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.

EW - Hager 2 Pole 6kA B-6A 30mA A Class RCBO AD906J

Hager 2 Pole 6kA B-6A 30mA A Class RCBO AD906J for sale in stores and online from Electrical Wholesaler for 1 day delivery

www.electricalwholesaler.ie

 

[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.

EW - Hager 2 Pole 6kA B-6A 30mA A Class RCBO AD906J

Hager 2 Pole 6kA B-6A 30mA A Class RCBO AD906J for sale in stores and online from Electrical Wholesaler for 1 day delivery

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?

 

[mattg4321]

Yes you have missed something!

Both circuit line and neutral go into the top of the rcbo. There is a neutral lead from the rcbo to the neutral bar.

 

[Mike Johnson]

Thanks matt432, must get out more does not apply now days. ?

 

[LastManOnline]

There is a neutral lead from the rcbo to the neutral bar.

I always use dual module rcbo, s (Hagar or GE) where space allows. Single module only where space restricted. A CU with dual module rcbo, s is the easiest CU to install that has ever been invented. The dual module buzz bar means no neutral fly leads. A joy to work with.

 

[mattg4321]

I always use dual module rcbo, s (Hagar or GE) where space allows. Single module only where space restricted. A CU with dual module rcbo, s is the easiest CU to install that has ever been invented. The dual module buzz bar means no neutral fly leads. A joy to work with.

Not readily available here in England.

 

[Mike Johnson]

EW - Hager 2 Pole 6kA B-6A 30mA A Class RCBO AD906J

Hager 2 Pole 6kA B-6A 30mA A Class RCBO AD906J for sale in stores and online from Electrical Wholesaler for 1 day delivery

www.electricalwholesaler.ie

 

[pc1966]

EW - Hager 2 Pole 6kA B-6A 30mA A Class RCBO AD906J

Hager 2 Pole 6kA B-6A 30mA A Class RCBO AD906J for sale in stores and online from Electrical Wholesaler for 1 day delivery

www.electricalwholesaler.ie

That is an ROI site? As above, not UK available (to any sane definition of "available" without having currency conversion and import issues).

 

[Mike Johnson]

Luckily I bought all mine before Jan 1st so no duty, but a little research and: https://www.electricalwholesaler.ie...tbreakers/hagerrcbo2p1pn6kab6a30maaclassad906 available in the UK.

And: Chint Double Pole RCBO's - https://www.expertelectrical.co.uk/chint-nb1l-double-pole-rcbos

And: 40 Amp 30mA RCBO - Type A - B Curve - 2 Module - Contactum - https://www.tlc-direct.co.uk/Products/CPBR402.html?

 

[pc1966]

Luckily I bought all mine before Jan 1st so no duty, but a little research and: https://www.electricalwholesaler.ie...tbreakers/hagerrcbo2p1pn6kab6a30maaclassad906 available in the UK.

And: Chint Double Pole RCBO's - https://www.expertelectrical.co.uk/chint-nb1l-double-pole-rcbos

And: 40 Amp 30mA RCBO - Type A - B Curve - 2 Module - Contactum - https://www.tlc-direct.co.uk/Products/CPBR402.html?

Yes, but none of them fit a UK-style CU busbar arrangement do they?

We have never had problems getting DP RCBO as standard fitting for a caravan supply, the problem if finding RCBOs for a CU that are neutral switching, but thankfully now a few are (Wylex, Crabtree, Fusebox).

Doing away with flying leads and simply having a neutral busbar would be the answer, but that is not likely here for some time I suspect...

 

[nicebutdim]

Is a neutral busbar worth the additional space required for 2 module RCBOs?

Would those Hagar RCBOs have any benefit over Crabtree, Wylex or Fusebox 1P+N single module RCBOs in a domestic application, other than flylead?

 

[Mike Johnson]

Yes, but none of them fit a UK-style CU busbar arrangement do they?

Yes the do, and use a 13mm pitch dual busbar: A9XPH224 | Schneider Electric Acti 9 2 Phase Busbar, 24 Module, 415V, 18mm Pitch | RS Components - https://uk.rs-online.com/web/p/busbars/7762724/

 

[Mike Johnson]

Should have said 18mm pitch busbar.

 

[bigspark17]

Why not test N-earth and then test live - earth. What are you gaining/preventing by joining them together?

 

[mattg4321]

Yes the do, and use a 13mm pitch dual busbar: A9XPH224 | Schneider Electric Acti 9 2 Phase Busbar, 24 Module, 415V, 18mm Pitch | RS Components - https://uk.rs-online.com/web/p/busbars/7762724/
View attachment 64782

A wylex enclosure and main switch. Hager devices and Schneider bus bar!

Mixing and matching is not allowed here now.

As above, no major U.K. supplier has a CU with that sort of arrangement. Possibly SBS, but I’d rather use a manufacturer where parts will be more likely to be readily available long term and available locally on the shelf.

 

[pc1966]

Should have said 18mm pitch busbar.

Also that is for the Acti9 range of industrial enclosures, not the Easy9 range usually sold for domestic.

Sure it can be done, but it is not something you can just buy "off the shelf" in any real sense in the UK.

 

[pc1966]

Would those Hagar RCBOs have any benefit over Crabtree, Wylex or Fusebox 1P+N single module RCBOs in a domestic application, other than flylead?

For the typical UK case where N is very much at a low potential to E by design and installation verification, then no.

They seem to bo common in the EU where they have TT as the norm and perhaps traditionally did not have N as near Earth potential. Either as historically it was more like a split-phase supply taking 2 of a 3-phase line set, or for whatever reason they demanded over-current protection on the N side.

The "neutral switching" 1P+N RCBO you see here will detect and isolate an earth fault that happens via the N side, but they do not detect over-current on that side as that is not a UK requirement going back a long, long way. Even when the 13A plug design was introduced in the 40s it was line-side fuse only as installations could be trusted to have N approx E in potential.