Protection of Meter Tails and Length

[Swa33er]

Good Afternoon All,

I have just completed a Periodic test on a house and have a question about the meter tails.
The house is 14 years old so has 25mm meter tails. The CU is in the garage and the meter box is around 7m away on an external wall as you'd expect. Looking at it, I imagine that the tails run from the garage, through the joists in the ceiling of the hall and downstairs WC, then drop down inside the wall and enter the meter box. Due to the fact that I can't actually see where they run, I can only assume they run through the joists with no mechanical protection and then drop down the wall in steel conduits to the meter box.
I know DNO now stipulate that if the meter tails are in excess of a 3m run then you should install an additional protective device at the nearest point to the supply inside of the customers premises. My question is, would the house fail on a periodic test due to this not being in place?

Thanks in Advance, JT

 

[davesparks]

My question is, would the house fail on a periodic test due to this not being in place?

It cannot fail on anything, the overall outcome can only be either satisfactory or unsatisfactory, there is no pass or fail option.

I would record this as an observation yes and code it as appropriate. I would consider C3 at a minimum for the length of the tails and being buried witjout suitable protection (assuming this is the case, you need to confirm this though)

 

[telectrix]

all depends on where the tails are buried. >50mm deep in walls... no code. < 50mm deep without mechanical protection... C3 or maybe a C2 if there's a risk of penetration by screws or nails. as for the >3m withoult Sw/Fuse, not sure if there's a reg. in BS7671 for this. it's more of a DNO requirement.

 

[Swa33er]

Thanks guys, sorry for the poor description of pass/fail, that was just bad wording on my part. I know I did a job about 8 years ago where we wired houses with the tails being about 10m from the meter box. Back then we were only required to bury the tails 50mm deep in the wall in 25mm steel conduit. I haven't had anything to do with wiring houses since. So the only way to check whether or not that the tails are mechanically protected when they drop down the wall and how deep they are buried would be to take a best guess at where they drop and remove a section of the plaster board to check? Customer will be thrilled with that I imagine And just to reiterate, it does HAVE to be checked?

 

[HappyHippyDad]

When you say they drop down the wall into the consumer unit in 'steel conduit' is that an assumption or can you see the steel conduit? (Youve just answered that, thanks @Swa33er )

These codes are such a judgement call sometimes aren't they!

Can we tell for sure the tails are buried in the wall, if so are they > or < 50mm?? It will be impossible to determine so what do we code it? We're not going to put FI because we're not going to start digging out the wall to find out so it's probably going to be a NV in reality. Which probably means leaving live tails buried in a wall <50mm without mechanical protection.

I think if I could see that the tails came down the wall NOT in line with the consumer unit then i would give a C2, if they were in the zone with the CU then a C3, but again, perhaps they have mechanical protection and you just cant see it!!!! Arghhhh!

@davesparks when you say a C3 at a 'minimum' what deciding factors would make you change it to a C2?

 

[Swa33er]

When you say they drop down the wall into the consumer unit in 'steel conduit' is that an assumption or can you see the steel conduit? (Youve just answered that, thanks @Swa33er )

These codes are such a judgement call sometimes aren't they!

Can we tell for sure the tails are buried in the wall, if so are they > or < 50mm?? It will be impossible to determine so what do we code it? We're not going to put FI because we're not going to start digging out the wall to find out so it's probably going to be a NV in reality. Which probably means leaving live tails buried in a wall <50mm without mechanical protection.

I think if I could see that the tails came down the wall NOT in line with the consumer unit then i would give a C2, if they were in the zone with the CU then a C3, but again, perhaps they have mechanical protection and you just cant see it!!!! Arghhhh!

@davesparks when you say a C3 at a 'minimum' what deciding factors would make you change it to a C2?

I'm assuming at this stage because there is no way to see currently. The house was built by a 'reputable' house builder so you can only hope that it was done correctly to suit the Regs at that time. But we all know that even though it should have been, by no means can it be taken for granted.

 

[Wilko]

Hi - I’ve been to a few jobs where unprotected tails in dot and dab have been penetrated during kitchen renovation and they were all un-safe after that. So if I knew that’s what was done I’d rate it C2.

However, with wall finishes etc we often can’t know the depth or mechanical protection status by inspection alone. And likely the Customer will quite reasonably require that you don’t damage their property, so this aspect is likely to be an agreed Limitation in the Report.

 

[HappyHippyDad]

Thanks guys, sorry for the poor description of pass/fail, that was just bad wording on my part. I know I did a job about 8 years ago where we wired houses with the tails being about 10m from the meter box. Back then we were only required to bury the tails 50mm deep in the wall in 25mm steel conduit. I haven't had anything to do with wiring houses since. So the only way to check whether or not that the tails are mechanically protected when they drop down the wall and how deep they are buried would be to take a best guess at where they drop and remove a section of the plaster board to check? Customer will be thrilled with that I imagine And just to reiterate, it does HAVE to be checked?

The IET EICR forms actually says..
"It should be noted that cables concealed within trunking and conduits, under floors, in roof spaces, and generally within the fabric of the building or
underground, have not been inspected unless specifically agreed between the client and inspector"
so you're not really going to know what is going on with those tails, they may have a 3mm steel sheet over them! Although probably not.
As @Wilko has said, it's going to be an agreed limitation, but again that probably means leaving tails unprotected. it's quite frustrating as as an electrician carrying out an EICR you want to be as sure as you can that when you write 'satisfactory' it really means that.

 

[Swa33er]

Also, while I have your attention gents, another question, I had a quick look over a property the other day that had been recently rewired, they were wanting additional power to their garage. But when I was taking a look I noticed that one of the ring mains in the house had been wired in 2.5mm 3 core cable. I'm presuming that it was maybe done to save on cost if they had already had the cable or whatever but it's certainly not something I have seen before or would ever think of doing. Is it even allowed?

 

[Wilko]

Hi - do you mean 3 core flex?

 

[HappyHippyDad]

Hi - do you mean 3 core flex?

That was my question too.
If so, unorthodox but fine.

 

[davesparks]

I know I did a job about 8 years ago where we wired houses with the tails being about 10m from the meter box. Back then we were only required to bury the tails 50mm deep in the wall in 25mm steel conduit.

That was not compliant 8 years ago, the 3m rule was the same.
[automerge]1599421773[/automerge]

Also, while I have your attention gents, another question, I had a quick look over a property the other day that had been recently rewired, they were wanting additional power to their garage. But when I was taking a look I noticed that one of the ring mains in the house had been wired in 2.5mm 3 core cable. I'm presuming that it was maybe done to save on cost if they had already had the cable or whatever but it's certainly not something I have seen before or would ever think of doing. Is it even allowed?

Yes 2.5mm cable is allowed for ring circuits, it is normally the minimum required size.
As long as the type of cable is suitable for the installation method then it is fine.

What type of cable is it? Just saying 3 core could mean a variety of different cables.