Electrical sockets for obsy, recommendations please

[Chris]

Hi folks,

I need to get power to my obsy before I can make any more progress. The previous owner of our house already ran outdoor cable through metal pipe to a double (indoor) socket in the pre-existing shed. I'm thinking all I need to do is make a hole in the obsy and connect up better outdoor sockets, and more of them.

I've had a look at DIY shops etc and can't decide what to get so can anyone recommend any suitable sockets please? and how many sockets would people advice?

Thanks,

Chris

[Mikea]

Does the cable come from it's own fuse/breaker on the distribution board or is it spurred off a ring?

[Chris]

Its from a simple plug and socket to which i'll be adding a plug in circuit breaker.

Thanks,

[Islander]

If the building is weather tight then any decent quality socket and patress will suit. You should assess the suitability of the current (groan) installation though.

What is the likely demand?

What size and type of cable is it?

How long is the run?

Does it run of of its own breaker and is it RCD protected?

What are the earthing arrangements?

Are there any substantial metal parts in the building?

If in doubt, consult an electrician. If you're in England or Wales it's a notifiable job and could affect your insurance. You can DIY but you should let the local building control department know and they'll want it properly tested.

[Chris]

Thanks Islander, likely demand would be the following: lamp, my HEQ5 mount, de-humidifier, laptop, and possibly a small heater for the warm room although I'm not sure about the last one with the current arrangements.

I've just had a look at the cable and its grey, rectangular with rough dimensions of 12-14mm by 5-6mm. There seems to be a green/yellow earth wire running parallel to the pipe which runs into the house below the window sill and dissapears under the floor boards. The pipe runs approximately 40 feet. RCD will just be the one that I'm going to plug in the wall in the house, unless this is unsuitable. Metal parts in the obsy would be the scope and mount I guess, the main structure is wood, even my pier adaptor is wood:D

Chris

Its raining outside, but I can take a few pics if it helps with the advice?

[Chris]

I can run a couple of things from my power tank, so hopefully the main demand would just be the dehumidifier.

I've ventured out with man-flu to take some pics in the dark and rain:D

The pipe runs down the passage way about 15' before going under ground for a good 25'.

The last picture is to show how the cable changes to indoor cable and a simple plug and socket behind our sofa, this is where I'm planning to plug in a breaker.

Excuse the mud and moss in the passage way its over due a clean:)

[Chris]

My father in law whos a retired BT engineer had a look while ago and he said it was all ok apart from it needing some sealant down the end of the pipe to stop the rain water getting in, he has been known to get the odd thing wrong though I'm honestly not sure if the person who installed this was competent or not, or whether they had it approved?

[Mikea]

I'll let a qualified sparky comment, but I wouldn't approve it!

[Chris]

what would you rectify mike? I need to find out how to make it better?

[Islander]

Sounds like 2.5mm2 twin and earth with an additional earth run alongside although you'd need to verify that the green cable actually is an earth cable before you attempted to use it as such - earth cables are usually green/yellow which makes me wonder about the age of this installation or the competence of the installer. Other points to note are that steel conduit should be terminated into an adaptable box either inside or outside of the house and should be properly earthed. It's not clear how the T&E is joined to the flex with the plug either. I wouldn't be happy with this. It needs to be checked properly really.

One of the problems with exporting electricity to external buildings is that you're taking it out of the protected zone formed by the main earth. You can end up with potential differences between the exported earth and local earth (pier parts, etc) and this can lead to a dangerous shock hazard.

The usual way of doing this is a steel wire armoured cable of sufficient capacity either buried or clipped to a suitable permanent supporting structure along its length terminated into the consumer unit at one end and a smaller consumer unit at the other and protected by a suitable breaker and RCD or combined unit at the house CU.

[Chris]

Thanks for helping me see whats wrong Islander:) I've ventured out for a second look and the grey twin cable enters a black box under the window sill and the flex appears the other side. At least 5" of flex is out side the building pinned under the window sill before entering the house. The box has additional insulation tape wrapped around it which does look a bit dodgy so I will remove the box and add extra conduit to meet it, also I'll check that its earthed and properly sealed, if not then I'll change it for a better adaptable box at the very least.

I followed the green wire down the garden and its connected to a rusty metal pole sticking out the ground about half way down the garden so its some kind of earth, I'm not sure what for though?

I'll have to look and see exactly whats happening at the shed end with regards to earthing, my guess is it was just earthed at the socket.

I take it that I'll need to find something large and metal to earth it to in the obsy? if the outdoor cable contains an earth which I hope it does, should I stick some metal in the ground by the obsy and connect the cable earth to it?

Thanks

[Islander]

Don't disconnect the green wire whatever you do. You might have a TT earthing arrangement which depends on an earth rod rather than the earth being brought in with the supply.

[Mikea]

Why would the earth rod be so far away - and isn't the earth conductor a little on the small side for a TT arrangement?

Anyway, Islander sounds like he knows what he is talking about - I'm saying no more!

[Chris]

Don't disconnect the green wire whatever you do. You might have a TT earthing arrangement which depends on an earth rod rather than the earth being brought in with the supply.

I will leave it well alone in that case Islander, thanks for the heads up:)! so am I getting this right, this is the earthing for the main circuit? its rusty though!, maybe I shouldn't leave it alone, should I cut the power off completely and try and clean up the connection so it actually works properly, or is the rusty pole ok?

[Chris]

Why would the earth rod be so far away - and isn't the earth conductor a little on the small side for a TT arrangement?

