80amp DP Isolator and a 100amp Main Switch do you need both!

[rustynails]

I've seen various posts about this but wanted to start a new one, nothing like repitition. I am installing a new CU and it currently has an 80amp DP isolator between the service head and two split old wylex rewirable boards. I will be installing a 14 way board which comes with an 100amp Main Switch and every circuit will be protected by an RCBO. Seeing as it's illegal to tamper with the service fuse... I guess it is advisable to leave the DP isolator in place, it just seems unecessary.

Anyone have any thoughts on this...

 

[rustynails]

I dont know what the problem is here you have a 60A DNO fuse a Wylex 100mA RCD 80A rated switch that supplies a consumer unit that has a 100A rated switch inside it so what am I missing here

No problem, just wanted to see what people thought about having two pieces of isolating equipment between the CU and the Service Head. Personally, I think it's a little old school to have a further isolator outside the consumer unit. I'm all for keeping it neat and tidy within the consumer unit. Then all the end user has to understand is that if they have a power problem then all the on/off switches are in one place, easily accesible.

I was just waying up the advantages/disadvantages of keeping the old isolator in place. One of the disadvantages of removing it would be losing an 100ma RCD on the main switch. Without an RCD the main switch wont trip which I think is a bit annoying because in the new RCBO board the home owner would have to go along turning circuit after circuit back on, without an overall control. Not sure I rate that, seeing as thats what the owner had before, although RCBO's will be a significant step forward instead of the current rewirable situation.

One possibility would be to buy a different main switch with 100ma RCD, pull the fuse and get rid of the old wylex isolator allowing the owner to keep control over all the circuits in the event of a problem, although the RCBO's are very safe so I'm splitting hairs...

 

[Heisenberg]

Is it considered acceptable to have any sort of RCCB as a main switch? Surely even a 100mA one might allow for nuisance tripping :confused5: albeit not as much as a 30mA device.

 

[Guest55]

If theres a 100ma stand-alone rcd i'm instantly thinking TT unless i'm missing something ???
Has the OP confirmed supply earthing configuration ??
Lots of other basic errors being made in this thread sadly.

 

[telectrix]

the whole point of the up front isolator is to enable safe isolation of the CU without resorting to cutting seals.

 

[oldtimer]

this is getting silly so I am unsubscribing

 

[rustynails]

If theres a 100ma stand-alone rcd i'm instantly thinking TT unless i'm missing something ???
Has the OP confirmed supply earthing configuration ??
Lots of other basic errors being made in this thread sadly.

It is a TT with a high 386 Ohm ze reading as well...

 

[Guest55]

It is a TT with a high 386 Ohm ze reading as well...

This info may of been helpful at the beginning of the thread ??? :-/
Anyway if youre gonna fit a new dual rcd CU i'd be replacing the 100ma rcd with a DP switch.
And the rod Ra could do with improving as well.

 

[rustynails]

This info may of been helpful at the beginning of the thread ??? :-/

How's that then? The original post was about getting rid of an electricity isolator switch and replacing it with a main switch inside a new board.

Anyway if youre gonna fit a new dual rcd CU i'd be replacing the 100ma rcd with a DP switch.

The new board will have a dp 100A main switch and all circuits will be RCBO'd.

And the rod Ra could do with improving as well.

I'm going to have to fit another rod to try and bring that reading down hopefully.

 

[telectrix]

start by replacing the rod with screwed together 5/8" rods. go at least 3 ft. from the house wall to avoid bob the builders rubble.