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UK diy (uk.d-i-y) For the discussion of all topics related to diy (do-it-yourself) in the UK. All levels of experience and proficency are welcome to join in to ask questions or offer solutions. |
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#1
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Earthing back boxes and socket outlets
Just came to fit some socket outlets from Toolstation and realised the
faceplate screws aren't connected to earth. They're the top ones in this pic: http://i46.tinypic.com/9glo1z.jpg Older MK version with earth connection is below. I thought all sockets followed the MK pattern with the result that using either the earth connection on the faceplate or the earth connection in the back box would result in everything being connected to earth. But if someone made the earth connection to the back box on the Toolstation version, any connected appliance (double insulation and plastic earth prongs aside) wouldn't be earthed. Is that right? Is this something new? Or something cheap? |
#2
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Earthing back boxes and socket outlets
On 15/02/2013 20:15, mike wrote:
Just came to fit some socket outlets from Toolstation and realised the faceplate screws aren't connected to earth. They're the top ones in this pic: http://i46.tinypic.com/9glo1z.jpg Older MK version with earth connection is below. I thought all sockets followed the MK pattern with the result that using either the earth connection on the faceplate or the earth connection in the back box would result in everything being connected to earth. But if someone made the earth connection to the back box on the Toolstation version, any connected appliance (double insulation and plastic earth prongs aside) wouldn't be earthed. Is that right? Is this something new? Or something cheap? I thought that each connection had to be made separately, and relying on the faceplate being in contact with the back box was a no-no. Even if, as in the MK case, it might actually be connected. -- Rod |
#3
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Earthing back boxes and socket outlets
In article
, mike writes Just came to fit some socket outlets from Toolstation and realised the faceplate screws aren't connected to earth. They're the top ones in this pic: http://i46.tinypic.com/9glo1z.jpg Older MK version with earth connection is below. I thought all sockets followed the MK pattern with the result that using either the earth connection on the faceplate or the earth connection in the back box would result in everything being connected to earth. But if someone made the earth connection to the back box on the Toolstation version, any connected appliance (double insulation and plastic earth prongs aside) wouldn't be earthed. Is that right? Is this something new? Or something cheap? If we simplify the situation by assuming a surface mounted plastic patress then we have exposed metal parts (fixing screws) that can readily come into contact with the basic insulation on the conductors (the brown and blue cores) when the box is assembled. Rules are that exposed metal parts need to be separated from live conductors by 2 layers of insulation (double insulated)[1] or if there is only one layer of insulation be earthed. Given that, I can't see how these parts can be compliant. Given the supplier I am not that shockedg, it wouldn't be the first time a buyer has bought on cost only to be bitten in the arse when they find out they have worthless **** in the warehouse. Oooh, pass me another budget lasagne Neddy . . . . [1] Special case of reinforced insulation set aside for this example -- fred it's a ba-na-na . . . . |
#4
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Earthing back boxes and socket outlets
On 15/02/2013 20:15, mike wrote:
Just came to fit some socket outlets from Toolstation and realised the faceplate screws aren't connected to earth. They're the top ones in this pic: http://i46.tinypic.com/9glo1z.jpg Older MK version with earth connection is below. I thought all sockets followed the MK pattern with the result that using either the earth connection on the faceplate or the earth connection in the back box would result in everything being connected to earth. As you have seen, not always... But if someone made the earth connection to the back box on the Toolstation version, any connected appliance (double insulation and plastic earth prongs aside) wouldn't be earthed. Is that right? No, because the circuit earth wires will always be connected to the earth terminal on the socket face plate. You would not simply terminate the circuit earth wires on the backbox and rely on that to make an earth connection to the backbox. With a "normal" socket that has earthed screw holes the reverse situation is allowable - i.e. you can re;y on them to earth the backbox (assuming it has at least one fixed tag), however good practice would suggest adding a separate fly lead between circuit terminal and the earth terminal on the back box. Is this something new? Or something cheap? No and yes. -- Cheers, John. /================================================== ===============\ | Internode Ltd - http://www.internode.co.uk | |-----------------------------------------------------------------| | John Rumm - john(at)internode(dot)co(dot)uk | \================================================= ================/ |
#5
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Earthing back boxes and socket outlets
In article
