Global IR testing on RCBO populated CU

[Midwest]

I shall be replacing my dual RCD CU, for a all RCBO populated CU. A question or two about technique for IR testing.

For the IR test, I've read here before that a global IR test is preferable. With older types of RCBO's that wasn't possible, without disconnecting cables, which ended up with the testing of each individual circuit.

I'm installing a Hager CU, with their miniature ADA RCBO. The MI state an IR test can be carried out on the RCBO terminals, circuit connected with the RCBO turned off. As I've a few different sorts of luminaire connected, I will be doing live/neutral to to earth.

How do you carry out such a test? I've seen some stackable MFT leads, so you can combine live & neutral together?

 

[SparkyChick]

Just disconnect the circuit conductors, whack them in a Wago with a fly lead and test between the fly lead and the earth bar. Or use a jumper cable if you want to be sure (I have a set of Kewtech leads that are stackable or that can take a croc clip on each end). but for the most part I put one lead on the earth bar with a croc clip and then put the other conductors in the other croc clip.

But, I would definitely not be test from the RCBO terminals. The neutral fly leads can cause issues, as can functional earths. So, yes... pain in the posterior, but I disconnect the circuit under test and take it from there.

 

[Ian1981]

A global IR test is done with the main switch in the open position and all the final circuits in parallel, mcb’s closed, not possible to do with all ocpd’s being rcbos.

Hager rcbos allow for IR test at their terminals as it’s stated on the device, with obviously the ocpd in the open position

 

[pc1966]

Look out for RCBO with functional earths as they show up when doing global or L+N to E testing. The Hager commercial RCBO have them but I don't know about the domestic ones.

 

[Midwest]

A global IR test is done with the main switch in the open position and all the final circuits in parallel, mcb’s closed, not possible to do with all ocpd’s being rcbos.

Hager rcbos allow for IR test at their terminals as it’s stated on the device, with obviously the ocpd in the open position

I've seen those stackable leads, so at least your testing circuit live against all neutrals, but I guess its just testing one circuit at a time really.

 

[Midwest]

Look out for RCBO with functional earths as they show up when doing global or L+N to E testing. The Hager commercial RCBO have them but I don't know about the domestic ones.

The newer Hager miniature RCBO's, doesn't have a functional earth. One less thing I guess.

 

[Lucien Nunes]

The most searching test. more so than a global test, is to test the circuits individually with all other conductors earthed. With DP switching in RCBOs, that's easy to achieve. Lock off the main switch and link the line, neutral and earth busbars in the CU together (preferably connect to the line busbar via an MCB to avoid blowing the DNO fuse if the link is accidentally left in when re-energised).

Then flip off each RCBO in turn, test the circuit at its outgoing terminals , flip it back on and move to the next circuit.

 

[Midwest]

The most searching test. more so than a global test, is to test the circuits individually with all other conductors earthed. With DP switching in RCBOs, that's easy to achieve. Lock off the main switch and link the line, neutral and earth busbars in the CU together (preferably connect to the line busbar via an MCB to avoid blowing the DNO fuse if the link is accidentally left in when re-energised).

Then flip off each RCBO in turn, test the circuit at its outgoing terminals , flip it back on and move to the next circuit.

The Hager ADA aren't DP (or switched neutral), so not an option for me.

 

[Lucien Nunes]

Because these RCBOs have no functional earth connection, if you are only testing from (L+N paralleled) to earth I think you're good go with a global test. With all RCBOs on, all terminals of each RCBO are connected together, so they cannot influence the test nor are they subjected in any way to test voltage.

 

[Midwest]

Because these RCBOs have no functional earth connection, if you are only testing from (L+N paralleled) to earth I think you're good go with a global test. With all RCBOs on, all terminals of each RCBO are connected together, so they cannot influence the test nor are they subjected in any way to test voltage.

The MI say to test from the load terminals, with the RCBO in the 'off' position. Too frightened to turn them 'on'. ?

 

[mattg4321]

I was looking at that marking on the Hager ADA RCBO's last week and thinking it doesn't really help all that much as they don't have a switched neutral. Very annoying they didn't incorporate this when designing the RCBO a couple of years ago.

 

[Mike Johnson]

The only problem with switched neutral RCBO's is they are dual module, not a problem in a continental type CU but very restrictive in a normal UK domestic board, I had to use single module RCBO's for the lighting circuits due to lack of room.

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[Midwest]

The only problem with switched neutral RCBO's is they are dual module, not a problem in a continental type CU but very restrictive in a normal UK domestic board, I had to use single module RCBO's for the lighting circuits due to lack of room.

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www.electricalwholesaler.ie

I’ve installed another CU in my garage, that Wylex NM with switched neutral RCBO’s.

 

[mattg4321]

The Wylex, Crabtree and Fusebox switched neutral rcbo are all single module

 

[Mike Johnson]

I would like to believe that, but the neutral from the circuit is still attached to the connector block in the CU and therefore has not been isolated. It can't isolate the neutral if the circuit does not pass through the RCBO or have a missed something here?