Garden consumer unit

If it is suitable for the environment.

 

Theoretically yes, although there are limited circumstances where that would be necessary as opposed to the (sometimes easier) alternatives. Also, installing a new CU isn’t really a job for a DIYer.

You really need to give us a bit more information on what you’re trying to achieve, and why you want a secondary CU.

 

What's the rating of the breaker feeding the cct?

 

Circuit.

 

Don't sound promising here. I know I keep banging on about this but circuits feeding equipment outside the zone protected by the equipotential bonding will have a shorter disconnection time than those in the zone (house). To ensure this on alny supply type, it is advisable not to export the CPC from the supply, but to use an earth electrode locally to the new CCU and fit a 30mA rcd to protect all circuits. If the CCU is in a damp area it should be non flammable non metallic as would be used in agriculture and horticulture.

 

Might help if you could direct me as to the applicable Regulations in BS7671.

 

would you not negate that by picking the correct (larger) size cpc? More so for supplies directly outside the house lights/socket.

agree on going down the bottom of the garden depending on size etc. each job is different and takes that in to account.

i have heard of what you mentioned about exporting it and i think it was more to do with the dno and are different regs, also something about the incoming cable gland to the sub ccu needs to be plastic not metal so that it doesn’t do what you mentioned. That was word of mouth though and haven’t looked in to it personally (as I haven’t needed to).

if anyone has any further info would be good to know.

 

Depends on circumstances but might be easier to run a direct supply, eg SWA, to a socket radial circuit (no CU) then fuse down for lights. A new CU is probably unnecessary unless you’re going for high powered tools / equipment and various sheds etc.

 

As the DNOs will tell you, use of TNCS earthing is not recommended in BS7671 Section 705 due to the reasons that Bob gave. See 16.4 in the SP Energy guidance
https://www.spenergynetworks.co.uk/userfiles/file/EART-01-002.pdf

Some DNOs may just refuse to connect a new supply depending on the circumstances.

Unless carefully planned and specified, use of a DNO TNCS earth is not a good idea for a garden installation.

 

Section 705 refers to agricultural installations. There's a lot of talk regarding livestock and the use of 100ma and 300ma RCDs. There's also a reference to electric fences. SP Energy 16.4 also refers to Section 705. I don't think it is intended to address somebodies garden.

 

Not really sure how that is applicable. #8 refers to shorter disconnection times, outside zones etc.....
I am interested where this is referenced.

 

It is a bit of a mess unfortunately. It used to be in the PME Regulations, which were a supplement to the old Supply Regulations, and were both Statutory Documents. Unfortunately, when the UK government of the day wrote and implemented the ESQCR regulations, the PME regulations were forgotten about and not included. They do still exist very much in the "DNO World" for ensuring connections to the public supply are safe, and have had to be incorporated into the various DNOs Technical Guides, which in general are for DNO staff only, albeit a few DNOs have made their various Technical Guides available on the internet.

 

And how do the DNO "police" the installation after their meter and how is it their business?

 

The ESQCR makes it their business. My employer (a DNO) insists on a Test Certificate from a person or company registered as "Competent" for Building Regulations "Part P" signoff for a new property, re-wire of an existing property, or certain other specified works such as solar, battery or wind generation. No certificate, no supply. Simple.

 

https://www.legislation.gov.uk/uksi/2002/2665/regulation/9/made

 

If the installation is TT earthed, disconnection times are shorter, unless you fulfil requirements that cannot be fulfilled outdoors in a garden, because you are outside any equipotential zone you may have created within the indoor installation.

 

Indeed. The DNO I worked for was the same. Different DNO as I’m in Scotland.