do you have to fit a dual rcd board

[chrisreid186]

just wondering what the deal is if you change say a old style re-wire able C.U to a board with 1 rcd covering all circuits? (providing all bonding and testing is ok)

does this comply to the regs?
would this be passed by a scheme?

by doing this you have made the board a lot safer

i know normally you would either use a dual rcd or put in rcbo's to minimise the inconvenience if there was a fault (e.g tripping the ring takes everything out)

also where do you stand if for whatever reason the customer doesn't want 2 RCD's/ RCBO's??

thanks in advance

 

[telectrix]

any circuit with cables buried in walls without earthed metallic protection require RCD. if you are installing a new CU it must be to current regs. i.e.17th. so, in 9 case out of 10, you need to fit as a minimum requirement, a dual RCD board.

 

[nickblake]

No you cannot use a single RCD to protect the whole board this is due to inconvieniant tripping .you need to protect using either a dual RCD board or boards with individual RCBO's , if they want to upgrade its far more benificial to change to a dual RCD board as they should be wired light up sockets down sockets up lights down so if a single RCD trips you dont loose the whole house ,it wouldnt be passed by a scheme as it contraviens the 17th edition regs

 

[i=p/u]

isnt it just sockets and bathrooms in domestic need rcd protection?? is bathroom lights included too???

 

[fire]

by putting one rcd for all the circuit it would not comply with the regs read regulation 341.

 

[telectrix]

isnt it just sockets and bathrooms in domestic need rcd protection?? is bathroom lights included too???

see my earlier post

 

[nickblake]

isnt it just sockets and bathrooms in domestic need rcd protection?? is bathroom lights included too???

nope its basically all circuits see telectrix post explains it all

 

[i=p/u]

if they burried 50mm in, they dont need rcd (lights, cookers, and others) maybe im wrong?

 

[telectrix]

when have you seen cables chased 2" deep????? ok if in a studded wall, but how can you tell if they are less than 50mm deep? knock a nail in, see if it sparks??

 

[i=p/u]

aye suppose, ,,,,,,im learning. cheers

 

[nickblake]

agree with telextrix on this one even stud wall are not 50mm as the timbers used in studs are 75 x 50mm so even if dead center 37.5mm so not 50mm ,you are right in saying at a depth of 50mm or more but as blocks and bricks tend to be 75mm the its the same as a stud very difficult to get to meet that unless its a cavity all of course ,then its not that easy as you could have hollow blocks and risk going through the wall

 

[telectrix]

agree with telextrix on this one even stud wall are not 50mm as the timbers used in studs are 75 x 50mm so even if dead center 37.5mm so not 50mm ,you are right in saying at a depth of 50mm or more but as blocks and bricks tend to be 75mm the its the same as a stud very difficult to get to meet that unless its a cavity all of course ,then its not that easy as you could have hollow blocks and risk going through the wall

37.5 +10 for the board.still under 50.

 

[chrisreid186]

ok so its pretty much set in stone that you need to use either dual rcd or rcbo's. (apart from a couple of scenarios e.g surface mounted lights etc..)

what if you had this set up

20a night storage .... 20a night storage .... 30ma RCD (fed by E7tails) 6a lights ... 20amp undersink w/h ... 32a ring ... 32a cooker ... 32a shower... 30ma RCD... main switch (fed by normal tails)


am i right in saying you would have to put the lights on a RCBO ( for regulation 341)

is there anything stopping you having E7 and normal circuits in one board ?

are night storage heaters bad for earth leakage? would this show up if you did a I.R test between live and earth on the flex connected to the heater or would earth leakage only be present when the element hot?

is it against the regs to use a RCD as a main switch on the E7 (shown above in bold )

cheers for your help much appreciated

 

[Des 56]

A single rcd covering the whole of an installation

I have done just that recently

It complies with current regs,"honestly"

For a start,a property can have more than one installation

When it covers the whole of the property,deviations to current regs can be cited,"minimise inconveniance"

I am not so struck with shock and horror when it is mentioned, as many seem to be

Instead of proclaiming that 2 rcds must be used,
It would be interesting to hear of "why" you think there is a need to minimise inconveniance,practically,what is the situation that demonstrates this requirement

If a situation can be given as an example, and other ways of minimising inconveniance can be given,then where lies the "You must have a 2xrcd 17th edition board" (whatever that is supposed to be)

My view on the matter is that they brought in the all encompassing "requirement for rcds for everything in most circumstances" then realised that in practice this was a naive action because of the reality and real world away from the desktop fantasy land

The consequence of the rcd everything,was boards with rcbo's
Expensive and not very accepted because of the cost
It was then dreamed up to have 2 rcds and split the circuits,then cross their fingers this covered the inconveniance issue

The 16th ed. where the split board was in use (and the best system that I have encountered through the different editions) could have been adapted to rcd the special locations and leave the other rcd unpoteced side circuits alone

The fob that is the dual rcd board and accepted as the right thing to have,has only been adapted in spite of its shortfalls ,not because it was the best means of complying with the over the top requirments

Its good to know that they are getting back to reality with some of their proposed changes

 

[fire]

there are some grey areas when it comes to using rcd, personally i would put a split board and use rcds they are not that expensive its only when you want to use rcbos that gets really xpensive.

better be safe that sorry, use rcd and i think the futture will probably be rcbos on everything.