, mike wrote: Just came to fit some socket outlets from Toolstation and realised the faceplate screws aren't connected to earth. They're the top ones in this pic: http://i46.tinypic.com/9glo1z.jpg Older MK version with earth connection is below. I thought all sockets followed the MK pattern with the result that using either the earth connection on the faceplate or the earth connection in the back box would result in everything being connected to earth. But if someone made the earth connection to the back box on the Toolstation version, any connected appliance (double insulation and plastic earth prongs aside) wouldn't be earthed. Is that right? Is this something new? Or something cheap? It's best practice to run an earth wire between the socket and earth terminal on a metal back box. That's why it's there. -- *Cleaned by Stevie Wonder, checked by David Blunkett* Dave Plowman London SW To e-mail, change noise into sound. |
#6
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Earthing back boxes and socket outlets
On 15/02/2013 22:29, John Rumm wrote:
On 15/02/2013 20:15, mike wrote: Just came to fit some socket outlets from Toolstation and realised the faceplate screws aren't connected to earth. They're the top ones in this pic: http://i46.tinypic.com/9glo1z.jpg Older MK version with earth connection is below. I thought all sockets followed the MK pattern with the result that using either the earth connection on the faceplate or the earth connection in the back box would result in everything being connected to earth. As you have seen, not always... Don't think I've ever seen them before - I always assumed the earthed screw holes were mandatory But if someone made the earth connection to the back box on the Toolstation version, any connected appliance (double insulation and plastic earth prongs aside) wouldn't be earthed. Is that right? No, because the circuit earth wires will always be connected to the earth terminal on the socket face plate. You would not simply terminate the circuit earth wires on the backbox and rely on that to make an earth connection to the backbox. With a "normal" socket that has earthed screw holes the reverse situation is allowable - i.e. you can re;y on them to earth the backbox (assuming it has at least one fixed tag), however good practice would suggest adding a separate fly lead between circuit terminal and the earth terminal on the back box. So, if you have sockets with earthed screw holes does that mean you actually don't need the fly lead twixt socket and backbox? I thought it must be a belt-and-braces thing or something, but didn't think you could just do away with the flylead? -- David |
#7
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Earthing back boxes and socket outlets
On 16/02/2013 00:50, Lobster wrote:
On 15/02/2013 22:29, John Rumm wrote: On 15/02/2013 20:15, mike wrote: Just came to fit some socket outlets from Toolstation and realised the faceplate screws aren't connected to earth. They're the top ones in this pic: http://i46.tinypic.com/9glo1z.jpg Older MK version with earth connection is below. I thought all sockets followed the MK pattern with the result that using either the earth connection on the faceplate or the earth connection in the back box would result in everything being connected to earth. As you have seen, not always... Don't think I've ever seen them before - I always assumed the earthed screw holes were mandatory But if someone made the earth connection to the back box on the Toolstation version, any connected appliance (double insulation and plastic earth prongs aside) wouldn't be earthed. Is that right? No, because the circuit earth wires will always be connected to the earth terminal on the socket face plate. You would not simply terminate the circuit earth wires on the backbox and rely on that to make an earth connection to the backbox. With a "normal" socket that has earthed screw holes the reverse situation is allowable - i.e. you can re;y on them to earth the backbox (assuming it has at least one fixed tag), however good practice would suggest adding a separate fly lead between circuit terminal and the earth terminal on the back box. So, if you have sockets with earthed screw holes does that mean you actually don't need the fly lead twixt socket and backbox? I thought it must be a belt-and-braces thing or something, but didn't think you could just do away with the flylead? IIUC, so long as the box has at least one fixed lug, then you can do without the discrete fly lead. -- Cheers, John. /================================================== ===============\ | Internode Ltd - http://www.internode.co.uk | |-----------------------------------------------------------------| | John Rumm - john(at)internode(dot)co(dot)uk | \================================================= ================/ |
#8
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Earthing back boxes and socket outlets
In article ,
