Solar to Power the Water Heater?

I am preparing to enter ‘old age’ a little later this year and, while cold showers are wonderfully beneficial – I wrote about them here, the last few have convinced me that I ought to think about a heater to warm up the water. I think I may be on the edge of heart attack with each one so I better start thinking about avoiding that.

While parked with shore power, heating water is not a problem. Missy’s eleven gallon Kuuma heater does a fine job. The problem I have is when boondocking – without shore power.

There are no shortage of options but there are a shortage of options that I like! A solar water heater is one, a diesel fired hydronic/water heater is another. The original plan was to use a diesel fired hydronic heater and the engine to warm glycol that heated the water in the hot water tank – or be connected to shore power. I’m now steering away from hydronics for Missy.

Having experimented a few years back with solar water heater with my hot tub (here and here), I can tell you first-hand that the sun will most certainly make water hot – scolding hot. In fact, the problem that I had with my experiment is that the water was too hot and all my tubing and fittings were too cheap to handle it over the long haul (so they leaked, cracked, broke, etc…).

For Missy, I was thinking of one of these professionally made SW-38 solar water heater panel/collectors.  Then using some quality pipe down to my hot water heater that has a built in heat exchanger.

I still have this solar water heater controller from the hot tub experiments. It monitors the temperature of the water in the tank and in the collector and then enables the water pump when appropriate.

Missy doesn’t really care about the little bit of weight (possibly as much as 50 lbs including glycol?? – just guessing) that it will require or the little bit of electrical power required to run the water pump.

It is all pretty simple. However; I do not like creating things that require maintenance or babysitting and that’s what I’m afraid of doing. Whenever I start experimenting with liquids, I seem to end up with leaks. That is the reason I am loath to cut into the engine coolant system to connect to the heat exchanger in the hot water heater. Ignore the fact that I already have a coolant leak back there… 🙁

Another possibility is to simply use the existing solar electricity to power the water heater. To do this, I would need to connect the Kuuma hot water heater to the 120 VAC load center, install a switch, and let Missy’s electric solar panels and battery bank provide the power to heat the water.

Since I like simple (and inexpensive), I decided to try running the water heater from inverter this past weekend.

This required a bit of rewiring. The water heater power cable had to move from the #2 leg of the 50 amp shore power system to leg one – which is powered from shore power or inverter. That was a quick and easy task though.

To control when the heater is on, I installed a 25 amp solid state, 120 VAC relay between the 120 VAC distribution panel to the water heater. This relay was mounted to a steel rail in the basement – to act as a heat sink – and connected to a switch in my electrical cabinet in the house.

I flipped the water heater switch and the inverter and solar panels came to life!

The solar panels producing 50 amps at 24 VDC (double that for 12 VDC), the batteries were discharging at about 5 amps (at 24 VDC). The water heater worked for about an hour before having the full eleven gallons up to temperature. The 120 VAC relay and surrounding metal was warm but certainly not hot.

What else could I do but jump in the shower?!?!

Ahhh – it was a wonderful HOT shower!

I think I have found my solution for hot water. For me, it is far easier to work with photoelectric solar panels – even install more of them – than it is to mess with plumbing water to the roof. Of course, the current solution requires a good bit of sun but who wants to take a shower on a cloudy day?!?

I updated the electrical system diagram on the Electrical System Design post but here it is again.