Amtech Software Update Zs Calculation Issues.

I don't use Amtech, but it strikes me you might be relying on it, as if it is always the last word in design, rather than as just some software that automates some rather repetitive calculations, you could at least in principle, do by hand, perhaps more slowly, with the relevant data sheets in front of you.

In these tricky cases, would it help to ask how would you be dealing with it, if you were in fact calculating manually ?

I suspect you would simply say - 'designed to BS7671 (2020 or whatever)' rather than 'designed to BS7671 (latest edit) ' which in fact contractually is very common. Certainly for big jobs that last several years, some change of regulations in mid-build is almost inevitable, and the legal types hedge this by fixing at handshake time exactly which edition of which regulations apply to the whole programme of works or to sub-sections of it.

It is almost never that stuff that has already started needs to  be undone and redone just because the calculations use the old assumptions ...

The other part of your question seems to be 'is there a legacy mode' that allows you to check designs that should have complied in the past. That I don't know, and is really a question for the software authors.

In general , in the field the problems of a high  Zs can be reduced by making sure that conduit, or cable trays etc are in parallel with the CPC, or by running an additional one along side, and the shock risk can be mitigated by use of RCD or earth fault relay, if the design allows. Or failing that,. as you note, the nuclear option is to spec shorter, fatter cables  or a smaller fuse or MCB  !!

How sure are you of the actual Zs at the origin ?

Mike.

I don't use Amtech, but it strikes me you might be relying on it, as if it is always the last word in design, rather than as just some software that automates some rather repetitive calculations, you could at least in principle, do by hand, perhaps more slowly, with the relevant data sheets in front of you.

In these tricky cases, would it help to ask how would you be dealing with it, if you were in fact calculating manually ?

I suspect you would simply say - 'designed to BS7671 (2020 or whatever)' rather than 'designed to BS7671 (latest edit) ' which in fact contractually is very common. Certainly for big jobs that last several years, some change of regulations in mid-build is almost inevitable, and the legal types hedge this by fixing at handshake time exactly which edition of which regulations apply to the whole programme of works or to sub-sections of it.

It is almost never that stuff that has already started needs to  be undone and redone just because the calculations use the old assumptions ...

The other part of your question seems to be 'is there a legacy mode' that allows you to check designs that should have complied in the past. That I don't know, and is really a question for the software authors.

In general , in the field the problems of a high  Zs can be reduced by making sure that conduit, or cable trays etc are in parallel with the CPC, or by running an additional one along side, and the shock risk can be mitigated by use of RCD or earth fault relay, if the design allows. Or failing that,. as you note, the nuclear option is to spec shorter, fatter cables  or a smaller fuse or MCB  !!

How sure are you of the actual Zs at the origin ?

Mike.