The best method of connecting a PV system in is by splitting the tails, installing a henley block and a new set of tails to a seperate garage unit / dual pole MCB (or dual pole RCD + single pole MCB). This does pose difficulties in terms of safely isolating the supply while installing the henley block in most situations where a suppliers cut out isn't present, but it is the best and safest way of doing it all round, so IMO the arcane rules not allowing the pulling of suppliers fuses take second preference to the safety of my staff and customers.... not entirely sure how you want to teach this though.
Installing to a spare way on a none RCD board is fine in theory, but leaves it open to being a problem in future if a new board is installed and it ends up being put on the load side of a shared RCD at that point.
In theory installing to the load side of a shared RCD should be safe, and the ESC allow for it in their guidance, as when the RCD trips, although the inverter is still operating for a short time afterwards (up to 5 seconds), the inverter is then isolated from earth, so there is no return path to the inveter via any fault to earth, so it ends up temporarily being a separated circuit.... but there is considerable debate about this, and in some situations it seems to make the RCD test not work properly, so is causing problems with other electricians doing PIRs (or whatever they're now called) after the PV has been installed.
There is another very good reason not to do this, which is that all inverters feed earth leakage current down the earth line, which on TL inverters is usually in the region of 10mA, so if they're sharing a 30mA RCD this makes the chances of nuisance tripping far higher from as little as 5-10mA (depending on the actual exact setting of the RCD) from other circuits. The manufacturers guidance is for 100mA RCDs to be used when used on shared circuits, to avoid this, but this would conflict with BS7671 in most situations where the 30mA RCD is a requirement for the shared circuits.
So basically it's generally considered very bad practice to install to the load side of a shared RCD even if some guidance does say it's ok, so please don't be teaching your students to do it.... but also please understand the mechanism by which it can actually be shown to still be safe and regs compliant, if not a good idea.
The alternative is a high integrity board set up with the PV connected to a way that's not protected by the shared RCDs, which is fine if it's a possibility, but is rarely the case.
we've got loads of
photos of solar installations on our website . If you post up any that you like, I can try to dig out the big version to email to you.
Also, if you're actually planning on training sparks up for solar installations for MCS standards, please try to set up some sort of arrangement with local solar companies to take on a few of the course members each time to get experience on a few jobs before they go off by themselves, as with the best will in the world, you can't teach this properly in the classroom by itself. I'd also ask if any would be willing to come in and do some training, or a q&A session or something if you're not experienced in solar, as you can't beat hands on experience.
