Review of ImmerSUN: using solar electricity to heat water
Posted by Chris Rudge on 27 November 2012 at 9:28 am
This relevant newcomer to the market of power optimisation of solar PV systems seems to have taken off in a big way due to facilities, design and marketing. Certainly this little unit is well packaged and documented.
Unlike most of the other PV power optimisation units currently on the market, the ImmerSUN unit does not need you to install a new immersion element or power reducing device. It detects how much power is being exported and sends that power to your immersion heater.
As can be seen from the photos the ImmerSUN is quite straightforward to fit and install. It simply puts a CT clip on your incoming power cable and diverts the immersion heater circuit through it. This, along with all the other units, is critical. Your immersion heater needs to have its own dedicated circuit. Our electricians have found immersion heaters connected to the boiler or socket circuits, which while it may not be dangerous, does mean they will need to be re-wired to function correctly.
The trade off for a simple electrical installation is the set up! There are a number of calibration processes to proceed through, one of which involves running off some of your hot water to ensure the immersion heater will switch on, though it is all straightforward stuff, it is a little time consuming.
Another feature includes the ability to ‘daisy chain’ up to 4 ImmerSUN units
While the cost of the unit is probably higher than most immersion switch units, its ease of installation and function makes it far more economic. It will cost between £500 and £700 fully installed (depending on the complexity of your installation).
The ideal location for installation is right next to your consumer unit (fuse box) as you’ll need to divert the immersion heater circuit through the ImmerSUN. Your electrician will open your consumer unit and modify the wiring.
The supplied CT (current transducer) clip is simply clipped over one of the ‘tails’ coming in from your electricity meter. This clip will measure the amount of power being exported from the house to enable the ImmerSUN unit to divert the right amount of power to your immersion heater. The supplied CT cable is around a metre long, which will be adequate for most purposes, but can be extended with suitable cable to around 50mtrs if needed.
Could not be simpler, once it's switched on leave it alone and it will constantly measure the amount of power being exported from the house, and divert this to your immersion heater. This could be a few hundred watts to start pre heating the water, right up to a full 3kw, depending on the size of your PV system.We have found from our customers that during sunny weather, they have not needed to switch on their gas/oil boiler at all. The ImmerSUN has provides all their hot water needs.
There are a few features that are available in addition to the basic installation. For electricity only users, there is the option to set up a timer to switch the immersion on, just like the old timer, plus a 1 hour boost function. For other fuel users there are such functions as de strat pump function which will operate the aux relay for operating a pump to circulate water eliminating stratospheric layers in the cylinder.. All clever stuff!
The ImmerSUN is so much easier to install than the other types we have installed, including our own Immersion Switch unit. Though it has a higher purchase cost, you can use your existing 3kW immersion heater, and it ONLY uses excess power.
Being picky, I would suggest the manufacturers could look at options of being able to flip the case around to be able to bring the cables out the top as well. Sometimes it just works better to take cables out the top of a housing.
For those who like a bit more detail:
a standard installation you will have 3 cables to the unit.
1. 16A feed from consumer unit
2. 16A cable to Immersion Heater
3. The CT clip cable.
As you will leave the standard 3kw immersion heater installed in your hot water cylinder, once the above three cables are connected, you are ready to switch on and calibrate the unit for your installation.
Referring to the instructions, you are able to carry out the following one time system calibration:
1. Turn On Heater. The unit is now looking to measure your immersion heater current. You need to ensure the thermostat is on, ideally run off a bucket load or more of hot water to ensure the immersion heater is switching on.
2. Turn Off Inverter. The ImmerSun is now looking to see the direction of current flow to ensure it switches on only when exporting power. This aspect of the setup can only be carried out in full daylight, preferably sunlight, so the ImmerSun can detect a good current flow.
3. If no errors come back, then that’s it!.
There are quite a number of alternative switching arrangements using the auxiliary relay that’s built into the ImmerSUN, but nearly all the installations we have carried out have been basic immersion switching.
More information about solar switching devices from YouGen
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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