second rcd

[johnad]

i have just found out how to post my pictures
this is the exsisting rcd before the cu

is this what you say it is ?

 

[ban-all-sheds]

thanks for all the help
so i need to out the exsisting rcd then i need a 100ma rcd across the whole lot, are all 100ma time delay

No.

if i then use a 30ma for all sockets and this will trip in the event of a fault leaving other curcuits working

Yup

i was intending to use mk or wylex whats best ?

Neither.

is it best to do this all in the same enclosure or put up a separate 100ma rcd then a split load unit ?

A separate RCD will cost more, and not provide any different functionality from using the same device as the main incomer in a split-load board...

(i cant find an earth rod anywhere)
the earting looks like its on water, gas, bath, and sink only ?

I think everybody has been assuming that the presence of that RCD means you have a TT supply, but this may not be the case.

Can you trace the earth cables from the CU and the service pipes to see where they go?

Can you post a photo of the service head, and main earth terminal etc?

Does the RCD work if you press the test button?

Do you know how old your installation is?

 

[johnad]

so you don't think MK or wylex are any good.
looks like i should go for the hager split load board you recommended
yes the test button works.
the service head has no main earth on the cable and is not PME.
the only earthing is a earth block with 6mm cables going to the cu, gas main, main water, the main rcd and the bathroom.
i have lifted the boards and as far as i can see there is no other earthing
but i haven't got into it that far so i cant be sure,
the installation has some gray cable and some white and a wylex cu with the old push button breakers so i assume that bits have been done at different times.
i do intend to rewire the lot.
thanks for the info.

 

[johnad]

i was just having another look at the diagram of the hager split load unit
if the two rcd's are independent ie both fed from the main incomer then do i still need a 100ma time delay one or can they both be 30ma.
all i want is to protect some curcuits (garden/garage etc) separately

 

[mapj1]

To clarify - if you really don't have a company earth or an external earth rod, then you have a TT supply as it used to be in the days when main water pipes were lead (I presume they have been changed for copper of polyethylene by now?). You should look for somewhere where the earth is pretty much permanently moist to add the earth spike as a first step, and it matters little if you have an RCD as the main incomer in a plastic split load box or a single box, that is then feeding one or more more 'normal' consumer units, (which may then be metal if you like) but in either case the electrical effect is the same.
Most 100mA RCDs are not time delay sadly, and a fair number of suppliers are a bit woolly on this point in their data too.
Personally I think the maker of the trip is not as important as the quality of the box it goes into - you don't want a flexi- CU with not enough mounting holes, where there is no room to put the wires in properly. (Volex are have bad name for that sort of 'over economy', but most sparks have their personal hates / favourites. It doesn't mean its no good at all, or actively dangerous if installed carefully, but it might be the difference between an easy job, and a messy one.)
I presume in practice the trip doesn't fire very often at the moment, so there is not a great risk to the 'one fault trips all' problem, after all the company fuse is a single point of failure, but if it never blows who cares...
however, if you anticipate much tripping and wish to avoid the 100mA delay RCD, you could have more than one plastic box with an RCD incomer in each, say one for lights one for power. It doesn't need to be time delay then, as there is no risk of a 'race', as they are independent.
Probably worth costing up the different options.
regards M.

 

[plugwash]

you are supposed to have a single point of isolation for the system.

it depends on how good a job you want to do. one option is to use 30ma rcds and stagger the lights between cuircuits on different rcds so that even if one of the rcds goes there is still plenty of light from other nearby rooms.

 

[ban-all-sheds]

Or just put in a few emergency luminaires.

 

[HDRW]

you are supposed to have a single point of isolation for the system.

Is this a general requirement or just in this case? I have Economy 7 and there are two CUs (one for the storage heating and one for the rest) so there are two points of isolation.

Cheers,

Howard