RCD and no CPC. Testing and Sup Bonding Question

[mattcos1972]

OK....
Have a lighting system with no CPC and have just updated the CU to a 17th edition slit, dual RCD board. When testing the lighting circuit, all I have done is test the Insulation Line / Neutral and polarity, and left Xs on the R1+R2, Zs and Live / Earth Insulation. Is there any way to test the RCD on the circuit?

Also with regard to supplementary bonding in the bathroom. As all circuits in the house are now RCD protected I have not installed supplementary bonding in the bathroom, is this still acceptable even though there is no cpc in the lighting circuit (which includes lighting in the bathroom).

Sorry if this seems a bit "simple" of me, but I am thinking that the circuit is still RCD protected (even without a CPC) so therefore supplementary bonding would not be required, but I cannot substantiate the RCD disconnection time on that particular circuit (although it performs fine on all other circuits) as I don't know how to test it!!

 

[acat]

Best Practice Guides | Electrical Safety Council

Have a look at the above link they have a few best practice guides the first one deals with your situation.

Hope it helps.


Chris

 

[mattcos1972]

Best Practice Guides | Electrical Safety Council

Have a look at the above link they have a few best practice guides the first one deals with your situation.

Hope it helps.


Chris

Hi Chris,
Thanks for that chap.
I read through the relevant literature and it fell short of covering that particular issue, so I called up the ECS and they put me onto the NIC (who will be doing my assessment).
They were really helpful actually, as I had a few questions about general stuff to ask....but with regards to this particular issue the non CPC lighting circuit IS considered to be RCD protected (officially, if you like) even though you cannot physically test it; therefore if the disconnection times are met (with regards to 701.415.2) there is no need to supplementary bond in the bathroom.

Hope that helps anyone else who may have come across this situation.

 

[acat]

Thanks for the input however that has left me totally confused an RCD detects leakage to earth so how can it be RCD protected with no earth to leak to. I suppose they are looking at leakage to earth rather than leakage to cpc earth.


Chris

PS Good luck with your assessment.

 

[DurhamSparky]

suggestion!! hmmm may not be correct but may do the trick!!

RCD as normal and connect a wander lead to the EARTh bit of your meter and connect to any Pipework in bathroom if not plastic then go back to the CU and attach to earth rail..!!

may not give you a true reading but you are able to test the RCD on that circuit !! and also check to see if your bonding works!!

steve

 

[mattcos1972]

Thanks for the input however that has left me totally confused an RCD detects leakage to earth so how can it be RCD protected with no earth to leak to. I suppose they are looking at leakage to earth rather than leakage to cpc earth.


Chris

PS Good luck with your assessment.

Hey Chris,
They recently explained the ins and outs of an RCD at college, and I was awake for some of it
Basically the RCD detects imbalances in the current running through it. During normal operating the Line / Neutral load is balanced but if for instance a person were to touch a live part on an RCD protected circuit then current would be passed through that person and that would upset the balance of flow through the RCD, causing it to trip. The RCD is not actually hooked up to the CPC at all in the CU.

As always......I could be wrong!! lol

suggestion!! hmmm may not be correct but may do the trick!!

RCD as normal and connect a wander lead to the EARTh bit of your meter and connect to any Pipework in bathroom if not plastic then go back to the CU and attach to earth rail..!!

may not give you a true reading but you are able to test the RCD on that circuit !! and also check to see if your bonding works!!

steve

Bloomin hell Steve.....You are the "Solutions" man!!

 

[DurhamSparky]

i may be wrong and i will happily be corrected by other members of the forum!!


my motto in life mate is work with what your given not what you need!! I mastered that trade in the Royal Navy unfortunately!!


steve

matt why dont you get a roll of single earth wire 1.0/1.5 mm will do trick and run it with the lighting circuit if you can, that way your assessor will be impressed that you made a gray stituation Good!

 

[mattcos1972]

matt why dont you get a roll of single earth wire 1.0/1.5 mm will do trick and run it with the lighting circuit if you can, that way your assessor will be impressed that you made a gray stituation Good!

I would Steve, but everything to do with the lighting is in the ceiling and I am ground floor conversion. It was no prob til about 3 years ago when my neighbour had laminated floor put in all through his place, now Its gonna have to be ceilings out for any alterations / additions! grrr!

No matter, I will address it all in time.

 

[WayneL]

Just an additional point, chaps

You don't have to test the RCD on that circuit - you can test it on any circuit (eg socket outlet) or, you can test it at the CU.

It's not an 'every circuit' test - you only have to do the test sequence once (per RCD)

 

[Sintra]

Or test at the RCD with the load disconnected.

 

[fletchflash]

the NIC said it is considered RCD protected even untested? what if its faulty from the box.

As said before an RCD does not need an earth to operate as under fault conditions it will detect an inbalance, lots of makes of RCD dont have a trailing lead to the earth bar so are not connected to earth anyway. As long as some current leaks somewhere, like down a DIY'ers metal hammer and nail the RCD will operate

To test at the CU, switch all MCB's off, clip your tester to earth bar and use your probes in the load side terminals of the rcd. This is also a good way to test RCBO's on lighting circuits/ smoke alarms etc

 

[mattcos1972]

the NIC said it is considered RCD protected even untested? what if its faulty from the box.

As said before an RCD does not need an earth to operate as under fault conditions it will detect an inbalance, lots of makes of RCD dont have a trailing lead to the earth bar so are not connected to earth anyway. As long as some current leaks somewhere, like down a DIY'ers metal hammer and nail the RCD will operate

To test at the CU, switch all MCB's off, clip your tester to earth bar and use your probes in the load side terminals of the rcd. This is also a good way to test RCBO's on lighting circuits/ smoke alarms etc

Cheers for that fletchflash.
The NIC said it was acceptable as it was operational and tested on the other circuits.

 

[jamie-spark]

The nic testing and inspection book ( and not got my osg on me but im sure its the same ) says you test the rcd at its point of installation ie Consumer unit. Not at the end of the circuit

 

[zone77]

pls correct me if im wrong . going back to original post, i thought one of the conditions to emmit supp bonding was that the earth loop be within the breakers value (6amp type B being 6.12ohm). earth loop cannot be measured with no cpc so i would install the supp bonding