Meter tails no rcd in stud wall

newfutile

newfutile

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During an EICR meter tails were found entering the cavity and coming down a stud wall to a consumer unit about 5 meters (direct distance) away.
they do have an isolator but no rcd or other protection .

as cables buried in a wall have to have (RCD) Residual Current Device at 30mA and generally tails over 3 meters are not permitted by DNO ,how can this comply?
 
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As above I hate meter tails being snaked through a wall cavity or run up inside a stud wall with no way of knowing where they are actually sited

Made even worse if there is no RCD protection
 
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Are the tails definitely bare in the stud wall, or is it possible they have mechanical protection, complying with 522.6.204, (which I think would mean no RCD req'd)?

I have come across this a few years back in a new build, when putting up a cabinet in a toilet. The tails were installed in a steel stud wall, and my magnet picked up the mechanical protection. Thinking it was just another steel stud, I tried drilling it for a couple of minutes, before realising something was amiss and checked the other side of the wall to find the CU there!
 
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newfutile said:
During an EICR meter tails were found entering the cavity and coming down a stud wall to a consumer unit about 5 meters (direct distance) away.
they do have an isolator but no rcd or other protection .

as cables buried in a wall have to have (RCD) Residual Current Device at 30mA and generally tails over 3 meters are not permitted by DNO ,how can this comply?
Click to expand...
As @Pretty Mouth has said in his post. I have twice now installed tails like this, both times I have used mechanical protection (3mm steel) which may not be visible without chiselling a bit of the wall out.
 
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newfutile said:
During an EICR meter tails were found entering the cavity and coming down a stud wall to a consumer unit about 5 meters (direct distance) away.
they do have an isolator but no rcd or other protection .

as cables buried in a wall have to have (RCD) Residual Current Device at 30mA and generally tails over 3 meters are not permitted by DNO ,how can this comply?
Click to expand...

Cables buried in a wall don't have to have RCD protection, they can have other forms of protection.

As you are carrying out an EICR it is very difficult to confirm whether or not correct protection has been installed. Examination of cables buried within walls, under floors etc is a standard limitation.

You need to make a judgement call as to whether it is likely to comply or not. When was it installed, what is the general standard of the installation, what records are available?
 
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I watched that efixx vid, and re-watched it a couple of times, and then had a read through the regs mentioned.

433.3.1(iii), 434.3 (iv), and item (ii) of 434.2.1, these make me think that the tails are not restricted to 3m, as long as they are well protected mechanically, and that the DNO agrees that they are protected by their fuse.

Does anyone know under what circumstances a DNO would agree, or even disagree, to this?
 
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Pretty Mouth said:
I watched that efixx vid, and re-watched it a couple of times, and then had a read through the regs mentioned.

433.3.1(iii), 434.3 (iv), and item (ii) of 434.2.1, these make me think that the tails are not restricted to 3m, as long as they are well protected mechanically, and that the DNO agrees that they are protected by their fuse.

Does anyone know under what circumstances a DNO would agree, or even disagree, to this?
Click to expand...

They'll probably never agree to it, certainly not for small supplies.
I've found that DNO's generally allow between 3 and 4 metres of tails maximum.
 
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thanks for all the interesting input and advice, i also put the same question to NICEIC but im less than impressed with the reply:


Good Afternoon,

Thank You For Your Enquiry

Based on the information provided, our guidance is as follows;

There is not a specific regulation within BS7671 which states whether or not supply tails with no RCD protection with a length of run greater than 3metres would result in a satisfactory or unsatisfactory outcome.

Do you feel that there is a safety concern or do you feel that an improvement can be made? Please could you also clarify how the tails have been installed.

Once we get further clarification from yourself than we may be able to assist further with your query.

Regards,
 
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newfutile said:
thanks for all the interesting input and advice, i also put the same question to NICEIC but im less than impressed with the reply:


Good Afternoon,

Thank You For Your Enquiry

Based on the information provided, our guidance is as follows;

There is not a specific regulation within BS7671 which states whether or not supply tails with no RCD protection with a length of run greater than 3metres would result in a satisfactory or unsatisfactory outcome.

Do you feel that there is a safety concern or do you feel that an improvement can be made? Please could you also clarify how the tails have been installed.

Once we get further clarification from yourself than we may be able to assist further with your query.

Regards,
Click to expand...
Their response doesn't seem unreasonable. DNO conditions of supply and BS 7671 requirements are separate issues. It doesn't mean that the installation is not in breach of the former, however.
 
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End of the day it makes no difference to you wht the outcome of the eicr is….so if concerned give it C2 or fi and put the report to the person paying 😁
 
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davesparks said:
Cables buried in a wall don't have to have RCD protection, they can have other forms of protection.

As you are carrying out an EICR it is very difficult to confirm whether or not correct protection has been installed. Examination of cables buried within walls, under floors etc is a standard limitation.

You need to make a judgement call as to whether it is likely to comply or not. When was it installed, what is the general standard of the installation, what records are available?
Click to expand...

newfutile said:
During an EICR meter tails were found entering the cavity and coming down a stud wall to a consumer unit about 5 meters (direct distance) away.
they do have an isolator but no rcd or other protection .

as cables buried in a wall have to have (RCD) Residual Current Device at 30mA and generally tails over 3 meters are not permitted by DNO ,how can this comply?
Click to expand...
If tails are ran under plaster & not mechanically protected - they need an RCD.