Lobster wrote: On 15/02/2013 22:29, John Rumm wrote: On 15/02/2013 20:15, mike wrote: Just came to fit some socket outlets from Toolstation and realised the faceplate screws aren't connected to earth. They're the top ones in this pic: http://i46.tinypic.com/9glo1z.jpg Older MK version with earth connection is below. I thought all sockets followed the MK pattern with the result that using either the earth connection on the faceplate or the earth connection in the back box would result in everything being connected to earth. As you have seen, not always... Don't think I've ever seen them before - I always assumed the earthed screw holes were mandatory But if someone made the earth connection to the back box on the Toolstation version, any connected appliance (double insulation and plastic earth prongs aside) wouldn't be earthed. Is that right? No, because the circuit earth wires will always be connected to the earth terminal on the socket face plate. You would not simply terminate the circuit earth wires on the backbox and rely on that to make an earth connection to the backbox. With a "normal" socket that has earthed screw holes the reverse situation is allowable - i.e. you can re;y on them to earth the backbox (assuming it has at least one fixed tag), however good practice would suggest adding a separate fly lead between circuit terminal and the earth terminal on the back box. So, if you have sockets with earthed screw holes does that mean you actually don't need the fly lead twixt socket and backbox? I thought it must be a belt-and-braces thing or something, but didn't think you could just do away with the flylead? If the socket happend to be be hanging loose, how do you get earth continuity? -- From KT24 Using a RISC OS computer running v5.18 |
#9
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Earthing back boxes and socket outlets
On Feb 15, 10:29*pm, John Rumm wrote:
On 15/02/2013 20:15, mike wrote: But if someone made the earth connection to the back box on the Toolstation version, any connected appliance (double insulation and plastic earth prongs aside) wouldn't be earthed. *Is that right? No, because the circuit earth wires will always be connected to the earth terminal on the socket face plate. You would not simply terminate the circuit earth wires on the backbox and rely on that to make an earth connection to the backbox. So "no" in theory but "yes" in practice because there will inevitably be cases where people connect it to the back box earth. With a "normal" socket that has earthed screw holes the reverse situation is allowable - i.e. you can re;y on them to earth the backbox (assuming it has at least one fixed tag), however good practice would suggest adding a separate fly lead between circuit terminal and the earth terminal on the back box. If everything is reliably earthed via the socket screw in the situation you describe, how would it be any less reliable if the earth were connected to the back box rather than the face plate? |
#10
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Earthing back boxes and socket outlets
John Rumm wrote:
On 16/02/2013 00:50, Lobster wrote: On 15/02/2013 22:29, John Rumm wrote: On 15/02/2013 20:15, mike wrote: Just came to fit some socket outlets from Toolstation and realised the faceplate screws aren't connected to earth. They're the top ones in this pic: http://i46.tinypic.com/9glo1z.jpg Older MK version with earth connection is below. I thought all sockets followed the MK pattern with the result that using either the earth connection on the faceplate or the earth connection in the back box would result in everything being connected to earth. As you have seen, not always... Don't think I've ever seen them before - I always assumed the earthed screw holes were mandatory But if someone made the earth connection to the back box on the Toolstation version, any connected appliance (double insulation and plastic earth prongs aside) wouldn't be earthed. Is that right? No, because the circuit earth wires will always be connected to the earth terminal on the socket face plate. You would not simply terminate the circuit earth wires on the backbox and rely on that to make an earth connection to the backbox. With a "normal" socket that has earthed screw holes the reverse situation is allowable - i.e. you can re;y on them to earth the backbox (assuming it has at least one fixed tag), however good practice would suggest adding a separate fly lead between circuit terminal and the earth terminal on the back box. So, if you have sockets with earthed screw holes does that mean you actually don't need the fly lead twixt socket and backbox? I thought it must be a belt-and-braces thing or something, but didn't think you could just do away with the flylead? IIUC, so long as the box has at least one fixed lug, then you can do without the discrete fly lead. If the socket has just one earthed eyelet and this is at the adjustable lug side of the backbox then you also need to fit the flylead. -- Adam |
#11
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Earthing back boxes and socket outlets
"Lobster" wrote in message ... On 15/02/2013 22:29, John Rumm wrote: On 15/02/2013 20:15, mike wrote: Just came to fit some socket outlets from Toolstation and realised the faceplate screws aren't connected to earth. They're the top ones in this pic: http://i46.tinypic.com/9glo1z.jpg Older MK version with earth connection is below. I thought all sockets followed the MK pattern with the result that using either the earth connection on the faceplate or the earth connection in the back box would result in everything being connected to earth. As you have seen, not always... Don't think I've ever seen them before - I always assumed the earthed screw holes were mandatory But if someone made the earth connection to the back box on the Toolstation version, any connected appliance (double insulation and plastic earth prongs aside) wouldn't be earthed. Is that right? No, because the circuit earth wires will always be connected to the earth terminal on the socket face plate. You would not simply terminate the circuit earth wires on the backbox and rely on that to make an earth connection to the backbox. With a "normal" socket that has earthed screw holes the reverse situation is allowable - i.e. you can re;y on them to earth the backbox (assuming it has at least one fixed tag), however good practice would suggest adding a separate fly lead between circuit terminal and the