Solar & Earthing

[nitro23456]

Hi guys

Thinking of installing a simple solar system to power my home office (floor lamp, NAS, laptop). 2x 120w panels, mppt controller, 50a lithium battery and inverter. I've done the calculations and this should cover my needs.

I was going to just install and run a new double socket off of this and leave existing mains sockets in place. So basically a new solar powered double socket only.

My question is how do I earth this/does it need to be, as it will be stand alone and go nowhere near the house wiring/CU?

 

[motorbiking]

Inverter is earthed. UPS then comes off the inverter. Its a lot of work for 240w input. Have you looked at boat kits?

 

[nitro23456]

How is the inverter earthed? E.g. does it need its own ground rod/connecting to existing house main earth?

 

[ericmark]

If powering a single item it may be OK to have an IT system, as with a bathroom shaver socket. But in the main with multi-items we are looking and bonding rather than earthing, the problem is a TT system if connected to a TN-C-S system will allow the TN-C-S system to use the TT earth with a loss of PEN, so much depends on the resistance of the TT earth rod, with an earth rod with a 60Ω resistance not enough current will flow to cause a problem. But where I worked we had multi earth rods, so the resistance was less than 1Ω so a loss of PEN could mean 100's of amps could flow, so there was a huge resistor between the PEN and the site earth mats and rods. So with loss of PEN there was a limit to current flow.

I have seen earth wires melt between main house and radio shack with the loss of PEN, but the transmitters earth mat was rather large. With a single earth rod there is really no problem.

 

[bsr]

So in simple language, earth the inverter separately with a rod. Ensure that nothing is connected to both house and solar wiring at the same time.

But...
Most domestic inverters won't run without a grid connection. Will yours? It might be called "Islanding" mode.

Otherwise a canal boat kit is a good idea as suggested above.

 

[martygturner]

A good earth will save your life. Run an earth back to the main earth terminal in the house if its tns or tt ( earth comes from the sheathing of the mains cable as it enters the house or from an earth rod ) if its tncs - ie it comes from a neutral earth, bang in an earth rod.., do not use the house ring. And be diligent about switching the loads between the house circuit and the solar and the potential for a different path to earth for your kit, ie you holding a frayed extension lead..

But really 240w pv system...it would be cheaper and far more efficient to charge a battery off the grid leccy and use that to power an inverter.

I have a 4.5kw system and over winter I am lucky to get 3.5 kw on a bright day...angle of the sun over the horizon, how overcast is it, raining hard , length of day...etc etc I live outside of bristol with a clear sky south aspect. this morning at 9am it was fully overcast generating 730 watts, that's heating a hot water tank at the moment, slowly.

 

[nitro23456]

Thanks for the replies everyone. I think I've decided this isn't cost-effective or worth the hassle.

 

[flameport]

For something of that size, would be far easier to just buy a ready made kit, such as https://www.amazon.co.uk/Jackery-Generator-SolarSaga100W-Adventure-Emergency/dp/B09N8KBRRQ

 

[nitro23456]

But twice the price. Il be ĺeaving it I think.

Solar still doesn't seem a cost effective option.