Concern about electrical safety check

[glassescase]

I have just bought a "second hand" house and it came with an electrical safety check but I am concerned that the check may not be good and proper and so I have a few questions. I am in the UK.

I'm frightened to ask.

The house has two fuse boxes each with their own tails from the electric company fuse.
Is any check done to make sure the correct size of cable and colour code has been used when an electrical safety check is carried out?
Some of the power sockets in the same room are served from one mcb/rcd and other sockets in the same room are served by another mcb/rcd, is this acceptable? I consider it dangerous. There is no identifying feature to show they are served from different mcb's/rcd's There re two or 3 rooms like this.
I am not sure if they are served from the same fuse box.
The garage has a fuse board, the incoming supply comes from the house and there is a mcb/rcd in the house plus mcb's/rcd's in the garage. The black wire has been used as earth, is this acceptable? I cant recall the other two colours, may be grey and brown with grey as neutral.



thank you in advance

glassescase

[Neelix]

None of your observations are considered bad practice or dangerous except the "black" wire used as the earth

If you want to make 100% sure then commission your own EICR BUT I warn you there are a lot of so called inspectors out there just giving C1 and C2 codes to generate work

[Someone-Else]

Pictures always help

This safety check does it say EICR?

Having sockets from different mcb's (or consumers units) does not contravene any regs. In some ways it can be useful, since if one lot get turned off by an RCD the others can still be on. As for working on them, who ever does should always prove dead. They only need to be marked if on different phases.

The garage, I take it that it is supplied by a big thick black cable? (SWA) using a core for the earth is quite common, but it should be identified as earth.

Cable size for the consumers units will (should) be checked, 25mm is the norm, but as yours sounds "old" it will probably be 16mm

Now days the preferred option is to have all RCBO's as opposed to one or two RCD's but it's NOT retrospective.

In other words, as Neelix says, nothing to worry about.

[glassescase]

None of your observations are considered bad practice or dangerous except the "black" wire used as the earth

If you want to make 100% sure then commission your own EICR BUT I warn you there are a lot of so called inspectors out there just giving C1 and C2 codes to generate work

if some of the sockets were red I think it would be a bit more obvious that they may be from a different circuit. I am so glad the alarm bells were ringing and I checked with the vendor as I would not have expected sockets in the same room to be on different fuses, not if the sockets are all the same colour. I appreciate the reply, thank you

glassescase

[glassescase]

Pictures always help

This safety check does it say EICR?

Having sockets from different mcb's (or consumers units) does not contravene any regs. In some ways it can be useful, since if one lot get turned off by an RCD the others can still be on. As for working on them, who ever does should always prove dead. They only need to be marked if on different phases.

The garage, I take it that it is supplied by a big thick black cable? (SWA) using a core for the earth is quite common, but it should be identified as earth.

Cable size for the consumers units will (should) be checked, 25mm is the norm, but as yours sounds "old" it will probably be 16mm

Now days the preferred option is to have all RCBO's as opposed to one or two RCD's but it's NOT retrospective.

In other words, as Neelix says, nothing to worry about.

looks like a thick cable to the garage, now you mention it I do think the black has earth insulation tape wrapped around it to denote earth.

Thank you foe the reply, appreciate it

glassescase

[Neelix]

None of your observations are considered bad practice or dangerous except the "black" wire used as the earth

If you want to make 100% sure then commission your own EICR BUT I warn you there are a lot of so called inspectors out there just giving C1 and C2 codes to generate work

if some of the sockets were red I think it would be a bit more obvious that they may be from a different circuit. I am so glad the alarm bells were ringing and I checked with the vendor as I would not have expected sockets in the same room to be on different fuses, not if the sockets are all the same colour. I appreciate the reply, thank you

glassescase

I’ve seen sockets on 3 circuits in the same room ….