earth terminal on the back box. So, if you have sockets with earthed screw holes does that mean you actually don't need the fly lead twixt socket and backbox? I thought it must be a belt-and-braces thing or something, but didn't think you could just do away with the flylead? -- David With the 'main' earth connection in the circuit being the earth pin on the socket face, I can't imagine that anyone in their right mind would not make this the primary connection point for the safety earth wire(s). It would be madness to try to use the (sometimes present) faceplate fixing screw earth straps 'backwards' - that is to try to make the socket's primary earth *from* the backbox via the screws. If those screws were the slightest bit loose, or corroded, the earth could be almost totally ineffective. In a correct installation, the possibility of the faceplate screws becoming live is pretty damn small anyway, and almost non-existent if the backbox is plastic. Never-the-less, if the backbox is metal, I would always run a secondary flying earth wire to the earth terminal that is always present in such boxes, and then the faceplate screws would be earthed anyway, courtesy of the fact that they are screwed into the earthed backbox. In my opinion, within practical constraints, 'belt and braces' is good when it comes to electrics ... Arfa |
#12
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Earthing back boxes and socket outlets
On 16/02/2013 06:00, charles wrote:
In article , Lobster wrote: On 15/02/2013 22:29, John Rumm wrote: On 15/02/2013 20:15, mike wrote: Just came to fit some socket outlets from Toolstation and realised the faceplate screws aren't connected to earth. They're the top ones in this pic: http://i46.tinypic.com/9glo1z.jpg Older MK version with earth connection is below. I thought all sockets followed the MK pattern with the result that using either the earth connection on the faceplate or the earth connection in the back box would result in everything being connected to earth. As you have seen, not always... Don't think I've ever seen them before - I always assumed the earthed screw holes were mandatory But if someone made the earth connection to the back box on the Toolstation version, any connected appliance (double insulation and plastic earth prongs aside) wouldn't be earthed. Is that right? No, because the circuit earth wires will always be connected to the earth terminal on the socket face plate. You would not simply terminate the circuit earth wires on the backbox and rely on that to make an earth connection to the backbox. With a "normal" socket that has earthed screw holes the reverse situation is allowable - i.e. you can re;y on them to earth the backbox (assuming it has at least one fixed tag), however good practice would suggest adding a separate fly lead between circuit terminal and the earth terminal on the back box. So, if you have sockets with earthed screw holes does that mean you actually don't need the fly lead twixt socket and backbox? I thought it must be a belt-and-braces thing or something, but didn't think you could just do away with the flylead? If the socket happend to be be hanging loose, how do you get earth continuity? The circuit earth wires are always connected directly to the socket. So even with the socket completely disconnected from its backbox (which may be plastic remember), it still is both earthed, and providing earth continuity. -- Cheers, John. /================================================== ===============\ | Internode Ltd - http://www.internode.co.uk | |-----------------------------------------------------------------| | John Rumm - john(at)internode(dot)co(dot)uk | \================================================= ================/ |
#13
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Earthing back boxes and socket outlets
On 16/02/2013 10:21, Arfa Daily wrote:
"Lobster" wrote in message ... On 15/02/2013 22:29, John Rumm wrote: On 15/02/2013 20:15, mike wrote: Just came to fit some socket outlets from Toolstation and realised the faceplate screws aren't connected to earth. They're the top ones in this pic: http://i46.tinypic.com/9glo1z.jpg Older MK version with earth connection is below. I thought all sockets followed the MK pattern with the result that using either the earth connection on the faceplate or the earth connection in the back box would result in everything being connected to earth. As you have seen, not always... Don't think I've ever seen them before - I always assumed the earthed screw holes were mandatory But if someone made the earth connection to the back box on the Toolstation version, any connected appliance (double insulation and plastic earth prongs aside) wouldn't be earthed. Is that right? No, because the circuit earth wires will always be connected to the earth terminal on the socket face plate. You would not simply terminate the circuit earth wires on the backbox and rely on that to make an earth connection to the backbox. With a "normal" socket that has earthed screw holes the reverse situation is allowable - i.e. you can re;y on them to earth the backbox (assuming it has at least one fixed tag), however good practice would suggest adding a separate fly lead between circuit terminal and the earth terminal on the back box. So, if you have sockets with earthed screw holes does that mean you actually don't need the fly lead twixt socket and backbox? I thought it must be a belt-and-braces thing or something, but didn't think you could just do away with the flylead? -- David With the 'main' earth connection in the circuit being the earth pin on the socket face, I can't imagine that anyone in