Well, I decided to give it a try. We'll see what happens when Spring comes and
we get a few consecutive sunny days.
I rigged the 800w array to short out and left the 500w alone for now.
(I've been using the back-up AC power and it needs the solar a couple times a week).
I've connected to SSR to the lower heating element, across the 800w PV input.
The DC control input to the SSR is connected to a 12Vdc supply via a 2k resistor.
I have also connected a temperature controller's relay to SSR's the DC control.
When the temperature is below the setpoint (currently 70C), the contact is closed.
That shorts out the SSR input. Zero volts.
But when the water tank goes above 70C, the controller contacts will open,
allowing the SSR to turn on...
It should short the PV out and greatly slow down the heating.
In theory..
