Usually, there is a Henley block in place (after the utility meter) that allow multiple CUs to be connected.
No. That's uncommon.
It goes back to the days when homes had a separate off-peak meter.
We always had it, it is very useful.
We had multiple changes made over the years and never had a visit from the DNO for it. 1) EV charger 2) new kitchen unit 3) replacement of old board 4) rewire of old kitchen unit
Clearly the DP isolator is needed only if there's no henley box or your sparky is not used to work with it.
My suggestion would be to only show an (optional) earth on the new consumer unit to the left.
I have not seen regulations specifically for an off-grid system, I just follow what the DNO requires. But unless the normal earth is always available, a new one will be warranted for any off-grid/UPS use (if you plug it next to the grid input, it may help the rest of the local grid - but how can it be sized?). For an end user, the most important about following regulations is safety of their own installation.
It seems the wiring is simpler with the Solis, and there's no need to touch any MCB or switch around power outages. In my configuration, most circuits also work through grid faults.
Essentially with the Solis S6:
the grid port is used for export (even if it could feed some loads)
the backup port to feed UPS circuits on a CU
the smart port can be used as a lower priority backup or to connect a PV inverter
16kWh Seplos Fogstar battery; 8kW Solis S6-EH1P8K-L-PLUS hybrid inverter; Ohme Home Pro EV charger; 100Amp head, HA lab on mini PC
Certainly worthwhile considering Geya. They're a reputable Chinese manufacturer.
But not the left-hand of the two breakers because it's single-pole.
I'm unsure if it's clear from the photos, but these are centre-off switches.
Have you experience with using these manual change-over switches @batpred ?
Yes, the one I use is 125Amps double pole. Top powers the inverter, middle=off, bottom=connect backup loads to grid
I have not found a Geya consumer unit, so I guess it is amber on the regs...
Making sure to get the CU, switch, MCB and RCD from the same manufacturer (when having a powerful inverter) is a problem that most sparkys do not see as theirs. Of course the compliant solution may be lots of boxes under the stairs.
It may meet the regs but means the end user can have some additional trouble getting the lights back on. It can only become even more "interesting" when renting and talking to a property management agency...
16kWh Seplos Fogstar battery; 8kW Solis S6-EH1P8K-L-PLUS hybrid inverter; Ohme Home Pro EV charger; 100Amp head, HA lab on mini PC
For your PME (TN-S) supply the earth to each property is provided via the neutral wire. Your house earth connects to the Neutral at the Service Fuse.
The Neutral is itself tied to earth in the 'centre' of the substation transformer windings.
That doesnt seem quite the same description as the one here from the IET which says
"A TN-S system, shown in fig 1, has the neutral of the source of energy connected with earth at one point only, at or as near as is reasonably practicable to the source, and the consumer’s earthing terminal is typically connected to the metallic sheath or armour of the distributor’s service cable into the premises"
They provide these diagrams of which the second pretty accurately represents my arrangement. What Im struggling to understand is why this needs to change with an inverter, given that there is already a local earth point.
My supply is listed as TN-S on the most recent certificate I have, earthed via the 'suppliers facility'. From visual inspection that looks like a ~3mm twisted bare cable attached to the metallic outer sheath of the incomer
and had assumed that you were querying the designation of TN-S on the certificate, and the quality of the earth due it being merely 3mm of bare twisted metal.
I therefore jumped to the (incorrect) conclusion that the earth wire provided from your Service Fuse location was actually TN-C-S.
If your electrician is happy that the earth provided by the DNO is within resistance specification, then you shouldn't add a separate earth.
The earth wire in the mains supply cable would be sufficient, even if the inverter was working during a power-cut. That's because it remains connected to the grid earth, whilst using its internal 50Hz oscillator in 'off-grid' mode.
For your PME (TN-S) supply the earth to each property is provided via the neutral wire. Your house earth connects to the Neutral at the Service Fuse.
The Neutral is itself tied to earth in the 'centre' of the substation transformer windings.
That doesnt seem quite the same description as the one here from the IET which says
"A TN-S system, shown in fig 1, has the neutral of the source of energy connected with earth at one point only, at or as near as is reasonably practicable to the source, and the consumer’s earthing terminal is typically connected to the metallic sheath or armour of the distributor’s service cable into the premises"
They provide these diagrams of which the second pretty accurately represents my arrangement. What Im struggling to understand is why this needs to change with an inverter, given that there is already a local earth point.
I remember reading in some inverters. They mandate a separate earth arrangement for the inverter to work on UPS/backup/off-grid mode. It could be because in some countries it is not as easy to get a good earth (thinking about sand dunes..), the requirement could be very strictly defined, related to the backup load. The manufacturers sometimes have generic wording and some distributors take it as gospel over the local regulation.
As you stated, the resistance of earthing arrangements needs to be measured and could need upgrading. What could be acceptable in a flat is not for an apartment block, etc.
To be honest, it is something I am considering getting installed when I get a chance. I had a look at the last couple of EICRs for my home and they report different earthing methods. 🙄
