meter tails in cavity wall

[scott g]

just been to qoute a fuse board change meter tails in 16mm 80amp main fuse in meter head cutout
question is changing fuse board and tails but i think im going to have to put a 30ma 100 amp rcd time delay on
tails is this the only way to get round this problem with tails in cavity?

Do ‘meter tails’ concealed in walls or partitions need to be protected in accordance with Regulations 522.6.6 and/or 522.6.8?

NDA4
Yes. Meter tails concealed in a wall or partition at a depth of less than 50 mm from a surface must be protected in accordance with Regulation 522.6.6. Also, irrespective of the depth from a surface, meter tails concealed in a wall or partition having internal metallic parts (except nails and screws, etc) are subject to the requirements of Regulation 522.6.8.

However, additional protection for meter tails by means of an RCD is not an acceptable option in respect of Regulation 522.6.7 (which in consequence rules out reliance on 522.6.6(v), routing in the ‘safe zones’ alone), or in respect of Regulation 522.6.8(v). Also, for TT systems, the only option remaining is to provide suitable mechanical protection (that is, to comply with Regulations 522.6.8(iv) and/or 522.6.6(iv) as appropriate).

 

[jjjinx]

you haven't made your question very clear, r u saying that the meter tails are going through a wall cavity before they get to the meter from the supply fuse?

if that is the question, have you thought about either sticking the tails (if possible) in steel conduit or using SWA as they go through the wall?

 

[Amp David]

Been looking at a similar job,

Whats the best way to neatly and correctly terminate the SWA into the meter connections?

 

[Des 56]

If there are existing in the cavity already and they are to be changed
I pull the new ones through and use flexible ductingjng just in case of insulation problems

This is a popular dilemma for many sparks,some use safe zones and mechanical protection others use swa

Older farts like me, continue with poor cavity methods that the sparks with damp tracking concerns detest, and where thousands upon thousands of new builds have that same method

 

[jjjinx]

you can use some type of galvanised box that you earth to via the swa with a henley block inside going to tails or something like in the link.

Or use an stand alone 1 gang c/u can be plastic as long as theres no strain on the box from the swa making sure that the swa is earthed on the earthing block in the unit.

Buy Wylex Isolator Switch, 100A, Double Pole, 2 Module - WS102

100 Amp 5 Way SP Connector Block - MK

 

[Smugley]

Hi all, I'm interested to know if you interpret this requirement the same if the tails pass directly through the wall, as opposed to running for any length along the cavity, if you see what I mean.

 

[Spudnik]

Hi all, I'm interested to know if you interpret this requirement the same if the tails pass directly through the wall, as opposed to running for any length along the cavity, if you see what I mean.

RCD requirement?

In that case no as the cables are not buried.

IE from outside to inside straight through.

 

[scott g]

DNO policy whether you can put rcd in the meter box?
putting rcd on tails bad practice reg 311
is tails going through cavity more than 50mm so dont need rcd protection?

 

[AMC]

Hi there,

I'm just about to change the consumer unit and tails at clients house. Upgrade to 25mm tails and Dual RCD board from 100A fuse located in meter cupboard on external wall. My question is, what would be considered to be suitable containment for meter tails? Tails come from back of meter cupboard through wall into garage, then up wall, approximately 1 metre then into consumer unit. I am being especially cautious with my selection of equipment on this job as it's for my part p inspection in a fortnight!

 

[Spudnik]

2x2 PVC trunking or galv if you are feeling flush

 

[AMC]

Good idea! Thanks Jason. PVC it is. Also what is the deal with removing the knockouts on the top of the CU to run cables off to final circuits with trunking butted up againt CU? Tails and main earth coming in the bottom in trunking, again butted up to CU. I know they are **** hot on IP4X rating. Do you think the method described would be acceptable to them?

 

[johnboy6083]

just butt trunking upto CU, you dont need to use knockouts if they are not practical, you canmake any hole, as long as you gromet it. I always use a little decorators caulk, to bead around trunking, where it enters boxes ect, just looks good IMO, and takes 10secs

 

[Sintra]

Good idea! Thanks Jason. PVC it is. Also what is the deal with removing the knockouts on the top of the CU to run cables off to final circuits with trunking butted up againt CU? Tails and main earth coming in the bottom in trunking, again butted up to CU. I know they are **** hot on IP4X rating. Do you think the method described would be acceptable to them?

Please do not swear on the forums.

 

[ricardo123]

Tricky one this one, I have the same problem tomorrow, the old tails are run through the wall/cavity, if its a cavity how do you know whether there are any metal components in there, also in my case I am suspicious of the cable run and will find it hard to determine whether it meets the 50mm requirement. If it doesn't I assume it would need to be protected by an RCD if its not in the zones or less than 50mm away from the wall. If you were to use SWA you could take it into a galvanised box or trunking as has been said but this could look nasty in the room where the consumer unit is and you will have to gland it off at both ends of course. My solution for me is to use some PVC trunking and do it the best I can - it might not look great but at least you know you'll be complying with the regs. I unfortunately have a bit of a route to where the board is worst luck. Best of luck.

 

[miner69er]

following a course at the I.E.T in london we were 'advised' not to change the meter tails if it is not necessary. If the system is already existing on say 16mm tails and you are not planning to overload what is already in place then why cause the hassle and cost to you and the customer of trying to change the tails? it is a waste of time and copper. also if you can prove by calculations that the main earths do not require changing, then don't (as long as bonding complies with being min. half that size etc.) If you do periodic inspections you will see where they are coming from, just because it doesn't comply with the new 17th regs doesn't make it unsafe. If it was done correctly to an older reg then it can still be safe and useable. but hey we all have to make our own minds up don't we......

 

[ian]

If tails are running straight through a cavity there is no RCD protection required, if the cables are running up or along a cavity there is still no RCD protection required because they will be concealed greater than 50mm deep, however you my need to account for thermal characteristics etc.

If for any reason you do need to fit a rcd to meter tails because it concealed in a wall less than 50mm deep, there is not a lot of point fitting a RCD CU, just need to note it on the certificate as a deviation to the regs.

ian

 

[Burnt Fingers]

At some point and almost certainly to coincide with inspection my CU is going to have to move and I will need longer tails, through a cavity wall, with a total run of 1.5m to Henley block. I was going to use flexicon tubing for tails and cables (cavity is insulated, cables will be >50mm deep) because its easy to get up teh cavity and then very easy and neat to pass the cables. I'm wondering if flexicon tube counts as mechanical protection though - I'm referring to the plastic not the steel types.

I'm familiar with galv trunking, and SWA but 25mm SWA? Yikes. Any thoughts?

 

[Burnt Fingers]

Oh Forget that post. It will have to be galv for the tails