Dedicated Circuit

[ADS]

There's been quite a bit of discussion recently regarding CU changes and the paperwork involved.

It was pretty much settled that if you're not doing a PIR on the existing installation, then you issue an EIC with accompanying schedules for the CU install and connected circuits.

So, I have a question.

You're doing a CU swap in a domestic.

If the customer asks for an existing single-socket radial not to be put on an RCD (say, for an aquarium), what do you do?

We know that in the 17th you can have a dedicated, labelled socket outlet without RCD protection but......the cable feeding this socket is unlikely to be buried deeper than 50mm, nor is it likely to have mechanical protection.

The Regs say this cable should have 30 mA RCD protection and you're not allowed non-compliance on your EIC, but you also don't have to bring an existing installation up to 17th spec - so do you do as asked?

You also have to consider this guidance from the ESC best practise guide -

5.4. Where a consumer unit is being replaced, additional

protection by means of RCDs in accordance with Regulation 415.1 should be provided to the extent required by the current edition BS 7671, such as for:

 

[Badger]

There's been quite a bit of discussion recently regarding CU changes and the paperwork involved.It was pretty much settled that if you're not doing a PIR on the existing installation, then you issue an EIC with accompanying schedules for the CU install and connected circuits.

So, I have a question.

You're doing a CU swap in a domestic.

If the customer asks for an existing single-socket radial not to be put on an RCD (say, for an aquarium), what do you do?

We know that in the 17th you can have a dedicated, labelled socket outlet without RCD protection but......the cable feeding this socket is unlikely to be buried deeper than 50mm, nor is it likely to have mechanical protection.

The Regs say this cable should have 30 mA RCD protection and you're not allowed non-compliance on your EIC, but you also don't have to bring an existing installation up to 17th spec - so do you do as asked?

You also have to consider this guidance from the ESC best practise guide -

5.4. Where a consumer unit is being replaced, additional

protection by means of RCDs in accordance with Regulation 415.1 should be provided to the extent required by the current edition BS 7671, such as for:

 

[ADS]

Maybe that was a bad example of a reason then.

Lets's say, for whatever reason, he's adamant he doesn't want a particular single socket radial on an RCD, because he cannot afford loss of power to this socket.

 

[Badger]

id just turn round and say tarra if you expect me to install a c/u with a socket circuit feeding a water filled aquarium as that in my book is not safe to put fish tanks in place with out rcd protection

---------- AUTO MERGE Post added at 09:18 ---------- Previous post was at 09:17 ----------

just tell him what does he do in the event of a power cut :^O

---------- AUTO MERGE Post added at 09:24 ---------- Previous post was at 09:18 ----------

one other thing is get him to sign a disclaimer saying he takes responsibilty for the none rcd protected socket on the fish tank and if any injury or a death occurs because of the socket not being adacetly protected at 30mA then they will not try and sue you for neglect

---------- AUTO MERGE Post added at 09:25 ---------- Previous post was at 09:24 ----------

if that was the case then id put a 6amp or 10a mcb not 16

 

[Ali]

If his fish are that important to him, maybe he could live with some mini trunking and have the whole circuit surface mounted. More work and more money but at least it complies with the regs.

 

[Badger]

but my worry isnt the outlet itself its the fact filters lights heaters etc are in the water and hands etc can touch both live equipment and the water at the same time with rcd protection if a fault occured they would find that 1 rcbo would trip as only the fish tank is protected on that circuit

 

[S60TEM]

although not buried in the wall mini trunking would not be sufficient mechanical protection, it would still have to be earthed steel conduit.

 

[Sidewinder]

s60,

That is incorrect, for domestic T&E itself is sufficient mechanical protection if the cable is surface clipped and not in an area subjuct to increased risk of damage.

IF MT is insufficient then there are millions of domestic rewires in the public sector & millions of commercial installs that are non compliant.

 

[S60TEM]

learn something new everyday

 

[Andy™]

Maybe that was a bad example of a reason then.Lets's say, for whatever reason, he's adamant he doesn't want a particular single socket radial on an RCD, because he cannot afford loss of power to this socket.

as long as cable doesnt require RCD protection, there are expemtions to an RCD. i.e dedicated socket to fridge etc

 

[SPECIAL LOCATION]

:C

If a permanent supply is that essential..

1/ Install an UP's unit.

2/ Have the circuit supplied via an RCBO, or surface clipped then RCD socket outlet, so other circuits won't cause any disruptions.

because as Badger has said.. there is just as much risk, (if not greater), of a power cut as an RCD trip....

Why all the paranoia that because its got and RCD/RCBO in the circuit its going to be tripping off every other week..???????

:C :|

 

[ADS]

Amazing how sidetracked topics can get!!!

Forget the fish and their tank - that was just a daft example as to why he might not want the circuit tripping. :|

The whole point of my question was this -

The Regs allow for a dedicated, labelled socket outlet, for one item of equipment, to not be RCD protected - so I'm guessing there must be a demand for this, regardless of how reliable you think RCDs are, otherwise why bother?

Now, if this circuit already exists and you change the CU, what do you do about the requirement for cables buried less than 50 mm (as the circuit is likely to be)

That was the gist of my question.

 

[sellers]

bring them surface, or screw some steel plating on the wall over them?

I'f he's desperate for this tank not to be RCD'd install a new circuit surface, with a fused spur for the tank.

 

[NozSpark]

While you can get around the need to have the socket RCD protected, you cannot get around the <50mm bit (at the moment! - I thnk there will be a get out in Amd1 when it comes out)

 

[ADS]

So we'd have to say - 'No, I can't re-connect that circuit without RCD protection, as the cable routing/depth doesn't allow it'

And failing that, re-route or mechanically protect the cable, as some suggested.

You see, this is where it all gets confusing and annoying - it was safe enough when installed with the cables at a depth of less than 50mm, but you change the CU, making the installation safer as a whole, and suddenly that circuit isn't safe.

 

[spinlondon]

If you are being asked to install new circuit, irrespective of whether there is a CU change, the new circuit should comply with the Regs.

There are a number of methods of achieving this without resort to an RCD.

Running the cables on the surface, using a cable with an earthed sheath, using earthed conduit/trunking or providing mechanical protection.

In this instance, I'c suggest using a cable with an earthed sheath.

 

[PaulSC]

This is an interesting point. Before Christmas, I installed a high level socket in a bedroom for a customers LCD TV. He had no RCD protection on his old Wylex board, so I fed a FCU from the lighting circuit in the loft above in MT to a labelled ("AV use only") surface mount socket.

But where do you draw the line. My addition was compliant. But, the feed to the upstairs lighting circuit could well have been installed at less than 50mm somewhere along its run, though it would be almost impossible to verify without significant demolition/disruption. Is that my responsibility, or simply the bit I added?

 

[spinlondon]

You are just responsible for the part you have worked on.

In the case you have cited, everything complies no problem.

However if there was a shower in the room, you would have had to protect the lighting circuit with an RCD.

 

[Evans Electric]

Is'nt it strange that the thousands of miles of cable buried in walls were deemed to be quite safe for all those years , now everyone is paranoid about them .

 

[SLIPSHOD & SLAPDASH]

This is an interesting point. Before Christmas, I installed a high level socket in a bedroom for a customers LCD TV. He had no RCD protection on his old Wylex board, so I fed a FCU from the lighting circuit in the loft above in MT to a labelled ("AV use only") surface mount socket.

But what if he had run a lead out the window for his Tv in the garden