High RCD Trip Time Despite Good EFLZ

[batty]

how come?I have never had issues testing any at source.

what issue are you having?

---------- Post Auto-Merged at 23:41 ---------- Previous post was made at 23:37 ----------

that will be because they are mostly single pole and the rest of us are stuck in the dark ages with DP isolation in a fault scenario then.

I have found that MEM RCBO'S don't like being tested at the RCBO they won't trip out but if you test along the cable at the end they are fine although this may be my tester fluke 1652. Not sure were you are going with the double pole isolation but have a good idea though.

 

[steptoe]

I also use a fluke 1652,

and have never had an issue with any RCBO not tripping at source,

I have had an issue though with the probes not quite reaching the N terminal though,

maybe you need to rethink that part, (croc clip and screwdriver!? I didnt say that, its not to 7671 or EAWR)

IMHO SP isolation in the case of earth-N fault isnt really ideal, especially if it is an outside supply or on a TNCS/PME(gawd I hate saying that!)

 

[SidTheSparky]

I don't come to this forum all that often. I've just been looking back at the few posts i've put up. I was fairly newly back on the tools when I started this post, so I was a little rusty on some aspects of the Regs. I would like to say a big Thank You to all the people who have made useful, encouraging  and friendly replies.......that's why we post on forums, right?

I also think it's fair to say that I have to honestly stand back in amazement at the odd patronising/arrogant reply that has crept in - I'm sure it's nothing to be concerned about - very possibly just an angry Daily Mail reader putting the world to rights, lol.

 

[Sharpend]

The real question is; what would you do if the Internet wasn't available? Check the info some other way? The regs book or OSG perhaps?

Too much dependency on the Internet these days, too little thinking on ones own!!

 

[Steve3948]

I also use a fluke 1652,

and have never had an issue with any RCBO not tripping at source,

I have had an issue though with the probes not quite reaching the N terminal though,

maybe you need to rethink that part, (croc clip and screwdriver!? I didnt say that, its not to 7671 or EAWR)

IMHO SP isolation in the case of earth-N fault isnt really ideal, especially if it is an outside supply or on a TNCS/PME(gawd I hate saying that!)

Now up until last week I would have agreed with you, however testing at a school and they have Eaton Fuseboards, some with RCBO's in.

Like you say probes won't reach the live screw, so bare screwdriver and clipped on to that, still no trip, something about the screw heads.

Remove circuit pop in a couple of tails, crock onto them, trip no problem.

I think I read a post some time back with same issue but different manufacturer.

Surely the screw head cannot be insulated or isolated from the terminal.

 

[Sidewinder]

The sensing coil is fitted into the cable tunnel I think you will find!

 

[septiclecky]

Both lights on one MCB. Good point. I'll correct that. Thanks.

As for trip times - they ought to be <40ms @x1. Only the lights seem to be managing this. What puzzles me more is that they have a higher impedance than the socket circuits so they should take longer to trip. I've always taken it for granted that trip times would be higher for higher impedances. My recorded readings are somehow quirky.

Your talking through your backside that time is for x5 on 30mA and below RCDs. 

 

[Steve3948]

The sensing coil is fitted into the cable tunnel I think you will find!

Spot on I think, because I noticed the tunnel was a lot wider on the live compared to the neutral and very deep into the RCBO.

Will remember that for future reference.

Thanks to you both.

 

[septiclecky]

I have found that MEM RCBO'S don't like being tested at the RCBO they won't trip out but if you test along the cable at the end they are fine although this may be my tester fluke 1652. Not sure were you are going with the double pole isolation but have a good idea though.

If your talking about the Talisman 2 type where you add a pod to make it into a RCBO I got told by their helpdesk is because the sensing coil for the live is after the termination so it will not trip at the RCBO

 

[Sidewinder]

septic,

Please see above posts from myself & The Paddler!

 

[septiclecky]

septic,

Please see above posts from myself & The Paddler!

