If by the Master switch/breaker you mean the typical switch/incomer inside the original consumer unit/DB, then what you describe isn't that unusual. Good practice would have installed an extra "REC 4" type isolator before split - but there are arguments over whether this is strictly necessary (some deem the PV DB and the original to be separate installations, so can each have their own "main switch").

There are a couple of reasons for using an new DB rather than the existing one - either because there aren't enough spare ways in the original, or more likely these days, because of a recent regulation change, that the DB assembly need to be rated for the sum total of the ordinary supply plus the generation - e.g. for an ordinary setup with a 100A supplier's fuse and say 16A of local generation, you'd need a DB rated at 116A - which aren't particularly available. So a separate DB is often called for. Alternatively the grid supply could be downrated (e.g. from 100A to 80A) so that the total falls within the rating, but that's often not desirable (given existing loads etc).

Ideally (and probably legally) they should have got the DNO or supplier out to do a temporary disconnection rather than break the seals themselves, but as usual theory and practice don't always meet.

   - Andy.

If by the Master switch/breaker you mean the typical switch/incomer inside the original consumer unit/DB, then what you describe isn't that unusual. Good practice would have installed an extra "REC 4" type isolator before split - but there are arguments over whether this is strictly necessary (some deem the PV DB and the original to be separate installations, so can each have their own "main switch").

There are a couple of reasons for using an new DB rather than the existing one - either because there aren't enough spare ways in the original, or more likely these days, because of a recent regulation change, that the DB assembly need to be rated for the sum total of the ordinary supply plus the generation - e.g. for an ordinary setup with a 100A supplier's fuse and say 16A of local generation, you'd need a DB rated at 116A - which aren't particularly available. So a separate DB is often called for. Alternatively the grid supply could be downrated (e.g. from 100A to 80A) so that the total falls within the rating, but that's often not desirable (given existing loads etc).

Ideally (and probably legally) they should have got the DNO or supplier out to do a temporary disconnection rather than break the seals themselves, but as usual theory and practice don't always meet.

   - Andy.

Have you got a picture of before and after ? damaging the company fuse holders  sounds dog rough, though the rest of it might be OK -  what is the  longest length of wire only protected by the company fuse ? if the answer is more than perhaps 3m it is unliley to be right.

(officially the DNO come out and remove the seals and replace them later, but more often than not round here, the 'seal fairy' has visited, and magically the seals are gone and no-one seems to know quite when (!) .
Responsible persons then phone that in for replacement, or at least re-seal at least with some length of wire so that small children cannot get in without a bit of effort. - plain seals of the non dno kind are readily available on the web and can be used to make something safe until the DNO get round to it. example )

But yes, the decoupling of the metering companies from the network operators has led to a more general 'nobody knows/cares' attitude to fuse seals (not meter seals mind you) in some places - but not in others so be careful.

Two or more consumer units side by side from the same meter is OK, but good practice would like to see a master isolator between the meter and them, but not always done.

Mike.