Reduced r2 due to cladding

[Rockingit]

Industrial refit and we’ve screwed a bunch of metal clad 13’s onto walls which are corrugated metal sheet using self tappers. Just come to do dead tests and realised that r2 is about half the value of r1 and rn - the sheet is acting a conductor. Sup Bond the sheet or not? The same walls also have 32/3 socket outlets but they’re class 2 boxes, also the board is on the same walling. Structural is bonded back at the MET. So the low down is everything has an Earth path, just in an odd way!

 

[Strima]

Only other way is to chuck all the CPCs into Wagos to isolate them from parallel paths just to check your continuity.

If you IR the sheet it would come back as needing bonding so I would just do it anyway.

 

[westward10]

Strictly speaking you don't have a reduced r2. As above for initial verification you isolate the cpcs from the parallel paths to verify its integrity that is r2.

 

[PEG]

Hi bud,are these outlets on the inside or outside?
Can't imagine the sheet having to be treated different to the accessible metal clad unit,but prepared for discussion ?

....anywho...i've got me own problems...got to make an adapter to fill a 30" rubber mooring buoy with water,instead of air ?

 

[telectrix]

Hi bud,are these outlets on the inside or outside?
Can't imagine the sheet having to be treated different to the accessible metal clad unit,but prepared for discussion ?

....anywho...i've got me own problems...got to make an adapter to fill a 30" rubber mooring buoy with water,instead of air ?

adaptors.take your pick:

 

[Rockingit]

Strictly speaking you don't have a reduced r2. As above for initial verification you isolate the cpcs from the parallel paths to verify its integrity that is r2.

This is a true thing….. except it’s virtually impossible to isolate for testing as all the sockets are metal fixed. I’m happy I’ve continuity as I can see it all.

 

[Rockingit]

I’ve ended up just sticking a 16mm bond from the distro to the cladding, as much for show as anything else.

 

[westward10]

Just drop the front plates off to remove the parallel path, you should prove the r2 even though the cpc in reality probably serves no purpose.

 

[pc1966]

I was going to suggest that if the CPCs go only tho the actual plate/switch you could open and check that way, as poor/missing terminal use is more likely than an open CPC half-way a long a cable.

But @westward10 beat me to it by several hours!

 

[westward10]

I beat Usain to the last sausage roll in Greggs the other day.

 

[Lucien Nunes]

If the CPC is an insulated conductor e.g. conduit cable, then I would always test it before putting the fronts on, propping them clear of the boxes or any other metal if needed so that only the copper conductor and its connections are under test.

Much less practical is any kind of test involving a CPC via conduit / SWA / MICC which connects via the back box and hence is inseparable from the metal building structure after first fix. The chances of a secure MI gland failing to make effective contact are near zero, likewise well-erected conduit, so the likelihood of the test failing to spot a disconnect due to the parallel structure is small. In any case if the containment continuity is critical, the joints should be tested with the Ducter during erection.

 

[cliffed]

This is a true thing….. except it’s virtually impossible to isolate for testing as all the sockets are metal fixed. I’m happy I’ve continuity as I can see it all.

Agree especially if your doing an Eicr on a factory using Swa, trunking, etc R2 would be potentially lower than the R1 + R2 measured.
Thats only if you are recording that measurement by the way.