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Further Earth Bonding questions
Question 1. I have been examining my earth bonding and have found
that the earth connection between where the cable enters my house to the other size of the main fuse is made from earth cable that is only about 3mm thick at most and it is not insulated. Presumeably this is fairly old. This is only a short length about 25cm. There is then a copper covered cable that goes for about 6 metres to the meter. The earth connection into the consumer unit and connected to the gas and water is much more substantial and is insulated. Is there any danger posed by the thin link around the main fuse? Should I replace it? Question 2. (see previous post) In my laundry/shower/toilet room there is no earth bonding. I understand that I must link all the pipes together. However my radiator is on the otherside of the room and I don't want to rip up floor boards to fit the cable. Is it alright to route this via my cellar back to where the cold water pipe enters the room. This means that effectively the cable will be going around the outside of the room. Do I have to put the connection in the laundry room or can I make this in the cellar? Thanks as always Tim |
.....further question. I am installing additional sockets in my kitchen.
As this is being replastered I intend to cover the cables with capping/sheathing. If I use the galvanised type should this be earthed? |
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Thanks for the reply. I phoned up EDF our supplier and they agreed to
come out and inspect, which they did within 1 hour! I was very impressed. The engineer agreed that the earth wire was a bit suspect, but more importantly the MICC cable to the meter should now be replaced as it was so old. They are now arranging to connect a brand new cable all the way to the meter free of charge. He also recommended that I upraded my consumer unit to include RCD protection. Currently, I only have one RCD circuit which I installed, that is used to supply my laundry/ shower room. He reckons that for safety every circuit should be protected by an RCD as in his 30+ years experience he has known about deaths caused by people working on lighting circuits as well as mains circuits, but acknowledges that this is not in the current regs. The main issue here would be the cost of doing this via separate RCBOs instead of one RCB. Has anyone got a view on this, apart from the cost I think it would be a good idea. Maybe the only circuit I would not want on an RCB would be my alarm and freezer. Or are there problems with triggering on immersion heaters? Finally, as I understand the regs kitchens should now definitely be protected by an RCD. Do people run a separate ring or spur purely to supply their freezer in the kitchen, presumeably this needs to be hard wired to prevent people plugging things such as hedgecutters into it? As they are coming to do the replacement in the next few days I was thinking of connecting my CU to the meter via a 100A DP isolation switch, as at the moment neither the meter or main fuse have seals on them, which won't be the case after they have done the work on the connection. Does anyone have any information on whether this is allowed, it will make it a lot easier if I upgrade my CU (obviously before 2005 and part p!) |
In article ,
wrote: He reckons that for safety every circuit should be protected by an RCD as in his 30+ years experience he has known about deaths caused by people working on lighting circuits as well as mains circuits, but acknowledges that this is not in the current regs. The main issue here would be the cost of doing this via separate RCBOs instead of one RCB. Has anyone got a view on this, apart from the cost I think it would be a good idea. Maybe the only circuit I would not want on an RCB would be my alarm and freezer. Or are there problems with triggering on immersion heaters? Get a split load CU with more ways than you need. The spare ways can be just blanked off. That will allow you to move things to the non protected side if you have problems. -- *I have plenty of talent and vision. I just don't care. Dave Plowman London SW To e-mail, change noise into sound. |
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In message , Andrew Gabriel
writes In article , writes: He reckons that for safety every circuit should be protected by an RCD as in his 30+ years experience he has known about deaths caused by people working on lighting circuits as well as mains circuits, but The number of deaths caused by lighting circuits blacking out is probably at least a couple of orders of magnitude greater. And what were these people doing 'working' on lighting circuits which were still live anyway? -- Chris French, Leeds |
Not being careful enough, clearly, but his point was that an RCD would
always protect you. But as Andrew said, people are far more likely to have an accident because of the lights not working! |
On Tue, 14 Sep 2004 01:16:34 UTC, "Dave Plowman (News)"
wrote: In article , chris French wrote: And what were these people doing 'working' on lighting circuits which were still live anyway? Changing a bulb on a two way circuit springs to mind. Falling through the ceiling while working on the lighting circuits in the loft....! -- Bob Eager begin a new life...dump Windows! |
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In article ,
wrote: It will only reduce the severity of a shock you get if you get some part of your body between live and earth. If you put your finger across live and neutral (quite easy if doing something to lights) then the RCD will do nothing at all for you. Thought the time taken for the RCD to trip made this rather unlikely? -- *Why is the man who invests all your money called a broker? Dave Plowman London SW To e-mail, change noise into sound. |
tony sayer wrote:
