Installations should be divided up - Interpretation?

[RF Bloke]

17th ed states "Installations should be divided up into circuits so as to take account of danger and inconvenience caused by a single fault – e.g. such as a lighting circuit"

With the obvious lack of any specifc rules what is considered 'best practice' ?

For a small property that may in the past have had say just two lighting circuits, one for the 1st floor and the other for the ground floor, would it be expected for this to be split as left hand side of house and right to avoid all of the lighting dropping on a single floor?​

 

[telectrix]

no, you would try and put each existing circuit on separate rcds, after sorting out the borrowed neutral. of course. and separate the socket curcuits. each installation should be treated as individual, and common sense used. e.g. kitchen sockets separate to rest of ground floor sockets, when practicable.

 

[malcolmsanford]

That seems to be the modern way of wiring a normal domestic house that uses a split rcd board. A new installation or a rewire could very well be done "half and half", though it would mean more cable and until it is common practice may lead to a few scratch heads trying to work out what as been done.

Obviously on just a CU change then the best way to go would be the normal upstairs/downstairs on 2 different RCD.

Again though the use of RCBOs would negate the above.

Bottom line to this though is, that as your the designer you will decide which is the best way to adhere to part 314 of the regulations

 

[RF Bloke]

Gents,

I need to clarify a bit.

I am not talking about an existing installation but either a complete re-wire or brand new install.

Now, if I were to have just two lighting circuits (so just two breakers or two RBCO's or what have you) on the CU, then IF i had all the 1st floor on one and all the ground floor on the other, I think this would be bad practice regarding circuit division as a trip on any circuit takes out a whole floor of lights. However, if the building lighting is split left/right this doesn't happen.

In practice, where possible I would normally stick with traditional division with circuits for groups of ground floor rooms and the same for 1st floor rooms. Of course, kitchen on its own etc.

Steve

 

[malcolmsanford]

That seems to be the modern way of wiring a normal domestic house that uses a split rcd board. A new installation or a rewire could very well be done "half and half", though it would mean more cable and until it is common practice may lead to a few scratch heads trying to work out what as been done.

Obviously on just a CU change then the best way to go would be the normal upstairs/downstairs on 2 different RCD.

Again though the use of RCBOs would negate the above.

Bottom line to this though is, that as your the designer you will decide which is the best way to adhere to part 314 of the regulations

My OP did you read it

 

[RF Bloke]

Yes, I think we are on the same page!

Thanks for input.

Steve

 

[telectrix]

on a new install, it would be ideal to have 4 lighting circuits, and have 1 down and 1 up on 1 rcd and 1 up and 1 down on the other ( or rcbos. ). but then increased cost could lose you the job.

 

[malcolmsanford]

To be honest TeL I would always try and get the customer to have RCBO's as it is IMO the best way to go. I know it can be more expensive but I always like to think that cheapest is not always the best, and RCBO's are getting cheaper.

Unfortunately your right mate, espicially in todays market cheapest is king.

 

[Deleted member 26818]

The requirement to divide circuits 'to avoid danger and minimize inconvenience in the event of a fault', is not new to the 17th.
The addition of part (iii) to Reg. 314.1 is due to the fact that many installations in the past, have not 'taken account of danger that may arise in the event of the failure of a single circuit such as a lighting circuit'. It was felt that attention should be drawn to this.
There is also the fact that in order to comply with the requirements to provide RCD protection, people may decide to install front end RCDs.
Such would negate any division of circuits, as a fault on one circuit would then affect all the other circuits.
As a designer, it is up to you how you decide to take account of this. Splitting the circuits between up and down has been the generally accepted manner to achieve this for many years.
Some now split the circuits between left and right, or front and back.
You may decide that the danger is minimal, and place all the lighting on one circuit, or that it is not minimal and perhaps install emergency lighting.
The main thing is, is that you should take account.