failed Zs

[Deleted member 9648]

problem with RCBO is not only does it have to comply with Earth fault but overcurrent as well that will bring your loop impeadence down to meet trip time on over current

Zs has nothing whatsoever to do with overcurrent,only earth fault current.

 

[Guest55]

And as this is a multi-storey hotel, i know what i'd be doing!! lol!!

ordering room service and emptying mini-bar ?

 

[Engineer54]

Room service maybe, but the mini bar would still be pretty much in tack, i'm not a big drinker!! lol!!

I was thinking more of, well and truly covering my arse on that certificate!! lo!!

 

[i=p/u]

What happens when no cpc on older lighting circuits , how do you test if this circuit will disconnect ? Do you just add up R1+Rn to ze

 

[Guest55]

What happens when no cpc on older lighting circuits , how do you test if this circuit will disconnect ? Do you just add up R1+Rn to ze

well there is no Zs without an earth.
and a dead short between L & N will disconnect device fairly quickly without the need for any testing

 

[telectrix]

in this case the rcd would disconnect (assuming it works). you would not get a fault to earth except through a body.

 

[nicsin02]

I am just going to put these Zs fails a C2 fault and recommend the mcb get downgraded to either 16/20amp, I've always been led to believe that a 30mA RCD is for additional protection on a TN arrangement, I do alot of new build house tests where the full d/b is RCD protected and it would make the Zs test pointless if I went down the line of relying on the RCD for tripping times?

 

[Deleted member 9648]

I am just going to put these Zs fails a C2 fault and recommend the mcb get downgraded to either 16/20amp, I've always been led to believe that a 30mA RCD is for additional protection on a TN arrangement, I do alot of new build house tests where the full d/b is RCD protected and it would make the Zs test pointless if I went down the line of relying on the RCD for tripping times?

I understand what you are saying....but a new build TN system should be designed with OCPD disconnection times in mind. An EICR is only concerned with compliance with Bs 7671. IMO you would be wrong to code 2 a circuit which complies with the required disconnection times,reg 411.4.4 applies,and clearly states an RCD is a permitted device for earth fault protection.
An EICR is not about personal preferences.....good luck with claiming a circuit which complies with 411.4.4 is 'potentially dangerous'.

Edit
Just to add -you could always include a recommendation in your report that the issue is addressed,giving reasons. But a code 2 is an automatic 'unsatisfactory',potentially forcing the client to part with a wad of cash. It's going to be hard to justify your report when the client finds out he's spent a lot of hard earned on an install which actually complied with the regs.

 

[ojchurch]

I agree with you on new builds, should be designed to trip in time regardless of RCD. You would still need to carry out the test though to confirm CPC is continuous.
I was replying to nicsin02 (not great at this forum thing!):
I am just going to put these Zs fails a C2 fault and recommend the mcb get downgraded to either 16/20amp, I've always been led to believe that a 30mA RCD is for additional protection on a TN arrangement, I do alot of new build house tests where the full d/b is RCD protected and it would make the Zs test pointless if I went down the line of relying on the RCD for tripping times? !):

 

[telectrix]

as wiepuller said, a code C2 is a non satisfactory, potential danger, so a bit OTT. i'd go with C3, improvement recommended, and as your recommend downrate MCBs from 32A to 20A.

 

[Deleted member 9648]

I agree with you on new builds, should be designed to trip in time regardless of RCD. You would still need to carry out the test though to confirm CPC is continuous.
I was replying to nicsin02 (not great at this forum thing!):
I am just going to put these Zs fails a C2 fault and recommend the mcb get downgraded to either 16/20amp, I've always been led to believe that a 30mA RCD is for additional protection on a TN arrangement, I do alot of new build house tests where the full d/b is RCD protected and it would make the Zs test pointless if I went down the line of relying on the RCD for tripping times? !):

It can be either additional or earth fault protection,have you looked at 411.4.4?....which deals with TN systems.
And a new installation and initial verification is a different animal to an EICR....where the only consideration is compliance with 7671.

 

[ojchurch]

It can be either additional or earth fault protection,have you looked at 411.4.4?....which deals with TN systems.
And a new installation and initial verification is a different animal to an EICR....where the only consideration is compliance with 7671.

Maybe I haven't been clear, sorry, I don't often post on forums so am probably not used to the etiquette etc. I was responding to nicsin02's post which I then edited in after. Must get used to these symbols on the mobile format, reply with quote isn't obvious there.

I am fully aware what regulation 411.4.4 says and if I was carrying out an EICR to BS 7671 I would pass the circuit in question as long as all other requirements were met. Also obviously I would have to be sure the high reading was legitimately down to the combined cable runs & not other reasons. I would however detail my findings in the report and try and explain to the client in laymens terms what I had found and the ramifications.

I realise now that I didn't read the post correctly, I was on a tea break! I was trying to say that you still need to confirm continuity of CPC but nicsin02 was talking about not having to take the EFL reading, not confirming continuity of CPC. My bad.