Is an RCBO an adequate replacement for an isolator?

[Doctor Drivel]

They do not.

[Doctor Drivel]

as well as the one on your bum.

[geoff]

In message , Doctor Drivel writes

I thought that they were giving you tablets to stop those

[Doctor Drivel]

Maxie, have you been out on the town in Watford tonight? A great achievement! You never go roped in. The police never caught you mooning eh?

[Les Desser]

In article , John Rumm Sat, 14 Nov 2009 23:58:10 writes

That is where I got one a couple of years ago, but I no longer remember the Crabtree name/type. I suppose I can call Crabtree or whoever owns them now.

Its a dark brown unit about 4" high.

[geoff]

In message , Doctor Drivel writes

Ah - you're forgetting to take the little pink pills which keep your warped imagination under control

You're posting at 1:13 am

Shouldn't you be locked up at this hour ?

[Tim W]

Les Desser wibbled on Saturday 14 November 2009 22:54

The way to think about this is:

1) Is the cable protected by the fuse/mcb/rcbo adequately? In general, is the min cable current capacity (depending on what it's installed in) >= the breaker rating? *Usually* OK (bar exceptional installation conditions like buried in loads of insulation) for 2.5mm2 on a 20A breaker.

2) Is the disconnection time met? ie is the L-E impedance such that an overload or fault will trip the breaker in the required time to prevent the cable overheating. By implication, the same applies to the L-N impedance. The breaker type (B/C/D) or fuse curve has an effect here. This bit is concerned with the heating effect on the cable while carrying an overload current before the breaker has tripped. You can go wrong here with cables being too long.

3) Is the designed demand current of the circuit less than or equal to the breaker current.

4) Are the volt drops on the far end acceptable? Another area where excessive cable length can get you.

1+2 boil down to keeping the cable at or below its max operational temperature. 3 is common sense, or in other words you don't want the circuit tripping under expected/reasonable/design load conditions. 4 is to do with not upsetting the loads themselves.

Essentially you can do what you like if you meet the above conditions. So If you know that you are going to present say a 6kW load on one leg of your new 20A radial, you shouldn't do it. If you know that you won't, then you're fine.

Cheers

Tim

[Tim W]

Doctor Drivel wibbled on Sunday 15 November 2009 00:26

What is this fascination with blokes' bums?

Is you a batty boy? (Apologies to Ali G)

[Dave Plowman (News)]

Doubt it. Most gays are known for their quick wit.

[The Natural Philosopher]

Not most, just the ones you get to know about.

The rest are surly buggers, in every sense of the word ;-)

[John Rumm]

It sounds rather like he has been fantasising again.

[YAPH]

'Flyer through letterbox'? I think you've answered your own question ;-)

[Doctor Drivel]

Maxie, have you stopped swearing at people in the street yet? Amazing, I hope there is progress. Did you go disco dancing at teh weekend with you viz jacket on again? Fantastic indeed. Only Maxie can do that. Anyone who dances with bells on his ankles should really be noted.

And you being in a Paddy band as well.

[Doctor Drivel]

You are the one with the tattoo on it.

[Doctor Drivel]

How much did your tattoo cost? Was it painful to sit down when it was done?

[Tim W]

Doctor Drivel wibbled on Monday 16 November 2009 12:53

I thought Morris Dancing was illegal (Taste and Decency Act)?

[Tim W]

Doctor Drivel wibbled on Monday 16 November 2009 12:57

I'd be careful doing the peeping tom bit up my tree. The wind might blow you onto the level crossing round the corner. Be a shame to mess up our nice shiny newish trains.

[John Rumm]

Standard entry price...

It always is a pain squeezing into standard seating when you are tall.

[Doctor Drivel]

How dare you say Maxie is indecent - You scum!!!! He has put all that behind him now.

[Andy Wade]

I was wondering why the S/N ratio had suddenly dropped about 30 dB...

50 m^2 for the 20 A radial and 75 m^2 for the 32 A radial (with 4 mm^2 cable) - see the OSG.

Unfused 5 amp and 2 amp plugs to BS 546 are perfectly legal. The onus is on the installation designer to ensure that the flexes of all connected appliances are adequately protected. That's not usually any problem since BS 546 accessories are normally only used on lighting circuits.

That's not the reason - no appliance should be able to overload its own cord, or should have its own protection (like the fuse in a multi-way extension block). The issue is the fault (s/c) capability of the flex in relation to the I^2 * t let-through of the upstream circuit fuse or MCB.