EXTENDING POWER FROM ONE OUTDOOR SHED TO ANOTHER

[mobanded]

I AM NOT AN ELECTRICIAN SO PLEASE EXCUSE IF I GET SOME TERMS WRONG.

PLEASE ALSO NOTE THAT MY CONSUMER UNIT IS FULL AND THE COST OF REPLACING CU JUST TO RUN ANOTHER CIRCUIT OUTSIDE IS NOT AN OPTION. THE CONSUMER UNIT HAS AN OPENING IN A FALSE WALL TO ACCESS TRIP SWITCHES AND READ THE METER BUT TAKING OUT THE FALSE WALL AND REDECORATING ETC. WOULD MAKE IT TOO COSTLY.

I need to extend the power in one small shed to a birdhouse, which is some 20/25 metres away. Because the original fitting was done by a qualified electrician I presume it is a genuine job. Albeit it looks as though he took a spur from an existing ring circuit which has a 30amp fuse at the consumer unit.

In the shed the armoured cable is fed to a Wylex Fuse Box, which in turn has two circuits, one comprising a 5 amp fuse and the other a 15 amp fuse. The circuit with the 5 amp fuse goes to a light via a switch. The 15 amp circuit goes to a twin socket, into which is plugged a fridge. The other socket is used for plugging in a variety of garden type power tools using a plug in RCD.

My aim is to utilise this existing power and extend it to my birdhouse which is 20/25 metres away.

1. Should I dismantle the exisiting fuse box in the shed and replace it with a twin socket RCD power breaker from which I can run the fridge and light from the sockets?

2. Can I extend the armoured cable and run it to my additional shed/birdhouse and utilise the existing Wylex Fuse Box in that shed to build a lighting and power circuit?

3. If I can do the jobs in 1&2 is there a problem if I run the armoured cable , say 12 inches above ground, and tag it to a row of trees I have surrounding my garden or can I do the same using the garden fence? If I can avoid it I do not want to have to dig a an 18" trench to the birdhouse.

4. In the birdhouse I will be using a series of lights which I want to time to come on and off individually - my idea would be to put a series of twin sockets with plugged in timers and run an individual line to each light. Anyone any better ideas?

5. I would need only one twin socket power point socket so I could use a 120watt ceramic heater with a timer whenever the temperature fell to unacceptable level. I would also like to use an occasional vacuum cleaner but if this was a problem it is not essential.


Any advice would be most welcome.

 

[andy]

first of all, there is no need to shout

1. Should I dismantle the exisiting fuse box in the shed and replace it with a twin socket RCD power breaker from which I can run the fridge and light from the sockets?

i presume you mean change the CU for a garage/shed CU with and RCD? yes - i would advise you do this mainly for your own safety

2. Can I extend the armoured cable and run it to my additional shed/birdhouse and utilise the existing Wylex Fuse Box in that shed to build a lighting and power circuit?

yes. make sure you dont overload the circuit tho.what size SWA is currently supplyin the shed? also, is it fused before it leaves the house?

3. If I can do the jobs in 1&2 is there a problem if I run the armoured cable , say 12 inches above ground, and tag it to a row of trees I have surrounding my garden or can I do the same using the garden fence? If I can avoid it I do not want to have to dig a an 18" trench to the birdhouse.

bury it in the ground. no if's or but's

4. In the birdhouse I will be using a series of lights which I want to time to come on and off individually - my idea would be to put a series of twin sockets with plugged in timers and run an individual line to each light. Anyone any better ideas?

sounds OK to add timers, providing that the circuit is not overloaded. need to kno what size SWA is already used

5. I would need only one twin socket power point socket so I could use a 120watt ceramic heater with a timer whenever the temperature fell to unacceptable level. I would also like to use an occasional vacuum cleaner but if this was a problem it is not essential.

the heater should be OK, as it uses under 1A. hoover may cause a problem if too many items connected.


main things we need are:

what size SWA is used from house to shed?
is it connected via a FCU or any other means of switching before it leaves the house? what rating is the fuses/breakers?

the main thing im concerned about in this is the fact thats its spurred from the ring main. does this ring supply all or most of your house? problem being if it does, it might overload the circuit, in which case youll need to wire the shed back to the CU. instead of replacing the CU, you can split the meter tails and install another CU just for the shed power

 

[mobanded]

Do I find the size of the SWA by measuring the outer cable?

