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Old 10-14-2014, 09:55 PM   #1
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Dual Voltage (12v dc / 120v ac) Small Electric Water Heater

Let's give a big round of applause to tecnodave over at the Midnite Solar forum (midniteforum.com) for inventing the dual voltage 12v dc / 120 ac small electric water heater suitable for Sportsmobile use.

TecnoDave had previously mentioned in a post that he was using the "load" function of the Midnite Solar Kid solar charge controller to automatically divert excess pv charging to a 12V dc electric water heater once the house battery had obtained a full charge set point. He replied to a pm I sent him about his dual voltage small electric water heater and this is what he said:

"What is hard to find is a water heater tank that has two standard 1" NPT Threaded openings for elements in a small size form factor suitable for an RV. I used a standard GE brand water heater 6 gallon heater about 17" tall and 13" dia. which I removed the 120 volt 1800 watt element and replaced with a 24 volt 600 watt Missouri Wind and Solar DC element . I removed the drain plug and used a Camco Manufacturing water heater conversion kit which is meant for RV propane gas water heaters as an after market 120 volt 1000 watt heater which can be used togather with the gas. It is a special element and adapter which installs through the 1/2 (or 3/4" with adapter) inch drain plug opening. There are two thermostats.....the original GE which controls the CAMCO element.....and a DC one from Missouri Wind And Solar which controls the DC element. There are two co plater separate circuits for the AC and DC sides.

Every thing is off the shelf 12 volt / 120 volt water heater........nobody markets such a thing but the parts are out there.

I am going to post this as a new posting as folks still have not understood how I am doing this.

td"


Pretty friggin' cool, huh?

Just looking at the homedepot.com website there are some 2.5 and other small point of use electric water heaters which may be adaptable to tecnodave's design.
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Old 10-16-2014, 09:48 PM   #2
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Re: Dual Voltage (12v dc / 120v ac) Small Electric Water Hea

Quote:
Originally Posted by E350
Pretty friggin' cool, huh?

Just looking at the homedepot.com website there are some 2.5 and other small point of use electric water heaters which may be adaptable to tecnodave's design.
Way friggin' cool........need more details, especially using the excess solar to power the heater.

The 24V 600W heater element will be less than 600W when powered by 12V (like 300W).

I'm not quite following why the 120V 1800W element would be removed and a 120V 1000W element would be purchased and stuck in the other NPT hole.....????? If on shore power, why not just use the factory 1800W element? I'm sure there is a reason.
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Old 10-16-2014, 09:58 PM   #3
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Re: Dual Voltage (12v dc / 120v ac) Small Electric Water Hea

Bywonder: Here are the bread crumbs I followed. Search for tecnodave:

http://midniteforum.com/index.php?topic=2108.0

http://midniteforum.com/index.php?topic=2130.0

This is my rudimentary understanding and Quixote2's response in his thread:

viewtopic.php?f=13&t=14718&p=139340#p139340

tecnodave said he would do a write up on it. Let's watch the midniteforum.com for it. I may pm him and ask him to post here also if he doesn't mind.

The 12v dc submersible water heater element comes in three wattages 200, 300 and 600

My guess is that you pick the one which suits the effective wattage of your pv array. So since I have (80 x 4 = 320 watts) I would pick the 300 watt one (because the pv panels rarely operate at full wattage?). See:

http://store.mwands.com/dc-water-heater ... r-element/

I also think the deal is that you can find a 12v dc element which will fit in the 1" ac element port but you cannot find a 12v dc element which will fit in the 1/2" or 3/4" drain plug port -- but you can find 120v ac elements with adapters which will fit in the 1/2" and 3/4" drain plug port.
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Old 10-22-2014, 03:00 PM   #4
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Re: Dual Voltage (12v dc / 120v ac) Small Electric Water Hea

tecnodave just pm'd that he posted his instructions re the dual voltage water heater at midniteforum.com Here is the link:

http://midniteforum.com/index.php?topic=2140.0

Here is what tecnodave says in his initial post on that thread, part numbers are in the posts which follow in the same thread:

"I have made a dual voltage water heater for my motorhome which is primarily solar at 24 volts but can also be powered by the generator or shore power at 120 volts with no voltage conversion or inverter involved.

