Wiring garage sockets with steel conduit, how do I do this?

[shagster]

I'm planning a ring of sockets for a garage. I'd like to do this by taking steel conduit down from the plasterboarded ceiling and installing metal clad double sockets, probably about four of them, two either side of the garage. Above the plasterboard I can use T&E, inside the conduit it seems normal to use flexible, individual wires. I don't want to put conduit all the way round the garage to make a 'ring' since I want to put shelves and other units in between the sockets without interfering with the conduit.

So my question is really, how would you wire this? I start with T&E in the ceiling, then I could go: Bonding nipple, straight coupler then screwed nipple, taking T&E into tee box where I transition to the flexible with a choc block, then down the conduit to the socket with the flexible, then back up to the tee box again, another choc block, back to T&E out the other tee exit, screwed nipple, straight coupler, another bonding nipple taking me back to T&E, through a few joists and on to the next drop. The tee boxes would be above the plasterboard.

A simpler solution would be just push the T&E down the conduit. Since it's a single straight length it'll probably go OK, then I tee it into a normal junction box screwed to one of the ceiling joists. I just wonder if I'm committing some faux pas by putting T&E in a round steel conduit, or did I miss a better way of doing this?

The other thing is that I don't see any obvious way of earthing those 20mm conduit boxes. They have an M4 threaded hole in the back only. None of the electrical wholesalers seem to sell any kind of earthing clamp for M4 screws (or is the screw supposed to become the clamp?), so I decided it was best to earth the boxes with a 4mm dia uninsulated eyelet crimp. I'm curious what the professionals do in this regard - one wholesaler said most electricians don't earth the conduit (hence they didn't stock anything for this), which just sounds wrong.

thanks,
S.

 

[riveralt]

Is there a specific reason you want to use steel conduit - is the cable going to be damaged in anyway? If not just clip direct and use plastic backboxes and sockets or narrow plastic trunking.

Your biggest issue is how you are going to run power to these sockets?

Unless you are very careful you will require to notify your Local Authority Building Control and pay their fee before you start work on this project or you could hire an electrician.

The other thing is that your imply a 'ring' circuit but do you actually mean that. What do you intend to use the sockets for? If it is a new ring circuit then how would you test it - do you know how to test a ring final circuit?

 

[shagster]

Hi riveralt,

I don't have a clue how to test the ring or connect to the CU and and don't have any of the equipment to do so, at the moment I only want to understand how this would be done so I have a detailed and precise spec for the electrician.

I am assuming a ring is preferable for this kind of application, based on what I read here:
http://en.wikipedia.org/wiki/Ring_circuit. Do please let me know if there are better alternatives.

thanks,
S.

 

[ban-all-sheds]

I don't have a clue how to test the ring or connect to the CU and and don't have any of the equipment to do so, at the moment I only want to understand how this would be done so I have a detailed and precise spec for the electrician.

Then tell the electrician where you want the sockets and where you want to have shelves etc and just let him get on with it. There is absolutely no point in trying to tell him what to do down to the level of "use a straight coupler here" and "use a bit of choc-block there" etc.

He will know how to do it, and you don't.

I am assuming a ring is preferable for this kind of application, based on what I read here:
http://en.wikipedia.org/wiki/Ring_circuit. Do please let me know if there are better alternatives.

A radial.

Your plan for T/E in the conduit wouldn't put the sockets on a ring anyway.

 

[shagster]

Then tell the electrician where you want the sockets and where you want to have shelves etc and just let him get on with it. There is absolutely no point in trying to tell him what to do down to the level of "use a straight coupler here" and "use a bit of choc-block there" etc.

There is every point, as getting multiple quotes from multiple electricians based on a vague spec invariably results in them coming up with completely different work descriptions, and it's then impossible to compare the quoted work.

He will know how to do it, and you don't.

I came on the forum to find out how to do it. If you have a problem with me finding stuff out, then maybe you should just ignore my post and not answer it? Why would you have a problem with me asking?

Your plan for T/E in the conduit wouldn't put the sockets on a ring anyway.

See http://en.wikipedia.org/wiki/File:Ring_circuit.svg it shows a junction box and a length of cable to one of the sockets. Are you suggesting that prevents it from being described as a ring?

 

[EFLImpudence]

What is the best way to take out my appendix?

I want to know this so that I can tell my surgeon how do do it the way I want it done.

If he won't do it properly I'd rather it burst.

 

[ban-all-sheds]

There is every point, as getting multiple quotes from multiple electricians based on a vague spec invariably results in them coming up with completely different work descriptions, and it's then impossible to compare the quoted work.

I'm not talking about a vague spec - I'm talking about telling him what sockets you want where, and what other things you'll be putting in there which will impact the cable routes, rather than telling him "I want you to start with T&E in the ceiling, then Bonding nipple, straight coupler then screwed nipple, taking T&E into tee box where you transition to the flexible with a choc block, then down the conduit to the socket with the flexible, then back up to the tee box again, another choc block, back to T&E out the other tee exit, screwed nipple, straight coupler, another bonding nipple taking me back to T&E, through a few joists and on to the next drop."

I came on the forum to find out how to do it.

But you aren't going to be doing it.

If you have a problem with me finding stuff out, then maybe you should just ignore my post and not answer it? Why would you have a problem with me asking?

I don't have a problem with you asking it - I was just trying to save you a lot of wasted time delving into completely inappropriate details like that, and then wasting time getting electricians in, because I can assure you that if you try to tell them how to do it as per your ideas you'll never hear from them again.

See http://en.wikipedia.org/wiki/File:Ring_circuit.svg it shows a junction box and a length of cable to one of the sockets. Are you suggesting that prevents it from being described as a ring?

