Dodgy Electrics

[dampsquib]

Hi.
As I am looking to replace my shower soon, I though i'd check out the MCB and cabling to check it was OK for my new shower.

Funny thing is, as I flicked the MCB (which is in my front room) my tv reception died. I took a look in the loft, as something seemed not quite right! It seems the person who'd fitted the shower had run an extra double socket in the loft from the isolating pull switch, which powered the loft light and aerial booster!

Am I right in thinking this is a big no-no?

I'm going to take out the dodgy socket when I change the shower, but my question is now this. would it be OK to move the double socket onto another mains source, i.e. the closest one being the bathroom lighting circuit, or should I drop a line down to the upstairs ring main?

Thanks

DS

 

[didthathurt]

This spur socket is, I am guessing, connected using 2.5mm cable. This is a no-no because the current carrying capacity of the cable is less than that of the MCB protecting the cct so, in the event of an overload/fault, the cable may melt before the MCB trips.

What is also a no-no is connecting sockets into lighting ccts! A socket is designed to take a 13A fused plug, a lighting cct may well be constructed using cable whose max load may be as low as 10.5A and be protected by a 6A MCB.

Remove this spur and, if you need power there, create a spur from the nearest ring main.

 

[Steve]

What is also a no-no is connecting sockets into lighting ccts! A socket is designed to take a 13A fused plug, a lighting cct may well be constructed using cable whose max load may be as low as 10.5A and be protected by a 6A MCB.

actually, this is good. the socket and cable are protected from overload. if someone plugs in an electric heater etc, the MCB will trip. It is generally accepted to put a single socket on a lighting circuit for the purpose of having a TV booster. A round pin socket or FCU would be better, but theres nothing in the regs that states it is wrong to have a socket, and a lot of TV boosters are of the "wall-wart" variety, which are obviously impossible to get on an FCU.

 

[stem]

This is a no-no because the current carrying capacity of the cable is less than that of the MCB protecting the cct so, in the event of an overload/fault, the cable may melt before the MCB trips.

I agree that the shower circuit shouldn't feed a socket outlet, but as for the reason, what about 2.5mm T&E feeding an unfused spur from a ring on a 32A MCB doesn't that fall into the same category?

 

[didthathurt]

Agreed. But I take the view that if a socket is so placed at some point, someone will put something heavy into it and trip the breaker. In this instance, that leaves that person in the attic with no lights attempting to navigate back out. So, I know that from an electrical safety point of view, it's not a problem. From the wider perspective that the installation should be, in all ways, fit for purpose; and from the standpoint that a piece of installed equipment should be capable of doing the job it was manufactured to do; I still regard the fitting of a socket to a cct not capable of carrying the load that might reasonably be placed thereon as bad practise. The fact that, at the moment, an aerial booster will be connected to that socket does not mean that the next user will not try to run a power drll and a fan heater off it. As the pro who's been paid to supply a customer with an installation that will, under all conditions, never create a situation that places the end user in an avoidable hazardous situation, I would always decline to connect a socket in that way.

Secondly, yes, an unfused spur off a normal ring is very similar, but, the way I look at it, there are only 2 services on this radial. With the shower off, this one leg, at the end, could have to bear a load that is way beyond its capacity before the cct protection operates. At least on a spur from a ring, the protection and load capacity are a lot more closely matched.

 

[dampsquib]

Thanks for the replies, just for a quick aside, the spur socket is connected with the same 7.5mm twin and earth that's used for the shower.

 

[Adam_151]

Thanks for the replies, just for a quick aside, the spur socket is connected with the same 7.5mm twin and earth that's used for the shower.

There has never been such a cable size, do you have 6mm² CSA cable or 10mm² CSA cable? or are you quoting something other than mm² CSA?

 

[dampsquib]

Thanks for the replies, just for a quick aside, the spur socket is connected with the same 7.5mm twin and earth that's used for the shower.

There has never been such a cable size, do you have 6mm² CSA cable or 10mm² CSA cable? or are you quoting something other than mm² CSA?

True. I'm at work whilst typing this, and that's another figure I was working with! 6mm really.

 

[nozspark]

The easiest and proper way to rectify this is to:-

Firstly - disconnect the socket & lighting from the shower circuit NOW.

Secondly - change the socket to a 3A round pin and wire form an accessible light fitting - wire lights in loft from this, ensuring of course that the lighting circuit in question is capable of carrying the additional load..

Wire all the above in 1.0mm T&E and all should be fine.

 

[dampsquib]

Thanks for the responses. I've removed the sockets from the shower supply, and wired the loft light into the upstairs lighting circuit.

One more question if I may; my current shower is connected by 6mm t+e, and runs in surface mounted conduit from the MCB, onto a cable tray in the loft, then back into surface mounted conduit for presentation to the shower (approx 7 metre total run)

Current shower is 7.5Kw. The plan is, replace this with an 8.5 Kw shower, and also bury the cable and conduit into the bathroom wall prior to tiling.

Should I replace the 6mm T+E for 10mm, because a 2 foot section of the cable will be in the wall, as opposed to surface mounted conduit? It's an external wall if that makes any difference.

Thanks

 

[securespark]

This is a no-no because the current carrying capacity of the cable is less than that of the MCB protecting the cct so, in the event of an overload/fault, the cable may melt before the MCB trips.

Because that unfused spur should be limited to one 13A accessory.