Correct method of wiring a double socket

[bernardgreen]

Not sure if this has been covered already but I thought current guidelines were for a ring socket that an earth from each cable went to each of the earth connectors on the socket ?

That's what the diagram shows in the current on site guide anyways.

In my opinion both earth conductors should go into the same terminal. Putting them in separate terminals means both screws have to be tight to ensure continuity of the earth to other sockets.

I also gently twist bare earths together inside the sleeve to further reduce the risk of loosing earth continuity if the terminal becomes loose.

 

[ericmark]

Personally I fit a link from socket to back box when metal but if the hold down screws are tight these would auto earth the back box. My thoughts are people do slack of screws while papering so I always fit link.

As to LAN can't see it really matters but with TV one has to be really careful. The problem with an aerial is during an atmospheric storm there can be a huge voltage variation over the hight of a house. Sharp corners and any earthed parts will attract a lighting strike or if not direct lighting will pick up some of the voltage which can both harm TV and anyone touching the aerial.

So the aerial should NOT be earthed. Neither should it be fitted to a gable end or a soot lined chimney. In the box there should be de-coupling capacitors to stop you getting a shock when unplugging or plugging in aerial. Any earth must be after these capacitors.

Selecting the right TV outlet is important there are basically three types.
1) With simple de-coupling capacitors.
2) With band pass filters this may include a braid break or may not. These are for use with another similar device which combines signals the combiner should have any de-coupling capacitors required.
3) No de-coupling capacitors these are used to also carry DC voltage. Either to a Digi-eye in another room so you can change sky channels remotely or to a mast head amplifier the latter will have de-coupling capacitors fitted.

In my case there was a booster in the loft again de-coupling capacitors to booster but not from booster.

So one has to be wary when earthing a TV point it is bad enough when a near miss takes out the TV, Video, or other gear but to burn out all the earths in the house would mean a complete re-wire. So I personally would not take an earth to a stand alone TV socket.

 

[ban-all-sheds]

My thoughts are people do slack of screws while papering

Only the slapdash ones - the conscientious remove the accessories completely.

 

[JohnW2]

I thought it would be unsafe not to, there was a previous comment in the thread: 'There does not need to be a link from the earth terminal to the box if the box has one fixed lug, but it is considered good practice to do this.'

For a start, that is only an option with accessories (like sockets) which have an earth terminal - plastic light switches, for example, usually won't (but the heads of the screws, electrically connected to the back box, will be touchable). When there is an earth connection to the accessory, it used to be common practice to rely on the faceplate screws to establish a connection between the back box and the earth at the accessory, but, as you say, that is no longer considered good practice - for the sake of a small piece of wire, it's not really worth the risk.

I would add that the question/discussion is most often the other way around, relating to a metal-faced accessory and an earthed back-box. In that situation, relying on the faceplate screws to earth the accessory is even more dangerous - since, if someone is silly enough to undo the faceplate screws whilst the circuit is still live, once the screws are out, under fault conditions (conductor slipping out of terminal as the plate is pulled forward) the metal accessory could become live.

Kind Regards, John

 

[bernardgreen]

To reduce damage to equipment from lightning strikes the aerial down lead should be bought down below and about 6 inches to the side of the point of entry to the building. Then with a U bend bring the aerial lead back up to the entry point. Then fit a length of heavy gauge wire or other metal next to the downlead on the side of the U away from the entry point and connect this to a ground rod directly below.

The U is a half turn coil with a high impedance to the rapidly rising current of the lightning strike and this encourages the energy of the lightning strike to break through the insulation of the down lead and jump across the gap and go via the wire to earth.

This on its own will not fully protect equipment but by diverting most of the energy to ground outside the building damage inside the building is reduce.

 

[ban-all-sheds]

So is the conclusion to get yourself an aerial installer who learned his trade in the Massif Central?

 

[bernardgreen]

So is the conclusion to get yourself an aerial installer who learned his trade in the Massif Central?

In London a lot of those who strung long wire aerials for crystal sets used this method.

 

[fuzzytrifle]

So the aerial should NOT be earthed. Neither should it be fitted to a gable end or a soot lined chimney. In the box there should be de-coupling capacitors to stop you getting a shock when unplugging or plugging in aerial. Any earth must be after these capacitors.

Selecting the right TV outlet is important there are basically three types.
1) With simple de-coupling capacitors.
2) With band pass filters this may include a braid break or may not. These are for use with another similar device which combines signals the combiner should have any de-coupling capacitors required.
3) No de-coupling capacitors these are used to also carry DC voltage. Either to a Digi-eye in another room so you can change sky channels remotely or to a mast head amplifier the latter will have de-coupling capacitors fitted.

In my case there was a booster in the loft again de-coupling capacitors to booster but not from booster.

So one has to be wary when earthing a TV point it is bad enough when a near miss takes out the TV, Video, or other gear but to burn out all the earths in the house would mean a complete re-wire. So I personally would not take an earth to a stand alone TV socket.

I only got around to reading your post last night and have just checked all of the TV sockets in the house - all but one are MK grid TV/DAB sockets (K5852DAB) which have an earth connection on the back, 2 are linked to the back box, 2 aren't - the aerial is located in the loft space above an adjacent workshop and all 5 coax cables run underground through conduit which comes up inside the house. I have no idea why some of the sockets are earthed and others aren't, all have metal back boxes.

 

[SimonH2]

Not sure if this has been covered already but I thought current guidelines were for a ring socket that an earth from each cable went to each of the earth connectors on the socket ?

That's what the diagram shows in the current on site guide anyways.

That refers to circuits with high CPC currents. 7.5.3

Normally it makes no difference.

I normally use both terminals if there are two. I work on the basis that when testing, it should show up if any wire has come out - the ring won't have continuity but there will still be an earth path from each socket (including the one with the bad connection) to the CU. If you are in the habit of lightly twisting the CPCs and putting them in a single sleeve, then I reckon (particularly when the installation is new) you'd still show continuity even if the CPCs have come out of the terminal.

It also means less wires to keep in place while doing up the terminal !

 

[ban-all-sheds]

For high-integrity cpcs because of high current, you need two separate cpc rings if the circuit is a ring final.

//www.diynot.com/forums/viewtopic.php?t=132700&start=0

 

[SimonH2]

I'm not falling for that one.