Dual Voltage Water Heater. 12/24/120volt

[tecnodave]

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

[xsnrg]

Nice setup!  I am thinking about doing something like this, not for hot water, but for some extra heat in a shop with a loop of copper tube and some fins with a small pump/thermo to circulate. 

What setting on the KID are you using for the load?  Ideally, I would like to pull any extra juice from the panels that I can once the battery bank is floating, and send it to the element.  I do also have a load directly on the batteries (small) so it would be nice to favor keeping the bank topped off at float voltage while moving everything extra from the panels to the load terminals.  I haven't played with the settings for the load terminals yet enough to know if one of them would work this way or not.

[tecnodave]

@xnrg,

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

[tecnodave]

To all,


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

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.   <$70.00 for either. They are physically same size

tecno

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

Edited for addl info.

[Vic]

Hi td,

Neat idea.    Camco has a lot of useful and interesting products.

Poked around a bit and found this in the Camco site:
http://www.camco.net/Products/Item?prodID=10812#.VEf4g2d0zrd

Did not look on Amazon.   Thanks  for a great solution to a pesky problem.    Vic

[tecnodave]

Vic,

That is the kit.......gotta search because they call it "hybird heat" and searching for heater elements does not turn it up.  I have had some industrial heater elements that were 3/4 " NPT but that company has vanished. Does a real good job on those days when fog is too thick to get a full charge, running gen to top batteries tops off the hot water at the same time.

td

[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.



http://www.appliedgmc.com/prod.itml/icOid/518

[E350]

tecnodave and ZoNiE:  We have a parallel thread following this thread over at the Sportsmobileforum:

http://sportsmobileforum.com/viewtopic.php?f=14&t=14762&p=141663&sid=0fa799b515345c53f2b35ddaa8a45517#p141663

where boywonder posed this question:

"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?"

So what about this issue?  Can the engine overheat the waterheater and cause bad things to happen?

[Taos]

These heater core can operate at higher temp without boiling is they use antifreeze which protects agains freezing also raises the  boiling point and since the system is pressurized it raises the boiling point further and the protection against too much pressure in the system  is the radiator cap as it has a pressure relief built into the cap.

Don

[E350]

Emerson EH-1 Dual Voltage Water Heater posted on sportsmobile forum:

http://tapatalk.imageshack.com/v2/15/01/14/80c144375a48d6002fb18aa5888e2c2a.jpg

http://c.searspartsdirect.com/lis_png/PLDM/00024610-00001.png

[1der]

Resurrecting this thread as I am doing something similar for camper van and wanted feedback from those who have already gone down this path.  TIA 

What we have:
The KID, 300W panel, 400Ah battery bank/ 12 volt system
Over night draw down is usually 30 to 40 amps or so/ 92 to 90% SOC (temperarture adjucxted)
Running items during the day are Fridge, water pump, etc.  ~ 4 to 5 Amp per hr avg.

Desire is to utilize the extra 10 to 15Ah of available solar to heat water using the Load feature.  My batteries are usually topped off or at least tapering by 10:30/11am

Water Heater
Isotemp SPA 15:  High efficiency/temperature Marine/RV 4 Gal w 750w/120v heating element utilizing a mixing valve.
Mods to water heater:  Planning on ADDING a ~220W/12v Tubular/Hairpin immersion heating element with its own thermostat.  OEMHeaters can make this element to my spec.  It will be mounted in the existing water heater flange by drilling two new holes. Why 230w vs 300w? - The 300 watts would optimally want 100% output from the Panel, a rare occurrence.  A 220w element will be 40% more efficient than a 300w element at around 13 to 15 amps, which is what I would expect 75% of the time.

I will connect this element to the Load Terminals of the KID and use HighFlyer's settings:  PWM Divert and an offset of -.8 and a width of .5,  and will have a 30 amp breaker in this circuit.  The wire run is about 7 ft, looking to use 10ga (or maybe 8 ga).

I expect I will be able to raise the water temp by 40 to 60 degrees just by using the solar feed.  With the excellent insulation of the water heater and ability to achieve 140 to 160 degrees, there should be enough hot water for our limited usage.

I am super interested in what you have experienced with your set-ups and opinions/advice on what I have planned above.

