Retrofit RCD for 17th Edition ?

I apologise if this has been discussed before but there is a reference in the discussion on moving a 13A socket by 6 inches to adding an RCD in accordance with Edition 17, which I am taking as an 'all-house' RCD.

What options exist for doing this in a current design split supply CU with MCB's and an RCD for the sockets, cooker,etc? Can the main isolator switch be replaced, an external RCD fitted, or is it a new CU?

Rob

Reply to
robgraham
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robgraham coughed up some electrons that declared:

IANAQE (not qualified sparky)

Whole house RCD are deemed undesireable as a nusiance trip talks out the house, or your angle grinder trips the RCD plunging you into darkness while your up a ladder in the stairway, for an extreme example.

Seems 17th boards are tending towards 3 split ways (mixture of lighting/power across two splits and the third split for fire alarms or other special cases. You might get away with adding a 2nd RCB to a 2-split way board, but you should still have a single isolator that kill the entire board, so it's not as simple as chucking that out and replacing with an RCD. There might be too many mechanical problems (busbar arrangement, lack of space) to make converting it viable.

RCBOs are an option (the one I prefer).

Just stepping back - do you need to have your whole existing installation conform to the 17th suddenly?

If so, would your CU allow 1-module RCBOs to be fitted in place of the MCBs (need more vertical space).

Please wait for some more comments from better informed people than me before you do anything... I'm not the authority here and my writing skills sometimes don't come across clearly, I'm aware of that.

Cheers

Tim

Reply to
Tim S

A conventionally wired house - T&E cable under plaster - now needs 30 mA RCD protection for all circuits, but certainly not a single whole-house RCD. Viable options are to use two or more RCDs each feeding a group of circuits, to use RCBOs exclusively, or some combination of the two. Circuit grouping should be arranged so that any RCD trip will minimise inconvenience and will not cause complete loss of lighting.

If RCBOs are available to fit your existing CU then fitting one to each non-RCD protected circuit in the split-load board is probably the simplest option. Changing the main switch to an RCD won't work because you need independent parallel-fed RCDs.

You might find this useful:

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this:
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assuming that the present earthing arrangements are OK, there is absolutely no need to add RCD protection to existing lighting circuits etc. just for the sake of it. The new requirements only come into play if you are altering or extending an existing circuit, or providing a new circuit.

Reply to
Andy Wade

I've been thinking of adding a second RCD to my MK sentry box. The neutral busbar could be a problem. It is clipped in and would seem to require removing the CU to release the bus bar to fit a shorter split one. Are shorter neutral busbars available for this purpose, like the split load tails are?

Reply to
<me9

Thanks for the replies, guys - I now have to admit to being a bit unthinking it mentioning a 'whole house' RCD as I remember full well enough having to all to regularly go round to the old man's house next door to reset his RCD which did just kill everything..

The reason for asking is that I'm not too sure about the equipotential bonding in this property and I'm wondering if fitting RCD's to the lighting circuits would let me out of the chore of setting the bonding to rights.

Rob

Reply to
robgraham

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