What is hard to find is a water heater tank that has two standard 1" NPSM (national pipe straight thread mechanical --- the U.S. Standard for heater elements) threaded openings for elements in a small size form factor suitable for an RV.

I used a standard GE brand water heater 10 gallon heater about 17" tall and 13" dia which Had only one such opening.

I removed the 120 volt 1800 watt element and replaced with a 24 volt 600 watt Missouri Wind and Solar DC element . I removed the drain plug and used a Camco Manufacturing water heater conversion kit which is meant for RV propane gas water heaters as an after market 120 volt 1000 watt heater which can be used togather with the gas. It is a special element and adapter which installs through the 1/2 (or 3/4" with adapter) inch drain plug opening. There are two thermostats.....the original GE which controls the CAMCO element.....and a DC one from Missouri Wind And Solar which controls the DC element. There are two complete separate circuits for the AC and DC sides.

Every thing is off the shelf 12 or 24 volt / 120 volt water heater........nobody markets such a thing but the parts are out there.

24 volt power is supplied by load circuit of Kid #1 and 120 volts only from generator but I could run both but no need.

td"

"I did a bit of research on CAMCO to get these part numbers:

http://www.camco.net

Kit is called water heater hybird conversion kit.......two are available

CAMCO Item # 11673. For 6 gallon heater. 425 watts at 120 volt
CAMCO item # 11773 For 10 gallon heater, 725 watts at 120 volts

These are not standard screw in elements......they are shipped with a compression fitting which installs into a 1/2 " or 3/4". NPT threaded opening, with the included adapter fitting it screwed into the G-E water heater with no problem.

Get these at CAMCO site on Amazon for the best price

tecno

I think that the 1000 watt one that I have is old stock and discontinued"

"I am still experimenting with this. Basic setup is load mode=battery, Function = PWM Divert,
Setup = offset -2, width -1----changing setup values will alter the balance with battery charging and diversion.

It takes some tinkering to achieve a balance of topping the batteries off and getting enough power for heating water. I have local coastal fog/cloud cover so I need to tinker this a lot to keep a balance. Some days I shut of diversion to be sure I get full charge. I am way over paneled to accommodate my variable coastal conditions, I live only 6 miles from that big pond------the Pacific Ocean.

Tecno"


Reprinted with permission.

For more discussion regarding the load diversion settings on the solar charge controller, see the continued discussion in the link above.
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Old 10-22-2014, 09:12 PM   #5
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Re: Dual Voltage (12v dc / 120v ac) Small Electric Water Hea

Good stuff. I've been thinking about this quite a bit. Missouri wind and solar sells 12V 200, 300 and 600W elements (and 24V elements, but not useful for me)

I did a back-of-the-envelope calculation the other day and IIRC the 200W element will heat up 3 gallons of water 40 deg F (say from 80 deg F to 120 deg F) in about 90 minutes assuming no heat loss from the water (not reality but gives you rough sizing data).

If one just wants a 12V water heater powered by solar (and you have time to wait for the water to heat up, then you just need a small electric water heater; remove the 120V element and install a 12V element. My panel is 120W so it will take longer than the above calc.

I'm thinking of wiring my solar charger output to a double throw switch. When the switch is off, the charger is charging the house batts. When the switch is on, it heats the water tank. For motorcycle/mountain bike riding, flip the switch when starting the ride and have warm/hot water when you get back 3-4 hours later....may be better than a sun shower.

.....or perhaps a roof mount sun shower contraption that also has the heater element connected to the solar..........

......or add a second panel that just heats the water....