Thanks!  Ray





 

[tecnodave]

Ray,

I would use an off the shelf heater element and use the load feature of the kid to control the maximum current you want to divert to the water heater, it can be set to whatever you want and get 200 watts from a 300 watt element without a problem. You will need to tinker with the PWM values a bit to get the proper minimum charge for your battery.

I switch my systems around a lot and now I am using Trace C-40 controllers in diversion mode which is controlled by a relay from port 1 of the Classic which switches pots on the C-40......the C-40 has analog pots to set the charge set points and I have a patch panel with two sets of pots, one for Classic in control, one for standalone...usually set high as a dummy value so the C-40 does not operate unless controlled by the Classic..........patched into the C-40's..too complicated but I want the Classic to be the master of the system and the Kid as helper

I am way....way....way....over paneled....nearly 5kw. For the RV and shop , that big pond the Pacific Ocean is 6 miles away so I get really dynamic weather and no direct sun for days at a time but I still have enough power that I have not started my Onan generator in over a year to charge batteries.

My biggest problem is having too much power in full sun so I am using 3 diversion systems, a C-40 diversion controller on each Classic driving a 600 watt 24 volt element....plus direct PV diversion using a relay on the one Classic using 105 volt strings of 72 cell panels....voltage rises on adsorb to 112 volts and makes Classic work harder than it should. connecting a 1250 watt 120 volt element across PV in brings down the voltage to 80-90 leaving plenty for the Classic to top off the batteries. If I have extended heat spell I turn off strings of panels to keep the voltage from raising too high.

I'm using a 12 gallon standard tank water heater with a side tank ( custom made) which has 6 threaded holes for standard water heater elements plumbed directly to the main tank using hot out and drain fittings for circulating loop.

My RV is not a down the roader.......it's an early 80's 454 carbureted gas hog that is living out its life's in the Santa Cruz Mountains as a movable house......the county building department has no authority over a state registered motor vehicle........walla.....no permits required!   Haha 5kw.  solar and no government say so!

I am unaware of the type of heater that you want to modify but if you modify there goes the warranty

I think high flyer and I were doing the same thing with the Kid but the issues I have is my system is so large I wanted the master controller to be in charge and multiple controllers in any system is tricky.
That is the base reason why I have twin systems.......much better control....I can connect both systems together when I run big loads such as mig welding for long time.....but I always separate the systems so the batteries can recover. And my battery sets are not matched by any means.  I just could not pass us 4 Rolls-Surette S-530 L-16's for $20.00 /set. 

Let me know how it's working out.....I'm going to buy one of the 24/48 volt elements from NAWS to replace the smaller ones I'm using now....they have two elements in one housing.....I'm thinking one on each kid.........the Kid measures current on the negative wire so the element return must go to the load terminals of the Kid.....not to ground! Otherwise the Kid will not know the diversion current and can't regulate

Td

[Highflyer]

1DER,

I would agree with T Dave that you should use a standard 300 watt 12 volt DC element.  They are easy to control with a Kid.  Go take a look at the "load" section of the Kid and see if you understand the load limit (it is adjustable).  If you do, set it to 13 amps and move on if that is the limit you want to set.  It is that easy.  Further, In PWM divert, if your settings are right, the batteries get the power first and the rest of the power is available for the load. 

I would use a 300 watt 12V DC element, set the load limit to 30 amps and set the PWM right and move on.  Don't make this more complicated than it needs to be.  The kid will prioritize the power as you set it up. 

Ryan calls this a "waist not" mode.


BTW glad to hear you are going to add a thermostat for the Kid powered heater.  Mine are heating a 700 gallon Tilapia system in the barn, and if I was not there to turn it off at times, lunch would have been served.  I am however using a few more panels and heaters than you 

[russ_drinkwater]

You could run the exhaust pipe of your backup generator through the middle of your hot water tank for freebie heating of the water
when using geny!
Can use the same idea if you have a wood burning stove. Run the chimney through the hot water tank. Sealed pipe of course.

[CDN-VT]

normal don't run :chimney through the hot water tank..

I run a seamless / extruded SS 318 pipe SCH40  bent to the top exhaust of the stove . My first one was the same but in the fire box in 1965 , 2014 unit is out of wood hit's . This is for an Airtight wood stove , and then we have Boiler rules & then EPA .

the norm is to make you PAY taxes for usage or they regulate it to skim cream.

NO FREE HEAT !!
Like the Dual Voltage Water Heater. 12/24/120volt !!!!

VT