Help with shed wiring please

[Gazo]

I am planning on wiring my new shed soon but need to check I am doing things right.
I have read a bit about part P and understand I have to have it all checked, but would like to do all the work myself.

I have added a diagram on how I think the shed would be wired just need to check I am doing it right.

Any help appreciated

Thanks

Gary

Shed Wiring

• Gazo
• 23 Jun 2008
• 1

 

[Spark123]

4mm feed doesn't seem very big, considering you are wanting a 32A welder socket!
Also, the main RCD isn't a good idea imho, a problem with the welder / portable appliance will mean your lights will go out!
Low energy lights take a few moments to warm up, is this acceptable on a sensor? What type of sensor?
Seems like a lot of 5A circuits to me!
What are the sockets going to be used for?

 

[Taylortwocities]

There's a lot to think about there. Some immediate questions:
What is your welder rated at?
What's the length of the run from the main house?
How will the SWA be run (buried, sky hooks??)
How will you connect it there?
You cannot get consumer units with those fuse ratings any more. They died many years ago!
What else is in the shed (water supply etc?)
What is your supply type?
Do you have the correct, calibrated equipment to test all of this and issue an electrical installation certificate?

There's a few to start with. More will follow......

PS You may find this helpful http://www2.theiet.org/Publish/Wire...matters_electrical_installations_outdoors.pdf

 

[Gazo]

Welder is only a small portable type capable of running from a normal house socket I thought I would just add the blue socket as a deadicated welder socket.
sensor is rated 500w low energy or 2000w standard, it's 360 degree standalone sensor.

Sockets will be used mainly for drill chargers, small stand drill (375w) radio etc etc

Thanks
Gary

 

[Gazo]

Think welder is rated 7amp only a small hobby mig welder.

length from house is 25m
SWA cable will be buried and concreted over.

I will be running 6mm flat from 32a deadicated cooker switch behind my cooker (we use gas) then into heavy junction box then SWA up the garden.

No water supply

Supply type ???

I would get it all tested before it's all connected at the house.

Thanks for the replies

 

[ban-all-sheds]

4mm feed doesn't seem very big, considering you are wanting a 32A welder socket!

Can't see how he'd get any discrimination - it can't come off an MCB bigger than 32A at the house end..

Also, the use of 2.5mm² for all the final circuits is a curious mix of overkill (on the 5A circuits) and inadequate (on the 30A one).

Think welder is rated 7amp only a small hobby mig welder.

Then why a 32A 60309 socket (which you aren't supposed to use in household environments anyway)?

length from house is 25m

Almost certainly too far - have you worked out the volt-drop of that run plus the internal 6mm² circuit?

SWA cable will be buried and concreted over.

Depth? Warning? Protection?

I will be running 6mm flat from 32a deadicated cooker switch behind my cooker (we use gas) then into heavy junction box then SWA up the garden.

If it starts out at 6mm², why did you think it would be OK to drop to 4mm² for the armoured?

When you say "heavy junction box", what do you mean? Will you be able to gland the SWA into it?

Supply type ???

Don't ask us - it's your supply...

I would get it all tested before it's all connected at the house.

By whom, and on what basis? Will you have concreted over the SWA by then?

 

[Taylortwocities]

My advice is to find a registered electrician and work with him so you do most of the work. Most registered electricians will not and are not allowed to test and certify work done by someone else.
He can advise you the best way of doing the job.
You see, you fell at the first fence. Supply type is a key issue.
If you have a TT system then you'll need an earth electrode out at the shed. There's things to think about if you are exporting the earth if you have TNC-S. etc etc.
Have you worked out the volt drop for your load over 25metres. I would say 4mm would be too small.
Also, (I assume the cooker circuit is not being used for ANYTHING??)
If this circuit starts off as 6mm then you cannot just tack a length of 4mm on to it. You should stay in 6mm. You'll probably need 6mm all the way in any case or you wont have enough volts when the welder fires up...you'll need to do the cable cals to sort it out.

Looking at your shed wiring
Lighting can be in 1mm (you wont get 2.5 into most lighting terminations) MCB 6A
Sockets yes in 2.5mm MCB 16A or 20A
You cannot use 2.5mm cable for the MIG welder off a 32A MCB - it will need to be 4mm or 6mm. You may need to use a C curve MCB not the regular B curve - the inrush current may be too much for a B.

here endeth the free consultancy. Bed time for me.

PS Damn you and your fast fingers BAS!

 

[ban-all-sheds]

Ha ha - not me pipped at the post this time....

 

[Gazo]

Thanks all alot to think about.
Reason for going 2.5mm on lights is simply because I have a brand new 100m coil of it here and the same with the 4mm SWA cable I had a part roll given to me.

Not sure what you mean when you say what supply ???
Correct cooker circuit is not being used.
I did check the wire length for voltage drop and it came in at 4mm is suitable but I did not consider the 6mm which is 10m and the 4mm SWA would be about 13 - 15m

And yes 6mm would be used for the 30a welder socket
I will be getting everything checked by my brother in law who is a fully qualified leccy

 

[ban-all-sheds]

Thanks all alot to think about.
Reason for going 2.5mm on lights is simply because I have a brand new 100m coil of it here and the same with the 4mm SWA cable I had a part roll given to me.

Yes, but if they aren't suitable....

Not sure what you mean when you say what supply ???

Is your supply TN-S, TN-C-S (PME) or TT?

I did check the wire length for voltage drop and it came in at 4mm is suitable but I did not consider the 6mm which is 10m and the 4mm SWA would be about 13 - 15m

length from house is 25m

And yes 6mm would be used for the 30a welder socket

The welder only draws 7A!

You do realise that you'll have to replace the flex on the welder as well...

I will be getting everything checked by my brother in law who is a fully qualified leccy

Fair enough, as long as you don't think that'll make it all legal.

 

[MarkBarl]

Thanks all alot to think about.
Reason for going 2.5mm on lights is simply because I have a brand new 100m coil of it here and the same with the 4mm SWA cable I had a part roll given to me.

Fair play if it will fit into the fittings. And from what I can see, 4mm SWA is rated at 42Amps so should be sufficient if the voltage drop is OK.

And yes 6mm would be used for the 30a welder socket
I will be getting everything checked by my brother in law who is a fully qualified leccy

A qualified Electrician and a Part P registered competent person are not the same. I believe that under most Part P schemes they are not allowed to certify work that they have not carried out. It would be advisable to notify the local authority before starting the work and have your brother in law run the tests etc and then have the local authority inspect and issue the certificate. Belt and braces and covers your a** if there are any problems in the future.

 

[ban-all-sheds]

And from what I can see, 4mm SWA is rated at 42Amps

Only if it has thermosetting insulation (e.g. XLPE), because to take 42 amps it has to run at 90°C.

And then anything it's connected to, or other cables it's joined to, have to be rated at 90°C as well.

If it's PVC cable, or if it is terminated in or connected to anything that's only rated to 70°C then it can not carry 42A....

 

[Gazo]

Thanks for all the help guys much appreciated.

My brother in law said he is familiar with part P and said he would check it all out before I get it checked.

I just wanted to make sure I was doing things right before I call people in to check it, did not want to find things wrong and need a second visit.

I am hoping the 2.5mm flat will fit the lights if not I am sure I can lay my hands on some 1.5mm

 

[Gazo]

Is your supply TN-S, TN-C-S (PME) or TT?

How can I tell

 

[GaryMo]

Why type and rating of protective device currently feeds your old cooker point?