Immersion solar controller switch

[Scobo]

Morning guys, first post here so please be gentle.
We had solar panels fitted recently and I bought one of these to control our immersion automatically when the panels generate enough power ... http://www.reuk.co.uk/Water-Heating-with-Surplus-Solar-PV.htm
Unfortunately, our electrician has failed to show up 3 times to fit it.
So I'm thinking of having a stab at it myself as I have some basic knowledge of electrics and have fitted new sockets and light fittings myself in the past.
My question is, can I fit it in parallel with our existing timer switch and if so, does it have to be on the same feed from the consumer unit or can I use a separate feed from a socket ?

 

[bernardgreen]

That controller does not detect that that the panels are producing surplus energy that can be used for water heating. It detects that the sunlight is above a threshold level and assumes that there will be spare for water heating.

The spectral response of the light dependent resistor may not match that of the photo voltaic panels so may in some weather conditions give false indications that there is surplus power

 

[Scobo]

That controller does not detect that that the panels are producing surplus energy that can be used for water heating. It detects that the sunlight is above a threshold level and assumes that there will be spare for water heating.

The spectral response of the light dependent resistor may not match that of the photo voltaic panels so may in some weather conditions give false indications that there is surplus power

Yes, I understand how it works and I'm aware of its limitations and that it won't be as accurate as a CT based controller.
This is just a cheaper alternative I found to some of the more expensive controllers until they come down in price a bit and it's had decent feedback.

 

[Scobo]

Edit : Before I posted this there was a post from someone else about a similar product which appears to have been deleted possibly as they were advertising their own product.

Thanks but I already have a power reducer fitted to lower the power of the immersion to 1.4kw and the controller is now fitted also and working great.
Total cost of the parts was £80.
A neat tip I got from another forum was to place the light sensor over the LED of our import meter. The controller now switches on the immersion whenever the LED is solid red meaning we are generating more than we're using.
I've monitored our usage for the past couple of weeks and its saving around 2 kwh a day on average.