Would You Believe It?

[securespark]

For the first time in my electrical career, I am filling out an EIC having tested some sub-mains feeding outhouses of a domestic property.

The supply to the main CU is TN-C-S. The feed to the sub main is in standard T&E, on a B32 breaker.

How best do I complete the EIC?

Rating of main fuse: 32A?

TN-C-S or TN-S?

Etcetera....

Please help!

 

[Adam_151]

TN-C-S

Main fuse still the DNOs cutout

Fill the first part of the EIC as if it were for the main installation, but be clear on scope of work

Have one pair of schedules for the main board (with all circuits listed, but a line through the data of circuits that arn't submains if they are not part of the test), and then an additional pair of schedules pair of schedules for each sub board

Chance Ze on the subboard schedules to Zdb and write the Zs of the submain circuit there. Similar with PFC on the shedules, write the PFC at the board to which the schedule applies. TNC-S though on all schedules (its still TNC-S; combined on DNO, separated after, *not* TNS; separated all the way back to star point)

 

[securespark]

I was leaning towards TN-C-S, however, what made me doubt it was the fact that although the main supply to the main DB is TN-C-S, the supply to the sub db (which I'm filling out the form for) is three wire.

Thanks for the clarification.

I can't believe I've been in this game for well over 20 years & have not come across this situation before!!

 

[ban-all-sheds]

You sometimes see mini-CUs suggested for a set of cooking appliances where a traditional CCU doesn't give the flexibility for a separate hob, oven & hood.

Don't know how often it's actually done, but would you follow the same plan?

Secure - the earthing arrangement question is clearer if you imagine your outhouse board supplied by long tails and a long main earth direct from the incoming supply via a henley block and the MET. The fact that you've put a protective device in the phase conductor doesn't change anything.

 

[securespark]

Ban, thanks. I now realise that putting a protective device in does not alter the arrangement.

 

[securespark]

Adam

If I can pick your brain again...

When it comes to supply conductor csa and main earthing csa, and for meb's etc, is that for the sub db or the main one??

I guess the sub one, so I'd be recording the size of the conductors feeding the sub db and meb details for the outhouse, yes?

While I'm here, exposed catnics I guess should be bonded?

 

[Pensdown]

Adam

If I can pick your brain again...

When it comes to supply conductor csa and main earthing csa, and for meb's etc, is that for the sub db or the main one??

I guess the sub one, so I'd be recording the size of the conductors feeding the sub db and meb details for the outhouse, yes??

Just to confirm what Adam has said, the Supply conductor CSA and main earthing CSA refer to the origin, just like any other EIC and are entered on page 2

The only difference with submains and sub DB's/CU's is you need to complete another pair of schedules.

The first pair, pages 4&5 are completed for the submain, cables size, method of installation, CSA size etc, just like you would for a sub circuit. The test results for the submain circuit are entered as normal.

On the second set of schedules, pages 6&7 you enter the details of the final subcircuits which are fed from the submain CU/DB. You also need to complete the box top left which is Zs etc at the sub CU/DB.

While I'm here, exposed catnics I guess should be bonded?

Have you been reading the 15th again......

 

[securespark]

Thanks.

Eeeeh, I do get thoroughly confused. Maybe I should burn all my old Ed's?



Actually, having had a quick look at the yellow 16th OSG, it says structural steel is an ex-c-p.......but I don't have access at the moment to my brown 16th OSG.

 

[Pensdown]

Structural steel is an ECP and if the lintel is connected to the structural steel the main bond would cover it.

But in a conventional brick built property it's no more of an ECP than a steel window or a door handle.

As for the previous editions.....can you post the burning on UTube?

 

[securespark]

.....It'll be burning for days....

Point taken about it being no more of a ex-c-p than a metal window frame or such-like.

But you must admit, it is rather confusing, ex-c-p's bonding etc...

Let's go back to the days of the 14th (hang on - hear me out!!) when the regs were much more explicit about do's & don't's.

You must bond this, you need not bond that etc...