Hi all and thanks in advance for your help. I am sending power to my shed about 25 mtrs from the house. My plan is to connect to the cooker mcb in the consumer unit (it is not in use) Run 2.5mm twin and earth to a new consumer unit in the shed. (i have not enough cable to run double) The new consumer unit will have all sockets on a 25 amp MCB ring main and three strip lights on a 6amp MCB also ring main but sigularly switched. My concern is, will it be safe to run a hobby mig welder? It is the single 27 amp 2.5 twin and earth that concerns me. This is going undergroung and being sheathed. Thanks everyone for your help.
Wireing a shed.
- Thread starter chris rushton
- Start date
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What rating MCB are you planning to protect it with? T & E is not suitable for use outside or underground, you need SWA.
I know it's not the right stuff but,,, Done it before and i lived there for thirty years and the present people still use it. It is going inside conduit. The mcb in the consumer unit in the house is 35 amps. the mcb in the shed is "5 amps. thanks for your advice.
Unusual rating. Are you sure? You'll need to reduce that for 2.5mm².
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Where is BAS?
Kind Regards, John
Kind Regards, John
Sorry. The MCB in the house is32ma
Do you mean 32A? As I wrote, you'll have to reduce that for 2.5mm², and T & E is not suitable for this purpose.
Why do you want a consumer unit in the shed?
Is the consumer unit in the house RCD protected?
Why do you want a consumer unit in the shed?
Is the consumer unit in the house RCD protected?
Yes it is in the house. I want a small consumer unit in the shed with lower amps so as not to trip the house. Also, i will be able to isolate the shed when i am not there.
What is in the house? An RCD? What's the tripping current of the RCD?
You don't need a consumer unit in the shed to isolate it, you need the isolation in the house for when your T & E fails.
You don't need a consumer unit in the shed to isolate it, you need the isolation in the house for when your T & E fails.
Why do you ask?
Are you unable to tell that the OP doesn't know anywhere near enough to be contemplating this sort of work and is proposing a right pigs ear of a job, or are you unwilling to tell him?
I generally defer to those who I believe are more accomplished than myself in relation to a particular task.
Kind Regards, John
Then why are you proposing to use it?
What kind of person knows he's using the wrong cable but goes ahead anyway?
This is a new circuit.
It is notifiable works, so you would need to apply to your local authority for you to carry out this as a DIY project (and pay their fee).
They will inspect the work at various stages and will expect that what you are doing (design, installation and testing) meets BS7671.
Almost everything you have described as your plan does not comply.
With respect. You have come on here to ask for help.
You have been given aadvice and yet you seem to think that arguing your case is the right thing to do.
1. 32A MCB in house through 2.5mm² cable - wrong
2. T&E cable outside - wrong
3.
extra 4. 25metres, 2.5mm cable, MIG welder. Did you even think about volt drop?
It is notifiable works, so you would need to apply to your local authority for you to carry out this as a DIY project (and pay their fee).
They will inspect the work at various stages and will expect that what you are doing (design, installation and testing) meets BS7671.
Almost everything you have described as your plan does not comply.
With respect. You have come on here to ask for help.
You have been given aadvice and yet you seem to think that arguing your case is the right thing to do.
1. 32A MCB in house through 2.5mm² cable - wrong
2. T&E cable outside - wrong
3.
eh? what? For a MIG welder……ROFL. You'd probably need C curve MCBs for that (in the house too), in any case, and a whole lot more than 5 amps.
extra 4. 25metres, 2.5mm cable, MIG welder. Did you even think about volt drop?
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Maximum current rating of twin and earth thermoplastic cable is 27A (ref method C) we would consider a 25A MCB but in a wall often down to 21A (ref method 100 or 102) so more normal size would be 20A MCB. Which at 25 meters will result in a 9 volt drop which exceeds that allowed for lights but is within that allowed for sockets. It may well power an inverter welder but is really too small at that length for the simpler welding sets. Twin and earth is not suitable for outdoors. Strip lights I assume means fluorescent and with a standard ballast these do not like volt drop, you would need the HF electronic ballast to ensure the lights don't fail every time you strike an arc.
What cable size did your voltage drop calculations produce?
What voltage drop will you get with that?
What will it contribute to the fault-loop impedance of the final circuits in the shed?
Why do you think a CU is necessary there?
Why do you think that your design should be based on what cable you happen to have to hand?
What made you decide that a ring was a better idea than a radial?
Why on earth are you planning a ring for a lighting circuit?
On the basis of the evidence so far, I'd say that there's a significant chance that it won't be.
On the subject of safety, what tests will you be carrying out on the installation in the shed - what sequence will you do them in and at what point will you energise the installation? For each test do you know what is being measured, why it is important, how you would carry out the test, and with what equipment, and what sort of results you would expect to get if everything was OK?
You can't use that. But even if you could - why do you describe it as "27 amp" cable? What's the installation method for cable installed that way, and what would be the current carrying capacity of 2.5mm² T/E with that method?
Please note that none of the questions I have asked are rhetorical - they are all real and genuine questions, and if you are competent to do this work you will be able to answer them.
Also, are you aware that what you are proposing is notifiable, so you need to apply for Building Regulations approval in advance?
And are you aware that you need permission from your DNO to use a welder?
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