Hi Between the meter and the CU I have an old black 60A trip switch with a yellow button on it to test the trip. I had someone look at it and he said that these were no longer legal and I would have to replace it. Is this right and if so what should it be replaced with? Thanks KBG
Hi the device you have is an old voltage operated RCD now illegal as they tend not to work when needed to. If you have an overhead supply then you need to change this for a new RCD to comply with the regs, But if you are not on an overhead supply then you will be ok with the RCD in your new fuseboard. If you have an overhead supply , then the advice i gave earlier will be different with regards to fuseboard extensions. Let me know and i will explain more NIck
Thanks for advice. I have overhead supply upto about 20m of house then it comes down the pole and underground to front wall of property. Is this underground or overhead? If its underground what do with this trip switch? If its overhead what type of RCD do I use to replace it? thanks for your help KBG
Have you also got an earth rod as your main means of earthing? if so you have whats called a TT system, everything on the power side must be protected by an RCD and normally 2 rcd's a 100ma main rcd covering everything then a 30ma covering the power circuits and circuits normally protected by an RCD hope this helps Nick
Hi yes I have an earth rod. So am I right in thinking I should have a 100ma RCD in place of the old Trip and then rely on the 30ma RCD on my new CU. Am I treating this as overhead feed? If I had underground feed should I have just replaced the trip with a new isolator switch? thanks for all your help. KBG
Not quite no, you need to have a 100ma rcd protecting the whole installation and a 30mma protecting the sockets shower etc if you did as you said then the 30ma RCD would also be protecting everything aswell. You need to have a special type of 100ma RCD called a time lagged RCD which will offer a certain amount of descrimination between faults or else both will trip at the same time in event of an earth fault. Nick
Sorry to be a pain, I have a 6+6 split load CU. The shower etc are on the RCD side, so do I take out the old trip outside and replace it with a time delay 100ma RCD? thanks KBG
The best way is to remove the 100a main switch on your board and replace it with a 100ma time delayed rcd made by the same manafacturer if possible. MK do one im sure. Explain to your wholesaler what you are trying to do and its a TT installation and he should be able to sort you out with something. Then all you do is remove your black box, replace the tails with new from the meter and bobs your uncle. Nick
thanks Sparky your a star. I am buying a new CU as I need some extra circuits so can I buy a CU with the type of switch you suggest already fitted or is it best to buy a CU box and make up the configuration myself? I was going to get a split load CU, is this still a good idea? As well as the old trip switch by the meter there is a big old isolator switch which I think was there when the property had night storage heaters. Should that be replaced as well? I really appreciate your help. Thanks KBG
Hi the device you have is an old voltage operated RCD for future reference: are these older types easy enough to identify?
Yep. Voltage Operated trips will have earth wires going into them and out to a stake. RCD's will just have the meter tails passing through them.
Whichever way you look at it the old black box has to go. Do as i said before and install a 100ma RCD and a 30ma rcd in ther same board and make sure the 100ma is a type S or time delayed RCD . Also make sure the main earth to your rod is big enough 10mm is fine. Hope this helps Nick
I have overhead supply upto about 20m of house then it comes down the pole and underground to front wall of property. Is this underground or overhead? If there is a transformer mounted on the pole that the underground cable is connected to then it will be classed as an underground supply. If, as I suspect, the transformer is mounted on a pole some distance along the overhead line supplying the U/G cable then it will be classed as an overhead supply. :} G
Thanks for all your help. One thing I don't understand is why is my system different, i.e TT as explained by Sparky as it seems to be the same as everyone else. Supply in to CU and earth cable to bar in ground? Thanks KBG
How can it be different and the same as everyone else? Not everyone else has their own earth rod, only people with a TT supply. Read all about it here: http://www.tlc-direct.co.uk/Book/5.2.1.htm
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