Outbuilding electrics that require amending

[smileymiley]

Hi Guys

Having recently moved into a new house, I have come to realise recently that there are some sub-standard electrics powering up two sheds in my back-garden. Some advice is required (and would be very much appreciated), to assist my knowledge in whether the current configuration is a)dangerous, and b) my best options to rectify and make safe.

Having inspected the wiring last week I have noticed that my two sheds (one brick outbuilding and one large wooden shed) have both been powered up from a single spur taken from a kitchen socket. This has been run with a 3 core flex, unsure what gauge but it seems to me to be an insufficient thickness. This is then routed (not in conduit) approx 12m through a covered passageway between the terraced houses, under a 1 metre opening (which is susceptible to weathering), and into the first outbuilding shed. Two double sockets are supplied in here, after which a junction box to shielded cable which is then run under ground to the bottom shed, a further 20m. Within the bottom shed there are 4x2 way sockets and lighting, all of the above supplied from this single kitchen spur.

I am extremely worried having discovered this that the wiring is dangerous ? What could be the outcome of this ? Wiring catching alight and burning out ? Worse ? Should I disconnect this immediately to avoid such a disaster ? NB. I have been using a tumble drier in the brick shed for 3 months with no disasterous consequences (yet !).

Of course I realise that this is going to be needed to be sorted asap, and won't be undertaking this work myself as I am an electronic engineer and not an electrican, but want to understand the extent of the work that is required.

I do have the additional problem of a 6-way consumer unit (with no RCD)and which all MCBs are currently employed for other tasks (2 lighting rings (5A), 2 ringmains (30A each), 1 cooker (45A), 1 immersion heating (15A).

Is it a necessity in this circumstance to replace the consumer unit for (8/10 way) to allow a free MCB for the purpose of supplying the outside sheds ? Are there any other options i.e. having a 2 way consumer unit added within one of the current ringmains for the house (and not spurred), which then goes on to supply the sheds ?

Of course I want to ensure that I am able to sleep at night and make these electrics safe ! This being a family home with my 2 young children and wife and since detecting the work that the previous billy bodger owner had carried out, I am concerned that this could put my family at risk and potentially cause a house fire.

Your responses would be very much appreciated.

 

[JohnD]

You currently have a risk of electric shock in the shed, or from the cable if it should be damaged, as well as a risk of fire as the cable does not sound to be separately fused and is on a 30Amp supply.

From the MCB ratings you mention, I think you probably have an oldish Wylex Standard consumer unit in Cream with push-button MCBs. There are many of these doing sterling service and yours is probably fine, however you have no room for expansion and can't easily fit an RCD. You ought to check your main earthing to see if it is up to standard (this is usually a very easy DIY job if not)

I would suggest you have an additional consumer unit fitted, to provide the outdoor circuits and also to give room for future expansion (so rather than buy a 2-way one, consider having a bigger one of a good-quality make that can take on the other house circuits when the time comes to replace your old CU.

You can either have an RCD+MCB or an RBCO to feed the shed supply, or else feed it from an MCB as a sub-main, and have a small CU with RCD in the brick shed. It is usually considered more convenient to have the RCD in the shed so that you can reset it if you're working in there and it trips.

This work is subject to Building Regulations so it would be simplest to find a well-recommended local electrician who is a member of a self-certification scheme, if not you will have to pay the local authority to inspect.

The electrician will advise on type of cable to use, and whether to run it underground or suspended, as well as the method of earthing in the shed. You may want one or two weatherproof outdoor sockets and lamps fitted at the same time. The existing undergound cable might or might not be adequately armoured and deep to re-use.

 

[smileymiley]

Many thanks for your reply. This answers many of my concerns.

Just to clarify your advice;

Are you suggesting placing a second consumer unit alongside the existing 6 way unit, which would be connected in parallel from the meter, purchase just one or a couple of MCB's to carry out the job required for the sheds in view of using this as the Main CU when the time arises ?

Would it not be easier to migrate the old CU supplies at the same time, perhaps buy a CU kit box with MCBs included (i.e. split load 10 / 12 way with RCD protection) ?? Would this be a significant amount of more work for the electrician to do if already having to install and connect a new one anyway ?

Also is your suggestion for a further small CU in the shed a requirement, or a convenience comment based on the RCD tripping etc. I assume directly from the Main CU will provide it's own RCD protection and hence this is more a convenience item to save running in and out resetting RCD if it does trip ( although not compulsory ? )

Do you have any suggestions based on experiences as to which manufacturer CU to use, Volex/Marbo/Crabtree/Wylex/MK (just going through my Screwfix catalogue ! ) Not gonna buy it yet, although would be good to have a recommendation that I can pass to the electrician of which unit I would like to have fitted.

I am unsure whether the original CU is a Wylex or not. I know it has flick switches on the MCBs as opposed to push button, not that this is concern, your comments are still relevant and well appreciated.

Many thanks.

 

[JohnD]

Many thanks for your reply. This answers many of my concerns.

