wiring at 50mm below surface

[electricphil]

We are having a conservatory built and the electrics are part of the package. I was surprised to see the cables for the sockets being installed at floor level. The electrician explained that when the plaster board was fitted the wiring would be 50mm below the surface. Comments!

 

[Billythekid]

We are having a conservatory built and the electrics are part of the package. I was surprised to see the cables for the sockets being installed at floor level. The electrician explained that when the plaster board was fitted the wiring would be 50mm below the surface. Comments!

Interesting, perhaps jumbo studs are being utilised?
Or is the installation of plasterboard to be "dot 'n' dabbed" only?

Cables do not have to be installed at a depth >50mm, providing that additional protective measures are utilised.

Regards

Billy

 

[LlandrilloSpark]

Any domestic wiring which is newly installed below a finished depth of 50mm needs RCD protection

 

[Darkwood]

New sockets so will require RCD protection regardless, ask them why they are going the extra mile to get them below 50mm or is it just as easy so less chance of damaging them.

 

[Octopus]

How many sockets are there? Are they fitting a FCU off the ring?

 

[Darkwood]

Any domestic wiring which is newly installed below a finished depth of 50mm needs RCD protection

Its a very loose quote there, this isn't the case and may mislead the OP.

 

[staggie65]

Placed meter tails in zone, more than 50mm depth but my ECA assessor didn't like it. He said it complied but that a hazard still remained. Did he have a point?

 

[Darkwood]

Placed meter tails in zone, more than 50mm depth but my ECA assessor didn't like it. He said it complied but that a hazard still remained. Did he have a point?

I would be weary of burying meter tails, were they RCD protected? also if passing through wall they should go through suitable mechanical protected, you get a bigger bang for your buck when the protection is the main cutout. I kind of agree although within regs i would consider this poor practice buts thats my personal view others may differ.

 

[Deleted member 26818]

All concealed cables require some form of additional protection, and have done so for a number of years.
One method is to bury the cables at least 50mm from the surface.
If that is not possible, then an option is to use cables which incorporate an earthed sheath such as Flexishield or SWA.
Another method would be to run the cables inside earthed conduit or trunking.
You could provide mechanical protection, sufficient to prevent penetration by screws or nails.
The final option is to install the cables within prescribed zones often refered to as safe zones, and provide 30mA RCD protection.
From the OP, it would appear that the cables are not being run in safe zones, so 30mA RCD protection is not an option.
Unless the cables used incorporate an earthed metallic sheath and as it appears that no earthed conduit or trunking is being used.
The only options available are mechanical protection or installing the cables at a depth greater than 50mm.
Seems to me that an awful lot of plasterboard would be required to provide a depth of 50mm.
Some plasterboard is manufactured with insulation fixed to the back, the insulation could be 50mm thick, and if the cables were covered by such that would satisfy the 50mm requirement.

 

[stratplus]

As regards protecting meter tails when going through a wall I take it if a garage board was being fitted inside the property with split tails at the meter outside should these be sleeved??

 

[Deleted member 26818]

Conductors that are unsheathed should be provided with mechanical protection, such as being run in conduit or trunking.
Sheathed conductors do not necessarily require further mechanical protection.

 

[Darkwood]

I was always taught way back in my college days that if you go through an outside wall especially a cavity wall due to the increased risk of falling loose material dropping on the cables within the wall then mechanical protection needs to be provided hence i always fit a 2" pipe unless the cable itself provides suitable mechanical protection.

 

[Deleted member 26818]

The sheath is mechanical protection.
It's up to you to decide whether it provides sufficient protection, or whether further protection is required.

 

[Darkwood]

The sheath is not mechanical protection par se' it is environmental protection of the inner insulation with limited mechanical protective properties and it wont provide much resistance to falling debris within a cavity wall that can be dropping from the full height of the house, this has been brought up numerous times on here and at work with clark of work and the running theme is a conduit/pipe is required to give added protection and yes even if your just running a wire to an outside light.. the reason its often ignored is its usually overlooked by councils and Clark of Jerks but when they remember they will have you fit the relevant protection.

 

[Deleted member 26818]

Darkwood, your first sentance states that a sheath is not mechanical protection, then states that it provides 'limited' mechanical protection.
Which is it to be?
Yes it won't provide much protection against large or heavy particles of debris dropping the full height of a house within a cavity wall.
However many properties do not have cavity walls, some that do have meter cupboards inset into the cavity wall and often external meter cupboards are placed under windows.
In many instances debris dropping onto cables is not a consideration and in many other instances the drop is not the full height of a house.
As such sheathed conductors do not necessarily require further mechanical protection.