their right mind would not make this the primary connection point for the safety earth wire(s). It would be madness to try to use the (sometimes present) faceplate fixing screw earth straps 'backwards' - that is to try to make the socket's primary earth *from* the backbox via the screws. If those screws were the slightest bit loose, or corroded, the earth could be almost totally ineffective. Indeed, I did wonder if some suggestions here were suggesting this back to front connection scheme! About the only time I can envisage something similar to that being "normal" would be on a wiring system that relies on with cable sheath (e.g. MICC) or conduit to provide the CPC. However even there one ought to be using a banjo tag or similar on the gland to connect the socket earth, rather than the earth tag on the box. In a correct installation, the possibility of the faceplate screws becoming live is pretty damn small anyway, and almost non-existent if the backbox is plastic. Never-the-less, if the backbox is metal, I would always run a secondary flying earth wire to the earth terminal that is always present in such boxes, and then the faceplate screws would be earthed anyway, courtesy of the fact that they are screwed into the earthed backbox. In my opinion, within practical constraints, 'belt and braces' is good when it comes to electrics ... No harm in that... The screws themselves probably represent relatively little risk - even if you could make contact to them, the contact area is small and would be very difficult to maintain contact with under shock conditions (rather like trying to electrocute yourself in a BC lamp holder!) Obviously on a metal clad faceplate, the issue becomes more significant. -- Cheers, John. /================================================== ===============\ | Internode Ltd - http://www.internode.co.uk | |-----------------------------------------------------------------| | John Rumm - john(at)internode(dot)co(dot)uk | \================================================= ================/ |
#14
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Earthing back boxes and socket outlets
Dave Plowman (News) wrote:
In article , mike wrote: Just came to fit some socket outlets from Toolstation and realised the faceplate screws aren't connected to earth. They're the top ones in this pic: http://i46.tinypic.com/9glo1z.jpg Older MK version with earth connection is below. I thought all sockets followed the MK pattern with the result that using either the earth connection on the faceplate or the earth connection in the back box would result in everything being connected to earth. But if someone made the earth connection to the back box on the Toolstation version, any connected appliance (double insulation and plastic earth prongs aside) wouldn't be earthed. Is that right? Is this something new? Or something cheap? It's best practice to run an earth wire between the socket and earth terminal on a metal back box. That's why it's there. Best practice and electricians? Pull the other one:-). I fit the flyleads in older houses where there are damp problems and where the spec says I have to. Any competent DIYer should be fitting the flylead as they are not on price. The sockets in question were brought to the attention of this group last year by SteveWalker. They are Toolstation's "Contractor Pack", marked HLM. -- Adam |
#15
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Earthing back boxes and socket outlets
On 16/02/2013 09:21, mike wrote:
On Feb 15, 10:29 pm, John Rumm wrote: On 15/02/2013 20:15, mike wrote: But if someone made the earth connection to the back box on the Toolstation version, any connected appliance (double insulation and plastic earth prongs aside) wouldn't be earthed. Is that right? No, because the circuit earth wires will always be connected to the earth terminal on the socket face plate. You would not simply terminate the circuit earth wires on the backbox and rely on that to make an earth connection to the backbox. So "no" in theory but "yes" in practice because there will inevitably be cases where people connect it to the back box earth. Excluding cases conduit/sheath/armour earthing is in use it seems relatively unlikely - its not as if its any easier to connect two wires to the box and four to the socket... I have seen countless examples of no flying lead betwixt socket and box, but don't recall ever seeing the being being used at a primary connection point. With a "normal" socket that has earthed screw holes the reverse situation is allowable - i.e. you can re;y on them to earth the backbox (assuming it has at least one fixed tag), however good practice would suggest adding a separate fly lead between circuit terminal and the earth terminal on the back box. If everything is reliably earthed via the socket screw in the situation you describe, how would it be any less reliable if the earth were connected to the back box rather than the face plate? Because in reality its a less reliable connection... While not desirable, an unearthed backbox is unlikely to kill you, but an unearthed socket might. Imagine a situation where some one is decorating and has release socket screws to get paper etc behind the faceplate. Anything plugged into that socket *must* still be earthed, but whether the box still is in those circumstances is less important. -- Cheers, John. /================================================== ===============\ | Internode Ltd - http://www.internode.co.uk | |-----------------------------------------------------------------| | John Rumm - john(at)internode(dot)co(dot)uk | \================================================= ================/ |