 

[mapj1]

If the cable is modern, the info you need will be embossed on the outside, along with the makers name etc.
At the risk of being a frightful bore, if you are in England or Wales, such work is now notifiable to building control, for local authority inspection (costly), or should be done by a type scheme memeber spark who can self certify.
I'd suggest however, that in this case, as the legally prefferred alternative of throwing an extension lead accross the grass, or whatever, is far more dangerous, you should certainly do something like you are suggesting.
If you can get the cable high enough, overhead may be a substitute for buried see the TLC websitehttp://www.tlc-direct.co.uk/Book/7.13.1.htm although in many cases 3.5m may be higher than you wish...
Although you may very well find that strict compliance with voltage drop requirements makes your existing installation a bit "thin" if you can suffer the lights flickering when a vacuum cleaner is plugged in you will almost certainly suffer nothing worse, if you do as you suggest, or even have the birdhouse 'plugged in' to the existing shed.

So extension lead, cheap legal but please watch for damage to the flex over time statistically this is the most dangerous option.
DIY overhead or buried wiring, will be almost certainly safer, and what you are suggesting will work, at least for a few lamps and a hoover!

BUT to be legal after Jan 1 05 such work has to be appproved by local authority or done by a sparks, and comes with the full hassles of meeting every dot and comma of the british standards, which may mean up rating the original feed.

 

[mobanded]

Hi Mapj.
Thanks for your very interesting response. Can I just clarify that the use of a heavy duty cable on a reel to send power to my birdhouse on a moreorless continual basis is OK?

In reality I would have small wattage lights on for perhaps a maximum of 4 hours a day; and the 1200 watt heater on for maybe 8 hours overnight, but only when freezing weather was forecast.

I have a heavy duty cable reel which is 45 metres long and has two sockets. It gives a warning on the drum that the maximum allowable load is 3120W/240V when fully unwound. This would seem to be be suitable for what I need and would save an awful lot of hassle and money - especially with these new regulations.

I could run the cable from an RCD breaker plug via my trees and/or fence to the birdhouse. It would be no problem to ensure the cable was well above ground level.

There has to be some sort of catch! - hasn't there?

 

[mapj1]

It is only just OK to run an extension lead, as over time sunlight will weaken the plastic insulation, and take care the ends should be inside and arranged that any water drops run away from anything critical.
If you do this please, please Inspect the condition of the extension cable regularly (every few weeks) and be prepared to change it after a few years as needed.
What I was trying to say is that yes, of course an extension lead is legal, but I don't really approve, rather I think this is the really big hole in the regulations, as we all know that really almost any permanenent installation, even one that didn't exactly meet the letter of the regs, would in reality be so much better from a safety perspective !!
Obviously when you sell the property you wind the cable in and take it with you, and as its not fixed wiring that's fine.
M.

 

[plugwash]

yeah the volt drop will be terrible if you put a heavy load on an extention lead like that.

I also tend to agree with mapj1 SWA running exposed outside is a hell of a lot better than flex running flex outside.

you aren't really supposed to attach cables to fences. not sure about trees but the most important thing is that what you attach it to is solid

three main questions still remain:

1: how far is it from the house to the existing shed?
2: what size is the existing armoured cable?
3: is the spur off the ring in the house fused in any way

 

[mobanded]

For mapj1. You are right; using the extension lead isn't the solution but thanks for the information (we pensioners are always looking for way to save money).

Back to my original problem:

Having taken on board the comments of mapj1, andrew2022 and plugwash, may I outline an alternative route from the house to the birdhouse, NOT using the existing armoured cable, but opting for a power source coming out of a ring main at the opposite end of the house, which will cut in half the size of the trench I need to dig. It will also save on the quantity of armoured cabling I need to buy.


The location of my Consumer Unit was/is on the old garage wall. The garage has since been converted into a granny flat and the CU is now situated behind a false skimmed, decorated wall. Access to it is through a small panel in the false wall and there is just enough space to read the meter and reset the trips switches, if needed. There can be no question of adding a new circuit to this CU and therefore I am left with the option of taking a Spur from an existing ring ciruit.

On the CU are 6 mini-trips, 2 of which are marked for PLUGS. These 2 mini trips are each marked 30A.

