" temperature (70 degrees F) and wanted it to
get to 140 degrees, you would have to raise the water temperature 70
degrees F, which would require 0 BTU per pound, or 3486 BTUs for 6
gallons.
If you had a 1000 watt element, it would require just over an hour
to deliver this much energy, and that is assuming no lost heat.
An element that only drew 30 amps off the 12 volt system would only
be able to deliver 360 watts. I am afraid that heat losses would
prevent this from ever getting the water heated.
It might keep the water fairly hot, if it had already been heated by
some other means.
: The problem is that you will have to give up your 115 volt element
: because most water heaters only have a boss for one element. To get the
: 115 volt element to work off of your generator you need to step up its
: voltage with a simple inverter that can be constructed from about 20$
: worth of parts from Radio Shack (if you need help, send me an e-mail).
: THEN: P=12VOLTS FRON GEN * 10AMPS = 120 WATTS VOLTAGE FROM INVERTER =
: SQUARE ROOT OF 120*8.8 = 32VOLTS
I would sure like to see your circuit that would create a 120 watt
step up power supply from $20 worth of parts, obtainable at Radio
Shack. Such a circuit could certainly be built, I just doubt the cost
figure, and unless Radio Shack in your area carries a lot more stuff
than the ones in my area, you aren't likely to find the necessary
magnetics.
Rod McInnis
Ken Eitenmiller
Sorry about that. I asked my wife and she said that it was closer to 3
hrs than 1. If we turned it on in the morning, we had hot water by
noon.
As for the power supply, Audio tranformer, strip windings, rewire 12
volts center tapped #14 varnished wire, 64 volts center tapped same
wire, flyback signal winding, 4 diodes, 2 transistors, 4 resistors, and
2 capacitors tuned to run around 1000 hz. About $20 or a little less.
Joe Kovacs
>>Hot showers sure are nice & I've got a water maker installed. Is there a
>>12 volt DC water heater element on the market I can install? Any other
>>ideas?
As others have said, It's considered that the current draw
makes real 12v heating elements impractical.
All right, other ideas. Cobble a diesel glow plug or two?
That's about the limit for 12v. Maybe it'll work. After
all, you _are roughing it, the wind's free, and you can take
23 hours (47? 71?) to heat the tank. And it works OK now,
any improvement's gravy.
Joe Kovacs
Guelph Ontario Canada
Jeff Nicholas
Defender has one listed in their 1996 catalog on page 95 - about $600.
Glenn Wells,62b-295,7247817
Why not dump your excess 12 power into the hot water tank
by way of the 110VAC terminals? Be sure to disconnenct
prior to using shore power again.
In article 56...@li.net, Pat Long <pl...@li.net> () writes:
>My sailboat has a hot water tank that can be heated by running the
>engine or plugging into dockside AC. I'm installing a wind generator
>with a regulator with a divert function when my batteries are fully
>charged. I would like to use the excess power generated to heat water.
Paul Mathews
Glenn Wells,62b-295,7247817 wrote:
>
> Why not dump your excess 12 power into the hot water tank
> by way of the 110VAC terminals? Be sure to disconnenct
> prior to using shore power again.
>
> >12 volt DC water heater element on the market I can install? Any other
> >ideas?
Perhaps this has already been suggested: heating elements often have a
cold resistance much lower than their hot resistance. I presume that
your wind generator can only supply a couple hundred Watts at most,
which is not going to heat the element to full temperature in any case.
Consequently, you may be able to simply use the 110V element itself.
Your wind generator probably puts out somewhat more than 12V. For a
1000Watt 110VAC element, you might expect to measure as little as 3 Ohms
cold resistance. This means that you could put about 5 Amps into it at
15VDC, for a 75Watt input. (Of course, it will take about 12 times as
long for it to heat the water.)
Anyone who doubts this conjecture can try the following experiment if
you have the means: Measure the current of a 12V lightbulb. Measure
the current of 2 such lamps in series. The current will be quite a bit
more than half that of the single lamp, AND, both bulbs will give off
appreciable light, even though they are being operated at far below
their rated voltage. This is because of the positive temperature
coefficient of the resistance of the filaments. The same effect occurs
to a lesser degree with most heating elements.
--
Paul Mathews, consulting engineer
AEngineering Co.
opt...@whidbey.com
non-contact sensing and optoelectronics specialists
P.Bennett
In article <55tk53$a...@hearye.mlb.semi.harris.com>, g...@mlb.semi.harris.com writes...
>
>
> Why not dump your excess 12 power into the hot water tank
> by way of the 110VAC terminals? Be sure to disconnenct
> prior to using shore power again.
