Identifying which cable

[andyv1]

I'm installing a diverter to send surplus solar electricity to my immersion heater. The best location for this is in my garage, but I have to identify which cable to splice into. I can find the cable at the fuse box but it then turns into a mass of cables in the loft which are not labelled.

Is there a short cut to working out which cables are which without disconnecting everything at the fuse box? It's a 2.5mm2 cable and there are at least 8 or 9 alternatives to choose from.

Thanks for any advice.

 

[EFLImpudence]

Is that allowed?

If it is and you are competent to do the work then I think you should know the answer to your question.

 

[JohnW2]

Is that allowed? If it is and you are competent to do the work then I think you should know the answer to your question.

Yes, both those points occurred to me, too.

I also wondered how on earth one could divert just 'surplus' solar power (whatever that means) to an immersion heater.

Kind Regards, John

 

[PrenticeBoyofDerry]

Is there a short cut to working out which cables are which without disconnecting everything at the fuse box? It's a 2.5mm2 cable and there are at least 8 or 9 alternatives to choose from.

Not foolproof, but isolate all circuits but the immersion circuit. You will need a non-contact voltage stick/pen. Then you can test each cable individually for voltage. but make sure you have the cable being tested a good distance from the rest. Once you pick up a voltage, you then turn that circuit off, test again this time for no voltage. Then turn all circuits back on, other than the immersion and test that it remains dead!

Then hopefully that will ID the circuit, but when splicing into it, again isolate all circuits. Then once spliced, you can then do an r1+r2 on it, to establish you have the correct circuit!

 

[PrenticeBoyofDerry]

Yes, both those points occurred to me, too.

I also wondered how on earth one could divert just 'surplus' solar power (whatever that means) to an immersion heater.

Divert by using a power diverter, simples!
I do not believe there is anything illegal, in exporting surplus PV energy!

 

[JohnW2]

Divert by using a power diverter, simples!

That much was apparent from what the OP said What I'm less sure of is what constitutes 'surplus' solar power and how one (or 'a diverter') can 'divert' just that component of the total amount of solar power being generated.

Kind Regards, John

 

[PrenticeBoyofDerry]

Surplus energy is the stuff that is not used up and goes back as part of the FIT. But it is not a requirement that all surplus energy is returned via FIT.

Edit: But it can only really be used efficiently to heat water.

 

[Iggifer]

There used to be a device called an Immersun that did this exact job. They've recently gone out of business but there's others. Think that's what I'd do if I was getting PV now with the rubbish FIT

 

[Adam_151]

That much was apparent from what the OP said What I'm less sure of is what constitutes 'surplus' solar power and how one (or 'a diverter') can 'divert' just that component of the total amount of solar power being generated.

Kind Regards, John

Its just a unit with a contactor, which switches the immersion circuit on when there is sufficent generation capacity to run the water heater (and whatever other base load there is) without drawing load from the grid. Which it'll probably works out from a CTs around the supply tails / and connection to the inverter, John

 

[JohnW2]

Its just a unit with a contactor, which switches the immersion circuit on when there is sufficent generation capacity to run the water heater (and whatever other base load there is) without drawing load from the grid. Which it'll probably works out from a CTs around the supply tails / and connection to the inverter, John

Thanks. As you imply, that's not a trivial exercise, but definitely do-able! However, in terms of what the OP has asked, it could presumably well require connections to things (e.g. CTs, as you mention) would not be available if one just 'broke into' the cable (in his garage).

Kind Regards, John

 

[Adam_151]

Actually, I've just looked at the Immersun unit mentioned, and there is even more to it, that one seems to modulate the current drawn by the water heater (and in a true sine format - which I wondered about.... the heater would not care a jot if it was a chopped up waveform.... but the inverter on the geneation, might? - I don't know.... I presume there is a reason they have gone to teh expense of making the output a true sine wave)

 

[JohnW2]

I presume there is a reason they have gone to teh expense of making the output a true sine wave

I suppose there must be some reason but, like you, I wouldn't have thought that a heater element would care a jot about the waveform - it would even be happy with DC!

Kind Regards, John

 

[JohnD]

seems to modulate the current

Are you sure?

Surely it reduces the voltage. Like an older dimmer switch.

I have an iBoost, it cost me about £200. It controls its output voltage to the immersion circuit such that about a quarter or half a kW is exported. If less, it cuts supply to the immersion. If more it increases the voltage towards the 240v available.

It is not an off/off contactor.

Bearing in mind that in summer I normally heat the cylinder with my gas boiler, and in summer the cost of gas used is about 16p per day, it's an interesting curiosity, but really not an economic proposition. Consider how many sunny summer days it would take to repay my investment.

If you lived in an all-electric house you might as well install a timer to heat your cylinder around noon every day, rain or shine, and save £190; or just operate your appliances, one at a time, during daylight hours, to use whatever happens to be available.

 

[Lectrician]

That much was apparent from what the OP said What I'm less sure of is what constitutes 'surplus' solar power and how one (or 'a diverter') can 'divert' just that component of the total amount of solar power being generated.

Kind Regards, John

Domestic solar installs receive a payment based on a percentage for energy sold back to grid. This is above and beyond the money paid for generation via the generation fit meter. As this surplus is not metered by an export meter on domestics, using it makes sense.

There are devices which monitor the current in your tails. If a back flow occurs, it directs power to your immersion. These devices also alter the voltage of the immersion, to accurately divert the energy to closely match the back flow.

The device is meant to go as close as possible to the immersion, a wireless connection used to the tails monitor.

 

[Echo the husky]

it would even be happy with DC!

The rod stat might not be so happy though!