If I take a spur from a twin socket in the lounge (whihc goes back to one of the 30A mini trips) by drilling a hole behind the socket and through the wall, to the outside surface then I will have a straight run of about 12 metres to the birdhouse.

So here is what I now propose:

1. At the house end, the armoured cable would be fitted via appropriate glands to a weatherproof box. The positive, negative and earth feeds from the armoured cable (when stripped of its external bits) would be secured into individual chocolate boxes inside the weatherproof box. A lead of sufficient 3 core internal cable would be connected into the back of the lounge twin socket, through the wall, and into the weatherproof box before finally connecting the appropriate cable ends to the matching chocolate boxes. Sealant to be placed around the weatherproof box to ensure no water can run down the side wall and into it. AT least one, possibly two cable clips would secure the outer armoured cable to the wall so as to stop any chance of the cable being disturbed inside the weatherproof box. Is this outline correct?

3. Dig a trench (minimum depth 18") for the 12 metres from the house to the shed. Lay the armoured cable, cover with gravel ( I have some spare bags to utilise). I need to know size of recommended cable please .

4 At the birdhouse end run the armoured cable inside and attach to a Garage Consumer Unit. Run separate lighting and ring circuit from this GCU. Suggestions as to type of GCU please.

I am hoping I have addressed all the points you made and await a blessing or otherwise to what I would like to do.

 

[plugwash]

If I take a spur from a twin socket in the lounge (whihc goes back to one of the 30A mini trips) by drilling a hole behind the socket and through the wall, to the outside surface then I will have a straight run of about 12 metres to the birdhouse.

sounds reasonable considering that a new cuircuit is an option you have ruled out and considering the loading.

1. At the house end, the armoured cable would be fitted via appropriate glands to a weatherproof box. The positive, negative and earth feeds from the armoured cable (when stripped of its external bits) would be secured into individual chocolate boxes inside the weatherproof box. A lead of sufficient 3 core internal cable would be connected into the back of the lounge twin socket, through the wall, and into the weatherproof box before finally connecting the appropriate cable ends to the matching chocolate boxes. Sealant to be placed around the weatherproof box to ensure no water can run down the side wall and into it. AT least one, possibly two cable clips would secure the outer armoured cable to the wall so as to stop any chance of the cable being disturbed inside the weatherproof box. Is this outline correct?

different sparkys have different opinions on this but i personally belive jointing outside is best avoided whereever possible.

also you probablly wan't rcd protection and you should really fuse the spur from the ring so i would do it as follows.

run from the socket to a rcd fcu in a normal flush box.
http://www.tlc-direct.co.uk/Main_In...tected_Range/RCD_Protected_Range_2/index.html

if you are carefull and you make the hole in the wall large enough you should be able to gland straight into the back of the flush box before screwing it into the wall.

3. Dig a trench (minimum depth 18") for the 12 metres from the house to the shed. Lay the armoured cable, cover with gravel ( I have some spare bags to utilise). I need to know size of recommended cable please .

its a pretty shourt run so 2.5mm should be fine.

4 At the birdhouse end run the armoured cable inside and attach to a Garage Consumer Unit. Run separate lighting and ring circuit from this GCU. Suggestions as to type of GCU please.

suggest a metalclad CU as its much easier to gland to metal boxes. No need for a rcd here as you have a rcd fcu at the house end.

 

[dw3101]

The only kind of wire you should be putting in the 'back' of a socket should be twin and earth..

do as said..

Get a galvanised adaptable box, or weatherproof one and terminate the armoured cable in here.. earth properly (id use a three core to be sure though if you havent terminated before) dont stip the inner insulation... drill a hole all the way through the cavity..drilling on a slight angle up if from outside.. fit a rcd fused spur on the inside and terminate the armoured (inner) directly in this..then run 2.5mm to the nearest socket... if possible split the ring..ie take one of the legs of the ring from the nearest socket to the fused spur and then run another 2.5 from the spur back to the socket.

HTH and doesnt conflict with others.

David

 

[mobanded]

Hi Pugwash.

Your advice re:run from the socket to a rcd fcu in a normal flush box.

If I replace my existing indoor twin socket with a Twin RCD Socket 30mA, would this negate the need to fit an rcd fcu on the outside wall? I ask the question simply because I have one unused.

 

[plugwash]

no the rcd in a socket only protects the socket outlets not stuff spurred off the socket.

 

[mobanded]

To all concerned:

Thanks very much for your help and information.