>
This would be a fairly futile exercise. A 1200 Watt 120V heater element would
have a resistance of 12 ohms. At 12 volts, this element would draw 1 amp, or
12 watts - which probably won't be enough to keep the water warm, let alone
heat it.
Ramon Gandia
Glenn Wells wrote:
>
> Why not dump your excess 12 power into the hot water tank
> by way of the 110VAC terminals? Be sure to disconnenct
> prior to using shore power again.
>
> >My sailboat has a hot water tank that can be heated by running the
> >engine or plugging into dockside AC. I'm installing a wind generator
> >with a regulator with a divert function when my batteries are fully
> >charged. I would like to use the excess power generated to heat water.
> >12 volt DC water heater element on the market I can install? Any other
> >ideas?
The regular 110 volt element will not work. For
instance, if the 110 volt element is 2.2 kilowatts, it
draws 20 amperes on a.c. I = P/E or 2200/110 = 20 a.
The resistance is R = E/I = 110/20 = 5.5 ohms. This
resistance across a 13 volt source will draw only
I = 13/5.5 = 2.36 amperes. P = EI = 13*2.36 = 30.6 watts.
Thirty watts is insignificant power for a water heater. As
has been pointed out earlier in the thread, it takes a full
kilowatt-hour to heat 6 gallons of water from 70 to 140
degrees.
You could put in a lower resistance element (several ideas
come to mind), but at some point the wind generator will
be at full load. Most wind generators are in the 2 amp to
10 amp range. Even at a full 10 amps, the circuit will
only supply 130 watts, which is not enough to get any
significant amount of water warm.
If you intend to provide a load for the wind generator so
it doesn't run away with no load, then, o.k., use it to
heat something. But if your intentions are to have a wind
generator to get water hot, be advised no reasonable wind
generator can be installed in even a 100 foot boat that will
do the job of heating even a small 15 or 20 gallon domestic
water heater's tank.
The only sensible way to heat water is with a heat exchanger
to the engine.
The heat exchanger is typically a coil of pipe thru which
the engine's coolant flows. This coil is immersed in the
water tank. If you use Prestone in the coolant, be advised
that any Prestone (Ethylene Glycol) leakage into drinking
water is soon fatal, and long before then horrible kidney
damage/ailments and brain damage will result. If you
circulate anti-freeze solution in your drinking water tank,
or any tank that could be drank out of accidentally such
as a shower, toothbrush water etc, you must use either the
non-lethal Propylene Glycol, straight water (dangerous to
the health of your engine), or a double heat exchanger.
And even then, I would be scared lest some yo-yo in a
marina put the wrong Prestone in the engine's system.
The conversion of mechanical power to electric power is
not too efficient. Nor is the heat value of fuel convert
easily to mechanical power.
Fuel delivers a theoretical maximum of about 26% to the
engine's output. Typical is like 15%. The conversion of
engine rotation to electric power is about 80% efficient,
typically. Thus, your real-world fuel-engine-electricity-
heat is about 12% of the heat value contained in the fuel.
The rest of the heat energy in the fuel goes out the
exhaust, the engine cooling, or heat from alternators
windings, belts, couplings, etc. Much better to use
the fuel to burn a flame to heat the water.
Consider Solar. Even in northern latitudes, you can
get lots of heat from the sun. Witness the Solar
Shower, which is just a black enema bag suspended from
the rigging, with a shower head instead of an enema
probe. It heats a gallon or two of water in less than
an hour. Solar energy is several kilowatts per square
meter, much better than most sources.
For a permanent installation you can do a couple of things
to improve on this. (1) Mount your tank, or day tank,
on deck and paint it black. (2) Mount your tank, or day
tank UNDER the deck, with a tinted Lexan window leading
to it. Insulate the tank under the deck. (3) Install
a solar heat collector on deck, and pipe it to the tank.
The solar collector is usually a black-painted copper pipe
at the focal point of a parabolic reflector, so that the
sun ray's are collected in the aperture of the reflector
and concentrated on the pipe. Thus the effective exposed
area is that of the reflector, not the pipe's. These
solar collectors are often designed to produce lots of
concentrated solar energy even when the reflector is not
aimed directly at the sun. Clever optics. They are rugged.
May I also suggest just boiling a kettle on the stove and
transfusing your hot water to the bath tub? Via pouring
or pumping....
--
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Ramon Gandia, Nome, Alaska | To deter Spammers, e-mail address
AL7X S/V Seven Stars | is not machine readable. Convert
tel 907-443-2437 fax 2487 | by hand! ----> rfg @ nome DOT net
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