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Review of the SOLiC 200 Immersion Controller

Posted by Chris Rudge on 11 August 2014 at 9:06 am

In the quest to test as many of the current immersion heater controllers that let you use all your excess solar PV generated power, I got hold of a SOLiC 200 immersion controller to try out.

My first impression was that unlike most of the other immersion controllers that are on the market, this little unit was really basic, a box with three lights! No digital display or other high technology to be seen.

Opening the unit, I found a circuit board with a decent set of connection terminals, and plenty of space for manoeuvring cables. One end of the housing is used for cable entry through pre made 20mm holes, plenty big enough for up to 6mm cable. Though the unit is supplied with blind grommets to pop into the cable access holes, you could also use 20mm compression glands, which fit nicely and would hold the cables in place.

On my test installation

The house has a 2kWp solar PV and a 150ltr hot water cylinder. As with many other immersion controllers, the SOLiC 200 needs to be installed by the main consumer unit (fuse box), and have access to the main incoming ‘tails’ from the electricity meter. As you will see from the inside view photo, the instructions are really not needed for the wiring, as all is printed inside, so wiring was simplicity itself.

I needed to remove the Immersion heater feed cable from inside the consumer unit MCB, and extend with another piece of 2.5mm T&E cable to reach the SOLiC 200 location. Another length of 2.5mm T&E cable was cut to connect the SOLiC 200 incoming power back onto the MCB inside the consumer unit. Ensure all Earth connections are insulated and connected inside the consumer unit and SOLiC 200!!

That was it for wiring! Though this installation was a test and cable dressing was not at the top of the list, I had the installation completed in 15 minutes. So easy!

Before switch on the current clamp needs to be installed. The SOLiC 200 current clamp cable is about a metre long and the clamp needs to be clipped around the live incoming cable. If there is enough space, you can do this inside the consumer unit, but outside is easier if you can get to it.

Switch on

Checking the instructions first, I was pleased to find that I just needed to make sure the hot water tank needed heating up, thus the immersion would be heating, and switch the solar PV system off. Switching on, the unit goes through a self check and makes sure you have the current clip the right way. Once a green and red LED are lit, I switched the solar PV system back on. After three minutes the third LED lit up green to show power is being fed into the Immersion heater. That’s it!

I found the unit really easy to install. Though there are no little extras that other units such as the Immersun2 will have, the SOLiC 200 has been designed by a seasoned MOD electronics designer to quick and easy to operate. Once in place, it will be soldier proof! The only user interface control that will get used is a handy 30 minute immersion heater boost button.


The test SOLiC 200 has been running for over a month now during the summer 2014, and has provided a tank of hot water every day from a 2kWp solar PV system. There is no indication of just how much power is being sent to the immersion heater, nor any display besides the green or red lights, but this is reflected in the cost of around £225 for the DIY install. An installer should not charge more than £100 to carry out an installation, as it's so easy.

For people who simply want a ‘fit and forget’ device, the SOLiC 200 does this very well, being inexpensive in comparison to other types. The only thing I found annoying during the installation were the tiny lid fixing screws which are inserted at the ends and easily lost. Other than this, I can see the whole unit has been thought through for minimum hassle installation and low cost.

More information

I missed out information on the alternative operating mode, as I feel this would not get used so much, but you can find all the information on the unit, with stockists at Earthwise Products

More on YouGen

YouGen guide to solar electrcity

More from the blog

Win a SOLiC 200 immersion controller worth £210

The benefits of using solar PV to power your immersion

How to use excess solar electricity for water heating

About the author: Chris Rudge is a qualified electrician who specialises in renewable energy.

If you have a question about anything in the above blog, please ask it in the comments section below.

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12 comments - read them below or add one


sugga12Comment left on: 1 September 2020 at 8:14 am

I see that the Wattson Optiplug with a Watson controller plus does the basic relay function, and compares export with house consumption.  I find very little technical info on thier 'intelligent' control. 

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sarganComment left on: 23 June 2016 at 11:13 am

Read the threads here on ‘Intelligent switches’ plus did a lot of looking around & comparison.

Now you can get dual output, WiFi sender, phone apps, logging, colour LCD readouts … all nice but all really just fluffy stuff.

What I wanted was to divert as much surplus power as possible to my standard HW system .. no need to change immersion or thermostats.

Every £1 you spend on this switch will directly affect how long it takes to repay the investment … after looking at the various models out there, I went for Solic 200

Bought, it arrived next day  (Sat morning) it was simple to install ... I extended existing T&E cable to immersion with one of these:

made the job safe & easy to achieve.

Once wiring complete, Powered system on ... automated setup took less than 2 mins ... and now all working fine.

Can recommend the Soilic 200  .... the only manufacturer I found that is prepared to put a 10 yr warranty on the product - speaks volumes to me

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AitorComment left on: 16 September 2014 at 8:15 am

I already have Solar PV and am going to install a new gas boiler and thermal store.