You were proposing to have every socket on a spur.

 

[riveralt]

Hi riveralt,

I don't have a clue how to test the ring or connect to the CU and and don't have any of the equipment to do so, at the moment I only want to understand how this would be done so I have a detailed and precise spec for the electrician.
I am assuming a ring is preferable for this kind of application, based on what I read here:
http://en.wikipedia.org/wiki/Ring_circuit. Do please let me know if there are better alternatives.
thanks,
S.

The electrician should advise you of the best installation method based on your requirements.
So you really need to decide what you intend to use the garage sockets for. If it is for garden machinery and normal garage work that is one thing - but if you intend to run a kiln or something that draws a lot of power then that is another.
Based on your requirements and the current installation the electrician would make proposals that best meets those requirements. That may involve tapping into the existing ring or radial final circuit - creating a new ring final circuit or creating a new radial final circuit.
He would advice you on how those cables are protected and to be honest for most garages unless you're the type to throw things at walls (e.g. having a dart board) then either the cable would be clipped direct or you would use micro trunking.
Steel conduit is expensive and not really necessary in most domestic environments.
The point about testing is that is it considerably more time consuming and some will say difficult to test a ring final circuit rather than a radial. But in either case if you complete the installtion yourself then you should complete the appropriate tests.

 

[Space cat]

See http://en.wikipedia.org/wiki/File:Ring_circuit.svg it shows a junction box and a length of cable to one of the sockets. Are you suggesting that prevents it from being described as a ring?

The socket you refer to is a spur from a ring. Yes, you can put spurs on a ring but, from what you describe, you want to make them all spurs! That's a terrible way to go about it, not least because a double socket on the end of a spur potentially overloads 2.5mm cable. (If you look around the forum you'll find many posts on this subject.) Do the job properly. Run the cable directly from socket to socket (that's two cables in each piece of conduit) and dispense with the junction boxes.

I don't see any obvious way of earthing those 20mm conduit boxes.

No junction boxes; no problem.

 

[shagster]

What is the best way to take out my appendix?
I want to know this so that I can tell my surgeon how do do it the way I want it done.
If he won't do it properly I'd rather it burst.

That's a really appalling analogy. You are assuming there is only one surgeon available. If there was more than one surgeon and more than one technique, you'd research which technique you preferred then you'd find a surgeon who was prepared to conduct the operation in that manner.

And since you're curious about operations, having done your research and discovered that most surgeons use anaesthetic, you'd be in a much better position than the poor schmuck who believes the surgeon when told 'you don't need an anaesthetic for that'. You can at least ask the question "Aren't you going to give me an anaesthetic?" instead of grinning and bearing the excruciating pain that ensues.

Of course, that was an extreme example, but you get the drift. The more you know, the better it is. I've never found an exception to this rule.

 

[shagster]

terrible way to go about it, not least because a double socket on the end of a spur potentially overloads 2.5mm cable. (If you look around the forum you'll find many posts on this subject.)

Ahhhh! <head slap> Of course it does. You don't get the benefit of the 'ring' current on any socket at all. Why didn't anyone else want to tell me that?

Do the job properly. Run the cable directly from socket to socket (that's two cables in each piece of conduit) and dispense with the junction boxes.

Two? Doesn't doing the job properly require a copper earth? I heard the conduit earth route can break down over time.

No junction boxes; no problem.

So just earthing at the sockets then. OK.

thanks,
S

 

[EFLImpudence]

Fair enough.

However, there are a large number of enquirers on the forum who state that they are asking so that they can be sure the electrician is not going to rip them off or want to do what they can before the electrician comes back from holiday or want to save the electrician some time, hence themselves some money, when it is obvious they are going to do it themselves even though they do not know the first thing about it and it may be illegal.

Perhaps the crying wolf scenario in your case. I hope so.

 

[riveralt]

That's a terrible way to go about it, not least because a double socket on the end of a spur potentially overloads 2.5mm cable.

Yes if it is enclosed in conduit but not if it reference method C clipped direct.

 

[shagster]

Fair enough.

However, there are a large number of enquirers on the forum who state that they are asking so that they can be sure the electrician is not going to rip them off or want to do what they can before the electrician comes back from holiday or want to save the electrician some time, hence themselves some money, when it is obvious they are going to do it themselves even though they do not know the first thing about it and it may be illegal.

Perhaps the crying wolf scenario in your case. I hope so.

Well obviously I wouldn't say if that were the case, so you'd never know, but what I would say is that I've done stuff in the past that would be considered 'illegal'. People do something illegal and dangerous every time they speed, and who hasn't done that? However, you have to take a balanced view.

Couple of years back I was putting in a dimmer switch in my living room and I realised when I took the switch off the wall the cables from the switch went through the side of the box into another adjacent switch box, except they didn't go through the knock-out, they went through that little hole that gets made when they fold the screw hole up. I guess the guy installing it did a 'risk assessment', and his solution? Use nylon screws to screw the faceplates of both switches to the box. I'd always wondered why only the 'outside' two screws were metal

Did I call someone? Did I f***. I simply knocked out the knock-out and corrected it. There was no way I was paying even £20 for someone to fix that.

However, something like a new circuit for the garage is a completely different thing. I've no wish to buy the equipment needed to test the work. The garage is new build, and requires sign-off for all wiring otherwise I may have trouble selling the house.

regards,
S.

 

[Space cat]

Two? Doesn't doing the job properly require a copper earth? I heard the conduit earth route can break down over time.

Sorry, I didn't make that very clear. Looking back, I see that you envisaged using individual cores. I meant two twin and earth cables in each conduit.