New RCD tripping

[Andy™]

Any neutral on an energised circuit supplying a load will be 'live' once disconnected

just saying

yep. always check neutrals are dead after disconnecting them. probably dont teach you that on many courses

 

[Mell]

No they never mentioned it at all as I remembered.

 

[Murdoch]

Hi Murdock 

Yes the walls are plastered just not painted or wallpapered and no carpets and yes I've researched about borrowed neutrals and I read about once you pull a borrowed neutral it then becomes live thanks for the advice, I'm just wondering because there has not been any heating on for a few weeks and this damp weather could moister be an issue.

Thanks.

Mel 

is this a complete refurb and all new wiring?

 

[Mell]

I believe it has had new wiring my friend only just purchased the house at auction and looks new just missing the db hence why she asked me, now got this challenge but I see it as a learning curve.

 

[Andy™]

have you tested the RCD on its own with nothing connected to the load side?

 

[Mell]

How would I test the RCD without any loads 

 

[poni]

How would I test the RCD without any loads

????????

still a bit green only passed my exams a few

How would I test the RCD without any loads

months back 

????????  What !!!

 

[Mell]

I've never had to test one before I've an idea what to do but rather it be clarified first.

 

[Andy™]

I've never had to test one before I've an idea what to do but rather it be clarified first.

how about you tell us how you think it should be done first...

 

[SPECIAL LOCATION]

I've never had to test one before I've an idea what to do but rather it be clarified first.

If that's then case then I would suggest you shouldn't be working alone unsupervised...

Do you have a copy of BS7671 and the On-Site-Guide..?    :C

It may be a good idea to buy a copy if you haven't..

Then read it..

There IS a dedicated section all about RCD's!!

:coat

( plus I would have thought testing RCD's would have come up in your inspection & test exam that you say you recently passed? )..

What exactly were you taught to do with regard to RCD's on the courses you have taken, making you consider yourself able to install and test a modern domestic consumer unit & its associated RCD's?

opcorn

 

[kerching]

Which Inspection and Test Exam was it?

 

[OnOff]

Been up in the loft? Got any rat chewed cables, junction boxes under leaks, even mice and slugs in junction boxes etc, outside fittings and so on. 

 

[Murdoch]

I've never had to test one before I've an idea what to do but rather it be clarified first.

This really is the thread that keeps giving ............

And as its a rewire you don't even know if it been properly wired ................. talk about a poisoned chalice 

but it only a few cables what could possibly go wrong ?

 

[Mell]

Yes I have got the on site guide and a copy of the bs7671 18th edition and it does not say how to test an RCD without a load, only where and when to use them, the only way I have been taught to test RCDs is to do the ramp test as per the schedule of results which  on my meter does 6 tests 1x the load, 5x the load and half x the load and record the results which at 5x the load should be less than 40ms and then you test the manual RCD button, now my RCD is tripping on the last test of the half x the load which it shouldn't hence why I asked the question and in answer to your question how would I test a RCD without a load I would switch all loads off remove the neutrals and stick my probes on the load side of the RCD and do a ramp test, I'm not sure if that's correct but that's why I'm asking. As for my exams I've done I can only tell you what I've been taught I can't help that,  I got all my pass certification and been told I can go out and do electrics, my stupid questions are down to inexperience and lack of knowledge hence why I am asking you guys cause obviously they don't teach these things.

 

[Mell]

Hi Murdoch yes I checked all the cable runs I could possible do and did continuity tests to check what cable did  and where it went luckily they where labelled up, I going back after work today to do what you suggested.