....or...

still thinking
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Old 10-24-2014, 05:18 PM   #6
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Re: Dual Voltage (12v dc / 120v ac) Small Electric Water Hea

Quote:
Originally Posted by boywonder
I'm thinking of wiring my solar charger output to a double throw switch. When the switch is off, the charger is charging the house batts.
Be sure the switch is sized, and don't have an "off" off, I had a switch to turn the readout panel off from before I had solar and when the solar panels were working and I turned it off, it got hot fast. Not sure why but I'm leery of switches in the solar panel system now.
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Old 11-14-2014, 06:06 PM   #7
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Re: Dual Voltage (12v dc / 120v ac) Small Electric Water Hea

Quoted from ZoNiE's recent post on the same subject in the Midniteforum.com

http://midniteforum.com/index.php?topic=2140.0#msg20517

Check out the engine loop for heating the water with the engine while driving, or for us diesel guys preheating the engine before starting:

ZoNiE: "Here is a nice 6 gal water tank. Stainless steel, takes a water heater element, and has an engine loop as well that can be connected to the cooling system on the coach engine or with a hydronic boiler. I had one in my GMC motorhome."





$299 at:

http://www.appliedgmc.com/prod.itml/icOid/518
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Old 11-15-2014, 09:06 AM   #8
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Re: Dual Voltage (12v dc / 120v ac) Small Electric Water Hea

Excellent! keep 'em coming!

I have a basic question about these units that have an engine coolant loop. All modern engines have a coolant temp that is much higher than a safe temp for hot water, and many coolant temps can routinely exceed 212F with a typical radiator cap. How do these units deal with that? Your home water heater is required to have a T/P (temp/pressure) relief valve to prevent them from exploding. If coolant is flowing through one side of these units, what prevents the water in the other loop from boiling/venting/etc?
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Old 11-15-2014, 10:54 AM   #9
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Re: Dual Voltage (12v dc / 120v ac) Small Electric Water Hea

boywonder: Good question. I posted your question over at the midniteforum.com in tecnodave's thread on the same subject, so we will see what their response is.
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Old 11-16-2014, 12:23 AM   #10
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Re: Dual Voltage (12v dc / 120v ac) Small Electric Water Hea

I dont think its the first. My 2001 250 Traverse camper has a built in under counter 12V/120V water heater..

Quote:
Originally Posted by E350
Let's give a big round of applause to tecnodave over at the Midnite Solar forum (midniteforum.com) for inventing the dual voltage 12v dc / 120 ac small electric water heater suitable for Sportsmobile use.

TecnoDave had previously mentioned in a post that he was using the "load" function of the Midnite Solar Kid solar charge controller to automatically divert excess pv charging to a 12V dc electric water heater once the house battery had obtained a full charge set point. He replied to a pm I sent him about his dual voltage small electric water heater and this is what he said:

"What is hard to find is a water heater tank that has two standard 1" NPT Threaded openings for elements in a small size form factor suitable for an RV. I used a standard GE brand water heater 6 gallon heater about 17" tall and 13" dia. which I removed the 120 volt 1800 watt element and replaced with a 24 volt 600 watt Missouri Wind and Solar DC element . I removed the drain plug and used a Camco Manufacturing water heater conversion kit
which is meant for RV propane gas water heaters as an after market 120 volt 1000 watt
heater which can be used togather with the gas. It is a special element and adapter which installs through the 1/2 (or 3/4" with adapter) inch drain plug opening. There are two thermostats.....the original GE which controls the CAMCO element.....and a DC one from Missouri Wind And Solar which controls the DC element. There are two co plater separate circuits for the AC and DC sides.

Every thing is off the shelf 12 volt / 120 volt water heater........nobody markets such a thing but the parts are out there.


I am going to post this as a new posting as folks still have not understood how I am doing this.

td"


Pretty friggin' cool, huh?

Just looking at the homedepot.com website there are some 2.5 and other small point of use electric water heaters which may be adaptable to tecnodave's design.
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