Ask The Trades - Print Page

Ask The Trades
https://www.askthetrades.co.uk/cgi-bin/yabb/YaBB.pl DIY Forum >> Electrical Questions >> External Cabling in the Garden https://www.askthetrades.co.uk/cgi-bin/yabb/YaBB.pl?num=1089393180 Message started by Green_Fingers on Jul 9^th, 2004, 6:13pm

Title: External Cabling in the Garden
Post by Green_Fingers on Jul 9^th, 2004, 6:13pm

A good while back I had some cable laid under the patio into the garden for future use - most probably pond pump and garden lighting.

The sparkie taped up the end of the cable out there where the wind blows and the rain falls.

I'm getting twitchy - especially as I periodically suffer from a power mains ring gremlin causing the central trip switch to go - tho' no individual power circuit's switch (RCB?) trips and the house lighting remains unaffected.

Yep I've had the system checked twice now by competent sparkies and tho there were a couple of issues sorted, the phantom tripping continues.

What device should I get to terminate the 12mm cable rather than rely on the sparkie's red tape?

Yours thankfully, Green Fingers

PS Liked the jokes! ;D

Title: Re: External Cabling in the Garden
Post by greg on Jul 9^th, 2004, 6:16pm

Surely the cable is on its own breaker tho and the breaker will be in the off position so cant see how this would cause nuisance tripping?

Title: Re: External Cabling in the Garden
Post by Green_Fingers on Jul 9^th, 2004, 6:41pm

Thanks for the quick response. Cable isn't on a specially/new dedicated RCB. Its linked (a spur probably)into one of the (5) power main rings/circuits in the house - each of which has its own trip. (It does have its own wall switch inside the conservatory)

Title: Re: External Cabling in the Garden
Post by rabbit_rabbit on Jul 9^th, 2004, 8:05pm

There SHOULD be an RCD dedicated to the outside cable. Is the isolating switch in OFF position if not then switch it OFF. If it is OFF then it aint this cable, asuming switch is OK.

What do you mean by: "The sparkie taped up the end of the cable out there where the wind blows and the rain falls."

And waht do you mean by: "I periodically suffer from a power mains ring gremlin causing the central trip switch" The incoming RCD (assuming you have TT supply - overheadd cables)?

12mm cable seems somewhat large csa for a simple pond pump and lighting - unless ya live at Buckingham Palace - Charles.

RR

Title: Re: External Cabling in the Garden
Post by Lectrician on Jul 9^th, 2004, 8:29pm

12mm i assume as overall diameter.

No need for specific RCD for outdoor kit, it can share one with your ring mains if is a split load board used. (although it is better on its own).

Even if it had its own MCB, and this was off, then the N would still be connected, and the RCD could still trip.

Best to disconnect, not terminate the end.

If you want to terminate it, i would use a 'pot end', which is basically a resin joint with only one entry(or the second entry closed off). Cut all armours off, cut each conductor to a diferent length, and fill the joint.

Very surpised he livened it up at all :-)

BTW, TT systems are predominantly overhead, but can also be from undergorund networks.

Title: Re: External Cabling in the Garden
Post by HandyMac on Jul 9^th, 2004, 9:38pm

wrote on Jul 9^th, 2004, 8:29pm:

BTW, TT systems are predominantly overhead, but can also be from undergorund networks

I have a question for interests sake only.....

Where I grew up as a child in a council house, the mains came to the property via 2 wires strung from the telegraph pole outside the house. I didn't take much notice of it back then other than trying to throw things up to hang off the wires. Dunno when the house was built, I would assume 1940/50's.

Would that arrangement describe a TT system?

I don't recall ever finding a stake for earthing and I was always digging around the property, I always assumed they must've tied the earth to the neutral at the house end.

Andrew

Title: Re: External Cabling in the Garden
Post by rabbit_rabbit on Jul 9^th, 2004, 10:04pm

As Lec is implying one cannot really generalize Handy.

For example you can have overhead cables and have a PME (Protective Multiple Earth) which makes what many would think as a TT arrangement (overhead cables) is actually TN-C-S (Terra-Neutral-Common-Split).

Lec: agreed but I have a habit of automatically fitting RCD's to outside circuits like I breath automatically. God knows why coz as ya say if the CU has an RCD 30mA then why not. One probable reason I do it is so the client can isolate that ONE circuit as RCD's in CU's tend to be expensive and RCBO's even more expensive.

12mm probably outside dia.

RR

Title: Re: External Cabling in the Garden
Post by plugwash on Jul 9^th, 2004, 10:07pm

if there are 2 (and only 2) seperate wires to your house it has to be TT (consumer provides earth independent of REC)

the drop to the property from the tied down (as in neutral rodded down at frequent intervals) main cables for a PME (where earth is tired to neutral) has to be concentric

older TT installs were often earthed via water pipes rather than a rod being used this worked extremely well when all water pipes were metal but problems with it arose as water pipes were replaced with plastic and it is no longer allowed by wiring regs

i belive it is still permitted to have a TT earthed via burried structual steel but normal british houses don't have much of this ;)

Title: Re: External Cabling in the Garden
Post by rabbit_rabbit on Jul 9^th, 2004, 10:11pm

I did not mention number of cables on overhead supply Plug - but agreed 2 and 2 then it has to be TT.

Ray

Title: Re: External Cabling in the Garden
Post by HandyMac on Jul 10^th, 2004, 6:53am

Thanks guys. And I reckon with that house they most likely used water pipes to provide the earth. Even the outside guttering and drainpipes were metal so it stands to reason that the incoming water supply was as well.

Definitely only 2 wires coming in.

Andrew

Title: Re: External Cabling in the Garden
Post by Lectrician on Jul 10^th, 2004, 9:06am

TN-C-S = terra neutral combined seperate.

meaning N and E combined in supply and seperate in installation

the N combined with the E utilises a PEN or CNE conductor.

In the old school days, all overhead where TT, but as time has gone by, most overheads are PME complient.

Im PME is available, it may not be used in some instances anyway, eg. swimming pools, petrol station forecourts etc

Title: Re: External Cabling in the Garden
Post by Green_Fingers on Jul 12^th, 2004, 2:02pm

Hi to all contributors. Referring back to my original question, a lot of what Lectrician said rang bells with me, particularly regarding a connected Neutral causing problems. I'm sure I heard that when I had a sparkie explain why a gremlin might exist. I like the simple and cheap! disconnect idea!!

When the patio was laid the contractors had this 12mm diameter (external) black "heavy rubber" cable laid under the paviours and out into a bed of cobbles. Yes the end of the cable lying hidden among the cobbles it is taped up with some red insulating tape.

I'm off to switch all power to the house off then disconnect the cable.

MANY THANKS TO YOU ALL. :)

Title: Re: External Cabling in the Garden
Post by ban-all-sheds on Jul 12^th, 2004, 2:28pm

wrote on Jul 12^th, 2004, 2:02pm:

When the patio was laid the contractors had this 12mm diameter (external) black "heavy rubber" cable laid under the paviours and out into a bed of cobbles.

Is it not Steel-wire Armoured (SWA) cable, then?

You shouldn't just bury an unprotected cable. If it's not SWA, is it in any sort of conduit? Do you know how deep it is buried? Do you know if there is warning tape above it?

Sounds like there might be a number of things wrong here....

Title: Re: External Cabling in the Garden
Post by Green_Fingers on Jul 12^th, 2004, 5:57pm

Thanks ban_all-sheds.

Green_Fingers will keep all 10 digits by ensuring good practice is followed. A proper sparkie will be employed!!

Cheers ;D