ewarnerusa wrote:

StirCrazy,
It has definitely crossed my mind from the start of this little project. I admit that I have been hoping that the 6 gallons of water as a heat sink will never be able to reach the blow off valve setpoint with this diversion load. Assuming I am leaving the propane water heater burner off. But if the diversion load gets disconnected, then I have all my panels directly wired to the batteries with no control. Which scenario is worse?

I also don't know why my sig won't show up? The box is checked.

pianotuna wrote:

Hi temp:

https://www.amazon.ca/010832-Black-High-........mperature-Shrink-Tube/dp/B001HYQQ9W?th=1

Thick wall construction and remains flexible

Operating temperature range: -67°F to 275°F; apply at 120 to 180°F using heat gun

ewarnerusa wrote:

Success and failure today in a test run in the driveway. Nice clear sunny spring day.

I had spring fever so I dewinterized last night. Rinsed and filled fresh water system. It got down to 45F overnight and I'm assuming water started at that ambient temp.

Batteries were in 14.5V absorption by mid morning. All seemed well, but the wires got quite hot where they terminate at the element. This was with <10A current from the panels, well below the 300 watt rating. I confirmed that the element was not drawing from the battery.
I noticed the warm wires during bench testing, too. Wires feel progressively cooler the further from the element. The 8 gauge wiring I put in for supplying the current did not get warm. The heat shrinking around where the wiring terminates at the element started giving off smoke. I kept an eye on it and after 15 min or so it stopped smoking. What was once rubbery is now brittle.


I saw a max of 21A from the panels. I didn't have the laptop running at this point to see what the SCC said the diversion current was. I'm kicking myself for not putting my clamp meter on the wire at the element, but my hunch is around 19A. By early evening the water was hot! I measured 117F out of the kitchen tap.

But unfortunately the wiring looks cooked and I don't really trust it now. It needs some kind of high temperature heat shrink reapplied first. I just broke away the brittle stuff that was formerly the heat shrink and this is what is beneath it.

ewarnerusa wrote:

Yes, the element says "12V 300W 22-12"
The insulation on the unit I have was white. I'll repost a pic from a page or 2 before this one. To show the writing and a better look at what the insulation looked like before it was cooked.

StirCrazy wrote:

...so your hot rod is rated for 12V and I didn't see a +/- range on the website. how much voltage were your solar panels sending to the heater?...

ewarnerusa wrote:



I have also wondered about the voltage at the diversion load. When I connect to the SCC via laptop, the software provides me a diversion load current measurement as well as a load voltage. The current value is consistent with what I expect based on the other meters I have (one on solar array output, another bi-directional one on primary battery connection). But the load voltage confuses me as it is fluctuating at levels well below 12V and I wonder if it is not what I think it is? I have not taken a multimeter to leads, although now I have some wire exposure to take a measurement from!

During my test run, the element wiring began to feel warm as soon as diversion current began to pass to it. And it began to "cook" when there was <10A of current. This seems like well below any scenario where there could be more than 300 watts of power. The panels' open circuit voltages are 22.4 and 24.3 (2 different types of panels), so it seems to me that there isn't a V*I scenario that exceeds 300 watts.

In diversion load configuration, the wiring is for the panels to be directly connected to the batteries rather than to the SCC. The SCC leads that were formerly array input become diversion load output. A diversion load configuration is applied and DIP switches must be changed on the SCC.