[Someone-Else]

if some of the sockets were red

Or blue

blue.jpg (13.13 KiB) Viewed 1927 times

or pink

pink2.jpg (10.34 KiB) Viewed 1927 times

Yep, they really do exist, and green, chocolate white, duck egg, blue oh, and purple AND they make switches too

[glassescase]

I was thinking Red as I have seen those on Essential service ccts

glassescase

[Someone-Else]

oh. The red ones, they are often NOT ordinary sockets, but they do look like they are.


At first glance they look like normal sockets

s1.jpg (18.59 KiB) Viewed 1908 times

But as you can see, they are not normal sockets, but they are red.

s2.jpg (13.81 KiB) Viewed 1908 times

You push in the plug and twist, red is the most common colour, but you can get them in blue. They can be labelled as required, EPOS (Electronic Point Of Sale (Till to you and me) clean earth, what ever you like, its just to stop other stuff being plugged into them. Oh, you can't plug a blue plug into a red socket and vice versa.

[ericmark]

Only in the UK do we have the ring final, plus some countries which were connected to UK in the past, most countries and also UK before WW2 would have a fuse in the distribution unit for every socket, and still in a kitchen common to have most the sockets on a kitchen ring final and an odd one powered from the cooker supply.

Most houses are a compromise, I have seem supply to the freezer independent too, before rules changed on RCD protection, it was permitted to have a non RCD protected supply to the freezer. Each edition of the wiring regulations is not retrospective, it has a date after which new designs must follow it, but you can still follow the old design if you wish.

[glassescase]

Only in the UK do we have the ring final, plus some countries which were connected to UK in the past, most countries and also UK before WW2 would have a fuse in the distribution unit for every socket, and still in a kitchen common to have most the sockets on a kitchen ring final and an odd one powered from the cooker supply.

Most houses are a compromise, I have seem supply to the freezer independent too, before rules changed on RCD protection, it was permitted to have a non RCD protected supply to the freezer. Each edition of the wiring regulations is not retrospective, it has a date after which new designs must follow it, but you can still follow the old design if you wish.

Ring final, not a term I have heard before.
Is there a "better way" to wire a house then the UK method? I take UK method as ring main upstairs, ring main down stairs, kitchen ring main, lights upstairs, lights down stairs, cooker
Perhaps you could have rooms A, B and C served from one MCB and D, E and F which are on the same floor served from another MCB but the fuse board needs to be very clearly marked

glassescase

[Scotty001]

I personally would like a 50/50 split for each floor and 50/50 split for each room, minimum 2 circuits on each floor and room for sockets with every other socket on an alternating circuit.

Likewise for lighting, that way if you had an issue on one circuit, half of the sockets and half of the lights in every room and every floor would still be active (not so much if only a single light in each room)

My wiring is a little all over the place so being who I am I've drawn up a little house plan with all the lights and sockets and marked exactly which RCBO reeds each one, this is in a plastic wallet taped inside the cons unit. (it still doesn't stop me from proving the circ is dead before working on it after Isolating the RCBO, that would be stupid.

[Someone-Else]

Ring final is the correct name, but often shortened to ring.
Most houses only have 2 rings, kitchen, rest of house.
There is a "better way" each socket has its own MCB, that way, in theory you don't need a fuse in the plug................just like the Americans do.
The ring circuit came about after the war, there was a copper shortage so to save copper the ring final was invented, with the average of one socket in the corner of most rooms.

The disadvantage with the American system having no fuse in the plug, you can get a dead short on something and that somethings cable can overheat and melt causing a fire, they also have sockets in the bathroom, they find it odd that we don't have sockets in the bathroom, but then they also find it odd that we have two taps, one hot one cold.

Of course the advent of the RCBO has improved things, before if there was a slight earth fault, nothing much happened, no RCD's only re-wireable fuses, then MCB's came into widespread use, then the RCD (Its was preceded by the ELCB*) one RCD would control all MCB's, which obviously meant a slight earth fault and click, no lights no TV no freezer, so the split board came out, two RCD's. Then the RCBO cost came down and now all new installations have them, and the latest must have is surge protection, I wonder what is next.