And if you look we posted them all all around the same time :innocent

 

[batty]

So after all this it's true you can't test memshield 2 RCBO's at the RCBO you have to test them in circuit. Are memshield 3 the same?

 

[SidTheSparky]

The real question is; what would you do if the Internet wasn't available? Check the info some other way? The regs book or OSG perhaps?

Too much dependency on the Internet these days, too little thinking on ones own!!

Like I said - I was quite newly back on tools and rusty with Regulations.

I was in the early stages of learning how to set up and run my business (finding premises, vehicle, insurances, learning basic tax and book keeping etc etc). On top of that there's family life to keep on top of whilst trying to earn money. That's a lot of things to fit into one mind, given that it was within a relatively short period time. I wasn't the first in this position. I won't be the last. Being busy and having no colleagues or business partner to talk to, meant that it was easy for me to end up taking the wrong line of thought - I genuinenly thought I was stuck with an problem.

That's where a forum should come into its own.

When people kindly told me where to look, I looked there and there was nothing wrong with the RCDs which I thought were giving me trouble (even though I felt silly afterwards for not seeing what was obvious and right in front of me).

Back in the day, even great engineers like James Watt and Matthew Boulton didn't just happen to know all the answers - they visited forums and exchanged thoughts and ideas to keep them on the right line of thought - that's one of the things that made them so great.

Anyway, I ended up doing my C&G 2382-10 and 2391 to bring me back up to speed. You never know - I might even ask a less lame question when I'm stuck in future....

 

[SidTheSparky]

Your talking through your backside that time is for x5 on 30mA and below RCDs. 

1) Thanks for your reply Septiclecky. ??!!?? 2 YEARS after I posted ??!!!?? Better late than never I suppose, lol.

2) Learn some manners. I don't know what the forum sponsors think, but it doesn't reflect well.

 

[kme]

Sid - with all respect to ALL contributors - You must remember that every one of us has issues and problems at various times; which can affect the nature of a reply. Similarly, some members are blunt, to the point of offence  -others are eternally sarcastic. It doesn`t mean they`re unwilling to help - if that were the case, they wouldn`t bother to respond at all. 

I have found, with this, as with many forums, to take every reply as a good thing; and try to extract the info in a post, without getting sidetracked by the nature of the reply - a sarcastic, or terse reply is no less useful than a flowery, polite one; if it provides the information you need; or a pointer in the right direction.

Just my thoughts, anyway.

KME

 

[says-les]

I agree with all that KME said.  Sid please don't be put off by negative comments bordering in the personal which is disallowed on any forum.

My view is that the line conductor has to be passed through the pod for about an inch or so for two reasons:

so that it will reach the normal terminal of the MCB and so that it is passed through the CT of the pod so that current balance can be monitored by the pod.

So if we test the RCCD at the line terminal we are on the Source side of the CT not the Load side, and therefor the test current cannot be detected as an intentional controlled imbalance current.

I like you have recently undated myself on the 17th edition and on the Inspection and Testing Courses.  In my case I have taught the Regs since the 14th edition but I am still learning, solely because of the internet and this and other forums.

The forum members have corrected me in this respect recently - see my original post re why the Site Guide includes RCCB's in the table that gives Zs max values.  I am even in the process of updating the thinking of several people involved in teaching the Regs to apprentices and older sparks.

Contrary to the comment made by someone on here about how the Internet has made us less self reliant, I believe in my case that it has enhanced my learning and indeed corrected it.  I am 68 but still on the tools.

 

[says-les]

I agree with all that KME said.  Sid please don't be put off by negative comments, bordering in the personal which is normally disallowed on any forum.

My view is that the line conductor has to be passed through the pod for about an inch or so for two reasons:

so that it will reach the normal terminal of the MCB, and so that it is passed through the CT of the pod, in order that current balance can be monitored by the pod.

