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coolcatkelso · 31 Oct 2018

Hi Guys

I'm currently upgrade inthe electrics I .the garage and office, I have installed a dual rcd consume u it with the following.

6amp
16amp
32 amp breaker
Rcd
6amp
16amp
32amp
Rcd again

I have a ring circuit in the garage with 6 double sockets (fridge freezer, chest freezer, and drill chargers), these are connected to the 32amp.

On the second 32amo, I have 10 double sockets, 12 PC monitors, 2 computers, printer etc

Currently from the house to garage is 6mm twin and Earth feeding everything.

Am I better to upgrade this to 10mm twin and Earth which I have, or do I need to get 16mm armoured?

The 6mm in use (old system) is burried underground in conduit and has been down there about 8 years with no issues unless I plug heavy tools in (circular sarlw and Hoover at same time) then it trips

Taylortwocities · 31 Oct 2018

I'm confused about almost all of this. Particularly this bit

coolcatkelso said:
The 6mm in use (old system) is burried underground in conduit and has been down there about 8 years with no issues unless I plug heavy tools in (circular sarlw and Hoover at same time) then it trips

How can a 6mm cable trip?

coolcatkelso · 31 Oct 2018

I don't know why it trips but it does in the house. The current setup just now is...

32amo (in house) goes 6mm to garage (10m) underground, into a double socket then everything else is just dangerous.. double socket radial, then the office goes from a plug to a double socket then four way to four way to way. Hence why Im changing it.

I don't know if it's tripping because it's only a 13amp fuse in the plugs and just dam right dangerous.

So would the 6mm feed be fine, or upgrade this too?

ban-all-sheds · 31 Oct 2018

coolcatkelso said:
Currently from the house to garage is 6mm twin and Earth feeding everything.

Am I better to upgrade this to 10mm twin and Earth which I have, or do I need to get 16mm armoured?

I fail to understand how you can not know what size and type of cable to use for that AND think that you are competent to install a consumer unit and several final circuits.

Asking that question shows that you do not know how to do circuit design, and yet you don't think that should be a bar to you doing work like this.

What are you going to do about signing this?

I being the person responsible for the design, construction, inspection & testing of the electrical installation (as indicated by my signature below), particulars of which are described above, having exercised reasonable skill and care when carrying out the design, construction, inspection & testing hereby CERTIFY that the said work for which I have been responsible is to the best of my knowledge and belief in accordance with BS 7671:2008, amended to 2015 except for the departures, if any, detailed as follows:

What are you going to do about testing?

ban-all-sheds · 31 Oct 2018

coolcatkelso said:
I don't know why it trips but it does in the house. The current setup just now is...

32amo (in house) goes 6mm to garage (10m) underground, into a double socket then everything else is just dangerous.. double socket radial, then the office goes from a plug to a double socket then four way to four way to way. Hence why Im changing it.

I don't know if it's tripping because it's only a 13amp fuse in the plugs and just dam right dangerous.

So would the 6mm feed be fine, or upgrade this too?

PLEASE get an electrician - you don't have a clue.

coolcatkelso · 31 Oct 2018

I won't be testing it, I will be getting a electrician in to inspect and test but obviously want to save as much as possible

Installing the consumer unit was easy, installing the ring circuit and sockets was easy, I'm simply asking a question as to which is best practice, 10mm or 16mm armoured.

Taylortwocities · 31 Oct 2018

16 is bigger than 10. But why not go for 35? That’s even bigger.

coolcatkelso · 31 Oct 2018

It's a simple enough question. I'm competent enough to know how to wire it up, I'm simply asking which would be the correct cable to use, 10mm or swa 16mm?

For the record, I didn't do the previous wiring up, which is why I'm changing it

Taylortwocities · 31 Oct 2018

coolcatkelso said:
I don't know why it trips but it does in the house.