Thanks 

Mel 

 

[Sidney]

Yes I have got the on site guide and a copy of the bs7671 18th edition and it does not say how to test an RCD without a load, only where and when to use them, the only way I have been taught to test RCDs is to do the ramp test as per the schedule of results which  on my meter does 6 tests 1x the load, 5x the load and half x the load and record the results which at 5x the load should be less than 40ms and then you test the manual RCD button, now my RCD is tripping on the last test of the half x the load which it shouldn't hence why I asked the question and in answer to your question how would I test a RCD without a load I would switch all loads off remove the neutrals and stick my probes on the load side of the RCD and do a ramp test, I'm not sure if that's correct but that's why I'm asking. As for my exams I've done I can only tell you what I've been taught I can't help that,  I got all my pass certification and been told I can go out and do electrics, my stupid questions are down to inexperience and lack of knowledge hence why I am asking you guys cause obviously they don't teach these things.

RCDs should be tested without any load as the load may interfere with the test current from the meter.

Isolate and remove the conductors (L+N) from the load side of the RCD, then energise and test using your probes on the output terminal clamp screws of the RCD. Due to the design of modern switchgear, distribution boards and GS38 compliant test probes there's a very limited risk of you coming into contact with live parts and getting a shock.

And stop just pulling the neutrals out, you're creating a hazard by doing this. I always disconnect line, neutral earth and reconnect earth, neutral and live. That way I'm significantly reducing my risk of something going wrong.

When IR testing you need to leave all CPCs and earth bonds in place, if you have a fault on a backbox and the CPC isn't tied to earth then how will the fault be identified as there's no path to earth. The only testing you should be doing with the CPCs disconnected is when doing your R1+R2 to prevent parallel paths skewing your test results.

 

[SPECIAL LOCATION]

Yes I have got the on site guide and a copy of the bs7671 18th edition and it does not say how to test an RCD without a load, 

really?    

have you tried On-Site-Guide top of page 118.  11.1?

Also IF you have done a proper inspection & test course then I would have thought you would also have a copy of Guidance Note 3.

"Inspection & Testing"..

where starting from page 74 you have section 2.6.19 "Operation & Functional Testing of RCDs"

I got all my pass certification and been told I can go out and do electrics, my stupid questions are down to inexperience and lack of knowledge hence why I am asking you guys cause obviously they don't teach these things.

This is basic stuff that IMHO is not an option extra that can be omitted from any training..

I am sure when I did my C&G's at college, we had to go through using all the expected test equipment how to use it,

what are the expected results should be,

how to identify potential problems where results are not as expected,

how to document results on the relevant paperwork etc.. etc..

Either you have not done the correct courses to be working unsupervised..

Or your training provider has ripped you off big time...

(which if true petty much confirms the general opinion that a short course is not worth the paper it was written on..)

I am wondering if they have only taught you the updates courses which are intended to bring someone already qualified to earlier regs up to speed with the latest amendments?  and not a full electrical installation course? 

:C

 

[SPECIAL LOCATION]

I believe it has had new wiring my friend only just purchased the house at auction and looks new just missing the db hence why she asked me, now got this challenge but I see it as a learning curve.

So this is an empty property, part finished project that was stopped for some reason?

So there could well have been an upset previous electrician who was not paid fully for their labour...

Possibly left a deliberate fault somewhere?

The most basic rule you must ALWAYS follow on fault investigation is..

Assume nothing is correct, and that everything is faulty until you have proved otherwise yourself.

Go back to the beginning 

If you verify Earth loop & Polarity at the supply..

Test your CU polarity across all your bus-bars & RCD terminals

Test all RCD's (RCBO's) are working within spec before you connect anything onto them..

Then work through your circuits individually verify CPC continuity,

connect it onto your earth bar,

verify IR,

Connect it up verify ZS..

Move  on to next circuit...

If you have a fault that is tripping all the time you should find that no problem at all..

Its intermittent faults that are the real sod!

:coffee  

 

[Andy™]

 the only way I have been taught to test RCDs is to do the ramp test as per the schedule of results

ramp test is not checking trip times... its something different to trip times and not required by BS7671 although it can help with fault finding....

 

[Mell]

Thanks guys for all you input and I have taken it all in.

Thanks

Mel