Solar twin immersion heater which one to use

[Mashamlad]

We have twin immersion heaters on an unvented cylinder and the bottom one is currently connected via a 4 noks power reducer from our solar panels. It all works well (a number of years) . My question is can I connect the top one too ,or would I be better connecting to the top one . I ask because sometimes (wash days etc) the water temp for showers isn’t that hot.
It’s also come to light after a number of years ( my fault) that approx 50% at time of our generation goes to the grid and we only get 7p per unit back.!
Thanks in advance for any info or suggestions.

 

[Murdochcat]

Run your boiler for a limited periods for hot water during the winter?

Connecting both at the same time will achieve nothing as there obviously isn’t enough surplus energy to heat the tank using 1 immersion

 

[JohnD]

Use as much solar power as you can by heating the lower element.

On days when it is not sunny there will be negligible solar so you will have to top up hot water with your other energy source. Energy from gas is about a quarter the price of energy from electricity.

How do you cause the immersion heater to run on solar power but not on costly grid power?

 

[Mashamlad]

The immersion only works off the solar power (which runs through a converter). Hence the question would I be better connecting to the top element and warming water from the top down or am I better leaving as is and heating from bottom up …or connecting both.

 

[JohnD]

Bottom one.

The top one does not heat water downwards, the hot water will stratify and collect only at the top. It will not heat water lower than itself.

Though I would wire the top one so it can be supplied from the mains, for topping up on cloudy days.