You still haven't said what trips?

coolcatkelso · 31 Oct 2018

The 32amp in the house which currently feeds everything but o my if I plug in the circlular saw at 2600w and a 1200w Hoover, but I think it's because the socket they are plugged into runs of a plug plugged into another socket .

The trip isn't the issue tho once I've connected the new board up as I don't think it's caused by the 6mm cable

mattylad · 1 Nov 2018

The 32amp what? an MCB or the RCD?

Your 6mm cable is adequate for the load, it is very unlikely to be that causing the tripping.
Maybe your circular saw or vacuum have a fault?

John D v2.0 · 1 Nov 2018

This thread is a disaster, sizing cables is not a trivial exercise, you would have to calculate the demand first then size the protective device and cable based on the installation method, grouping factor plus volt drop and other derating factors. Yes installing is easy but knowing you're installing the right thing is the tricky part.
If a protective device is tripping then the reason and the original circuit design needs finding out rather then just changing all the switchgear and hoping it wasn't rated like that for a reason.

ban-all-sheds · 1 Nov 2018

coolcatkelso said:
I won't be testing it, I will be getting a electrician in to inspect and test but obviously want to save as much as possible

Installing the consumer unit was easy, installing the ring circuit and sockets was easy, I'm simply asking a question as to which is best practice, 10mm or 16mm armoured.

I being the person responsible for the design, construction, inspection & testing of the electrical installation (as indicated by my signature below), particulars of which are described above, having exercised reasonable skill and care when carrying out the design, construction, inspection & testing hereby CERTIFY that the said work for which I have been responsible is to the best of my knowledge and belief in accordance with BS 7671:2008, amended to 2015 except for the departures, if any, detailed as follows:

The thing is, installing new CUs, outside supplies, submains etc is not a trivial job, and I can assure you that it involves knowing far more than you think it does.

Asking questions here can be a useful part of a learning process, but they are not a substitute for proper structured studying. The key term there is "learning process" - you cannot learn all the things you need to know just by asking questions here. It isn't structured enough - it won't provide you with a way to progress where each step builds on what you learned before.

You can't carry out a job of this magnitude by asking whatever random questions happen to occur to you. You've already shown that you have some dodgy misconceptions - what if you get something wrong because you have no idea your knowledge is wrong? What if you miss something because you simply have no idea it even exists, and just don't realise you don't know it?

PLEASE GET AN ELECTRICIAN.

flameport · 1 Nov 2018

coolcatkelso said:
I'm simply asking which would be the correct cable to use, 10mm or swa 16mm?

Many other sizes of cable are available.

As for the size and type required:

what is the total load for this new consumer unit
how long is the cable from the supply to the consumer unit
how / where will the cable be installed
what type of earthing is provided at the supply
what will the cable be connected to at the supply end
are there any extraneous conductive parts at the office/garage?

coolcatkelso · 1 Nov 2018

It's the 32amp mcb that trips with the saw and Hoover on together.

The total load will be 12 monitors, 2 PC's, chest freezer, fridge freezer, and 3 lights and a printer.

The garage is attached to the side of the house, so wiring route from cu to new cu would be approx 10m, I intend to drill through underground and come out under the house cu and run the cable up through the cupboard in conduit, as with the garage.

The house is owned by housing association and it's checked and tested every year, and passes it's electric inspection, so I would assume that everything is fine, but he doesn't plug in high powered items at the same time.

Everything at the moment is 6mm from cu to garage so I would assume by that ,that 6mm would handle everything as I haven't added anything in. But is 6mm safe enough or am I on it's limit.

These forums are great for a quick answer, like I said, I know enough to be able to install a ring circuit and cu unit safely, but in doubt as to the correct size of cable, internet calculation says 10mm if above ground and 16 swa if going underground ( I assume in case of digging)

I don't just want to throw in a 10mm cable cos it's cheaper, I would rather to it right hence why I asked the question in here.

I appreciate what all tradesmen do, and the skills they bring to the job, but some people like myself like to get their own hands dirty and try other things. I'm a roofer to trade

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