#16
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Earthing back boxes and socket outlets
On Sat, 16 Feb 2013 01:21:13 -0800 (PST), mike
wrote: On Feb 15, 10:29*pm, John Rumm wrote: On 15/02/2013 20:15, mike wrote: But if someone made the earth connection to the back box on the Toolstation version, any connected appliance (double insulation and plastic earth prongs aside) wouldn't be earthed. *Is that right? No, because the circuit earth wires will always be connected to the earth terminal on the socket face plate. You would not simply terminate the circuit earth wires on the backbox and rely on that to make an earth connection to the backbox. So "no" in theory but "yes" in practice because there will inevitably be cases where people connect it to the back box earth. With a "normal" socket that has earthed screw holes the reverse situation is allowable - i.e. you can re;y on them to earth the backbox (assuming it has at least one fixed tag), however good practice would suggest adding a separate fly lead between circuit terminal and the earth terminal on the back box. If everything is reliably earthed via the socket screw in the situation you describe, how would it be any less reliable if the earth were connected to the back box rather than the face plate? Very often the earth lug on the back box isn't large enough to take three 2.5mm wires. -- Frank Erskine |
#17
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Earthing back boxes and socket outlets
In article ,
ARW wrote: It's best practice to run an earth wire between the socket and earth terminal on a metal back box. That's why it's there. Best practice and electricians? Pull the other one:-). ;-) But if I were an electrician I'd make sure the terminal screws were left loose to. I fit the flyleads in older houses where there are damp problems and where the spec says I have to. Any competent DIYer should be fitting the flylead as they are not on price. Quite. The sockets in question were brought to the attention of this group last year by SteveWalker. They are Toolstation's "Contractor Pack", marked HLM. Seems they saved 0.0001p by not running the earth strip to the screw holes. -- *Middle age is when work is a lot less fun - and fun a lot more work. Dave Plowman London SW To e-mail, change noise into sound. |
#18
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Earthing back boxes and socket outlets
Dave Plowman (News) wrote:
In article , ARW wrote: It's best practice to run an earth wire between the socket and earth terminal on a metal back box. That's why it's there. Best practice and electricians? Pull the other one:-). ;-) But if I were an electrician I'd make sure the terminal screws were left loose to. That's not always true. Sometimes they overtighten the screws to see if they can snap off half of the screws head. It's a fine balancing act to decide which one to do. I fit the flyleads in older houses where there are damp problems and where the spec says I have to. Any competent DIYer should be fitting the flylead as they are not on price. Quite. The sockets in question were brought to the attention of this group last year by SteveWalker. They are Toolstation's "Contractor Pack", marked HLM. Seems they saved 0.0001p by not running the earth strip to the screw holes. I would not normally buy electrical stuff from Toolstation. Steve Walkers post guaranteed that I would avoid those sockets should I ever have to buy from there. -- Adam |
#19
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Earthing back boxes and socket outlets
In article ,
ARW wrote: I would not normally buy electrical stuff from Toolstation. Steve Walkers post guaranteed that I would avoid those sockets should I ever have to buy from there. For myself, I tend to buy the fittings I like the look of, since you're likely to have to look at them for a long long time. Which usually means not the cheapest I can find. ;-) -- *Letting a cat out of the bag is easier than putting it back in * Dave Plowman London SW To e-mail, change noise into sound. |
#20
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Earthing back boxes and socket outlets
Dave Plowman (News) wrote:
In article , ARW wrote: I would not normally buy electrical stuff from Toolstation. Steve Walkers post guaranteed that I would avoid those sockets should I ever have to buy from there. For myself, I tend to buy the fittings I like the look of, since you're likely to have to look at them for a long long time. Which usually means not the cheapest I can find. ;-) That's how I choose my girlfriends. -- Adam |
#21
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Earthing back boxes and socket outlets
On Feb 16, 12:45*pm, John Rumm wrote:
On 16/02/2013 09:21, mike wrote: If everything is reliably earthed via the socket screw in the situation you describe, how would it be any less reliable if the earth were connected to the back box rather than the face plate? Because in reality its a less reliable connection... While not desirable, an unearthed backbox is unlikely to kill you, but an unearthed socket might. Imagine a situation where some one is decorating and has release socket screws to get paper etc behind the faceplate. Anything plugged into that socket *must* still be earthed, but whether the box still is in those circumstances is less important. I had thought of that situation and I take your point but, in fairness, you have introduced three further variables into the situation. Firstly, someone takes the socket off the wall; secondly, they plug something into it; thirdly, whatever is plugged in has a metal earth prong and needs an earth connection. In the