Electrical Advice Required

Unicorn

Unicorn

Unicorn

Soldato
Joined
24 Dec 2011
Posts
4,735
I am an electrician myself but i moved over to instrumentation side and mainly forgot what i knew so ill explain this simply

I currently have an old wire fuse board one circuit which is running a 6mm Twin through an outside wall (which has now been converted into a garage) across the wall and in again through the top into a cooker switch to power the oven.

I am wanting to tap into this supply to power the garage as i cannot fit another pair of mains tails safely to go into a separate board and i have no spare ways left on my existing board. The garage will have a ring main on that is all (Lighting is already run in from house wiring (Been there years as it was a car porch way)

Now would my thinking of uprating the cable to the new board to a 10mm twin and earth and running my oven feed from an mcb in the garage distribution board actually be acceptable? This is a job for my parents not for me.. I know how id do it but they want it cheap as possible and i don't want to take any stupid risks as we have no isolator on incoming tails and i won't rip the main fuse out

Advice/Opinion is appreciated im stuck here on how else this could actually be done.
 
Yes as far as I know off the top of my head (ill double check regs). I recently had to install a new Sub-CU in order to run a feed for their new cooker.

In essence the garage consumer unit would be treated exactly the same. 10mm should be more than enough assuming there won't be huge load on ring main.

The mcb on garage CU will be the main point of failure so its no different to new installations with old fuse wire style units.


Just to double check I'm not misreading/being thick you want to;

Run 10mm cable from main consumer(incoming supply) unit to a new garage consumer unit. You will then use the garage CU to run a new ring main and power the old cooker line?


Ill double check regs but I'm 98% sure you're good to go.
 
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If your putting by a CU in the garage why not just take this opportunity to update the existing one to one with more points and rcd protection and fit the garage ring to that.
 
Mynight said:
Yes as far as I know off the top of my head (ill double check regs). I recently had to install a new Sub-CU in order to run a feed for their new cooker.

In essence the garage consumer unit would be treated exactly the same. 10mm should be more than enough assuming there won't be huge load on ring main.

The mcb on garage CU will be the main point of failure so its no different to new installations with old fuse wire style units.


Just to double check I'm not misreading/being thick you want to;

Run 10mm cable from main consumer(incoming supply) unit to a new garage consumer unit. You will then use the garage CU to run a new ring main and power the old cooker line?


Ill double check regs but I'm 98% sure you're good to go.
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That is correct yes, I was sure i was ok with this but iv forgot my 17th edition course :')



I would update existing CU.. but its cost and my parents don't wana spend it. Would cost approx 30 more to put a better CU in and would require brick work etc. The existing box is squished in its home now there is no room for expansion unless i moved the box under the stairs. Which is impossible
 
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EDIT: Just saw your edit. Pointless to move the CU in that case.

From checking the regs it appears there isn't anything against this, so you're good to go with the original plan :)
 
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Mynight said:
Out of pure interest how many fuses are on the current CU? And if known what ratings are they?

Just going to cost up see if I can give you a cheap enough option. I assume you're installing yourself? (I managed to get a CU fully tripped (12set) for just shy of £20). The expensive part is if you're not doing it yourself. Even if the income fuse is crimped they normally have enough give to drop it out in order to isolate the CU(without breaking the seal). Of course not that I've ever done that :D

From checking the regs it appears there isn't anything against this, so you're good to go with the original plan :)
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The other plan of installing a newer CU for the house would be good if i had the room to do it. The original plan is still a go as it has to be. Picked up a CU 4 way populated with RCD (One made for garages) for 20. Can't moan at that :)

All the work will be done by myself but i don't like messing with the main fuses unless iv got too iv had a look at mine and theres no give to it its never been pulled so it seems so its pretty much ceased up
 
You can buy double stacked consumer units, most are around 300mm wide.

Have used a few in the past, where space has been tight.

Proteus do them, & MK use to offer a stacking kit for their consumer units, & Hager have a range as well.

http://www.hager.co.uk/news-exhibit...e/2012/product-update-|-august-2012/12946.htm


If your existing consumer unit is situated fair low, & your cables drops from above, a you can always mount the cu higher to give enough cable to connect lower section, & then use longer tails from consumer unit back to meter.
 
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Sorry you ninjaed my edit :D

I honestly think its one of the biggest pains in the bum to have to get the grid involved if you want to remove the 100amp :( (well legally anyway :D). A much unneeded expense.

