Insultion reistance testing on CUs with RCDs

bugaloo69 · Oct 8, 2012

Hi All.

New to the forum and this is my first post.

Insulation resistance test on CUs with RCDs.

Do the test at 250V initially to check anything connected, then disconnecting/bypassing any current/voltage using equipment on the circuits.

When testing each circuit separately, disconnecting the circuit under test from the MCB removes the RCD from the test!.

But on a global test at 500V L-E, L-N, N-E, how do you bypass/disconnect the RCD in a split load consumer unit?

If you disconnect the tails feeding the RCD, the circuits/busbar fed from the RCD/s will no longer have power as the busbar is fed from the RCD which inturn is fed from the main switch! Therfore;

Do you disconnect the tails from the incoming side of the RCD and connect to the outgoing side of the RCD, (same with the 2nd RCD on a split load)? Using the outgoing side of the RCD to connect the tails to the busbar?

Do you disconnect the tails from the incoming side of the RCD and connect to the busbar with ie: a croc clip.
Basically if you disconnect the RCD? hmmmmmmmm.

Other option is to leave everything connected and test from the outgoing side of the RCD (RCD open) and test those RCD circuits globally and the same with the second RCD if split load?

Many Thanks

Excellent forum

bugaloo69 · Oct 8, 2012

'Basically if you disconnect the RCD? hmmmmmmmm.'

Please ignore the above sentence in my post, don't know why that's there.

Thanks

trev · Oct 8, 2012

You've actually answered your own question mate

bugaloo69 · Oct 8, 2012

Hi Trev thanks for the reply.

You say i've answered my own question, does that mean I am correct and you can do a global test using option A or B or is option C the better option?

A-Do you disconnect the tails from the incoming side of the RCD and connect to the outgoing side of the RCD, (same with the 2nd RCD on a split load)? Using the outgoing side of the RCD to connect the tails to the busbar?

B-Do you disconnect the tails from the incoming side of the RCD and connect to the busbar with ie: a croc clip.
Basically if you disconnect the RCD? hmmmmmmmm.

C-Other option is to leave everything connected and test from the outgoing side of the RCD (RCD open) and test those RCD circuits globally and the same with the second RCD if split load?

Thanks again, there's alot of nonsense around but some intelligent chaps on here.