case of a socket screwed to the wall properly with the MK style earth connection to the mounting screws, if it provides a "reliable" earth to the mounting box it would necessarily have to work equally reliably to the earth terminal. I'm surprised the MK style earth connection isn't mandated but, as Adam has pointed out in another thread: 'From BS 1363-2 1995 (Specification of 13A switched and unswitched socket outlets) 10.3 If means are provided for electrically bonding the mounting box to the earthing circuit of the socket-outlet by means of the fixing screws the connection between the screw and the earthing terminal shall be of low resistance. Note the use of the word "if".' .... so the Toolstation sockets are just built-to-save-a-penny crap that sneak in under the wire. As for saying that, in practice, no-one would use the mounting box earth, you've surely seen work infinitely worse than that. I've just replaced a lighting circuit where a "professional" electrician had managed to cram sixteen cables and three connector blocks into one 30-amp junction box and, when he ran out of room for screwed connections, twisted wires together and wrapped them in insulation tape. It was like a rat's nest up a fish's arsehole. The earth wires that hadn't simply been cut off were twisted together unsheathed outside the junction box, the lid of which had been refixed at a jaunty angle with a woodscrew. Compared to that kind of workmanship, the mounting box earth seems like the height of British standards. |
#22
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Earthing back boxes and socket outlets
On 16/02/2013 15:10, mike wrote:
On Feb 16, 12:45 pm, John Rumm wrote: On 16/02/2013 09:21, mike wrote: If everything is reliably earthed via the socket screw in the situation you describe, how would it be any less reliable if the earth were connected to the back box rather than the face plate? Because in reality its a less reliable connection... While not desirable, an unearthed backbox is unlikely to kill you, but an unearthed socket might. Imagine a situation where some one is decorating and has release socket screws to get paper etc behind the faceplate. Anything plugged into that socket *must* still be earthed, but whether the box still is in those circumstances is less important. I had thought of that situation and I take your point but, in fairness, you have introduced three further variables into the situation. Firstly, someone takes the socket off the wall; secondly, they plug something into it; thirdly, whatever is plugged in has a metal earth prong and needs an earth connection. Indeed and I was really just highlighting that the primary earth connection are supposed to be to the socket and illustrating a situation were it could make a difference. In the case of a socket screwed to the wall properly with the MK style earth connection to the mounting screws, if it provides a "reliable" earth to the mounting box it would necessarily have to work equally reliably to the earth terminal. I'm surprised the MK style earth connection isn't mandated but, as Adam has pointed out in another thread: 'From BS 1363-2 1995 (Specification of 13A switched and unswitched socket outlets) 10.3 If means are provided for electrically bonding the mounting box to the earthing circuit of the socket-outlet by means of the fixing screws the connection between the screw and the earthing terminal shall be of low resistance. Note the use of the word "if".' I suppose playing devil's advocate, you could argue that its becoming less critical rather than more, as more installations are done with insulated backboxes (i.e. dry lining ones) these days. ... so the Toolstation sockets are just built-to-save-a-penny crap that sneak in under the wire. As for saying that, in practice, no-one would use the mounting box earth, you've surely seen work infinitely worse than that. I have seen plenty of crap work, just never seen an install where the primary connection has been made to the box. Daft situations like a ring (or worse a radial) where one earth is taken to the socket and the other to the box - with a result of loss of earth continuity if the faceplate is removed or a connection goes high impedance (more likely where the screwed connection is between dissimilar metals and the screw pressure does not make the contact point gas tight) I've just replaced a lighting circuit where a "professional" electrician had managed to cram sixteen cables and three connector blocks into one 30-amp junction box and, when he ran out of room for screwed connections, twisted wires together and wrapped them in insulation tape. It was like a rat's nest up a fish's arsehole. The earth wires that hadn't simply been cut off were twisted together unsheathed outside the junction box, the lid of which had been refixed at a jaunty angle with a woodscrew. Mmmm yummy ;-) Compared to that kind of workmanship, the mounting box earth seems like the height of British standards. In relative terms quite possibly, but it still does not make it good or sensible practice. -- Cheers, John. /================================================== ===============\ | Internode Ltd - http://www.internode.co.uk | |-----------------------------------------------------------------| | John Rumm - john(at)internode(dot)co(dot)uk | \================================================= ================/ |
#23
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Earthing back boxes and socket outlets
On 16/02/2013 12:37, ARW wrote:
