We have a unit which runs up to 22Amp and is tested for at least 6 hours at a time. We need to wire to the unit properly as we are using the standard 16A ring main and things are getting a little warm...
We have a consumer unit with 100 amp main trip and lots of different trips for different sections of the building.
I was looking at changing one of the unused 16A trips and put a 32A in it place. Then run wires 20m down the building (in conduit) to where the unit is tested then terminated to a 32A blue Euro connector attached to the wall.
Can this be done the way I described?
I also need to know what circuit type do I need run:- Radial or spur?
What gauge of wire is recommended
Do I change from the standard trip to the new RCD type
First I must point out Part P and the Electricity at work act and with your apparent lack of knowledge you would be contravening one or both.
According to type of building there may be many more rules. The need for many items like RCD would be dependent on the building and where it is farms have their own rules for example.
A radial and a spur are really the same thing it is called a spur when taken back to a ring and a radial if taken back to a radial or distribution unit. Spurs normally have a lower current carrying capacity than the parent supply. So spur normally limited to 3 meters length unless a fused spur.
So what you are talking about will be a radial.
Cable size depends on many factors. Of course it must be able to take the current which the protective device will allow so with a 32A MCB we would normally consider 6mm to be smallest cable but volt drop and earth loop impedance may mean a 16mm cable is required and you don't give enough information.
Running twin and earth cables in conduit is not easy it is designed for singles and it would be easier to use steel wire armoured cable and it would grand better reducing chance of water running down conduit into the socket.
Depending on where it may be required to have an interlocked isolator on the socket so it can't be plug in and out live.
However you seem to lack the knowledge and I would advise you get an electrician to do the work. Especially considering the price of test equipment needed to test and inspect before and after the work.
I would like to say and to allay your fears. I have no intention of doing this work myself. I know the rules!!
We do have a fully qualified electrician who does all the companies electrical work. The reason for the questions was that he is on holiday for 4 weeks and I wanted to know and surprise him before he came to start the work which we require him to do. Sorry if I gave the impression that I would do the work as you pointed out I don't have enough knowledge!!
I have a good working relationship with our sparky and I like learning what he does and why and that's why I wanted to surprise him for once.
Sorry to say not so easy. Earth loop impedance, volt drop, and protecting from mechanical damage plus rules on buried cables make it all too easy to get it wrong.
A SWA clipped direct to wall would need to be 4mm or bigger but run same cable through a ceiling space on hidden in a wall and you could need a 16mm cable so safe way is to wait for his return.
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