New RCD for Existing Modern CU + Live Water Shock!

[phykell]

My current CU/meter arrangement looks like this:

http://homepage.ntlworld.com/phykell/diy/cu.jpg

It's a modern CU but obviously it's not split load or anything like that, and now I know why I should've had an RCD fitted! ...

I tested a powerhead for an aquarium the other day in the sink and got a funny tingle from it. Suspecting the worst I dipped an mains tester screwdriver and the neon lit up! Obviously the seal had broken, but more importantly, if I'd had an RCD, it would've prevented such a potential disaster. If I'd put the powerhead in my marine (saltwater) tank, I might not be here today!

Anyway, I now want to put an RCD in so I'm looking for ideas. Should I just buy a new split load CU or is an RCD inserted between the meter and the CU adequate? I looked at the diagram kindly provided by this forum but I don't understand the terms TN-C-S, TN-S, etc. From what I can see, a TT arrangement would do fine, but what does the diagram mean exactly and what type is the one I've got already?

 

[2scoops0406]

I really don't wish to belittle your skills here, but I think from what you have said, you'd be best off calling an electrician.

 

[Lectrician]

Not one for a beginner.

Your intake looks like it is TT, with NO rcd - extremely leathal.

I cant see an earth connection to the elec boards REALLY OLD supply cable?!?! Maybe you can take a wider shot??

I would recommend a split board, and upgrade to TNS earthing (available if your cable is a lead covered one), or to PME TN-C-S (available if the elec board says so). If you are forced to use a TT, you will need a rod in the ground, and a split board with a 100mA delay RCD as the main sw, and a 30mA RCD on the split for the sockets.

You will need to upgrade the earth bonding to gas, oil, water etc.

 

[2scoops0406]

Your intake looks like it is TT, with NO rcd - extremely leathal.

As opposed to the slightly lethal variety

 

[Lectrician]

With this type of set up, he could have a fault to earth with NO fuse operating - earth could be anywhere from 0v upto the full 240v!!! Tingle?? Yep.

 

[dphomes]

I think its about time you get a professional in to check the wiring and the electrical supplier may need to upgade your meter. Your picture tells me that your grey cable wire is susspect and with your basic knowledge of electricity you are a danger to yourself and others. You been given a sign already lets hope you don't ignore our advice. An electrican is cheap a life is not.

 

[phykell]

There's another picture here, showing the earth arrangement:

http://homepage.ntlworld.com/phykell/diy/cu_earth.jpg

This shows the earth cable fixed to a rod, hopefully BS 951 The cable is then routed to the CU and there's another one bonded to the cold water pipe. Hopefully, this is adequate.

The point about getting the supplier to check the meter and possibly upgrade it is an interesting one. I'll check that out, thanks.

I take it then, my system is:

TT No earth provided by supplier; installation requires own earth rod (common with overhead supply lines).

I'll make every effort to have an RCD installed ASAP. Will it go between the CU and the meter then? Is this somthing an electrician can fit or does the supplier have to do it?

Incidentally, I'm a software engineer now, but I was an electronics graduate so I do know my way around electricity

 

[ban-all-sheds]

There's another picture here, showing the earth arrangement:

I wish you'd put your pictures in-line...

This shows the earth cable fixed to a rod, hopefully BS 951 The cable is then routed to the CU and there's another one bonded to the cold water pipe.

Is that rod indoors????

Hopefully, this is adequate.

Hoping it's OK is not a good plan for your earth and main bonding...

I'll make every effort to have an RCD installed ASAP. Will it go between the CU and the meter then?

It can go there, but that's a far from ideal solution. You should get rid of your non-split CU, have the whole installation on a time-delayed 100mA RCD, and all the socket circuits on a 30mA one.

Is this somthing an electrician can fit or does the supplier have to do it?

Electrician.

Incidentally, I'm a software engineer now, but I was an electronics graduate so I do know my way around electricity

Maybe, but not electrical installations.

 

[phykell]

There's another picture here, showing the earth arrangement:

I wish you'd put your pictures in-line... Of course - you'd have to host them somewhere that allows them to be linked to first....[/quote]
Sorry, I thought it might be bad form to post loads of pictures - bandwidth, etc. Anyway, I've fixed the links now, you should be able to see them, though I don't understand why you couldn't see them using my own web-site...

Is that rod indoors????

Shouldn't it be?

Hoping it's OK is not a good plan for your earth and main bonding...

Point taken

It can go there, but that's a far from ideal solution. You should get rid of your non-split CU, have the whole installation on a time-delayed 100mA RCD, and all the socket circuits on a 30mA one.

Thanks, that's the kind of info I'm looking for.

Electrician.

OK

Maybe, but not electrical installations.

