Emergency Power System

The wiring 'regs' certainly do not. Words like 'suitable for the application' 'good practice' and similar general thoughts abound. However there are often other standards that apply, building control regulations, fire regulations health authority regulations, fuel handling regulations, you name it there may well be a document for it.

But these are rarely specific as to the deep detail of how best to comply - there is no assumption that cable of a certain size or generators of a certain type will be appropriate,  rather the standards tend to indicate what the system must do in terms of  the performance of whatever fire suppression systems, emergency lights etc. that must operate during a power cut - in the sense that they must must allow time for folk to leave the building, or the ventilation must prevent the build up of dangerous fumes until everyone has left; or whatever the desired outcome is.

Much of the inner working of whatever system you care to assemble to achieve those goals is then left as a creative exercise for the design authority.

This is both a great freedom, and something of a curse, as it makes for some very nervous design engineers (I have heard the job described as 'controlled worrying' ), some really groundbreaking new solutions, and on the other hand, quite a few unmitigated cock-ups (plastic cladding on high rise accommodation anyone ?)  There are plenty of guidance documents for those who prefer a near "off the shelf" solution, but very few of these have requirements that are statutory.  The wiring regs  BS7671 for example are not a requirement, and not legally enforceable (law does require systems to be safe and fit for purpose however, and meeting a relevant standard is a good way to show you intended to meet the legal requirements if anyone needs to ask) . It is a very brave decision to depart too widely from the generally accepted practice, and your insurance may charge more, but you certainly can if you have good basis to do so.

I understand that much more of US practice is mandated in the sense of you can only follow the official guidance, with legal enforcement to make sure you do ?

The wiring 'regs' certainly do not. Words like 'suitable for the application' 'good practice' and similar general thoughts abound. However there are often other standards that apply, building control regulations, fire regulations health authority regulations, fuel handling regulations, you name it there may well be a document for it.

But these are rarely specific as to the deep detail of how best to comply - there is no assumption that cable of a certain size or generators of a certain type will be appropriate,  rather the standards tend to indicate what the system must do in terms of  the performance of whatever fire suppression systems, emergency lights etc. that must operate during a power cut - in the sense that they must must allow time for folk to leave the building, or the ventilation must prevent the build up of dangerous fumes until everyone has left; or whatever the desired outcome is.

Much of the inner working of whatever system you care to assemble to achieve those goals is then left as a creative exercise for the design authority.

This is both a great freedom, and something of a curse, as it makes for some very nervous design engineers (I have heard the job described as 'controlled worrying' ), some really groundbreaking new solutions, and on the other hand, quite a few unmitigated cock-ups (plastic cladding on high rise accommodation anyone ?)  There are plenty of guidance documents for those who prefer a near "off the shelf" solution, but very few of these have requirements that are statutory.  The wiring regs  BS7671 for example are not a requirement, and not legally enforceable (law does require systems to be safe and fit for purpose however, and meeting a relevant standard is a good way to show you intended to meet the legal requirements if anyone needs to ask) . It is a very brave decision to depart too widely from the generally accepted practice, and your insurance may charge more, but you certainly can if you have good basis to do so.

I understand that much more of US practice is mandated in the sense of you can only follow the official guidance, with legal enforcement to make sure you do ?