*ELCB is Earth Leakage Circuit Breaker, they worked on voltage not current and were not that good.
MCB is Miniature Circuit Breaker (Like a re-usable fuse that is very quick) it operates if too much current is being drawn.
RCD is Residual Current Device, it detects current not coming back, so it must be going to earth.
RCBO is cross between an MCB and an RCD as it does both things.

[ericmark]

A ring main refers to the method used to supply so a section can be isolated for maintenance common with a HV supply, any leg can take the full current, this is very different to a ring final which was designed at the end of WW2 so less cable would be required when the rebuilding program was started, with 7/0.029 cable being rated around 25 amp mark and the fuse being 30 amp, and a second 13 amp fuse being included in the plug.

The 7/0.029 cable is between 2.5 and 4 mm used today, and the fuse rating was lifted to 32 amp when replaced with a MCB, there is no fixed rating for cable it depends how installed, but regulations say most be 20 amp or more, we have also increased the permitted volt drop, so the 80 meters allowed with old system has increased to 106 meters, however again there is no fixed way to calculate volt drop, the 106 meters assumes 20 amp centre of ring final and 12 amp even spread, so the current used in the calculation is 26 amp not 32 amp.

In theory we can measure volt drop with a loop impedance meter, I was worried at one time over using too much cable and at a latter date some one highlighting the error and wanting me to correct the error, so I made a program to check the results from a loop impedance tester. This

loop-temp.jpg (97.74 KiB) Viewed 1853 times

was the result, used java script, but when I came to use it, realised the loop impedance tester is not that accurate, the reading can be 0.94, 0.96, 0.92 if taken three times, so the same with incoming supply, so the cable length would need to be well over to actually say an error has been made, so in real terms if under the rating required for the MCB then one is OK, so B type 32 amp 1.44 ohms was permitted, OK now 1.36 but BS7671 is not retrospective so 1.44 is still a pass.

Even if the earth loop impedance does exceed 1.44 ohms, where a RCD is used not sure if one can really say potentially dangerous? However the schedule of results should show readings, so easy enough to publish them if your worried, but when I saw the results from this house, it seems jackanory was involved, as the results did not match each other.

[glassescase]

Ring final is the correct name, but often shortened to ring.
Most houses only have 2 rings, kitchen, rest of house.
There is a "better way" each socket has its own MCB, that way, in theory you don't need a fuse in the plug................just like the Americans do.
The ring circuit came about after the war, there was a copper shortage so to save copper the ring final was invented, with the average of one socket in the corner of most rooms.

The disadvantage with the American system having no fuse in the plug, you can get a dead short on something and that somethings cable can overheat and melt causing a fire, they also have sockets in the bathroom, they find it odd that we don't have sockets in the bathroom, but then they also find it odd that we have two taps, one hot one cold.

Of course the advent of the RCBO has improved things, before if there was a slight earth fault, nothing much happened, no RCD's only re-wireable fuses, then MCB's came into widespread use, then the RCD (Its was preceded by the ELCB*) one RCD would control all MCB's, which obviously meant a slight earth fault and click, no lights no TV no freezer, so the split board came out, two RCD's. Then the RCBO cost came down and now all new installations have them, and the latest must have is surge protection, I wonder what is next.


*ELCB is Earth Leakage <a title="Shopping Link Added by SkimWords" class="skimwords-link" href="http://shop.ebay.co.uk/?_nkw=circuit+breaker" target="_blank" data-skim-node-id="98:*ELCBisEarthLeakageC_1" occurrence="1" data-skim-creative="300003" data-group-id="0" data-skimwords-word="circuit%20breaker" data-skimwords-id="877256">Circuit Breaker</a><span style="position: absolute;"></span><span style="position: absolute;"></span>, they worked on voltage not current and were not that good.
MCB is Miniature <span class="skimwords-potential">Circuit Breaker</span><span style="position: absolute;"></span><span style="position: absolute;"></span> (Like a re-usable fuse that is very quick) it operates if too much current is being drawn.
RCD is Residual Current Device, it detects current not coming back, so it must be going to earth.
RCBO is cross between an MCB and an RCD as it does both things.

where did the term "Ring Main" come from?

macafee2