Having a nice hot shower at the Off Grid Camper

[Dave Thacker]

I don't know everything about Troy's camper, but if it's a normal camper, it's got (or had) a 6 gallon hot water heater. I have had 4 RV's with such water heaters.

I've been wondering if Troy is overlooking a free (energy cost wise) hot shower.

My current camper for work, I have installed an electric probe heater in the drain plug. This is a product as I remember marketed under the name Lightening Rod. When I purchased it, they were available in 2 sizes. I got the smaller one intended for smaller tanks. I've noticed, even though I only got the 600 watt unit, it works just fine and it does not seem to take very long at all. I chose the smaller unit because I use a Honda 2000 generator and I didn't want to have to shut down the water heater to run the microwave or to let the refrigerator run on AC from the generator. Seemed like the smart thing to do at the time and I've been happy with that.

I have observed in a number of video's Troy mentions the nice charge controller from Arizona Wind and Sun has gone into "Absorption" charge mode fairly early in the day. Once the batteries are full, the rest of the energy above his needs is lost since he can store no more. In other words, this excess energy is not supplying any services, it's totally wasted.

Hey, sweep up all those messy electrons you're littering the land with!

So, I got to wondering:

How much energy is required to run the 600 watt heating probe?
How long would it have to run?
How many amps will this pull out of the battery bank if any?
How long will it take for the battery bank to recover?

So, lets get to calculating.

A single BTU is what is required to heat one pound of water and cause it to rise 1 degree Fahrenheit.
Water weighs about 8.34 pounds per gallon.
The 6 gallon heater contains 50 pounds of water (maybe a little less as some of it may be expansion chamber volume)

If we start at 70 degree and want to raise it 40 degrees to achieve 110 the math is like so:

50 pounds of water X 40 degrees temp rise = 2000 BTU's required.

A google search shows:

There are 3412 BTU's per 1000 watt hours or 1KWh.

2000 BTU Required /3412 Per KWH = 58% of 1000 watt hour or 580 watt hours. Or, one hour with a 580 watt heater.

Our 600 watt hour (600wh or .6kwh) heating element should increase the temperature of our 6 gallons of water in the tank 40 degrees in just short of 1 hour.

If we only shower on a sunny day, and we only shower after the charger reaches absorption mode, we can use the entire wattage of the solar panels to heat the water.

How many watts does Troy have? I'm not sure. But, lets say he has 400 watts for our calculation.

The difference between 600 watt demand and our 400 watt available supply is 200 watts. 200 watts at 12v is 200/12 = 16 amps.

Now in reality, he may have a few more watts and I'm not accounting for losses in the wiring and inverter. But suffice it to say, I am very confident for the 58 minutes Troy would have to turn on the 600 watt heating probe in the water heater, he'd be pulling no more than 20 amps out of his battery bank. 20 amps at 12v over one hour would be 20x12 or 240 watts net battery charge loss heating the water. 240 watts is .24kwh of energy.

If he has 400 watts going in from solar, this would mean when he turns off the heating probe, the charge would be returned to the battery bank in 240/400 of an hour or about

If his battery bank is 400 amps (Iforget it's size also). 400 amps x 12v = 4800 watts or 4.8kwh of capacity.

Using .24kwh of energy above production of power would drian his battery bank 5% (.24khw / 4.8kwh = .05 or 5%

Time to recharge after turning off the heating element is 240 watts lost / 400 watts input = 60% of an hour or 36 minutes.

Troy, all you need is a 600 watt lightening rod and you could be taking hot showers. No need to scream in that ice cold creek any more.

