Using a Classic with 12V heating element

[Mike W]

I've been reading posts concerning using excess solar energy to heat hot water and I'd like to see if I have it correct for my application.

On our boat in the Caribbean, I'm looking at using excess solar energy to heat water in our two 6 gallon hot water tanks. As we're normally at anchor, I'm replacing the 2000W AC elements with 200W 12V elements. We have three 245W solar panels connected to a Classic150 to keep the batteries charged. Typically by early afternoon we are in Float mode.

I have a DC SSR that I'm planning on driving from Aux 1or 2 in "Opportunity Hi" mode. The collective wisdom seems to be to use Aux 2 for it's PWM mode? My first thought had been to wire the SSR/elements to the batteries but seeing recent posts, I'm now wondering if I should wire to the PV output instead? Are there any changes I should make to the default Aux Opportunity settings?

Thanks for any advice you can offer.

Mike

[dgd]

Do you have an AC inverter connected to the batteries to power the water heaters? I assume you use grid  power for water heating when moored?
Because there are probably not very long DC power cable runs my initial thoughts would be to power the DC water heating from the batteries. Use the ssr to switch them into circuit using aux 2 waste not high
Two 200w elements loading the battery would not bother the Classic. It would be different if you had enough PV to force the Classic to current limit its output = get hot, and to do this had over 1200 watts (100amps at 12v) of DC water heating connected to the battery.
If that was the case then diverting DC power direct from the solar panels, or some of them, would be the way to go placing the ssr at the PV output. This works ok but needs to include a blocking diode before the ssr to ensure no possibility of the classic trying to feed amps to the elements and of course the ssr needs a snubber, fast Schottky diode,  to deal with possible inductive kickback voltage spikes.
(More likely with dump load resistors than with heating elements)

Anyway it's a good thing you want to do, better use free sun power then pay for grid power 

Dgd

[Mike W]

We do have an inverter on board but it's for short duration casual use such as the microwave. The water heaters only have a the 200W DC elements as we'll virtually never be tied up at a dock with access to grid power. (I removed the 2000W grid connect heaters and replaced them with the 12V elements) Where the SSR will be mounted I have easy access to PV output or the batteries.

Is "waste not" the same as "Opportunity"? I'm not on the boat with the Classic a the moment to query the Aux 2 options again.

I need a a way to generate hot water for on baord use, other than running the engines, so hopefully this is it.

Mike

[dgd]

Connect the ssr to the battery or DC power panel via a 50A DC breaker.
AUX2 opportunity may be the same as waste not, I'm not sure, I think it is.  Put the ssr on a heatsink and include the snubber diode

dgd

[audeojude]

I am wanting to convert a old force 10 6 gallon water heater to solar by using it as a dump load from our PV and Wind on our boat.  Where did you find a 12 volt heating element to replace your 110 one in your water heater to act as a diversion load.
scott
s/v Valkyr
Downeaster 38
http://www.downeasteryachts.com
http://www.scottcarle.com/wordpress

[Mike W]

Hi Scott,

Try googling "12V water heater elements" for more possible options. I know The Alt E store (www.altestore.com) has dual voltage elements (12/120) , Missouri Wind and solar (www.mwands.com) has 12V elements in several wattages  as does Mandalay Wind (www.mandalywind.com). You may also find stores carrying 12V elements on ebay.

Good luck!

Mike

[audeojude]

thank you very much