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?

 

[nicebutdim]

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.

Are those double module RCBOs providing over-current protection on N? The reason I ask is that Hagar market them as 1P+N, rather than DP, which is the same terminology used in the single module RCBOs we see.

I know my questions probably seem incredibly stupid, but it seemed like a good time to ask. What I'm driving at is whether or not 1P+N single modules would provide adequate protection in other European countries or if I'm missing something about their operation?

 

[pc1966]

Are those double module RCBOs providing over-current protection on N? The reason I ask is that Hagar market them as 1P+N, rather than DP, which is the same terminology used in the single module RCBOs we see.

You are right, they are 1P+N even though Hager sometimes refer to them as 2P. Oddly enough the 4P ones appear to really be 4 protected paths for over-current:

RCBOs B & C Curves 2 & 4 Pole RCBOs

RCBOs B & C Curves 2 & 4 Pole

www.hager.ie

I know my questions probably seem incredibly stupid, but it seemed like a good time to ask. What I'm driving at is whether or not 1P+N single modules would provide adequate protection in other European countries or if I'm missing something about their operation?

I don't know. You would need to check the local regs to see what is required.

My French is not up to decoding this to see if it really is 2P instead of 1P+N, and the picture is not quite good enough for me to see if the little printed schematic is showing the thermal/magnetic trip on both paths, but maybe someone on here can tell:

CDS722F - Hager

A la recherche de Interrupteur différentiel 2P 25A 30mA AC à bornes décalées SanVis CDS722F? Retrouvez toutes les informations pour Protection sur le site officiel Hager !

hager.com

 

[nicebutdim]

I'd always thought they were DP, but noticed the 1P+N designation on Hagar's website and my brain wont let the question go.

 

[Mike Johnson]

I have been told by the Electricity provider in France that the single module RCBO's do not comply, bit difficult to tie them down to why, but in essence I think they said because the isolation is not a 3mm air gap when tripped and the neutral only provides protection because it is dragged along with the tripping phase and does not have its own tripping mechanism.

 

[pc1966]

In the case of ROI I would not be surprised if it was a mix of the single-pole OCPD based on the historic ties with the UK regs, and the move to double-pole switching from more recent EU influence and/or historical use of TT or similar, leading the 1P+N being normal for RCBO.

Might explain the difference in part number for the same basic module size between the Hager .ie and .fr sites.

Maybe @Risteard knows more on the background?

 

[Mike Johnson]

You are right, they are 1P+N even though Hager sometimes refer to them as 2P. Oddly enough the 4P ones appear to really be 4 protected paths for over-current:

RCBOs B & C Curves 2 & 4 Pole RCBOs

RCBOs B & C Curves 2 & 4 Pole

www.hager.ie

I don't know. You would need to check the local regs to see what is required.

My French is not up to decoding this to see if it really is 2P instead of 1P+N, and the picture is not quite good enough for me to see if the little printed schematic is showing the thermal/magnetic trip on both paths, but maybe someone on here can tell:

CDS722F - Hager

A la recherche de Interrupteur différentiel 2P 25A 30mA AC à bornes décalées SanVis CDS722F? Retrouvez toutes les informations pour Protection sur le site officiel Hager !

hager.com

Interesting on the Hager French web site posted above in the description is says "With neutral pole cut NO.

 

[nicebutdim]

I have been told by the Electricity provider in France that the single module RCBO's do not comply, bit difficult to tie them down to why, but in essence I think they said because the isolation is not a 3mm air gap when tripped and the neutral only provides protection because it is dragged along with the tripping phase and does not have its own tripping mechanism.

There was a similar discussion which (I think) concluded that single module RCBOs did provide a 3mm air gap.

What I'm really curious about is why Hagar have designated these double module RCBOs 1P+N and not DP? The terminology suggests that N isolation operates in the same manner as single module units.

Edit: Just seen Mike's latest reply and the plot thickens!

 

[Mike Johnson]

My previous post was prompted by a visit from a French Consuel Inspector, so in essence it could just be his opinion, but certainly if the dual RCBO's do not have their own trip mechanism, why are they so big if the same can be made in a single module?

 

[nicebutdim]

My previous post was prompted by a visit from a French Consuel Inspector, so in essence it could just be his opinion, but certainly if the dual RCBO's do not have their own trip mechanism, why are they so big if the same can be made in a single module?

Technology continues to improve. What I'm wondering is whether or not there is any practical purpose for continuing to use two modules if one would suffice? I'd always assumed double modules RCBOs provided true DP isolation, but that Hagar link prompted me to ask questions.

My knowledge is extremely limited, but my capacity for asking questions knows no bounds.

 

[Mike Johnson]

This should be clearer:

 

[pc1966]

This should be clearer:

Well that clearly shows the thermal/magnetic element (square & curve zig-zag bit) is only in the line path.

 

[nicebutdim]

Crabtree single module

 

[Mike Johnson]

I thought that was what the ----- meant. ?

 

[pc1966]

The ----- always trip me!

 

[pc1966]

Crabtree single module

That shows the trip part as the 'X' crossing the live path just after the switch symbol.

I think it is often seen that a MCB/MCCB is shown just as an X on power schematics.