Anyway, Islander sounds like he knows what he is talking about - I'm saying no more!

Well thanks for your time Mike, all I know is that most people know more about electrics than me, its not my strong suit. If I had the money I would call in the pro's but I recken it would cost hundreds, I would have to sell a lot of stuff on ebay to get those kind of funds so I'll try and make it as good as I can for now.

[Islander]

I wouldn't touch it. If it is an earth rod then the last thing you want to do is introduce any fault conditions. It's advisable to have the whole thing checked by a professional really.

[freeflyjay]

I`m a sparky, and that is not a good install, it looks like a 2.5mm twin and earth cable run though 20mm conduit layed on the floor for protection, the conduit doesn`t appear to be earthed so not good,this is unlikely to have been done by a qualified person and really should be run in armard cable and backed up with an rcd,i work for bt as well but as an electrical engineer, a phone installer is not qualified for mains electrics or to advise if safe or not. i would have that removed and get a qualified electrian to do you a proper job, the cable used is not really designed to be used externally and will degrade over time, the green wire will be an earth, but not sure why it has been run without looking at it so donn`t disconnect it, if the earth cable is run to a spike driven into the ground then that would surgest a tt earthing system but if you live in a town that would be unlikely.

[Mikea]

Just make sure you use an RCD plug on the flex in your house - unless your main distribution board is already RCD protected (I'm guessing it won't be!).

Be safe!

[Islander]

Why would the earth rod be so far away - and isn't the earth conductor a little on the small side for a TT arrangement?

Anyway, Islander sounds like he knows what he is talking about - I'm saying no more!

Earth rods are placed in all sorts of weird and wonderful places - ground conductivity and hardness varies as does the laziness of electricians. TT uses a 4mm2 cable for mechanically unprotected rod connection BTW.

I'm not an electrician but I am a qualified electronics engineer (although I've not worked in that field for a long time), I've done a lot of my own household work and have taken the time to learn the essentials reg wise.

[Chris]

I wouldn't touch it. If it is an earth rod then the last thing you want to do is introduce any fault conditions. It's advisable to have the whole thing checked by a professional really.

ok I will leave it, the house elecrics look fairly recent in that the wires are the modern colours (I remember looking this up before wiring a new light switch), also I don't have any probs with the switches tripping out or any thing so I gather the main circuit is ok. I'll look into sparkies just in case I'm wrong about how much they charge, but if its anything like plumbers then it will be out my league! I got quoted 500+ to install a loo, this prompted me to do it my self for about 50 quid:) Maybe it would be cheaper to do a course in electrics?

[Islander]

Well thanks for your time Mike, all I know is that most people know more about electrics than me, its not my strong suit. If I had the money I would call in the pro's but I recken it would cost hundreds, I would have to sell a lot of stuff on ebay to get those kind of funds so I'll try and make it as good as I can for now.

Safety is always paramount. As little as 35mA can cause a fatal fibrillation if you're unfortunate enough to have a current pass across your chest.

[Chris]

I`m a sparky, and that is not a good install, it looks like a 2.5mm twin and earth cable run though 20mm conduit layed on the floor for protection, the conduit doesn`t appear to be earthed so not good,this is unlikely to have been done by a qualified person and really should be run in armard cable and backed up with an rcd,i work for bt as well but as an electrical engineer, a phone installer is not qualified for mains electrics or to advise if safe or not. i would have that removed and get a qualified electrian to do you a proper job, the cable used is not really designed to be used externally and will degrade over time, the green wire will be an earth, but not sure why it has been run without looking at it so donn`t disconnect it, if the earth cable is run to a spike driven into the ground then that would surgest a tt earthing system but if you live in a town that would be unlikely.

Thank for your advice:) I had a feeling I was going to need to rip the whole thing out and start again:D I guess a good compromise would be to redo the whole thing with armoured cable and done properly with some research, then get it signed off by an electrician:)?

Thanks

[Islander]

I`m a sparky, and that is not a good install, it looks like a 2.5mm twin and earth cable run though 20mm conduit layed on the floor for protection, the conduit doesn`t appear to be earthed so not good,this is unlikely to have been done by a qualified person and really should be run in armard cable and backed up with an rcd,i work for bt as well but as an electrical engineer, a phone installer is not qualified for mains electrics or to advise if safe or not. i would have that removed and get a qualified electrian to do you a proper job, the cable used is not really designed to be used externally and will degrade over time, the green wire will be an earth, but not sure why it has been run without looking at it so donn`t disconnect it, if the earth cable is run to a spike driven into the ground then that would surgest a tt earthing system but if you live in a town that would be unlikely.

A TN-S system with a failed sheath connection could have been converted to TT - it's been known.

[Chris]

Just make sure you use an RCD plug on the flex in your house - unless your main distribution board is already RCD protected (I'm guessing it won't be!).

Be safe!

Thanks will do:) I was always going to have an RCD in the house, I new that much at least:D

[Islander]

Thank for your advice:) I had a feeling I was going to need to rip the whole thing out and start again:D I guess a good compromise would be to redo the whole thing with armoured cable and done properly with some research, then get it signed off by an electrician:)?

Thanks

If you're competent to do this then you can do it yourself by notifying your local building control and having them inspect and test. It'll still cost you but it might be cheaper - ask your BC department for advice first. Be warned though, SWA is horrible stuff to handle and terminate if you're not used to it. If you decide to go with the electrician sign off, then they'll accept you digging the trench but they'll want to do the connection themselves. Discuss it with them before you do anything.