So if we test the RCCD at the line terminal we are on the Source side of the CT, not the Load side, and therefore the test current cannot be detected as an intentional controlled imbalance current.

I, like you, have recently updated myself on the 17th edition, and on the Inspection and Testing Courses.  In my case I have taught the Regs since the 14th edition but I am still learning, solely because of the internet and this and other forums.

The forum members have corrected me in this respect recently - see my original post re why the Site Guide includes RCCB's in the table that gives Zs max values.  I am even in the process of updating the thinking of several people involved in teaching the Regs to apprentices and older sparks.

Contrary to the comment made by someone on here, about how the Internet has made us less self reliant, I believe in my case that it has enhanced my learning and indeed corrected it.  I am 68 but still on the tools.  The complexity of the requirements of BS7671 has made it all more difficult for us mortals. Speak or write to a designer or consultant if you have serious doubt about things in BS7671.  After all, these guys are calling the tune and most of them are either degree people or off the tools, originally.  In fact, IMHO some of the burden should be removed from the spark on the job to a different level of qualified post within out Industry.  IET take note please, as well as all Trade Associations.

Cheers

 

[Sharpend]

Please do not read my post as a knock of the Internet or use of the forums, as I for one enjoy the banter and use of both, all I was driving at is that the standard stuff is generally covered between the Bs7671 and the OSG, both of which should be readily available to a qualified electrician.

I guess I am somewhat taken back by the number of questions on here and other forums that seem to be of a nature that I would expect any electrician worth his salt should have a good working knowledge of.

No offence meant.

 

[SBS Dave]

Hi Gordy,

You asked a question as to why Batty uses RCBOs and then answered your own question. You only have to track down a fault current, as a result of nuisance trip, when half the house circuits go off. On the subject of cost, since my RCBOs are £10.00 each, I couldn't compete on price, if you are installing MCBs @ £1.00 each.

But then, I wouldn't want to compete, if I can offer an averaged sized board for about £50.00 more than the Split Board. The secret of course, is to offer your customer the RCBO option.

SBS Dave

 

[SPECIAL LOCATION]

Replaced an old Wylex fuseboard (BS3036 fuses) the other day.

TNCS supply with Ze 0.14ohm........  < CUT >.........

Very quirky results.

Anyone ever had a similar problem?

Not really sure what to do. I've told customer that his RCD disconnection times are outside of BS7671 and I'll be stating that on the EIC. Trouble is I haven't sussed out exactly why.

I don't come to this forum all that often. I've just been looking back at the few posts i've put up. I was fairly newly back on the tools when I started this post, so I was a little rusty on some aspects of the Regs. I would like to say a big Thank You to all the people who have made useful, encouraging and friendly replies.......that's why we post on forums, right?

I also think it's fair to say that I have to honestly stand back in amazement at the odd patronising/arrogant reply that has crept in - I'm sure it's nothing to be concerned about - very possibly just an angry Daily Mail reader putting the world to rights, lol.

Like I said - I was quite newly back on tools and rusty with Regulations.

I was in the early stages of learning how to set up and run my business (finding premises, vehicle, insurances, learning basic tax and book keeping etc etc). On top of that there's family life to keep on top of whilst trying to earn money. That's a lot of things to fit into one mind, given that it was within a relatively short period time. I wasn't the first in this position. I won't be the last. Being busy and having no colleagues or business partner to talk to, meant that it was easy for me to end up taking the wrong line of thought - I genuinenly thought I was stuck with an problem.

That's where a forum should come into its own.

When people kindly told me where to look, I looked there and there was nothing wrong with the RCDs which I thought were giving me trouble (even though I felt silly afterwards for not seeing what was obvious and right in front of me).

Back in the day, even great engineers like James Watt and Matthew Boulton didn't just happen to know all the answers - they visited forums and exchanged thoughts and ideas to keep them on the right line of thought - that's one of the things that made them so great.

Anyway, I ended up doing my C&G 2382-10 and 2391 to bring me back up to speed. You never know - I might even ask a less lame question when I'm stuck in future....

