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?
....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?
From your bare description this sounds inadequate but for me to make useful observations you need to provide clearer information about your installation eg
approx age; if possible the earthing system (TT/TN-C-S/PME/TN-C are the most likely).
A 'schematic' of your installation would help. eg something like
incoming mains -> supplier's fuse -> supply meter -> main switch ->
consumer unit (or fuse box) ->house circuits
& any other boxes, indicating where the earth connects in & the connection to your water/gas/oil pipes. Any indication of cable sizes you can give would also help. Is there an earthing rod?
Much of the information (with diagrams) you want is in the IEE On-Site Guide (checkout amazon &/or the IEE web site to purchase)
If you can repost with above info will try to help.
that's right (see on-site guide)
However my radiator is on the otherside of the room and I
SFAIUI the bonding cable does not have to be within the room, though the clamp links to the metalwork do. Caution & ohms law suggest Prudence would keep the cable route as short as possible. It must also connect to the main house earth bonding (into the earth in a convenient socket seems to be OK SFAIUI).
also from your other post
....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?
FT&E PVC cable does not have to be covered with capping before plastering. It can be clipped to the wall and simply plastered over with the browning (undercoat) coat.
Capping (especially metal) provides some resistance to drawing pins and the like but isn't foolproof. Don't confuse it with conduit which usually comes in thick, nail resistant, tubes & is a diffeent kettle of fish (with different cable rating tables applying).
Capping does not need earthing. Conduit may do.
You may only route cable in 150mm wide bands, vertically and horizontally from a fitting (a switch, socket, light outlet etc) & along vertical wall corners and the ceiling/top of wall corner. Note routeing behind skirting boards doesn't normally meet these rules. If you depart from these routes (eg run diagonally across the wall) then the cable must be at least 50mm deep in the wall or run in earthed conduit (not capping). Again, rules are in the on-site guide.
BTW what do you mean when you refer to 'sheathing'? The grey (sometimes white) covering of FT&E cable is a sheath intended to protect the red & black insulation covering the copper cores from physical damage. If your reference to sheathing means you are not intending to use FT&E cable but individual L, N & E cables then they must be run in conduit. SFAIUI covering individual cables with capping is insufficient protection.
The earthing is TNS. i.e. supplied via the armoured cable coming in from the street. This looks to be at least 30 years old.
This goes into the suppliers fusebox. The other side of the fusebox is a a copper covered cable which goes to the meter.
The armoured cable and this copper covered cable are joined on the outside to continue the earth. This is done with uncovered stranded cable of about 3mm diameter.
--- ------------- ============= Fuse ================ -------> to meter
---| |------------- |----earth link-----|
From the meter the tails are connected to the consumer unit. The earth connection into the consumer unit is 10mm diameter insulated cable. The earth is then connected to the gas and water pipes, again using
10mm insulated cable.
As far as I can tell this part appears to be fairly modern and appears to be in line with my understanding of the regualations. It just seems strange that the incoming earth by the fuse seems so inadequate.
Where does the supply companies responsibility end, is it at the fuse or the meter. If at the meter, then I will be getting the electricity company in to replace this.
By sheathing I was referring to the capping. Thanks for the answer.
3mm dia is 7sq mm - ie actually stock size 6mm sq??
SFAIUI it may not need insulation - would depend on risk of incidental physical damage.
Presumeably this is
TFT but hard to be definite without seeing the set up.
Some thoughts:
loooking at the sizes specified in OSG table 10A (pg161) a 6mm sq earth might be possible in a small sized supply (or possibly was once?). On balance unlikely though, so:
*Perhaps* is the supply fuse box steel? It also sounds as if the ongoing cables are MICC (mineral insulated copper covered) cables.
If so that may be a partial explanation. *If* it is steel & the incomer is SWA then the box via the clamps at the inlet & outlet could be providing earth continuity. The 6mmsq link being to reinforce the earthing.
sorry - not following you here precisely - earth connection from where?
into the consumer unit is 10mm diameter insulated cable.
if you mean this is the main earthing conductor from the supply, then it could well be a tad too small - 16mmsq being more normal.
do you mean 10mmsq?
If so that appears to be correct for usual sized domestic installations (same OSG table).
(a) so far as the supply (other than earth is concerned), at the point the tails leave the elec co fuse or cut-out (if you have one), SFAIUI. The tails are yours & you have to supply them if you have a new or upgraded installation.
(b) earthing SFAIUI is the consumer's responsibility, but for certain supply specs (PME/TN-C-S & TN-S) the elec co has (again, SFAIUI) to supply an earth point. The rest is yours to worry about.
One way forward may be to check that everything your side of the supplied earthing point is hanky-dory then ask the elec co to check their earthing as it looks old/decayed/inadequate/some other sob reason. Check if they'll charge first, though.
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!)
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.
The number of deaths caused by lighting circuits blacking out is probably at least a couple of orders of magnitude greater.
I would say that no lighting circuit should share an RCD with anything else, and that they really don't merit an RCD each. There are probably many ways you can use the money far more effectively to improve your home safety.
You understand incorrectly in tht respect.
I run a non-RCD protected circuit to a kitchen. I use it for just about all the stationary appliances in the kitchen. The sockets are positioned in places which are not convenient for use for anything else, and plenty of accessible sockets are provided on an RCD protected ring for portable appliance (and outdoor use). I tend to earth-bond the area around the sink along the same lines as required for bathrooms (although not for kitchens), and that includes ensuring the earths of the two socket outlet circuits are bonded nearby.
It is allowed. They will fit it for free if you have the right type of switch. Go to an electrical wholesalers and explain what it's for, and they'll give you something suitable.
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!
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.
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.
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?
No it does happen and although it was some 25 years ago I still remember it very vividly!. It was from an electric drill metal cased in the one hand, literally!, and to a metal ladder in soft solid soil in the other hand making the earth connection. Apparently it was lead sheathed cable where the earth connection had come undone at the dist board and there was no direct connection but for the Capactive leakage in the house wiring. Very painful and I couldn't move or call out, total paralysis:((
Fortunately I was working with someone who cottoned on too what was happening, and he unplugged the drill. Apparently, he had a similar thing before with the same type of drill and he was able to kick the plug out of the socket. Thank god for the 1974 health and safety at work act!, double insulation, and RCD's:))
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. And no I'm not going back there as it was a very long time ago, and I still shiver whenever I go past there with what did happen, and how that might have ended up!.
At the hospital the doctor said if it had gone on for much longer the heart would have not worked properly etc, and that would have been that, and I'd have been in permanent "earth" connection.....
*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!.....
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.
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