CU

[saleem]

In a new split board which mcb,s should be closest to rcd or non rcd side .
50amp shower
32amp garage
32amp electric oven
32amp rings and 6amp lighting.
In previous post i have read that bigest should be closest to main incommer.50amp shover is bigest inmy split load.Sparky has just completed second fix.I have noticed that 50am shower mcb is fitted just before last one on rcd side.Is correct or it should have been next to rcd or it does not matter.

 

[Chri5]

Historically the higher the load the nearer the main incoming feed is standard.

It really shouldn't matter the common rail / copper buzz bar is designed to take the maximum load anywhere along it's length. There maybe some science to the higher the MCB rating, the nearer it should be. Although copper does break down over 20 years ++ I really wouldn't loose any sleep over it.

More interestingly I would check the rating for the RCD, since the shower doesn't have any diversity 50A on an 80A rated RCD rail with garage (32A??) plus rings for kitchen and ground floor would mean->

50A + (32A + 32A + 32A all with diversity) would be close to the 80A capacity of an RCD, add the cooker circuit and it's not likely to be high enough.

 

[saleem]

Historically the higher the load the nearer the main incoming feed is standard.

It really shouldn't matter the common rail / copper buzz bar is designed to take the maximum load anywhere along it's length. There maybe some science to the higher the MCB rating, the nearer it should be. Although copper does break down over 20 years ++ I really wouldn't loose any sleep over it.

More interestingly I would check the rating for the RCD, since the shower doesn't have any diversity 50A on an 80A rated RCD rail with garage (32A??) plus rings for kitchen and ground floor would mean->

50A + (32A + 32A + 32A all with diversity) would be close to the 80A capacity of an RCD, add the cooker circuit and it's not likely to be high enough.

ideally i wanted rcd protection to all rings+ shower and garage .Cooker does not need rcd protection.In total i have shower, garage and four rings.That means it is above the rcd,s 80 amp rating.What is solution to that.Should i get another board fitted and if so what type.Split load or RCD as a main switch.

 

[DESL]

Garage could have separate RCD CU fed from non RCD of main board.

Especially as garage circuit is more likely to supply equipment outdoors and when RCD trips no need to go in to house to reset.

Normal practise is to fit highest load MCB closest to RCD/Main Isolator and then have the rest in descending order. Only reason/rationale behind it is to have highest currents flowing through the shortest path.

 

[saleem]

Garage could have separate RCD CU fed from non RCD of main board.

Especially as garage circuit is more likely to supply equipment outdoors and when RCD trips no need to go in to house to reset.

Normal practise is to fit highest load MCB closest to RCD/Main Isolator and then have the rest in descending order. Only reason/rationale behind it is to have highest currents flowing through the shortest path.

I have already laid 6mm swa cable for garage.32amp mcb was alocated for garage on rcd side,though not connected to main board yet.For garage i have bought non rcd board which i might be able to swap for rcd one.what size rcd board is recomeded for garage.we only need 2 0r three sockets and couple of lights.In garage ,should sockets be on radial or as aring.How do you go by feedig rcd CU from non rcd main board.

 

[securespark]

In the same way as you would feed any board from any other with SWA!

 

[saleem]

Garage could have separate RCD CU fed from non RCD of main board.

Especially as garage circuit is more likely to supply equipment outdoors and when RCD trips no need to go in to house to reset.

Normal practise is to fit highest load MCB closest to RCD/Main Isolator and then have the rest in descending order. Only reason/rationale behind it is to have highest currents flowing through the shortest path.

as you said garage could have separate rcd cu.What size would you recomend.There would not be more than 3 sockets and 2 lights.What about lighting,are they going to be on rcd as well.What about if shower is taken out of main cu and placed in it,s own enclouser on rcd switch.If shower is on 50amp mcb at presant what size rcd main switch is needed if it is placed in it,s own enclouser.

 

[Steve]

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[JohnD]

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