Earthing a metal-plate phone socket

[AdamW]

I have just bought a load of stainless steel accessories. Obviously, the sockets and switches have the faceplate connected to the earth terminal. However, the phone socket I ordered ALSO requires an earth. It has the terminal and a note in the packet says it MUST be earthed. Presumably because phonelines can carry >50V, despite the pansy current carried.

There is a mains socket right next to the phone socket. Is it acceptable to run a short length of single-core cable from the phone socket earth to the mains socket earth, in the stud-wall cavity? Thus bonding the two faceplates at the same potential.

If so, is it acceptable to take a short length (8-10") of conductor out of a piece of T&E, earth sleeve it and use this?

 

[mapj1]

yes - so long as there is no actual connection to any part of the telephone circuit from the faceplate, it is then purely to stop it becoming live if a fault develops behind it or if your telephone cable is struck in a thunderstorm.
For a long time now the telephone network's own connection to earth (the third wire used for party lines that dissapeared into the front garden on most houses) has becoming more and more nebulous, as the metalwork is rotting off. Most new installations are only earthed at the exchange end, and are effectively floating at the users equipment.

 

[AdamW]

Cheers for that. There is no connection between the telephone system and the faceplate, the two are isolated by the plastic surrounding the phone connector and the IDC terminals.

 

[ban-all-sheds]

Then why does the faceplate need earthing?

 

[plugwash]

my guess is the manufacturer thought that since there would be phone wires in there with only single insulation the plate should be earthed

i dunno what the regs are on this (or even if regs writers ever thought of it) though i do know that cords with touchable pins on the phone/modem end are the norm so if they are allowed i can't imagine that phone lines could generally be considered as dangerous to touch.

 

[HDRW]

my guess is the manufacturer thought that since there would be phone wires in there with only single insulation the plate should be earthed

Or maybe in case a passing mains cable behind it makes contact with the faceplate? (You never know!) Or since it's screwed to a backbox, that it could be an extraneous earth?

i dunno what the regs are on this (or even if regs writers ever thought of it) though i do know that cords with touchable pins on the phone/modem end are the norm so if they are allowed i can't imagine that phone lines could generally be considered as dangerous to touch.

They are supposed to have the tag on the end of the catch broken off, so you can't disconnect them without using a tool (Swiss Army Knife toothpicks are good!). I don't know if you've ever got yourself across a phone line when it rings, but it's no fun, and I don't believe "they" expect you to touch it, hence the spring-loaded shutters over phone sockets.

Cheers,

Howard

 

[plugwash]

most phone cables have the tab shortened (its not broken off completely or the plug wouldn't stay in the socket) but most modem cables don't and neither do the cables for some cordless phones i've seen

and thats before we even mention structured cabling installs that do everything with cat5

 

[ban-all-sheds]

Or maybe in case a passing mains cable behind it makes contact with the faceplate?

You're not allowed to have mains cables in the same enclosure....

 

[Steve]

i dunno what the regs are on this (or even if regs writers ever thought of it) though i do know that cords with touchable pins on the phone/modem end are the norm so if they are allowed i can't imagine that phone lines could generally be considered as dangerous to touch

man came to install sky a few years ago, youngish fella. came to installing the phone extension, all indoors, he fitted the plug-in piggy-back start of the lead and to test it he stuck the other end of the lead in his mouth! Cant be that much voltage there, just enough to tingle. Though he only wired 2 of the wires up, so any phone plugged in at the TV would never ring

 

[HDRW]

man came to install sky a few years ago, youngish fella. came to installing the phone extension, all indoors, he fitted the plug-in piggy-back start of the lead and to test it he stuck the other end of the lead in his mouth! Cant be that much voltage there, just enough to tingle.

I see a Darwin Award in the making!

Did you know that a small but non-zero number of people die each year from testing PP3 (9V) batteries on their tongue?

Though he only wired 2 of the wires up, so any phone plugged in at the TV would never ring

You only have to connect the other one (assuming there is the opportunity to do so, and that he didn't cut back the other cores, and it's not a moulded-on plug). Terminals 2 and 5 should be wired already, and it's terminal 3 that you need to connect at both ends, then it should ring as well. Most people do 4 as well, so 2 complete pairs are connected.

Cheers,

Howard

 

[Adam_151]

You're not allowed to have mains cables in the same enclosure....

Shame no one told that to the person who fitted the tv point in this room, double accessory box, mounted vertically, single 13A socket in the top, tv point below.

 

[Big_Spark]

The faceplates of Telephone and other wiring accessories, when manufactured from any conductive material, nust be earthed in order to ensure they remain at the same potential as the rest of the installation.

The reasoning being not that a faulty cable may liven the accessory, but rather a fault in equipment plugged into the accessory, that may have a 230V 50Hz supply, develope a fault that could then cause a potentially dangerous voltage to occur on the faceplate, which if not earthed, or at a different potential to the rrest of the installation, would prevsent a significant danger to those who came into contact with it.

 

[Adam_151]

That makes sense FWL, I guess I should earth the screen on the RF tv cables, I have had a shock of them before, I think it must be the PSUs in tvs and video recorders leaking to to the RF connections?

 

[Big_Spark]

That makes sense FWL, I guess I should earth the screen on the RF tv cables, I have had a shock of them before, I think it must be the PSUs in tvs and video recorders leaking to to the RF connections?

100% correct, but I would be careful before Earthing the screening, if you currently have a leaking PSU in your TV, and an RCD in the system, you may intorduce nuisance tripping...you may also degrade your TV picture.

I suppose a little experiment couldn't hurt though..but ensure your safety at all times.

 

[stevesey]

man came to install sky a few years ago, youngish fella. came to installing the phone extension, all indoors, he fitted the plug-in piggy-back start of the lead and to test it he stuck the other end of the lead in his mouth! Cant be that much voltage there, just enough to tingle.

I see a Darwin Award in the making!

Did you know that a small but non-zero number of people die each year from testing PP3 (9V) batteries on their tongue?

Phone circuit is high (enough) impediance, unlike a PP3. Might have been interesting if someone rang while he had it in his mouth (but you did go on to say he didn't connect the ringer).

On the subject of PP3 injuries - I have burnt my leg putting an old PP3 from a radio mic in my pocket! My loose change shorted it out when I sat down (about 10 seconds later I stood up very quickly).