Can anyone recommend a thermal store?

Also, should I only use one energy source at a time to heat my water, or can I run both concurrently?

If I run both together (with solar via an intelligent controller), the gas boiler will always heat the water faster than the solar, so how do I get the most benefit from the solar?

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paul53Comment left on: 31 August 2014 at 7:28 pm

for  £50 pound  more  you  can  get a  solar immersion mark 5  same  installation  but  with  more  features ,can  send any  excess power  to the  immersion but has  the ability to  send  to  a second  load, so looking for  a  heater  to  use in winter evan if have to  fit  a dedicated  socket  for it. 

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JohncantorComment left on: 31 August 2014 at 9:59 am

I see that the Wattson Optiplug with a Watson controller plus does the basic relay function, and compares export with house consumption.  I find very little technical info on thier 'intelligent' control. 

I'm only guessing, but does it try switching a load, then remember the actual load so in the future it can switch it on only when it thinks there is enough sun. 

Anyone know where a more detailed spec is available?


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Robert Sebley

Robert SebleyComment left on: 30 August 2014 at 7:16 pm

Interested in what is commercially available to divert PV panel output to an immersion heater.  I had a go at making my own device and it has been running now quite successfully for a couple of years with savings to my gas bill.  It basically consists of a small solar panel (normally used to charge caravan 12v batteries) which operates a relay to switch mains power to the immersion heater. My PV installation is 3.76KW so with decent sunshine, for around 2 hours at midday there is enough output to operate the 3KW water heater without any mains power coming from the grid. (providing no big power consumption elsewhere in the house).  I don't understand how the Solic switches off on cloudy days or prevents excess power being taken from the grid for a 2KW PV installation

Happy to supply the circuit diagram if anyones interested.   

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JohncantorComment left on: 30 August 2014 at 3:56 pm

Chris,   Thanks for your thoughts on the Solic 200.   Do you know of a device with relay switch (not a triac) controlld by PV export?   I know that Immersun do this as final stage of their control, but I was surprised to see that there is no hysterysis in their control (just one cut-in threshold).  I want to actually fit something like a Solic 200 alongside a Relay that can switch on a heat pump.     i.e. I was thinking of sensing the difference between house load an PV input (letting the triac immersion take care of its self).    If PV- house load = say 3kw, turn on 2kW heat pump. Hold-on for a duratin.  If there is a net import, after a time period, turn heat pump off.   I do tend to fiddle with OpenenergyMonitor Arduinos and program code, but it always takes AGES loner than planned, so I would rather buy something ready made.      Any tips?  I'm sure there should be a demand for this type of control.  Ideally combined triac device with option to switch a relay as firsts priority control - with hysterysis and time delays     

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dee1kanbiComment left on: 17 August 2014 at 10:21 pm

hi thank you guys for replying. i know that all theses units is for heating the hot water in your cylinder but i wanted to know how we can heat water and pump it to our central heating system. 

i dont have any of these solar iboost, immersun, or solic 200 products but love to have one fitted oneday when i saved enough to buy one. 

anyways thank you again. 



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Ian Smith

Ian SmithComment left on: 14 August 2014 at 9:49 am

In considering the economics of these devices one should bear in mind that one may not continue to get the deemed export payment for the FIT once a smart meter is installed.

There is also an ethical dimension to their use. I know of two PV system owners who have elected not to fit such systems as they will contribute to an increase in emissions.  Prima facie it might seem that one is using emission free solar power to heat one's water but, if the diverter was not installed, and the power was exported, it would displace other generation on the system.  At the current carbon intensity of our electricity generation, the emissions saving from this export is greater than the emissions one would cause by heating the water with an efficient gas boiler.  This consideration will be relevant for those  installing renewable energy systems for climate change as opposed to economic reasons.



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Rudge Energy

Rudge EnergyComment left on: 13 August 2014 at 9:27 pm

Hi Dee1kanbi

The Solar iBoost and Immersun2 fundamentally work the same way as the Solic, though they have more features. 

They are designed to simply divert excess power from your PV to an immersion heater (or other 3kW heating element). They will not be able to work on standard central heating systems, which heat on demand.

However, we do have a few customers who have used these devices for heating storage heaters, which will work... But not in the winter when you really need it to :(


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Caitlin Moran

Caitlin MoranComment left on: 12 August 2014 at 12:24 pm

Hi @dee1kanbi

Although we don't have other reviews on immersun2 or the solar iboost, we do have a blog 'Using solar PV to heat your domestic hot water', which may help you. Chris has also reviewed some other products which are on the market, which you can see in Chris' blogs.

The YouGen Team

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dee1kanbiComment left on: 11 August 2014 at 5:44 pm

Has anyone used the solar iboost and immersun 2? I was to know what extras to these products do to this Solic 200. Does any of the ones i mentioned heat water for the central heating??

please reply

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