Readings

[JohnCunningham]

Hello all It's my first post!

If the earth cpc (earth wire on the T&E cable in old money) is not connected back to the main fuse board and hence "earthed " itself the earth wire sitting between the L&N acts as a center tap capacitor (apparently). I found this out after measuring up to 120V on the cpc of a lighting circuit without the cpc's linked in any way. The voltage varies with cable legnths but doesn't seem to get above 120v. Odd but true.

I spent a while testing and all Insulation resistance of all conductors 200M + and there were no other cross overs. NICEIC help desk had no answer but found an IEE paper on it somewhere on the internet.

Hope this helps

John

[Baracus]

There are several now with internal fuse, I think they had to start installing fuses after so many problems from them, blown dimmers, tripped MCB's etc.

But most will still fit the el'cheapo ones!

All I use is Osram a lot cheaper in the long run!

[Baracus]

. NICEIC help desk had no answer

Well thats only to be expected !

[Paul P]

during an alarm service last night I tested the 240v and got the following

L - N 240v

N - E 170v

L - E 70v

obviously adviced the customer to get an electrition(sic) in as a matter of urgency (ie straightaway) what could have been wrong?

and should I have powered them down?

You obviously have no earth at the control panel, if its metal then yes it should be powered down as the case will be at 170v.

[Paul P]

good sparky wouldnt put the lights ( or the freezer GRR ) on the RCD side - well except they now stuffed that too with the 17th edtn

I think you are only looking at the down side of the 17th edition on RCD

[luggsey]

Hello all It's my first post!

If the earth cpc (earth wire on the T&E cable in old money) is not connected back to the main fuse board and hence "earthed " itself the earth wire sitting between the L&N acts as a center tap capacitor (apparently). I found this out after measuring up to 120V on the cpc of a lighting circuit without the cpc's linked in any way. The voltage varies with cable legnths but doesn't seem to get above 120v. Odd but true.

I spent a while testing and all Insulation resistance of all conductors 200M + and there were no other cross overs. NICEIC help desk had no answer but found an IEE paper on it somewhere on the internet.

Hope this helps

John

How interesting! I'll try that when I get chance, .

[Guest anguscanplay]

I think you are only looking at the down side of the 17th edition on RCD

[JohnCunningham]

I went to a free NICEIC seminar about the 17th ed the other night. It seems that RCDs are the order of the day. Although not set in stone yet. we were informed that all wiring not 2" deep into walls would have to be protected by nail proof means if not in safe zones and if safe zones would not have to be protected but covered by 30 Ma rcd. This means all light drops have to be covered by an RCD to my understanding. All (everywhere) sockets that can be used by ordinary people would have to be RCD covered (not just to be used outside). Although you can have some non rcd sockets if they are labelled for that use only such as computer rings where earth leakage a problem and possibly a freezer circuit if you manage to comply somehow with all the other requirements.

We had a discussion about RCBO route and split RCD/RCD boards. Either way is a tad more pricey. I was hoping to get away with the rcd spur idea in bathroom ceiling on the rentals I test but looks that may not be the case. But then It hasn't been signed off yet so may all change.

John

that was the point I was making

[Baracus]

we were informed that all wiring not 2" deep into walls would have to be protected by nail proof means if not in safe zones and if safe zones would not have to be protected but covered by 30 Ma rcd.

That always made me laugh, by the time you track 3 inches into a wall there wouldnt be much left apart from an angry builder

All (everywhere) sockets that can be used by ordinary people would have to be RCD covered (not just to be used outside).

I always fit an RCD/RCBO for sockets regardless of location

Although you can have some non rcd sockets if they are labelled for that use only such as computer rings where earth leakage a problem

I never put any more than 6 computers on a ring there shouldnt be enough leakage to throw a 30mA

[luggsey]

That always made me laugh, by the time you track 3 inches into a wall there wouldnt be much left apart from an angry builder

I always fit an RCD/RCBO for sockets regardless of location

I never put any more than 6 computers on a ring there shouldnt be enough leakage to throw a 30mA

In the "old days" if six PC's had six CRT monitors and they all power up when the big switch is turned on they always seem to trip RCD's, not a problem now with TFT IMO.

The rule about 50mm of protection for burried cables has always been known, if less the 50mm you need earthed metalic protection against nails, I always think if you wire in a "zone" then that should be ok without metalic protection as to be honest most house wiring is less the 50mm deep as already mentioned.

RCD's are going to be almost standard for all sockets in houses in the 17th, and all bathroom wiring, a good thing IMO.

As to fridges, cut off the plug and wire to a spur, fixed appliance then not requiring an RCD, voids the warrenty on the fridge though!