Lighting Circuit Cross Over - Advice Please

[TheScullster]

Hi all

To clarify the subject text I am looking at a situation similar to upstairs/downstairs lighting rings and landing light feed. It is common practice to have the upstairs landing land controlled and powered from the downstairs lighting circuit. But this is counter intuitive for the electrician

ie he would normally expect that tripping the breaker for the upstairs lighting would make all upstairs lighting safe to work on. It is only the fact that this lighting arrangement is common place that seems to make it accepted practice.

So my question is:

I am considering putting the kitchen on a separate feed to lighten the load on the downstairs light circuit. But I intend to have one gang of a four gang switch in the kitchen controlling the dining room light, powered from the general downstairs circuit. So, isolating the kitchen feed will not make this switch safe.

Any suggestions on usual protocol in this case? Is it a problem? This lot will have to pass Part P muster of course.

TIA

Phil

[Owain]

If it's common practice he should expect it.

No, because MCBs in domestic dwellings are only single pole, so do not "isolate" the circuit. The isolation is provided by the Big Main Switch. Any sparkie who tests for live using his fingers deserves a tingle.

I'd put a small laminated label inside the switch box, mostly as an aid to fault-finding.

Owain

[Christian McArdle]

Only a brain dead one.

You basically have two choices. Either put all the light circuits on one circuit, even if this is not geographically continuous, or put different circuits into one multi-gang switch. Either approach is acceptable (provided that they are off one phase).

Personally, I prefer not to use geographical division of lighting anyway. I prefer random assignment to two circuits. This has the rather more significant advantage that in the event of a trip, a nearby light will still work. This is likely to be a much greater safety benefit than trying to protect incompetent electricians.

An electrician who "isolates" by just switching an MCB should know the risks of doing so. If I ever work in this condition, I assume that the entire system is still live. If I was to do otherwise, the entire isolator switch for the installation should be thrown.

Christian.