Cable run under floorboards

[Iain123]

Hi Group

Had a third party inspection by a NAPIT tester, to get building control approval for a pv installation.
He has failed the cable run in Twin and Earth under my floorboards even though its greater than 50mm from surface. No 30ma RCD fitted to this circuit.

I though it was acceptable if the cable was 50mm or greater from the top of the joists?
Thanks for advice in advance

Iain

 

[andyb]

Did he give you a reg No that you are falling foul of?

Unless it's relevant to PV which I have no experience of, there's nothing wrong with running cables below floorboards.
Your biggest concern would be building regs.

 

[Darkwood]

Is it 50mm from the ceiling below too? Edit - as Dave points out its not applicable anyway to running through floors.

Likewise I have no PV experience so leave that to the PV guys.

 

[HappyHippyDad]

Could you not just add an RCD?

 

[snowhead]

Is the cable visible for it's full length under the floor ?

 

[andyb]

Could you not just add an RCD?

I don't think that does it HHD, needs to be 50mm or mechanical protection or earthed conduit or etc etc.

 

[Iain123]

The inverter manufacturer SMA Sunny boy guidance says do not use an RCD with a tripping current of less than 100ma to prevent false tripping which the NAPIT tester will not accept (he wants a 30ma RCD.

The cable is fully visble for all of its run from airing cupboard and along landing.

I have not asked him yet to quote the reg he's failing it on.

 

[davesparks]

Since when has running a cable under floorboards/above a ceiling required RCD protection?
The 50mm reg is applied to cables buried in walls

 

[andyb]

The inverter manufacturer SMA Sunny boy guidance says do not use an RCD with a tripping current of less than 100ma to prevent false tripping which the NAPIT tester will not accept (he wants a 30ma RCD.

Is the cable installed in a wall then?

 

[Iain123]

Clipped direct to wall, not in wall and then under flooirboards

 

[andyb]

Since when has running a cable under floorboards/above a ceiling required RCD protection?

It doesn't.

The 50mm reg is applied to cables buried in walls

And cables below a floor Dave.

 

[andyb]

Clipped direct to wall, not in wall and then under flooirboards

Then I would say that you do not need an rcd, it sounds like the inverter manufacturer are saying that if you use an rcd then it should be 100ma. It doesn't sound to me that they are saying that they require one.

 

[davesparks]

And cables below a floor Dave.

Since when? There is no requirement for cables to be RCD protected purely due to be installed under a floor, regardless of whether they are 50mm deep or not!

If you think otherwise please do quote a regulation number to back this up.

 

[Iain123]

The inverter manufacturer says the inverter does not need an RCD, but if an RCD is used on the circuit it needs to be 100ma or greater.

 

[andyb]

Since when? There is no requirement for cables to be RCD protected purely due to be installed under a floor, regardless of whether they are 50mm deep or not!

If you think otherwise please do quote a regulation number to back this up.

Dave, could you please read my post again that you've taken my quote from.

You'll see that I'm agreeing with you that cables below the floor and above ceilings do not need rcd protection.

Post 11

 

[Darkwood]

Maybe he's pulled it because you are too close to the ends of the joist thus a structural issue?

If not ask for more details and regulations that you have supposedly broken.

 

[davesparks]

Dave, could you please read my post again that you've taken my quote from.

You'll see that I'm agreeing with you that cables below the floor and above ceilings do not need rcd protection.

Post 11

I stated that the 50mm rule only applies to walls (ie. T&E cables buried less than 50mm require RCD protection unless otherwise protected)
You replied stating that it also applies under floors

What is there to misunderstand?

 

[HappyHippyDad]

Dave, could you please read my post again that you've taken my quote from.

You'll see that I'm agreeing with you that cables below the floor and above ceilings do not need rcd protection.

Post 11

To be honest Andy I also read your post as meaning cables below need RCD protection, at least the second part looks like that and the first part looks like you don't think it needs RCD protection!

 

[andyb]

I stated that the 50mm rule only applies to walls (ie. T&E cables buried less than 50mm require RCD protection unless otherwise protected)
You replied stating that it also applies under floors

What is there to misunderstand?

The misunderstanding was because I took 'Since when has running a cable under floorboards/above a ceiling required RCD protection?' To mean just that and I agreed with you.

And 'The 50mm reg is applied to cables buried in wall' to mean that cables below floors do not need to be burried >50mm and I disagreed with that.

 

[andyb]

To be honest Andy I also read your post as meaning cables below need RCD protection, at least the second part looks like that and the first part looks like you don't think it needs RCD protection!

Fair enough HHD, but if you read my posts I've said that on the face of it this installation does not require an rcd.