Even if the shock is caused by you being between live and earth the RCD only reduces the *electrical* effect to (hopefully) sub-lethal levels. You will still get a jolt and if you are, for example, on a ladder may fall off and injure yourself just as badly as if the RCD had not been there. Beg to differ.. as someone who was glued to a ladder due to lack of an RCD:((. I really don't understand this on AC, I've never received a shock from AC which has 'glued' me to anything and I've only ever heard anecdotal evidence that this happens. Presumably you became 'unglued' at some point or you wouldn't be here to tell us about it! :-) Did you immediately try the same thing with an RCD on the circuit and find that was alright? -- Chris Green |
"Dave Plowman (News)" wrote:
In article , wrote: It will only reduce the severity of a shock you get if you get some part of your body between live and earth. If you put your finger across live and neutral (quite easy if doing something to lights) then the RCD will do nothing at all for you. Thought the time taken for the RCD to trip made this rather unlikely? The RCD won't *ever* trip if you put your finger across live and neutral, it dosn't trip on that sort of fault. -- Chris Green |
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I am coming round to the idea that I should replace my CU with a split
load type. However rewiring the kitchen to include a non rcd circuit for the freezer, fridge and dishwasher is going to be a right pain. Does the group have any views on whether having these on an rcd is really going to be a problem due to tripping. If I am out of the house on holiday for 2 weeks, I suppose there is a potential that the freezer might turn off and ruin my food, but I would expect my insurance company to pay out after the inevitable protracted dispute! What are the items generally not rcd protected? assume this is lights as mentioned previously, the alarm, garage (if separate protection available), immersion heater due to potential earth leakage...are there any others. |
tony sayer wrote:
In article , writes "Dave Plowman (News)" wrote: In article , wrote: It will only reduce the severity of a shock you get if you get some part of your body between live and earth. If you put your finger across live and neutral (quite easy if doing something to lights) then the RCD will do nothing at all for you. Thought the time taken for the RCD to trip made this rather unlikely? The RCD won't *ever* trip if you put your finger across live and neutral, it dosn't trip on that sort of fault. *Not strictly true, if you know how an RCD actually works. There will still be "some" leakage current through your body that does not go back via the neutral return so if that exceeds the RCD trip current, quite likely, then out she goes!..... Standing on a ladder on a wooden (probably) floor the leakage through your body to earth will be virtually non-existent. You'll probably have shoes with rubber/plastic soles as well. -- Chris Green |
In article ,
wrote: It will only reduce the severity of a shock you get if you get some part of your body between live and earth. If you put your finger across live and neutral (quite easy if doing something to lights) then the RCD will do nothing at all for you. Thought the time taken for the RCD to trip made this rather unlikely? The RCD won't *ever* trip if you put your finger across live and neutral, it dosn't trip on that sort of fault. You miss the point. You'd have to bridge line and neutral within the trip time of the RCD. That's what I was querying. I'm not, of course, saying they are perfect. But perhaps better than nothing? -- *When the going gets tough, the tough take a coffee break * Dave Plowman London SW To e-mail, change noise into sound. |
wrote in message
... I am coming round to the idea that I should replace my CU with a split load type. However rewiring the kitchen to include a non rcd circuit for the freezer, fridge and dishwasher is going to be a right pain. Does the group have any views on whether having these on an rcd is really going to be a problem due to tripping. If I am out of the house on holiday for 2 weeks, I suppose there is a potential that the freezer might turn off and ruin my food, but I would expect my insurance company to pay out after the inevitable protracted dispute! What are the items generally not rcd protected? assume this is lights as mentioned previously, the alarm, garage (if separate protection available), immersion heater due to potential earth leakage...are there any others. I'm very much in favour of individual RCBOs rather than split units. Advantages are that you know exactly which circuit is causing the problem, and that might help track down errant devices. Also, a fault caused by use of an appliance outside (those wires just keep dangling in the way of the hedge trimmer...) won't mean that you have to reset all the digital clocks in your house & any IT equipment doesn't have to suffer the indignancy of a rude shut-down. Disadvantages being the higher cost and sometimes a larger CU (RCBOs are often double width, though singles are available). -- Richard Sampson mail me at richard at olifant d-ot co do-t uk |
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In article , writes
tony sayer wrote: In article , writes "Dave Plowman (News)" wrote: In article , wrote: It will only reduce the severity of a shock you get if you get some part of your body between live and earth. If you put your finger across live and neutral (quite easy if doing something to lights) then the RCD will do nothing at all for you. Thought the time taken for the RCD to trip made this rather unlikely? The RCD won't *ever* trip if you put your finger across live and neutral, it dosn't trip on that sort of fault. *Not strictly true, if you know how an RCD actually works. There will still be "some" leakage current through your body that does not go back via the neutral return so if that exceeds the RCD trip current, quite likely, then out she goes!..... Standing on a ladder on a wooden (probably) floor the leakage through your body to earth will be virtually non-existent. You'll probably have shoes with rubber/plastic soles as well. Don't you believe it!. Well if you do, then grab the mains in one hand and note the results. Usual disclaimer don't they this at home unless by doing so you'll help the gene pool along....... -- Tony Sayer |
