All lights connected to 2 seperate circuits

[neljan]

I'm re-wiring my Mothers lights because the previous owner had installed loads of LEDs everywhere (I've so far removed 19 downlights from a 2 bed bungalow, lol) and also used junction boxes under floorboards (when he did bother to use them; some cables were connected with terminal blocks + tape) and I've just discovered that he's connected every single light in the property to both circuits/MCBs.

I can see the thinking behind it (If one MCB fails; all lights still work) but is this safe? I can't see it being acceptable by the regs. I'm going to split them anyway but was just wondering...

 

[bernardgreen]

If one MCB fails; all lights still work

MCBs fail by NOT disconnecting power when the circuit is being overloaded.

MCBs operate by disconnecting power when the circuit is being overloaded or ther is a serious fault in the wiring.

Having 2 MCBs in parallel ( as you appear to have ) could allow twice the safe current to flow in the wiring.

but is this safe?

It could be unsafe.

 

[JohnW2]

I can see the thinking behind it (If one MCB fails; all lights still work) but is this safe? I can't see it being acceptable by the regs. I'm going to split them anyway but was just wondering...

Even that thinking was flawed - with two MCBs in parallel, if a fault arises (anywhere) which causes one of the MCBs to operate, the fault will probably still be there (unless it was due to a lamp/bulb dying) so the other MCB will almost certainly then operate as well (if it didn't simultaneously with the first one tripping!) - thereby resulting in all lighting being lost.

The arrangement you have is unsatisfactory, and potentially 'unsafe', for all sorts of reasons. Split the circuits onto the two MCBs (as it should be). Apart from being 'safer', that then means that a single fault will only take out one of the two lighting circuits, so there would still be some operative lights in the house.

Kind Regards, John

 

[neljan]

Thanks very much for the clarification Bernard & John. Excellent.

 

[Iggifer]

Isn't this most likely to have happened by mistake at the hall/landing switch?

Or has he literally bridged the two circuits in the consumer unit?

 

[neljan]

He had two circuits going into the same ceiling rose. No bridge at the CSU.

All done now - 2 seperate circuits as god intended. Just need to move all of the remaining JBs from the joists and make all the wires neat.

What does it say in the regulations regarding the wiring. Don't they have to be a certain distance below floorboards and/or above insulation?