Will this CU take RCBOs?

[galliano2001]

Untitled

• galliano2001
• 28 Aug 2008
• 2

From the picture above would this CU take an RCBO? The reason i ask is that my lighting circuits are not on the RCD side of my box and the switches are not earthed (just single black and red). Would having these circuits on an RCBO be safer than current setup?

 

[electronicsuk]

From the picture above would this CU take an RCBO? The reason i ask is that my lighting circuits are not on the RCD side of my box and the switches are not earthed (just single black and red). Would having these circuits on an RCBO be safer than current setup?

No idea off the top of my head whether or not RCBOs are available for it, but if I had to guess then I'd say no.

If your lighting circuits do not have an earth then you should consider having them rewired sooner rather than later, although having an RCBO would be a sensible interim measure. You still MUST NOT, even with an RCBO, use any metal light fittings or switch plates without an earth connection. At all.

 

[aptsys]

The RCD looks identical to MK RCDs, so I wonder if the busbar position/size is the same as in MK boards allowing you to use MK RCBOs.

 

[galliano2001]

Thanks for the quick response. Re-wire is currently not on the cards due to recent decoration throughout house and a 4 week old baby!

So looking for increased safety until that can happen.

Bear with my ignorance for a second, if the switch faceplate is wired to the metal backbox that is sat in a masonry wall, how would an earthwire to a metal pole in the ground provide better earthing?

 

[sealeon]

If you do any work on the board you will be required to make sure your installation is up to standard and therefore rewire the lights it could be a catch twenty two situation

 

[ban-all-sheds]

Thanks for the quick response. Re-wire is currently not on the cards due to recent decoration throughout house and a 4 week old baby!

Why on earth did you decorate when you need a rewire?

Madness.

if the switch faceplate is wired to the metal backbox that is sat in a masonry wall,

If your switches have earth terminals they must need earthing.

You have no earth, therefore you must get rid of the metal switches.

Now.

And any lights that need earthing.

how would an earthwire to a metal pole in the ground provide better earthing?

It wouldn't - get rid of the switches and any Class I lights now.

 

[davy_owen_88]

Bear with my ignorance for a second, if the switch faceplate is wired to the metal backbox that is sat in a masonry wall, how would an earthwire to a metal pole in the ground provide better earthing?

It wouldn't - get rid of the switches and any Class I lights now.

I think you might have misread that BAS, or maybe its just me but I read his question to mean: 'Why does earthwire to a metal pole in the ground provide better earthing... than the metalbackbox that is sat in a masonry wall... which is in direct contact with the earth anyway?' Your answer implies than a correctly installed TT arrangement does not provide a better earth than nothing, which we both agree is not the case.

The reason an earth rod provides better earthing is:

1) Copper is a excellent conductor and masonry isn't.
2) An earth rod is driven into the ground, a wall merely sits on top.
3) Walls have a damp proof course which is usually a plastic membrane, this isolates the wall from earth, and keeps the walls dry, which in turn makes the wall even less conductive.

 

[securespark]

We don't know if it's a TT supply, but even if it is and a rod is installed, rcd back-up is still required.

 

[davy_owen_88]

If that was aimed at me secure then I agree, what I meant by my post was that his question sounded like he was comparing a rod in the ground (such as that of a TT installation) with a metal backbox sitting in a wall (such as any supply but without a connection to the MET).

Now I might have totally misinterpretted his question, but by his 'excuse my ignorance' comment, I'm guessing that he wanted to know why an earth rod is better than what he has now, which is nothing.

 

[galliano2001]

Right, lots of responses, so thanks to all. In order that i remember, BAS - bought the house two years ago mid refurb by another bloke, plastering was all done etc, im talking a lick of paint. If i had known what i know now before the place had been plastered then yes a re-wire would have been order of the day.Hindsight is not available to us mere mortals.

I don't have metal faceplates that are not earthed, the ones that are metal are in an extension that are earthed, not sure where you got the idea i had metal plates from?

The question regarding earthing was for information, thanks for the clear answer davy owen.

So, we all agree that a lighting rewire would be ideal, but in the interim an RCBO is better than doing nothing?

 

[GaryMo]

galliano2001, even though your switches may be plastic they probably still have metal screws entering metal boxes which can be touched.
If that's the case then look to replacing them with nylon 3.5mm socket screws.

 

[davy_owen_88]

An RCBO will cut off the supply if you, or a member of your family, has the misfortune to become an earth rod. In that respect it will be safer to fit an RCBO than not to but the issue is that relying on current passing through a human body to operate a protective device is crazy. As you have unearthed plastic faceplates with metal-backboxes, the first step would be to replace the screws with nylon equivalents or replace the frontplates to those which incorporate screw caps. This would remove any chance of a loose phase conductor in contact with the metal backbox allowing accessible parts to become live, and stay live until you touch them.

 

[comms]

Use one of these for each lighting circuit fused down to 5amp.

http://www.tlc-direct.co.uk/Images/Products/size_3/BRH92.JPG

Mcb > 1.5mm > rcd spur > lighting circuit cable on load terminals.

Might be better to get a sparks in to do it if you are unsure.

 

[ban-all-sheds]

If that was aimed at me secure then I agree, what I meant by my post was that his question sounded like he was comparing a rod in the ground (such as that of a TT installation) with a metal backbox sitting in a wall (such as any supply but without a connection to the MET).

Now I might have totally misinterpretted his question, but by his 'excuse my ignorance' comment, I'm guessing that he wanted to know why an earth rod is better than what he has now, which is nothing.

OK - I interpreted it as suggesting that he could run a connection from the back box/faceplate to an earth rod as an alternative to having a cpc on the circuit.

not sure where you got the idea i had metal plates from?

From this:

if the switch faceplate is wired to the metal backbox...

I couldn't see why or how you'd connect a plastic faceplate to the box...

 

[galliano2001]

BAS - that was a question from electronicsuk post about not using metal faceplates, i wanted to know the difference.

You may want to look at your keyboard, you seem to have a sticking fullstop key.