cu advice gladly needed ......

[ez2own]

Right gentlemen need to ask your advice , thanks in advance ..

Going to change cu to a 15 way with split rcd to bring up to 17th/part p , original board is 14 way with rcd protected on main switch only .
My only concern is small 4 way cu in garage ( if i rcd protect will possibly trip main board in house if anything went pear shaped , would i be best to leave small cu in garage with rcd protection , but place into house cu with rcd not connected to garage supply.
only supply garage has external is 2 lights on a motion sensor .or would no rcd in garage be a non comply ????

Thanks again ...

 

[GLENNSPARK]

that's what i'd do, as the house cu is being replaced anyway. Split board with rcbo/mcb on one neutral bar with the rcd covering the other, take the garage feed from an mcb. Alternatively as Nick suggested a high integrity board with 3 neutral bars.

Yes thankyou TQ and my origional post as regards this was to do just that......I don`t know where inline RCDs came from.........

 

[topquark]

If I changed this drawing, we could get some idea of where we’re coming from

View attachment 8238

ah, discriminate by using two different phases (I need help too!).

 

[nickblake]

An RCD could trip even if the garage is TT stick it in armoured on a MCB unprotected side garage supply on swa thats then protected problem solved

 

[nickblake]

This ones for Tony

 

[Knobhead]

Alternatively as Nick suggested a high integrity board with 3 neutral bars.

For god’s sake don’t suggest a MK high integrity board, we all know where the last post about one of them ended up! It was total bloody chaos

View attachment 8239

 

[GLENNSPARK]

An RCD could trip even if the garage is TT stick it in armoured on a MCB unprotected side garage supply on swa thats then protected problem solved

And this is what i was getting at 4 pages ago but it seemed to get lost in the translation.....should have made myself clearer...lol........

 

[Des 56]

I dont see that the individual characteristics of same spec rcds will make the slightest difference to which will go out first in fault situations

Its probable that any fault.where the leakage will more than likely be well above 30m/amp, will take both out together

Leakage at the house or the garage will likewise affect the balance of both rcds
If its appliance leakage or such,then possibly the characteristic of the 30 m/amp rcd may then play a part

I know people who used to use 100m/amp standard rcds on tt split boards not knowing they ought to have used time delay and the 100 m/amp standard would almost certainly go out along with the 30m/amps

 

[topquark]

For god’s sake don’t suggest a MK high integrity board, we all know where the last post about one of them ended up! It was total bloody chaos

View attachment 8239

especially with that lovely bit of extra copper

 

[Knobhead]

ah, discriminate by using two different phases (I need help too!).

It’s the effect of a lost neutral, but……

View attachment 8241

 

[malcolmsanford]

If using an armoured for the garage supply then you don`t need an rcd as it has an earthed metallic protection....so the best way is to run the garage armoured feed off an MCB without RCD and to RCD it at the garage board....this will give you the discrimination you need...........

As nowhere in the OP or other responses in the thread is any mention of the earthing system, would you recommend this if the house is a TT system Glenn?

 

[ez2own]

As nowhere in the OP or other responses in the thread is any mention of the earthing system, would you recommend this if the house is a TT system Glenn?

Some great feedback on this one topic , house is tncs , electrics installed 2005 main cu has normal mcb's with rcd protection on 100amp main switch only , swa to garage with 3 way cu again rcd protected on main switch . also to throw into the equation 3 way cu in conservatory same spec rcd protected main switch ( but the reason for making board 15 way is swa supplied to conservatory is terminated into main 100amp main fuse , customer wants board brought up to 17th ....


obviously the the consevatory swa put into main fuse has worked (been in 3 yrs ) , but would that be normal practice ???


thanks again people ....

 

[Guest123]

As nowhere in the OP or other responses in the thread is any mention of the earthing system

Well done Malc, I was reading through thinking to myself....we don't even know what system is present there.

Post 41 gives us the answer.:cyclist:

 

[GLENNSPARK]

As nowhere in the OP or other responses in the thread is any mention of the earthing system, would you recommend this if the house is a TT system Glenn?

no.....

 

[malcolmsanford]

no.....

good................................