Dave Plowman (News) wrote: In article , mike wrote: Just came to fit some socket outlets from Toolstation and realised the faceplate screws aren't connected to earth. They're the top ones in this pic: http://i46.tinypic.com/9glo1z.jpg Older MK version with earth connection is below. I thought all sockets followed the MK pattern with the result that using either the earth connection on the faceplate or the earth connection in the back box would result in everything being connected to earth. But if someone made the earth connection to the back box on the Toolstation version, any connected appliance (double insulation and plastic earth prongs aside) wouldn't be earthed. Is that right? Is this something new? Or something cheap? It's best practice to run an earth wire between the socket and earth terminal on a metal back box. That's why it's there. Best practice and electricians? Pull the other one:-). I fit the flyleads in older houses where there are damp problems and where the spec says I have to. Any competent DIYer should be fitting the flylead as they are not on price. The sockets in question were brought to the attention of this group last year by SteveWalker. They are Toolstation's "Contractor Pack", marked HLM. Thank you, I was just about to search for my original post, but I'll not bother now! SteveW |
#24
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Earthing back boxes and socket outlets
"Arfa Daily" writes:
"Lobster" wrote in message ... On 15/02/2013 22:29, John Rumm wrote: On 15/02/2013 20:15, mike wrote: Just came to fit some socket outlets from Toolstation and realised the faceplate screws aren't connected to earth. They're the top ones in this pic: http://i46.tinypic.com/9glo1z.jpg Older MK version with earth connection is below. I thought all sockets followed the MK pattern with the result that using either the earth connection on the faceplate or the earth connection in the back box would result in everything being connected to earth. As you have seen, not always... Don't think I've ever seen them before - I always assumed the earthed screw holes were mandatory But if someone made the earth connection to the back box on the Toolstation version, any connected appliance (double insulation and plastic earth prongs aside) wouldn't be earthed. Is that right? No, because the circuit earth wires will always be connected to the earth terminal on the socket face plate. You would not simply terminate the circuit earth wires on the backbox and rely on that to make an earth connection to the backbox. With a "normal" socket that has earthed screw holes the reverse situation is allowable - i.e. you can re;y on them to earth the backbox (assuming it has at least one fixed tag), however good practice would suggest adding a separate fly lead between circuit terminal and the earth terminal on the back box. So, if you have sockets with earthed screw holes does that mean you actually don't need the fly lead twixt socket and backbox? I thought it must be a belt-and-braces thing or something, but didn't think you could just do away with the flylead? -- David With the 'main' earth connection in the circuit being the earth pin on the socket face, I can't imagine that anyone in their right mind would not make this the primary connection point for the safety earth wire(s). It would be madness to try to use the (sometimes present) faceplate fixing screw earth straps 'backwards' - that is to try to make the socket's primary earth *from* the backbox via the screws. If those screws were the slightest bit loose, or corroded, the earth could be almost totally ineffective. In a correct installation, the possibility of the faceplate screws becoming live is pretty damn small anyway, and almost non-existent if the backbox is plastic. Never-the-less, if the backbox is metal, I would always run a secondary flying earth wire to the earth terminal that is always present in such boxes, and then the faceplate screws would be earthed anyway, courtesy of the fact that they are screwed into the earthed backbox. In my opinion, within practical constraints, 'belt and braces' is good when it comes to electrics ... Most of the sockets I've seen which were wired relatively recently have a squashed-flat loop in the earth wire to allow it to fit into the back box terminal, but the wire then continues on to the earth terminal on the socket. All one piece of wire so less risk of an open earth connection if there are loosely-fastened screws in back box and/or faceplate. I had assumed that was more or less a standard for a professional installation. -- Windmill, Use t m i l l J.R.R. Tolkien:- @ O n e t e l . c o m All that is gold does not glister / Not all who wander are lost |
#25
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Earthing back boxes and socket outlets
In article ,
Windmill wrote: Most of the sockets I've seen which were wired relatively recently have a squashed-flat loop in the earth wire to allow it to fit into the back box terminal, but the wire then continues on to the earth terminal on the socket. All one piece of wire so less risk of an open earth connection if there are loosely-fastened screws in back box and/or faceplate. I had assumed that was more or less a standard for a professional installation. Sounds like a rather fiddly way to do it. And slightly wasteful of cable - for those who worry about such things. ;-) I bought a 100m reel of 1.5 single green/yellow many many years ago just for this, and I'd expect it to see me out. ;-) But you can usually rescue some earth from cut-offs of the TW&E - and of course you will already have the sleeving. -- *When cheese gets its picture taken, what does it say? * Dave Plowman London SW To e-mail, change noise into sound. |
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