RCD won't trip

[SPECIAL LOCATION]

and the reason this doesn't happen on tns and tt, is due to electricity taking the easiest path. Which in that case would be down the neutral due to the higher resistance of the earth on those systems.

Correctemundo!!! ...

:Applaud

easiest path on TT & TNS will always go down the 'N'

so mucho tripo regulus

(thats the latin I think!?)

:C:|

 

[kme]

Could we just point out one other small point here..........?

When you`re going to test an RCD (in-service OR new), DON`T operate the test button until you`ve done your RCD trip tests!

Reason? You are checking the resultant times of supply disconnection under existing circumstances - as soon as you trip the RCD with the test button, you`ve altered the dynamic.

Oh. Nice diagram mister hamster There is a slight difference in the way the test button operates on electronic RCDs as against non-amplified ones

KME

 

[SPECIAL LOCATION]

Oh. Nice diagram mister hamster There is a slight difference in the way the test button operates on electronic RCDs as against non-amplified ones KME

Indeed...

I only copied out of the O-S-G and scrawled over it with my bestist coloured pens....

At least it shows the concept of whats going on and how a test button can appear to fail on a good working RCD

Guinness

 

[roys]

A picture paints a thousand words, like the diagram and explanation SL.

 

[Ali]

Thanks every one. I know a lot more now than I did yestaerday. I plan on explaining it all to my boss next week as if I worked it all out myself then hit him for a pay rise!!

 

[ProDave]

Thought it time for a picture.... :coffee

---------- AUTO MERGE Post added at 00:21 ---------- Previous post was at 00:16 ----------

Test load is typically 3400ohms so giving more like a 60+ma fault..

sometimes why your 30ma tester may not operate RCD then you do the test button..

it stuffs a bigger trip fault current down..

clears the cobwebs gets it working again..

after that it then works good with tester as well!

Looking at that diagram it is clear why the test button does not trip with a N/E fault.

BUT it looks to me like the polarity of that RCD is WRONG.

If the RCD had been wired to the opposite polarity, then the test fault would have been from the L on the output side to N on the input side, and would have tripped even with the N-E fault.

This highlights that SOME RCD's are polarity sensitive, and in this case the design of the CU may have used the RCD with the wrong polarity.

In any case, it will not affect it's tripping of a real fault, just the operation of the test button.

 

[Andy™]

even if the test button was wired on opposite sides, there would be no difference.

also, it WILL effect tripping in case of real fault. the 'fault' current can make its way back into neutral via the short in appliance, and go through RCD so less imbalance.

 

[ProDave]

even if the test button was wired on opposite sides' date=' there would be no difference.also, it WILL effect tripping in case of real fault. the 'fault' current can make its way back into neutral via the short in appliance, and go through RCD so less imbalance.[/quote']

Andy, WHAT exactly was unhelpful about my post #26

I was describing how, if it was wired the other way around, the TEST button would work even with the N-E fault.

With the N-E fault, as soon as any load is drawn of course the RCD would trip.

When I said "In any case, it will not affect it's tripping of a real fault, just the operation of the test button." I was refering to the polarity of the RCD, not the presence of the N-E fault, i.e irrespective of the polarity of the RCD, and imballance due to a real fault would still be detected and it would trip.

Of course, some manufacturers do state the polarity of their RCD, so you should stick to what they say, but many do not specify the polarity and can be wired wither way round, but a demonstrated the test button may not operate with a N-E fault when wired one way round.

If you are going to mark my post as unhelpful, I would really like to know what was unhelpful about it. I genuinely thought I was adding something to the explanation of why in some cases the test button does not work with a N-E fault.

 

[ianmacd]

Andy, WHAT exactly was unhelpful about my post #26

I still think those unhelpful post buttons cause more issues with people taking bad feedback too personally than they are intended to fix. Chances are if the post is delibertly unhelpful then the person getting the unhelpful feedback wont really care but it will affect people trying to help like Dave.

 

[ProDave]

go make a drawing like Specs has but with it the other wya around.whether the RCD test button is betwen incoming L & out N or incoming N & out L makes no difference. its still an imbalnce between both sides of test coil

I don't have a package handy to draw it, but looking at the above diagram, if the test load was between incoming N and outgoing L, then the imbalance current would pass through the top sensing coil only, and since that is NOT bypassed by any fault, it WOULD register the imbalance and the RCD would trip.

So my statement that IF the RCD was wired to the opposite polarity, then the test load imposed by the test switch would pass through the opposite coil, and so this time even with the N-E fault, the RCD would trip.

 

[Andy™]

I don't have a package handy to draw it, but looking at the above diagram, if the test load was between incoming N and outgoing L, then the imbalance current would pass through the top sensing coil only, and since that is NOT bypassed by any fault, it WOULD register the imbalance and the RCD would trip.

wrong. it will flow through the top sensing coil, but will then split (exactly the same as before). only difference will be the point of it splitting will be other side of the coil

 

[ProDave]

wrong. it will flow through the top sensing coil' date=' but will then split (exactly the same as before). only difference will be the point of it splitting will be other side of the coil[/quote']Here's the diagram you wanted, drawn by hand and scanned that shows how, if the RCD was the other way around, the test load from the test button is not bypassed, and the RDC WILL trip.

P.S, how do I embed the image so it appears in the post, rather than a link you have to click?

 

[Andy™]

you have that drawing with contacts of RCD open. in which case, the test button cannot work (since RCD would be off). if the contacts were closed, then the currect on the incoming neutral will also go through RCD coil, to earth fault, and back to MET. so just like Spec's drawing, RCD may still fail to trip. nothing has changed

(new image coming up once i make it)

---------- AUTO MERGE Post added at 17:34 ---------- Previous post was at 17:17 ----------

actually, i think dave may be right here(in that RCD will trip. but for a different reason to what he said)... the currect in the neutral coil is going the wrong way, so RCD imbalance will be greater... i.e that of the 'fault', and that if current flowing though neutral side...

 

[m4tty]

Here's the diagram you wanted, drawn by hand and scanned that shows how, if the RCD was the other way around, the test load from the test button is not bypassed, and the RDC WILL trip.P.S, how do I embed the image so it appears in the post, rather than a link you have to click?

If you click on attchments then select insert I think. Hth

 

[ProDave]

If you click on attchments then select insert I think. Hth

The only option I can find is "manage Attachments" which opens another window. From there I can choose to upload a file from my computer, but there's no option to insert it or otherwise choose the way it displays at all.

All I want to know is why do my pictures appear as a clicky link, whereas other people's pictures appear in the post?

Any answers from those that get their pictures to show in the thread or forum admin?

 

[m4tty]

When I click on manage attachments and upload the files then once uploaded click close this window then when back on the new post click on manage attachments again and There will be an option at the bottom of the drop down menu which says insert. Click on that and the pictures appear in the post rather than a link. Hope you can understand what I'm saying as I'm not good at explaning things. Cheers

 

[Andy™]

All I want to know is why do my pictures appear as a clicky link, whereas other people's pictures appear in the post?

Any answers from those that get their pictures to show in the thread or forum admin?

i use photobucket for my images. which then use IMG code to show them in the post. i can also make them appear as click links using URL code instead. never used the forum to host the image, so not sure how to get them to show in the post rather than a link