tony sayer wrote:
Standing on a ladder on a wooden (probably) floor the leakage through your body to earth will be virtually non-existent. You'll probably have shoes with rubber/plastic soles as well. Don't you believe it!. Well if you do, then grab the mains in one hand and note the results. Usual disclaimer don't they this at home unless by doing so you'll help the gene pool along....... Have *you* actually done it? I've hung on to the output of a Van de Graaf generator while simply standing on a piece of perspex and charged myself up to hundreds of thousands of volts if not millions - not a tingle, until someone walks to close to you. In reality in the house you have to be touching something metallic or standing on a wet (probably concrete) floor to get a shock. In ordinary shoes on a carpet you will feel *nothing* if you touch live mains with one finger (and, yes, I have done it occasionally when working on something live). Mostly one gets a shock because *both* hands are touching something conductive (and that's the worst for you too as the electricity runs across your chest). In workplaces where live working on benches is commonplace significant shock prevention is provided by a vinyl floor covering and training people to use only one hand. -- Chris Green |
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Dave Plowman (News) wrote:
You miss the point. You'd have to bridge line and neutral within the trip time of the RCD. That's what I was querying. Not if it's the N you touch first - there'd be naff-all current passing through you given the negligible potential between N and local earth, together with the much higher resistance which you present as a path to earth/transformer-return as compared to the copper path it's got. Then when you make contact with L (other side of the finger - possible finger-cooking but little likelihood of death; other hand - definite risk of fatality, hence the habit inculcated into generations of sparkies of working with one hand at a time) you become an attractive path for L-to-N current; and by far the greater part of the flow through you will be on the L-to-N path, which doesn't do anything to trip the RCD, rather than the L-to-E-via-shoes/clothes/whatever which the RCD is sensitive to. I'm not, of course, saying they are perfect. But perhaps better than nothing? Definitely better than nothing, but not a cure-all, and a possible source of a "risk compensation" effect - "oh, it's OK to work live on the electrics, I have a whole-house RCD"... Stefek |
"tony sayer" wrote
| The RCD won't *ever* trip if you put your finger across live and | neutral, it dosn't trip on that sort of fault. | *Not strictly true, if you know how an RCD actually works. There | will still be "some" leakage current through your body that does | not go back via the neutral return so if that exceeds the RCD | trip current, quite likely, then out she goes!..... | Standing on a ladder on a wooden (probably) floor the leakage | through your body to earth will be virtually non-existent. | You'll probably have shoes with rubber/plastic soles as well. | Don't you believe it!. Well if you do, then grab the mains in one | hand and note the results. I have done exactly this in the past, standing on rubber-backed carpet tiles on a dry suspended timber floor. I vibrated gently at 50Hz and the RCD did not trip. This was not a glancing touch as I was holding the L wire intending to put it into a replacement socket faceplate.[1] | Usual disclaimer don't they this at home unless by doing so you'll | help the gene pool along....... Glad I can do my bit for the gene pool without being forced into the messy business of procreation :-) Owain [1] I pulled out the fuse and checked the first socket. Dead. Checked the second socket. Dead. How the f'k was I supposed to guess the third socket in the lounge was on the garage circuit (garage being on opposite side of house, as well). |
In article , Owain owain41276@
stirlingcity.co.uk writes "tony sayer" wrote | The RCD won't *ever* trip if you put your finger across live and | neutral, it dosn't trip on that sort of fault. | *Not strictly true, if you know how an RCD actually works. There | will still be "some" leakage current through your body that does | not go back via the neutral return so if that exceeds the RCD | trip current, quite likely, then out she goes!..... | Standing on a ladder on a wooden (probably) floor the leakage | through your body to earth will be virtually non-existent. | You'll probably have shoes with rubber/plastic soles as well. | Don't you believe it!. Well if you do, then grab the mains in one | hand and note the results. I have done exactly this in the past, standing on rubber-backed carpet tiles on a dry suspended timber floor. I vibrated gently at 50Hz and the RCD did not trip. This was not a glancing touch as I was holding the L wire intending to put it into a replacement socket faceplate.[1] Course some people conduct better then others;!.... | Usual disclaimer don't they this at home unless by doing so you'll | help the gene pool along....... Glad I can do my bit for the gene pool without being forced into the messy business of procreation :-) Theres a howler there somewhere.... Owain [1] I pulled out the fuse and checked the first socket. Dead. Checked the second socket. Dead. How the f'k was I supposed to guess the third socket in the lounge was on the garage circuit (garage being on opposite side of house, as well). On three occasions over the years I've seen someone take apparently dead wires in their hands and mutter "I suppose this *is* dead"?. Touch them together, and you'll soon find out SEZ I:) On each occasion there was a flash and loud bang!, very loud in the first instance as it was a three phase supply. Last time was in the belfry of Ely Cathedral where once had been a mobile phone base station. The 'err "short circuit" took out most of the lights as well as disrupting a service. A bit of positive spin helped lots, "ere look arch-bish-whatever guv" "just imagine if that little lot had gone up by accident at night eh?" "wouldn't have any where to pray now would yer?" Seemed to earn a lot of brownie points:) -- Tony Sayer |
