Strange happenings with my solar setup?

[edina]

I'm using mine as a dump load.
Basically the load out of the charge controller is set to be on if the voltage is between 14.4v and if it drops below 12.6v the load switches off until the batteries recharge to 14.v again and so on.
All the load out does is switch a relay on so the direct current is then taken from the batteries.
When it was first installed and I had 20v showing coming in at the panels it would hold its own and heat the water. Then in approx 50mins the thermostat on the boiler would kick it off regardless of the voltage. Now as soon as I put the load on( bear in mind I'm in the south of France at the mo) the voltage "COMING IN" at the panels drops to approx 15-17v.
As said before this did t happen a few weeks ago back in sunny Wales?
G

As you are in hot temperatures are you opening your roof vents fully? If a roof vent casts a shadow on the panels the voltage wiil drop. Easily tested.

 

[yeoblade]

At higher temperatures the panels become less efficient and voltage drops, maybe.
I like the options on your controller with the effective use of the excess power

 

[gypo]

Good point about the roof vent being open, I did think of that. However this started a couple of weeks ago back home, but yes you are right it does affect the panels if the roof vents are open over them.
Thanks for the heads up all the same tho.
G