# Insulation Resistance Test on a CU with RCDs



## bugaloo69 (Oct 8, 2012)

Hi All.

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? 

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.

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


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