"tony sayer" wrote
| | Usual disclaimer don't they this at home unless by doing so | | you'll help the gene pool along....... | Glad I can do my bit for the gene pool without being forced | into the messy business of procreation :-) | Theres a howler there somewhere.... I am doing my best to avoid producing little howlers and continue to enjoy a good night's sleep, no vomit in the carpets, and no need to buy a people-carrier. | Last time was in the belfry of Ely Cathedral where once had been a | mobile phone base station. The 'err "short circuit" took out most | of the lights as well as disrupting a service. What's really fun is when there's no-one in the church office on a Sunday and an incoming phone call rings round all the extensions before ending up at the one hidden under the pulpit. | A bit of positive spin helped lots, | "ere look arch-bish-whatever guv" "just imagine if that little lot had | gone up by accident at night eh?" | "wouldn't have any where to pray now would yer?" "You wouldn't get any better if Jesus himeself was here, he was a chippie not a sparkie." Owain |
tony sayer wrote:
Thank god for the 1974 health and safety at work act!, double insulation, and RCD's:)) The 1989 Electricity at Work Regulations and regular inspection and testing in particular. In those days RCD's were almost unheard of but had one been in place it would have repeatedly tripped and shown up the "earth" fault. Errr, why would the RCD have tripped because of an open-circuit earth in the wiring? (I.e. it wouldn't.) -- Andy |
tony sayer wrote:
Don't you believe it!. Well if you do, then grab the mains in one hand and note the results. In typical dry indoor conditions you will feel nothing, as Chris rightly says. I've often demonstrated this to people, sometimes to their great surprise. It provokes thought. Don't try it outdoors though while standing on an aluminium ladder with its feet in damp soil... And don't try it if the frequency of the supply is a few orders of magnitude higher than 50 Hz or you'll discover the meanings of "earthed via a reactance" and "skin effect" at the same time. -- Andy |
In article ,
Owain wrote: "You wouldn't get any better if Jesus himeself was here, he was a chippie not a sparkie." Seen on a roadside pulpit:- Jesus was a carpenter. Come and join us. -- *Nothing is foolproof to a sufficiently talented fool. Dave Plowman London SW To e-mail, change noise into sound. |
In article , Andy Wade
writes tony sayer wrote: Thank god for the 1974 health and safety at work act!, double insulation, and RCD's:)) The 1989 Electricity at Work Regulations and regular inspection and testing in particular. Well the 1974 act was a good start, as up to that time the safety of employees wasn't a particular concern of employers as my dad found out one day when he went to adjust the height of a circular saw blade, and discovered the hard way that it didn't have the expected guard blade protecting its underside. He said afterwards that he didn't feel a thing at the moment it happened it was the shock of seeing four fingers missing that caused him to keel over..... In those days RCD's were almost unheard of but had one been in place it would have repeatedly tripped and shown up the "earth" fault. Errr, why would the RCD have tripped because of an open-circuit earth in the wiring? (I.e. it wouldn't.) Humm.... Well the earth had come off at the distribution board and the whole house was wired with this lead sheathed cable. So presuming that the lead sheathing was all bonded together then there would have been quite a lot of Capactive leakage from the live to earth, as one could assume that at some stage the un-earthed lead casing would be connected to another earth in the house, via lets say something like an immersion heater or similar appliance, so I reckon that their would have been sufficient Capactive and an unknown amount of resistive leakage sufficient to trip the RCD. There was quite enough current there to prevent me from doing anything about it, and FWIW I have very dry skin and my hands were very dry on that day, so I reckon that a trip would have been taken out. -- Tony Sayer |
In article , Andy Wade
writes tony sayer wrote: Don't you believe it!. Well if you do, then grab the mains in one hand and note the results. In typical dry indoor conditions you will feel nothing, as Chris rightly says. I've often demonstrated this to people, sometimes to their great surprise. It provokes thought. Depending on how moist your skin is. Mines very dry, scaly lizard like according to the missus, whilst hers is rather wet most of the time and No, she does have a dishwasher..... Don't try it outdoors though while standing on an aluminium ladder with its feet in damp soil... No... And don't try it if the frequency of the supply is a few orders of magnitude higher than 50 Hz or you'll discover the meanings of "earthed via a reactance" and "skin effect" at the same time. Yes and working with RF a lot of the time this is a good way to test if an aerial is radiating;) -- Tony Sayer |
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