MCB used as light switch

[Jas0n7]

in the tick box section of a nic peroidic form one of them says something along the lines of devices selected being used what they we're designed for. a breaker of any form is a proctective decive and not a switch!

 

[Sintra]

But still can be used for functional switching according to the brb.

 

[jaresquire]

You see it all the time, and in the absence of a centralized switch bank it is obviously easier. I have replaced zillions of fire and intruder batteries ruined by full discharge because the supply was turned off in this way.

 

[Adam W]

Why exactly do the staff do that?
Is the main switch/contactor faulty?

I too don't think it seems right for unskilled persons to be poking around in the consumer unit, apart from anything because they could accidently turn off something they shouldn't, or realise the main switch can save turning off 4 breakers without realising it turns off the freezer (or all the freezers if it's a frozen food shop).

 

[malcolmsanford]

This is another of these good practice issues. The bare facts are that according to table 53.2 a MCB can be used as a functional switch.

That makes about 80% of sparks cringe but it is widely used in retail outlets. I sub contracted quite a few outlets on a shopping centre near me and I reckon out of about 8 units I did 5 of them controlled the lights this way.

I spoke to the main contractor about this and asked why you couldn't put a fish key in, or a timer in or a bank of switches somewhere that customers could not get to and as a prank turn the lights off.

He told me the main reason was cost, if you worked out the amount of shops that a large retail organisation have then to run Switch Lines in every shop would increase the construction costs quite a bit. This is why most large Mega type shops now don't have false ceilings. You go into a Tesco Extra you will see all the air condition trunking, the Sparks cable tray, the plumbing pipes, it looks half finished but it is all to do with costs.

 

[Darkwood]

in the tick box section of a nic peroidic form one of them says something along the lines of devices selected being used what they we're designed for. a breaker of any form is a proctective decive and not a switch!

You may buy this device for your use of overload protection but if you get hold of the technical data for the device it has been also designed to be able to be used as a functional switch too with operations in the hundreds of thousands before mechanical failure and as i mentioned in previous post this exceeds your bog standard lightswitch for reliability and durability, note im refering to 60898 mcbs, most sparkies may never utilise this method in their whole career but it dosnt mean its wrong and its these sparkies who seem to frown on it and say its bad practice which is is not.

 

[baldsparkies]

When the 18th edition regs come out it may state in section 6 of regulation 549-211 That all qualified electricians should jump off a 100ft cliff at 5.30 on a friday afternoon.
I wonder how many will ? and shout before they hit the ground it's ok, its in the reeeeeeeeeeeeg's, splat.
An mcb is by definition an overcurrent disconnection device. it is designed with the primary task of disconnecting a fault current if and when it should occur. Its not and never has been a bl##dy light switch. Good electrical practice would dictate, light switches to manually turn of lights. I to have seen the practice many mant times, but for heavens sakes don't say its perfectly acceptable because a reg can be quoted. The regs are for guidance and they change like the wind, use sound judgement and common sense on this one. (Now Iv'e gone and done it !!)

 

[Darkwood]

I see this issue been a ' we will agree to disagree thing ' and yes Baldsparkie i agree what its initial design purposes are and it does this perfectly well but give technical at Hagar or Schneider(merlin/telemecanique as we know them) and then ask them about its mechanical attributes as a functional switch and you will be told it serves this purpose well beyond the reliabilty of the switch you just wired for joe blogs, and also in your defence you shouldnt really use this method in the majority of cases as you will fall foul of many other areas of the regs like access, health and safety of not trying to get to the board in the dark amongst a few i can mention, so most of the time yes common sense will denote you shouldnt consider this method but as mentioned in previous posts the multi-retail complexes are using this method more and more in the small shop units and put into the grand design so as to save money without contravention of other regulations, what it boils down to is that 'yes' it can be as originally asked be used as a functional switch but in doing so you musn't contravene other reg's so in the majority of cases using this method isnt an option anyway.

 

[baldsparkies]

Well put Darkwood, your a very diplomatic chap. But don't you just love these debates.
Back to topic, and a point worth cosidering, use of mcb's on lighting circuits containing emergency lighting, now that would throw a spanner into the proverbial.

 

[Darkwood]

Well put Darkwood, your a very diplomatic chap. But don't you just love these debates.
Back to topic, and a point worth cosidering, use of mcb's on lighting circuits containing emergency lighting, now that would throw a spanner into the proverbial.

I have a headache