[Dave Thacker]

Here is the 1000 watt unit from Camco listed on Amazon. I'm still looking for the 600 I have.

http://www.amazon.com/Lightning-Rod-Wat ... ank+heater

[Dave Thacker]

Here it is again??? Might be the smaller one, the probe looks shorter than the Amazon listing. And it's cheaper. Anything on Amazon is available 10-15% cheaper elsewhere if you dig. The commission to Amazon is 15%. Don't buy there and you don't pay it.

http://www.adventurerv.net/hott-rod-ele ... -1163.html

[Dave Thacker]

I was spelling it wrong. It's actually "Hott Rod". Here is the companies web site. It seems they've changed the product over the years. I remember them beeing 600 and 1000 watts. There are 450 watt and 675 watt versions now. You'd be fine with the 450. Would be close to running on your wasted solar overage, battery neutral.

450 watt part number HR6 (Intended for 6 gallon tanks)
675 watt part number HR10 (Intended for 10 gallon tanks)

http://www.hott-rod.com/

[Dave Thacker]

I'm having my memory refreshed as I continue to research links. There are two brands. The other one is "Hot Shot Lightning Rod". I see one on ebay with free shipping now for 69.99 This is the brand I have installed in my camper. The seller gives you the choice between the 425 watt for 6 gallon heaters and the 625 watt unit intended for 10 gallon units.

Here is the search string link:

http://www.ebay.com/sch/sis.html?_nkw=H ... t+110+volt+

It would be really cool if a fella could get a second bung fitting welded to the tank so you could run both the 110v heating element and stil run a anode rod plug at the same time. I've not run the anode in mine for years. I notice there are some cool anode rod plugs that have a built in drain. This would be great for winterizing. Something your not going to be doing.

[Triffidtraps]

In the UK they do a 12v immersion solar/wind immersion heater element. Which can be used to heat water in a standard water tank after your solar panels have finished topping off your batteries they can then be used for hot water. They start at just 150W up to 1100W a very useful way of using idling solar power which would be wasted.

[Dave Thacker]

Stick up the link. My search saw a few elements for 12v house type heaters. Nothing that small. Im seeing several off griders missing out on collecting this waste solar. Troy's system is pressurised. Lots of enegy lost to the ether........

[Triffidtraps]

Hi dave here is a sellers on ebay that does the 12v solar/water water heater elements. If you look at the listing priced £54.95 he lists 15x different sizes

sellers here
http://www.ebay.co.uk/sch/i.html?_from= ... ON&_sop=15

They start at just 150w & go up to 1100w depending on how much water you want to heat & how much spare solar/wind power you have available depending on your system.

If troy has spare solar power each day aftyer topping off his batteries he could use the spare solar power to make some free hot water.

[techman]

Hi guys,

I am thinking about using the sun to directly heat water for showering and maybe assist winter camper heating.

I removed the old electric hot water heater. It was defective and you could never run it off solar. Pulls too many amps.

I may use some black pvc hose out in the sun to heat up water in the summer. Lets see how that goes.

There is a nice propane hot water on demand heater for about $150 but then I need propane all the time.

I might also use my fireplace to heat water, but then in summer that is not nice using heat inside.

I may set up another fireplace outside with the only purpose of heating up shower water. Then run it into an insulated tank to shower with.

[Dave Thacker]

Solar hot water really is only practical with an insulated hot box with black tank inside, glass top, underground plumbing. Having water in black pipe or tank outside will give you a warm or hot shower, however, it's not a real off grid solution because it's not useful year around. Probably all the black pipe you see (if it's plastic) related to the swimming pool could have been a coil for on - roof solar heating of a pool.

You mentioned the electric water heater you had using too much energy. The energy is fixed, you can't use too much, the relationship between watts and heat is fixed. The solution I provided above is sustainable, year around and using waste you are tossing out. Try to find a free RV water heater in a camper being tossed out. Even if the propane side of it is bad, you would still use it with a heating probe. There is many reasons and long conditions of the market place that have established what an RV water heater looks like. Get yourself one, it's a very good highly engineered and thoroughly tested solution. You need more reliability in your systems, less complexity. This is the nexus of genius. Simple, effective & reliable.

Dave