A 30mA may trip before the board - would a 100mA RCD comply? Surely not???

Mmmm
 
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Don't forget that the requirement for RCD protection of buried cables only applies if they are less than 50mm from the surface. If we're talking lathe and plaster on proper 4" studs, there's a good chance they're outside the 'zone'.
 
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brianmoooore said:
Don't forget that the requirement for RCD protection of buried cables only applies if they are less than 50mm from the surface. If we're talking lathe and plaster on proper 4" studs, there's a good chance they're outside the 'zone'.
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If they’re under 50mm - ie under plaster they should be RCD’d?

But it the RCD is 30mA it’s like having a main switch as an RCD in the board - would a 100mA avoid discrimination?

But still wouldn’t be to regs?

Confused!!! 😂😂😂
 
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The tails to my flushed in consumer unit are in a stud wall for a short section, so to avoid the need for an RCD I put 32mm galv conduit into the stud wall for the tails, bushed into the side of the consumer unit.
 
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DarrenRB said:
Thanks for the reply - ‘NO’ 😂😂😂

How would you get around discrimination between a 30mA protecting buried tails & RCBO’s tripping?

I can’t see a workaround other than mechanical protection or a 16mm SWA with in-built mechanical protection 🤔
Click to expand...
That's pretty much the size of it. 522.6.204 (i) to (iv) are your options, earthed SWA/conduit/trunking/MICC etc, or very strong mechanical protection.
 
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Pretty Mouth said:
That's pretty much the size of it. 522.6.204 (i) to (iv) are your options, earthed SWA/conduit/trunking/MICC etc, or very strong mechanical protection.
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Yep….

That’s where I am…

BUT

I’m going to fit a 100mA to buried meter tails as remedial EICR work.

OK, it’s not to regs …. Shoot me.

A 30mA may discriminate - rendering the fancy RCBO board useless.

If Joe bloggs were to ---- a meter tail I’m sure they’d welcome any form of RCD opposed to the 60A DNO fuse tingle?

Common sense to me - I’ll say that in court should the need arise 😂😂😂

Explain to customer & admit to deviation on certificate.

Case for the defence rested m’Lord… 😁
 
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It will only discriminate if the earth leakage, including 'normal' leakage from all the circuits, is below the tripping threshold of the 100mA RCD, typically 60 - 70mA.
If the earth leakage is above this, then both the relevant 30mA RCBO and the 100mA supply RCD will trip.
 
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DarrenRB said:
Yep….

That’s where I am…

BUT

I’m going to fit a 100mA to buried meter tails as remedial EICR work.

OK, it’s not to regs …. Shoot me.

A 30mA may discriminate - rendering the fancy RCBO board useless.

If Joe bloggs were to ---- a meter tail I’m sure they’d welcome any form of RCD opposed to the 60A DNO fuse tingle?

Common sense to me - I’ll say that in court should the need arise 😂😂😂

Explain to customer & admit to deviation on certificate.

Case for the defence rested m’Lord… 😁
Click to expand...
BPG4 is giving this situation a C3, so wouldn't necessarily need remedying:

C3 - Absence of additional protection by RCD for cables installed at a depth of less than 50 mm from a surface of a wall or
partition where the cables do not incorporate an earthed metallic covering, are not enclosed in earthed metalwork, or are not mechanically protected against penetration by nails and the like.
 
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brianmoooore said:
It will only discriminate if the earth leakage, including 'normal' leakage from all the circuits, is below the tripping threshold of the 100mA RCD, typically 60 - 70mA.
If the earth leakage is above this, then both the relevant 30mA RCBO and the 100mA supply RCD will trip.
Click to expand...
Yep… understood!

In my head 😄….

If the downstream RCD has a higher trip fault current than the device connect to the final circuit …

In my theory the RCBO should arrest the fault & disconnect before reaching the dizzy heights of 60-70 mA.?

Ah well …, just a thought!

I know what I mean 🙄🙄🙄

Appreciate you taking the time to reply! 👍
 
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Pretty Mouth said:
BPG4 is giving this situation a C3, so wouldn't necessarily need remedying:

C3 - Absence of additional protection by RCD for cables installed at a depth of less than 50 mm from a surface of a wall or
partition where the cables do not incorporate an earthed metallic covering, are not enclosed in earthed metalwork, or are not mechanically protected against penetration by nails and the like.
Click to expand...
Yeah…. I just don’t think it’s safe for meter tails at potentially 100A

Popping a nail through a tail with no fault protection gives me the ‘heeby jeebys’ 😂😂😂

Is that a word?

Agree though… I’d code C3 for no RCD on lighting cables - usually do tbh.
 
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A fault of any magnitude would only occur if you have a line to neutral or line to earth (TN systems) fault. A line to neutral fault is possible and an RCD would not give protection from it. Should a nail penetrate line to an effective earth such as cable armour or steel conduit then again sufficient fault current would flow and in this case additional RCD protection is not required. Additional RCD protection gives protection from a negligible fault such as the nail becoming live and a person touching it and coming into contact with something which is earthed.
 
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I have encountered a situation where meter tails are placed in the wall more than 3 meters without an RCD. Usually, DNOs do not allow tails of this length without protection, and I did this: put tails in a metal tube or armoured cable to avoid the requirement for RCD. If tails go in ordinary PVC insulation, they should be protected by RCD or laid in a way that minimizes the risk of damage.
 
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newfutile

newfutile

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Meter tails no rcd in stud wall
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