Good luck and have fun :) Might be nice to get back to the grass roots :)
 
Mynight said:
Sorry you ninjaed my edit :D

I honestly think its one of the biggest pains in the bum to have to get the grid involved if you want to remove the 100amp :( (well legally anyway :D). A much unneeded expense.

Good luck and have fun :) Might be nice to get back to the grass roots :)
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Always on the ball :P

Ah i asked the suppliers if they would be ever so nice and come fit me an isolator (for free) .. Nah :') Told them ok ill work around it and they told me they could pull the main fuse cheaper but told them unless its free am not interested i have other ways to do the job



@Nightglow

Looking into these now. Would say my old CU is a wire fuse MK unit ;) May be out question
 
Just a quick thought.. On my existing board am i better going through the supply side of the board (incoming before or after main switch dependant on how i can get it in) or could put it on a fused way (with a 40 amp fuse wire)

(This is for the 10mm cable going out to my Sub-CU)
 
Just thinking 10mm cable has a max amp of 45amps you might want to check the cooker power and what they intend on running off the ring main. Unlikely to be an issue but better to double check maths now than be stuck resetting the mcbs if they're using the garage as well as cooking dinner.

The cost to remove fuse is extortion! Eon for example charge £50 to come down to take it out and another £50 to come put it back in :D

I haven't read it in the regs but I've always been taught its good practice to have a fuse between the main cu and secondary. Youd also need to look at upgrading the fuse wire.

Edit: Just an afterthought are you part P? If not youll have to get it signed off legally or notify the council.
 
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Mynight said:
Just thinking 10mm cable has a max amp of 45amps you might want to check the cooker power and what they intend on running off the ring main. Unlikely to be an issue but better to double check maths now than be stuck resetting the mcbs if they're using the garage as well as cooking dinner.

The cost to remove fuse is extortion! Eon for example charge £50 to come down to take it out and another £50 to come put it back in :D

I haven't read it in the regs but I've always been taught its good practice to have a fuse between the main cu and secondary. Youd also need to look at upgrading the fuse wire.

Edit: Just an afterthought are you part P? If not youll have to get it signed off legally or notify the council.
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Yeah I'm part P, done my regs course and inspection and testing etc. Was meant to go into house bashing and shop fitting but took a different root at end of my courses. As for the 10mm twin and earth I did some math on max load of cooker if I was to turn everything on at once I could comfortably use things in the garage still.
 
All rather Heath Robinson tapping in a cooker supply to provide power to a garage.:eek:
Better to do it properly & fit new consumer unit & provide a 40amp circuit wired in 10mm for the garage, then fit second consumer unit with 6a/32a mcbs in garage for lights, ring main.
 
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Unicorn said:
Yeah I'm part P, done my regs course and inspection and testing etc. Was meant to go into house bashing and shop fitting but took a different root at end of my courses. As for the 10mm twin and earth I did some math on max load of cooker if I was to turn everything on at once I could comfortably use things in the garage still.
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Good sorry just had to double check :) I would still advise coming from a fuse to the second CU.

Didn't mean to be condescending but thought better to ask than for you to get done.
 
Mynight said:
Good sorry just had to double check :) I would still advise coming from a fuse to the second CU.

Didn't mean to be condescending but thought better to ask than for you to get done.
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40A Fuse > 10mm T+E > Sub-CU

Sub-CU

40A RCD
32A MCB
6A MCB

The 32 will have the existing 6MM t+e hooked up to it to power the cooker


Does that sound right..

Sometimes wish i didn't go into instrumentation.. Better pay but this is very good stuff to remember also :') Most stuff i work with now is 12v or 5v for instrumentation and everythings in milliamps
 
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Yup thats fine use diversity you only need 13amp for the cooker so still gives you 27amps for the ring main.

Unlikely to be any issues at all :)
 
Mynight said:
Yup thats fine use diversity you only need 13amp so still gives you 27amps for the ring main.

Unlikely to be any issues at all :)
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Excellent :) Thanks so much for the help. This may get my head back in the regs book and studying up again. I am wanting to do my AM2 one day. We have a lathe but it draws 3kw .. Barely used if ever though as it is mine and im rarely doing machine works.

Just thought id knock that on there also got plenty of redundancy for that id assume?

Just waiting for that to change everything ^^ haha
 
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