 

[DuaneMHunt1976]

522.6.100

Onsite Guide
7.3 Installation Considerations
7.3.1 Floors and Ceilings
Where a low voltage cable is installed under a floor or above a ceiling it must be run in such a position that it is not liable to be damaged by contract with the floor or ceiling or the fixings thereof. A cable passing through a joist or ceiling support must :

I) be at least 50mm from the top or bottom, as appropirate or...
II) have earth armouing or an earthed metal sheath, or
III) be enclosed in earthed steel conduit or trunking, or
IV) be provided with mechanical protection sufficient to prevent penetration of the cable by nails, screws and the likes (NOTE: this requirement to prevent penetration is difficult to meet), or
V) from part of a SELV or PELV Circuit

 

[davesparks]

The misunderstanding was because I took 'Since when has running a cable under floorboards/above a ceiling required RCD protection?' To mean just that and I agreed with you.

And 'The 50mm reg is applied to cables buried in wall' to mean that cables below floors do not need to be burried >50mm and I disagreed with that.

You can disagree all you like, but that doesn't make it a regulation.

Cables can be run in notches provided steel plates are fitted over the notches. Purpose made plates are available for this exact purpose.

 

[davesparks]

522.6.100

Onsite Guide
7.3 Installation Considerations
7.3.1 Floors and Ceilings
Where a low voltage cable is installed under a floor or above a ceiling it must be run in such a position that it is not liable to be damaged by contract with the floor or ceiling or the fixings thereof. A cable passing through a joist or ceiling support must :

I) be at least 50mm from the top or bottom, as appropirate or...

522.6.100 does not exist

You have not included the 'or' so appear to be deliberately misrepresenting the regulation to falsely make a point.

If you are going to quote a regulation please quote the full regulation, not just part of it.

 

[andyb]

You can disagree all you like, but that doesn't make it a regulation.

Cables can be run in notches provided steel plates are fitted over the notches. Purpose made plates are available for this exact purpose.

You like an argument Dave,

I covered all that in post 6,

I'm just trying to help the op not show everybody how clever I am. So with that said I don't think that I can add much more to this thread and I'm getting bored with having to constantly defend myself.

 

[DuaneMHunt1976]

it was in the GREEN Version but isnt in the YELLOW
and have another look edited it just before your reply

 

[davesparks]

it was in the GREEN Version but isnt in the YELLOW
and have another look edited it just before your reply

And the green book is no longer in effect.

 

[DuaneMHunt1976]

yep and your CORRECT there, i didnt noticed they had taken it out

 

[davesparks]

They haven't taken it out, they've messed with the wording and remembered it.

They have to justify the ridiculous cost of a new book so they just remember a lot of regulations and adjust a few words to make the list of changes look bigger.

If you have a look at an old regs book, like the 13th edition you'll find that some regulations haven't changed at all, they just move them around and give them new numbers

 

[7029 dave]

You can disagree all you like, but that doesn't make it a regulation.

Cables can be run in notches provided steel plates are fitted over the notches. Purpose made plates are available for this exact purpose.

Would you.?That method is all them yesterdays. lol

 

[davesparks]

Would you.?That method is all them yesterdays. lol

Yes I would if necessary, same as I have done in the past.

 

[7029 dave]

Yes I would if necessary, same as I have done in the past.

Been in this game since 1979, and I can say never have, always drilled out timbers.

 

[davesparks]

Been in this game since 1979, and I can say never have, always drilled out timbers.

I've been in the job for 11 years and I've had notches cut in to timbers a few times.
It's always been on buildings with exposed timbers and ceilings fitted between timbers rather than below them. When you've only got an inch gap between the bottom of the floor and the top of the ceiling you don't really have much other choice. These have been new extensions to grade 1 listed buildings.

 

[Leesparkykent]

https://www.tlc-direct.co.uk/Main_I...Index/Necessities~Cable_Protection/index.html

For when you have to notch a joist.

 

[davesparks]

I hadn't realised they were NICEIC approved,
I'll have to stop using them now!

 

[7029 dave]

Yes I would if necessary, same as I have done in the past.

Skill sawed through an 6mm cooker circuit, notched, blew me blade to bits, an set blade just at floor board level.

 

[Leesparkykent]

I hadn't realised they were NICEIC approved,
I'll have to stop using them now!

Have your own ones made then you don't have to worry about the NICEIC approval :wink5:

 

[DPG]

They don't look very thick those plates - I'm trying to remember if there was a minimum thickness requirement. Daz

 

[DPG]

Actually, just I've just checked reg 522.6.204 and it just states 'sufficient to prevent penetration (oo err) of the cable. Daz

 

[DuaneMHunt1976]

So 522.6.100 of BS7671:2008 (2103) has moved to 522.6.201 & 522.6.204 in BS7671:2008 (2015)

Well done finding the Move DPG

 

[telectrix]

Skill sawed through an 6mm cooker circuit, notched, blew me blade to bits, an set blade just at floor board level.

if you cut floorboards with a chainsaw, then you deserve it.