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NAPIT Certification Scheme garage cu + Napit

Discuss garage cu + Napit in the Certification NICEIC, NAPIT, Stroma, BECSA Forum area at ElectriciansForums.net

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Hi All
Napit would like to see a circuit installed for my assesment,i have a installed a socket radial in my garage( garage is connected to the house) the consumer unit in the garage is a main swith/rccbo i have one light radial,one socket radial one outside light radial ( supplying one flood light ) i know that in a domestic you can not put upstaires/down stairs lights ,ect on the same rcd on a split board for obvious reasons but as i have only one of each on the consumer in garage and had a earth fault i will loose all circuits via the rcd tripping question is as its a garage only is this installation acceptable
thanks
Rich
 
S

Spudnik

What you are describing is fine for a garage, however, you should make sure that you do not have 2 30ma RCD's in line.

IE RCD protecting the supply to the garage and then RCD protecting the garage circuits, as you will not achieve discrimination between the two.
 
E

ezzzekiel

if its anything like usual assesment just wire a plug up and youll be fine
 
  • Thread Starter Thread Starter
  • #4
Hi jason 6930
the supply to the cu in the garage is via the house which is a split board so supply is on 30mA rcd.When testing cu in garage the rcd in the house will sometimes trip before the garage rcd what can i do to prevent this !!! should rcd in the house be a 63mA so discrimination can take place !!

thanksRich
 
G

Guest123

Hey mate

63mA RCD?? no such beast.

63A but still 30mA. If you already have 30mA protection on the sub-main feeding the garage and then 30mA protecting the garage circuits then as J sais there is no discrimination in the event of a fault so one or both may trip.

Goes against regs does this so you would need to ditch one of the 30mA either at the house end (if the sub doesn't need it - surface??) or in the garage as you already have 30mA at house end.

Hope this helps.
 
S

Spudnik

What he said really^^^^^^

Swap out the garage RCD for a normal main switch.

Trouble is, it will still take out the house if there is a fault in the garage at some point.

Nothing you can really do about that unless the supply to the garage does not need RCD protection due to it being SWA throughout its length etc.
 
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  • Thread Starter Thread Starter
  • #7
supply cable needs rcd protection so does garage cu so 2 rcds are needed any other ideas
thanks
 
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G

Guest123

Sorry mate let me explain, the 80A and 63A values on your RCD's are the overcurrent ratings i.e the amount of current thay will supply before overloading.

The mA value is still 30mA for both i.e the amount of fault current to earth they will allow before tripping out.

It is this 30mA value that cannot be duplicated in 1 crcuit as there is no discrimination so when a fault occurs there is no telling which one will trip out first thus causing inconvenience in the event of fault - ol' red does not like this so you need to remove one.
 
  • Thread Starter Thread Starter
  • #9
hi
sorry i am tied yes i under stand the ratings of rcds just not sure how to protect the sockets in the garage and supply from house cu when both need rcds
 
G

Guest123

This is one of those grey area's that the powers that be have created in their shiny red book.

Tell me again exactly how your sub-main from the house to the garage is installed?? and in what type of cable.

Cheers
 

old dog

-
Arms
hi if the cable from the house has adequate mechanical protection .
leave the rcd in the garage and swap the supply to the unprotected side on the cu
 
  • Thread Starter Thread Starter
  • #12
Hi lenny
16a 60898 mcb t+e 2.5mm from consumer unit in house through the wall and into the consumer unit 2 meters of the cable is cliped to joists above ceiling (Garage has i light radial 6a 60898 mcb and one socket radial 16a 60898 mcb)

Hi old dog
the sub main cable to garage runs straight from the back of the house cu is then clipped direct to joists for 2 meters then drops into the back of garage cu ,i feel your idea is a good one as as cable is more than 50mm deep as it passes through walls and is surface mounted so does not need rcd protection and hence can change supply to non rcd side of board
 
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S

Spudnik

Hi lenny
16a 60898 mcb t+e 2.5mm from consumer unit in house through the wall and into the consumer unit 2 meters of the cable is cliped to joists above ceiling (Garage has i light radial 6a 60898 mcb and one socket radial 16a 60898 mcb)

Hi old dog
the sub main cable to garage runs straight from the back of the house cu is then clipped direct to joists for 2 meters then drops into the back of garage cu ,i feel your idea is a good one as as cable is more than 50mm deep as it passes through walls and is surface mounted so does not need rcd protection and hence can change supply to non rcd side of board
Perfect. Providing there is space in the house CU.
 
G

Guest123

Hey.

I would say that the sub doesn't need RCD protection so you could drop this one and have the one in the garage protecting the garage circuits.

Another thing to consider now is that you have a 16A MCB protecting another 16A circuit and also a 6A circuit, not ideal really mate.

Suggest replacing 16A in house for 20A as again under overload conditions on your socket radial either of the two may operate NAPIT man probably will pick up on this.
 
  • Thread Starter Thread Starter
  • #15
yes i have a spare way on non rcd side i will do that many thanks for help!!

thanks lenny
i will do as you say and change supply mcb from house cu to 20a
many thanks mate
 
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P

pushrod

Is the CU in the house split load? If yes is it not possible to rearrange circuits so that the garage circuit comes off before the 2 rcd sections and so is not rcd protected. If the wiring to the garage is surface mounted am i right in thinking it does not have to be rcd protected - then you can have just one rcd at your garage . Feel free to shoot me down - i am just a beginner:p

Edit : oops hadn't seen there was a page 2 so didn't realise when i posted this that old dog had already suggested almost the exact same thing and thread had moved on- sorry!
 
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S

Spudnik

It sounds like it is an existing split load board with main switch and one RCD.

And yes, provided the cable is surface mounted then it doesnt not need RCD protection.
 
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