Just to clarify your advice;

Are you suggesting placing a second consumer unit alongside the existing 6 way unit, which would be connected in parallel from the meter, purchase just one or a couple of MCB's to carry out the job required for the sheds in view of using this as the Main CU when the time arises ? YES - a bigger one is not much more expensive than a little one, as you are mostly paying for an empty plastic box and some fresh air

Would it not be easier to migrate the old CU supplies at the same time, perhaps buy a CU kit box with MCBs included (i.e. split load 10 / 12 way with RCD protection) ?? YES Would this be a significant amount of more work for the electrician to do if already having to install and connect a new one anyway ? YES but if the extra cost is not a prob (it will involve a lot of testing, and possibly rectification of the old circuits - great - go ahead.

Also is your suggestion for a further small CU in the shed a requirement, or a convenience comment based on the RCD tripping etc. It's an option - your choice I assume directly from the Main CU will provide it's own RCD protection and hence this is more a convenience item to save running in and out resetting RCD if it does trip ( although not compulsory ? ) You can rely on an RCD in the house or an RCD in the shed - your choice. However I would advise against putting it on a split-load RCD with the house socket circuits, as you would lose all your house sockets in the event of e.g. a lawnmower or shed fault. I am a great believer in RCBOs which avoid this problem but can work out expensive if you have a lot of circuits which need RCD protection.

Do you have any suggestions based on experiences as to which manufacturer CU to use, Volex/Marbo/Crabtree/Wylex/MK (just going through my Screwfix catalogue ! ) You will notice that some are cheaper than others... this is a clue! My personal preference is MEM because they do a lot of very good Industrial gear so are very reliable and good quality - their RCBOs are Industrial quality but will fit the Domestic CUs. They are not widely used in Domestic installations as they are not often price-discounted by the sheds. But you need to see what brands your electrician likes, he will not thank you for choosing something he finds it difficult to work with and will probably increase his labour charge. Not gonna buy it yet, although would be good to have a recommendation that I can pass to the electrician of which unit I would like to have fitted. As before...

I am unsure whether the original CU is a Wylex or not. I know it has flick switches on the MCBs as opposed to push button, not that this is concern, your comments are still relevant and well appreciated. No prob - I was going by the 5A and 30A sizes - more recent ones are 6A and 32A - Wylex are the most common brand in older domestic installations.

Many thanks. Its a pleasure

 

[securespark]

You will notice John is a huge fan of RCBO's.....!!

Joking aside, IMO, they are the best option if you can afford them, as any earth faults on circuits protected by them only cause that RCBO to trip.

Whereas, with a normal split-load board, when an earth fault occurs, the RCD trips, switching off all circuits protected by the RCD.

And MEM are in my opinion too one of the best.

Some belting advice there!

 

[smileymiley]

JohnD / Securespark

Many thanks for your response guys.

Just one last quick question (sorry !)

As a short term safety fix for the original problems/dangers of the sub-standard wiring job, would it be acceptable / safer than currently, to place a fused spur (13A fuse say) between the kitchen spur and first shed socket, so if anything were to cause problems within the shed it would take out the fuse and not the whole house !

(NB these shed sockets are not used much, and going to be used even less now ! The one item I do use regularly is the tumble drier, with occasional lighting turned on in the other shed for short periods).

I have already made a couple of enquiries with local sparkies, and as you may expect at this time of year, rather than being days, the remedial work will probably roll over into next year

I appreciate all your help in this posting

Kind Regards

smileymiley

 

[JohnD]

Yes, but you can buy an FCU with incorporated RCD. Dearer but for your job is the better thing. If you just had a single outdoor socket it would be a reasonable solution.

For example

if the outgoing cable from the house is a flexible cord, and you happen to already have a "garden RCD adaptor" already (such as is used with lawn mowers) then that, with a 13A plug, would be an alternative. Though there is a risk that someone will remove the adaptor and put the plug straight into the socket. Sadly this more often happens when there is a fault that makes it trip (bit like people removing the batteries from their smoke alarms like the Fire Service often finds after a fatal fire. So this would be even less satisfactory.

 

[plugwash]

Joking aside, IMO, they are the best option if you can afford them, as any earth faults on circuits protected by them only cause that RCBO to trip.

RCD sockets are better (though even more expensive)

 

[303mc]

JohnD / Securespark

Many thanks for your response guys.

Just one last quick question (sorry !)

As a short term safety fix for the original problems/dangers of the sub-standard wiring job, would it be acceptable / safer than currently, to place a fused spur (13A fuse say) between the kitchen spur and first shed socket, so if anything were to cause problems within the shed it would take out the fuse and not the whole house !

(NB these shed sockets are not used much, and going to be used even less now ! The one item I do use regularly is the tumble drier, with occasional lighting turned on in the other shed for short periods).


smileymiley

Hi, It might be a good idea to check the flex to the shed is capable of carrying 13a for the tumble dryer, I think it should be at least 1.5mm?

Marc