Meter tails in cavity

mattg4321 · Jun 17, 2018

Ok own up who's done this?

I try my hardest to never do this but have, on very rare occasion installed meter tails in a cavity as the lesser of evils.

Would be interesting to hear real world thoughts on this and potential work arounds so you don't have to. I know someone on here posted a while back about some sort of capping that you could put over the tails so they couldn't be drilled. Not entirely convinced about that although I've not had a proper look at it in real life.

I had one recently where the meter box was on external wall and I needed to run an armoured from there to an internal consumer unit. Went to great trouble to avoid running the cable in the cavity and builder comes along and says why didn't you just push it up the cavity!

Spoon · Jun 17, 2018

Isn't the issue with bridging the gap so that water doesn't transfer from the outside wall to the inside wall?
You can stop this by installing the cable at an angle, so the water can't run down the cable to the inside wall. This is of course for installing the cable virtually horizontal.

Midwest · Jun 17, 2018

Think its the suggestion of such cable running vertically in the cavity, that allegedly can cause water breaching the cavity.

HandySparks · Jun 17, 2018

If the cavity is subsequently filled with insulation, the current carrying capacity of the cables will be significantly reduced.

Dillb · Jun 17, 2018

HandySparks said:
If the cavity is subsequently filled with insulation, the current carrying capacity of the cables will be significantly reduced.

Thats like wiring a conservatory and putting sockets on the wall attached to the house, they will need to be IP rated incase they ever take the conservatory down.

You can only allow for what is there when installing.

Deleted member 26818 · Jun 17, 2018

Dillb said:
Thats like wiring a conservatory and putting sockets on the wall attached to the house, they will need to be IP rated incase they ever take the conservatory down.

You can only allow for what is there when installing.

When working on the O2, we installed IP rated containment and accessories, just in case they ever removed the cover.
The fact that the internal structures are made from MDF not withstanding.

Des 56 · Jun 18, 2018

Put the cables in the cavity,tell no one you did so
Any officious council employee will be none the wiser

He will have the exact measure of wisdom whether he knows or not (regarding cables in cavities)
The measure of his wisdom means he would have no clue of what should be done if he objected in the first place

Spoon · Jun 18, 2018

Midwest said:
I though vertical trunking was required to have cable supports over certain lengths; was there some new reg or update on that in the last amendment.

Just been looking for this, cause I was curious.
We have:

522.8.4 Where conductors or cables are not supported continuously due to the method of installation, they shall be supported by suitable means at appropriate intervals in such a manner that the conductors or cables do not suffer damage by their own weight.

522.8.5 Every cable or conductor shall be supported in such a way that it is not exposed to undue mechanical strain and so that there is no appreciable mechanical strain on the terminations of the conductors, account being taken of mechanical strain imposed by the supported weight of the cable or conductor itself.

Neither of these state a measurement. The only one that does is regards to caravans..

721.522.8.1.3 All cables, unless enclosed in rigid conduit, and all flexible conduit shall be supported at intervals not exceeding 0.4 m for vertical runs and 0.25 m for horizontal runs.

HandySparks · Jun 18, 2018

Dillb said:
Thats like wiring a conservatory and putting sockets on the wall attached to the house, they will need to be IP rated incase they ever take the conservatory down.

You can only allow for what is there when installing.

Not really a fair analogy. If you demolish a conservatory, you'll want to remove the sockets and wiring with it. Cavity wall installation is a popular home improvement, ie not unusual. The installers may well be unaware of the cables in the cavity and are unlikely to do anything about it if they are.

telectrix · Jun 18, 2018

The installers may well be unaware of the cables in the cavity and are unlikely to do anything about it if they are.

they wouldn't give a sh*t anyway. bung it in as quick as possible, move on. sod any other trades being compromised.

DPG · Jun 18, 2018

Never a fan of cables in cavities. They will bridge the cavity in multiple locations - this can cause problems and is frowned upon. Traditional wall ties also bridge the gap, but they are designed so that any moisture is dropped down the cavity rather than tracking across.

And, as someone alluded to earlier, how do you support horizontal runs of cable in the cavity? It could be going through for several meters without any support other than where it is sat against the edge of a brick at either end.

And thirdly the issue of all that wall insulation being added at some point to nicely downrate the cable.

Just generally not a good thing to do.

Spoon · Jun 18, 2018

DPG said:
And, as someone alluded to earlier, how do you support horizontal runs of cable in the cavity? It could be going through for several meters without any support other than where it is sat against the edge of a brick at either end.

Just out of curiosity, what do you guys do then you put cable in the oval trunking like below?

[ElectriciansForums.net] Meter tails in cavity

What max length do you use.
As you see by my earlier post. There is no actual length specified in the regs.

DPG · Jun 18, 2018

Doesn't matter - the tubing supports it??

Dillb · Jun 18, 2018

DPG said:
Never a fan of cables in cavities. They will bridge the cavity in multiple locations - this can cause problems and is frowned upon. Traditional wall ties also bridge the gap, but they are designed so that any moisture is dropped down the cavity rather than tracking across.

And, as someone alluded to earlier, how do you support horizontal runs of cable in the cavity? It could be going through for several meters without any support other than where it is sat against the edge of a brick at either end.

And thirdly the issue of all that wall insulation being added at some point to nicely downrate the cable.

Just generally not a good thing to do.

So how do YOU pass a cable through a wall with a cavity in it?