Fair enough but I did design work on safety critical systems for gas and fire protection on oil rigs. Worth mentioning so you don't think I'm a potential Darwin award candidtate

 

[supersparks]

is it just me or are you having a blodey lotta work done on your house
(lookin at other pics, one in particular showing no ceilings )

also, why, in the shot with earth rod, is there a big burn mark on the wall

plumber been in you ouse recently

 

[ban-all-sheds]

There's another picture here, showing the earth arrangement:

I wish you'd put your pictures in-line... Of course - you'd have to host them somewhere that allows them to be linked to first....

Sorry, I thought it might be bad form to post loads of pictures - bandwidth, etc. Anyway, I've fixed the links now, you should be able to see them, though I don't understand why you couldn't see them using my own web-site...

I realise now why they didn't show up in my post above - the www.phykell.co.uk URL.

Is that rod indoors????

Shouldn't it be?

No - it should be somewhere where the soil doesn't dry out....

 

[phykell]

is it just me or are you having a blodey lotta work done on your house (lookin at other pics, one in particular showing no ceilings )

Yes. Isn't it best to do it all at once? It's just how it's turned out really. We bought a kitchen and started preparing the room. Unfortunately, once tiles and wallpaper were removed, I found huge cracks and loose masonry plus inadequate wooden lintels, one with a huge crack right in the centre. Then it was suggested we also move our boiler which because it was so old probably needed replacing anyway (over 20 years old). Removed the old ceiling cladding which was knackered and found that the flat roof was leaking so then we needed a new roof and got to see the awful wiring which meant a rethink on what to do about the meter. It just goes on and on! And I haven't mentioned the fact I'm getting my driveway block paved as well...

also, why, in the shot with earth rod, is there a big burn mark on the wall

Bloody hell, I'd never noticed that before! I'll take a stab in the dark and suggest it's from a candle during a power cut. I seem to remember we found candles and matches in there years ago.

plumber been in you ouse recently

Yes, but he ran out screaming! And yes, my family name really is "Addams" - LOL

No - it should be somewhere where the soil doesn't dry out....

Thanks for the info. What do you think I can do about this? It is next to an outbuilding which is built onto the side of the house. Obviously I have no idea how suitable it is as an earth because I don't know whether the soil dries out or not...

 

[ban-all-sheds]

No - it should be somewhere where the soil doesn't dry out....

Thanks for the info. What do you think I can do about this? It is next to an outbuilding which is built onto the side of the house. Obviously I have no idea how suitable it is as an earth because I don't know whether the soil dries out or not...

If it never gets rained on it's probably going to dry out. You could have someone come and measure it, but if you're going to do that you might as well have a new one put in outside. How far is it to the outside?

Alternatively you could ask the DNO to convert you to a PME supply.

 

[phykell]

If it never gets rained on it's probably going to dry out. You could have someone come and measure it, but if you're going to do that you might as well have a new one put in outside. How far is it to the outside?

It's about 5 metres, but another 5 metres to an area of soil.

Alternatively you could ask the DNO to convert you to a PME supply.

What's a DNO and what's a PME? Would they do this for free or is it something I need to pay for? If it's somthing that can be done and it's an improvement on my existing system, it's something I should probably have done now as I'm having my driveway block paved in November and I guess the DNO would need to dig my drive up possibly?

 

[ban-all-sheds]

If it never gets rained on it's probably going to dry out. You could have someone come and measure it, but if you're going to do that you might as well have a new one put in outside. How far is it to the outside?

It's about 5 metres, but another 5 metres to an area of soil.

Doesn't sound too far - use a nice thick cable. How easy would the installation be? Could it run above ground?

Alternatively you could ask the DNO to convert you to a PME supply.

What's a DNO and what's a PME?

DNO - Distribution Network Operator. Used to be called REC - Regional Electricity Company, but the same bunch of fools who thought that the way to organise a railway was to have the track and the trains owned by different companies (even with a railway system from Hornby you get everything in the same box FFS) decided that the people who made the electricity should be different from the people who owned the means of delivery into your house. So who you pay your bills to is not necessarily who owns the wires.

PME - Protective Multiple Earthing, aka TN-C-S. You can read all about it here: http://www.tlc-direct.co.uk/Book/5.2.1.htm

Would they do this for free or is it something I need to pay for? If it's somthing that can be done and it's an improvement on my existing system, it's something I should probably have done now as I'm having my driveway block paved in November and I guess the DNO would need to dig my drive up possibly

I'm Mr TN-Smug, so I've never had to ask. I don't know if they are obliged to do it if you ask, nor if they charge for it (but I can hazard a guess ). Wouldn't have thought they'd need to dig up your drive - it would depend on how close they wanted one of their multiple electrodes to be, but it would be foolish of you not to verify that with them.