I think the original topic of this thread is now covered and sorted...

But I just wanted to take a slight tangent off in relation to some of the later posts..

[======PLEASE NOTE THIS POST IS NO WAY MEANT AS A PERSONAL DIG AT SID-THE-SPARK.======].

I AM JUST USING THIS CONTENT AND POSTS AS A THOUGHT ABOUT WHAT ACTUALLY IS AN ACCEPTABLE RESPONSE ON A FORUM..]

looking at a few first impressions from the posts in the thread....

What expectation would the average competent person come to about the person asking the question..? 

1)

Someone who is recently back on the tools and just changed a fuse box for a (presumable paying) customer ought to be up to date with what the expected test result should be...?     Not just guessing what they think they should be..??

(notwithstanding any Part P compliance stuff! no mention of if england / Scotland etc..?)

2)

There is a big difference between someone struggling with RCD trip times for a test rig they are working on at a college course..

To some one doing real jobs for paying customers and not knowing what they are talking about..

3)

The On Site Guide costs around £25.. the index clearly gives RCD testing procedures and times..

even if someone cant be bothered to buy a copy of BS7671 what valid reason is there for not having a copy of the OSG..

with all of its general reference tables etc..  max ZS's, conductor resistance, cable capacities etc..

4)

If a person has a copy of the OSG logically that would be the first place to check before asking elsewhere (forums etc.)...

Irrespective of how good the internet is....

Often a person can be in a situation with no internet access but a hard copy book OSG in the van/toolbox is always accessible to double check figures if any doubts creep in during testing..

When out in the real world of work, especially if on site with other trades people and someone drops a bit of a clanger..

Drills a hole in wrong place, cuts cable too short, puts new light up in wrong location, goes to get the bacon sarnies and only gets 6 when you need 7, arrive on site but forgot to collect the extra coil of cable from the wholesalers .. etc.. etc.

They will have the mick taken out of them for the rest of the day/week/job.  It wont be a polite

"oh you have been a daft person drilling that hole straight through the bedroom wardrobe"

We do all make mistakes....

and generally.. have to take the flak for it!!

SO HERE IS THE QUESTION...

why do people somehow think an internet forum will be any different?

as long as there is no direct name calling, bad language, racist, religious, political abuse  etc..

WHAT EXACTLY IS THE ISSUE?

It just seems more and more nowadays that (like primary school sports day), everybody has to be a winner, doing it right, and no one can be told they have dropped one almighty clanger....

And it is always someone else's fault no one should tell the truth and give the blunt answer... 

A spade can no longer be a spade

It has to become a "long handled blade earth cutting tool"

I will just say in closing respect to SidTheSpark for admitting that he felt silly for missing the obvious...

Unfortunately there are a vast swath of incompetent persons out there asking the most basic questions that they should have grasped BEFORE commencing real work!

No matter how good any forum is..

IT SHOULD NOT BE A LAZY PERSONS EXCUSE FOR NOT BUYING AND USING THE BASIC INFORMATION IN THE INDUSTRY RECOGNISED GUIDANCE BOOKS / NOTES

If anyone posting a question expects people to give up their own time to answer their question....

they should have the decency to at least do their bit of homework first...

And if they havent...    just as on a real job, they must expect some ribbing for not doing the bleeding obvious first...

This forum has loads of members who have put a lot of time and effort into answering all sorts of sensibly posted and debated questions..  (I think Says-les post he just refers to as one example of good constructive debate)..

But I am not surprised if any other members like myself get a bit frustrated / impatient with someone who on the face of it is not just asking a question, but appear to out of their depth working on live sites possibly endangering third parties with their lack of knowledge.

Apologies if this posts offends anyone...

I am just curious as these sort of comments about how posts are answered do keep coming up..?

(with negative scoobs give to members who just state what is clearly obvious to a lot of people)

:coffee

:coat