consumer unit

[rzaxl]

so does any know what the procedure for using a 13amp plug powering a ccu, does anyone have any designs in mind

 

[Iggifer]

well, is your house consumer unit protected by an RCD? If not just stick it on a 13a and you're good to go

 

[riveralt]

so does any know what the procedure for using a 13amp plug powering a ccu, does anyone have any designs in mind

I have already told you what to do.

 

[rzaxl]

yep the house is ccu protected, so i take it the wiring diagram from the ccu switch will be switch neutral to 13a plug neutral, switch live to 13a live and ccu earth bar to 13a plug. can anyone confirm before i risk life & limb?

 

[rzaxl]

excellent i think i may have answered my own question

 

[EFLImpudence]

You will have a Live, Neutral and CPC entering your CU.

What would you normally do?

 

[rzaxl]

thats what i would do, im just a little bit nervous as this my first time at attempting this own my won

 

[riveralt]

thats what i would do, im just a little bit nervous as this my first time at attempting this own my won

How do you think a Consumer Unit main switch is wired?
If you don't know the answer to that question then perhaps you need to wait for your course to catch up with this knowledge.

 

[mfarrow]

If it were true TN-C-S-C (actually TN-C-S-C-S, I suppose!), with the earth pin of the plug connected to the neutral (which I assume mfarrow didn't mean)

No, earth pin wasn't connected to anything. I think you're right the first time to use the term TN-C-S. We don't count all the separate 'earths' that come off the DNO's PME system, so why do it when one comes off at the cutout? If the DNO taps an earth off the cable into my house 10 times, would that make it a TN-C-S-C-S-C-S-C-S-C-S-C-S-C-S-C-S-C-S-C-S-C-S? If we're saying in this situation that the cutout is the plug, and the main fuse a BS1362, then TN-C-S would be correct, wouldn't it?

Of course, depending on the type of supply, one might be creating a TN-C-S without the safety of PME, which it why caution should be observed; insulated CU; no Class I equipment etc.

 

[JohnW2]

I think you're right the first time to use the term TN-C-S. We don't count all the separate 'earths' that come off the DNO's PME system, so why do it when one comes off at the cutout?

At the level of 'an installation', the point in terms of regs is that one is not allowed to have a CNE conductor beyond the origin of an installation. In other words, one isn't allowed any further 'C' beyond the cutout.

If the DNO taps an earth off the cable into my house 10 times, would that make it a TN-C-S-C-S-C-S-C-S-C-S-C-S-C-S-C-S-C-S-C-S-C-S?

I wouldn't have thought so. To change from 'C' to 'S' requires that the fault path to your house has to split from a combined one to a separate one. To go back to 'C' requires that those two separate conductors thyen re-combine (not allowed within installations). Even though the CNE which enters your house may have multiple routes to earth, as far as your supply is concerned, it's still just TN-C-S. That's how I see it, anyway!

If we're saying in this situation that the cutout is the plug, and the main fuse a BS1362, then TN-C-S would be correct, wouldn't it?

Yes, but that's only in terms of that 'microcosm'.

Of course, depending on the type of supply, one might be creating a TN-C-S without the safety of PME, which it why caution should be observed; insulated CU; no Class I equipment etc.

That's true - although I have to say that I've rather lost faith in PME since westie told us how little it often means

Kind Regards, John

 

[mfarrow]

one isn't allowed any further 'C' beyond the cutout. To change from 'C' to 'S' requires that the fault path to your house has to split from a combined one to a separate one. To go back to 'C' requires that those two separate conductors then re-combine (not allowed within installations). Even though the CNE which enters your house may have multiple routes to earth, as far as your supply is concerned, it's still just TN-C-S. That's how I see it, anyway!

Yes I agree, I'm just trying to see what transpires if we were to over-analyse what we're dealing with I don't think there is a term for going from S to C, and I can't think of a circuit which does this outside our example.