Who trusts RCDs?

[Piratepete]

Hi Guys
Did a small job in a house - one additional socket. Then did an RCD test - x1 (240 mSec) and x5 failed miserably. did the test a couple more times. Some improvement but still failed. The RCD is an old Wylex WSES 80/2 so replacement means a new CU. Customer asked me to test it again - it passed and continued to do so! Stabilised at 106/10 mS. Asked him when he last pressed the Test button - 6 years ago!

I assume that it just got sticky from lack of use! Does this happen to modern RCDs? I must admit that though this is the first that I've tested which failed about 5 operations I've tested many which initially give high readings (though not failed) first time around.
It seems a bit crap if whether you die or not all depends on whether the householder has pressed the test button in the last 6 months!:icon13:
Pete

 

[Strima]

That reminds me, I haven't tested ours in the last five months... Best not stick my fingers in any sockets just yet.

 

[Engineer54]

You'll find that most homeowners won't test these RCD'S by pushing the test button, because after the first time, they realise, that they then have to go round the house resetting all the clocks on the various appliances... lol!!

 

[i=p/u]

if we didnt have so much faith in rcds, the electrical trade be booomin

 

[Knobhead]

So very true E54.

"It's in your interest". "To hell with that if it mucks up watching Crorrie"!

 

[Andy 7671]

If I knew more maths Id get the joke.


J integer is in there somewhere.?

Complex nos ...never got them first time round

 

[GLENNSPARK]

well i think theres too much emphasis on RCDs as the be all and end all.....even to the detrement of disconnection times for MCBs.....i think we rely too much on em above all else....they still have a way to go yet....

 

[fivestar]

I have to say that at least 1 in 5 of the RCD's I have tested over the last year (existing ones - not new installs) have failed. The majority of these have been newer ones as well - i.e. less than 5 years old.

 

[rich.250]

I have to say that at least 1 in 5 of the RCD's I have tested over the last year (existing ones - not new installs) have failed. The majority of these have been newer ones as well - i.e. less than 5 years old.

I had 4 new out of 15 that didn't work......
Shall I disclose the manufacturer?? LOL

 

[mogga]

I do mainly commercial PIRs n in the comments,observations 9 out of 10 times my first comment is "No evidence of RCD monthly testing being carried out as per manufactures recommendations" Even clients who have PPM in place dont have a RCD test listed

 

[TaffyDuck]

The old wylex ones are pretty reliable, I buy a few from Ebay from time to time so I dont have to change old CUs just because one item has gone. 4 out of 5 turn out to be in good working order.

 

[plugsandsparks]

Mine at home gets regularly tested with Mrs P&S cooking exploits, however its fair to say they are variable when in situ. 3 months or so ago came across a QOE board that had 3 RCBOs, tested them and all failed. Realised the place had been un-occupied for a while and there was evidence of dampness so gave the mechanism a couple of workings by hand and tested again, still no joy. Now i knew if i could not get these working it was goodnight board but still could not get them in tolerance, with one refusing point blank to trip at all. Anyway on my last attempt one blew up in my face, which was just the time for me to condemn the whole board, go for a coffee and a smoke.
BTW i have a load of QOE breakers if anyone needs some

 

[mhar]

At school we were taught to do the x.5, x1 and x 5 tests before the functional (red button) test as the object is not to try and get the thing to work for the purposes of testing but to test it's operation as it is, the thinking being if it misbehaves once, what is to stop it misbehaving again after you have left. We were told in no uncertain times that a first time fail is a fail, no argument, and the unit should be replaced

 

[plugsandsparks]

Fair point, but from my experience the second trip and subsequent re often better than the first, so rather than condemn what could be the whole board for a first trip failure, i test it to MY satisfaction

 

[Dave 85]

I generally trust em and never seen a newish one fail. I think its good that newly wired houses are usually 100% RCD protected. Cant see any downside of them apart from minor cost implication and occasional inconvenience. Its not as if they are replacing MCB's, its just additional protection.

 

[fivestar]

I have found quite a few new ones faulty, not just the old ones

 

[Engineer54]

At school we were taught to do the x.5, x1 and x 5 tests before the functional (red button) test as the object is not to try and get the thing to work for the purposes of testing but to test it's operation as it is, the thinking being if it misbehaves once, what is to stop it misbehaving again after you have left. We were told in no uncertain times that a first time fail is a fail, no argument, and the unit should be replaced

Seems these lecturers make up there own rules and standards, and have little or no time for manufacturers instructions/recommendations!! I wonder why on just about every MFT/RCD tester, the ''Auto'' sequence is 1/2 / X1 / X5 on both 0 and 180 degree's?? Perhaps the manufacturers don't know what they are doing...

As for a first fail and it's a dud, makes you wonder if they have ever been in the field?? Perhaps they have, and didn't last too long with any of their employers, and why they are teaching now. Trouble is, they are now teaching all the nonsense, prejudices and scaremongery that caused them to fail in the real world!! ...lol!!!

 

[GLENNSPARK]

Fair point, but from my experience the second trip and subsequent re often better than the first, so rather than condemn what could be the whole board for a first trip failure, i test it to MY satisfaction

if an RCD fails any tests its subjected to first time round (including the manual test)...it should be condemned...

 

[Engineer54]

if an RCD fails any tests its subjected to first time round (including the manual test)...it should be condemned...

Wouldn't agree with that statement at all!! In a perfect world maybe, where they have been regually tested by the house owner or whoever!! But they are all too often not checked at all from the day they were installed and the mechanical side of these units could well stick until operated a few times... and perfectly fine thereafter!!

 

[plugsandsparks]

Guys its nice to have these sentiments but look at it from another point of view.

RCDs dont get tested every 3 months - do they ? - NO

When they trip for the first time having never been surprised perhaps in their life before, they can be a little slow off the mark. Its OK as i am a little slow in the morning as well. BUT i do get better as the day goes along and you know there's nothing wrong with me (i think). So you are faced with obsolete breakers and a new board circa £300 but hey although it was slow on X1 0 it actually passed X1 180 and X5s. So you try the test button, wow its electric now and you run another test, it passes, you have a coffee and try again and compare results... now we are cooking. I pass it ..

My example was a little extreme with 3 RCBOs failing and quite frankly i did not like the look of the DB but thats a difficult sell to the client "Hey P&S does not like the look of our stuff" So i gave the DB ample opporunity to re-deam itself and when the smell of the fried RCBO wofted into the air, i had no problem convincing the client its a bad board and must go, much better than saying "hey guys these rcds have failed first trip, so the whole lot has to go"
They say "have you tested it again?"
I say "yes its fine now but my school says i must condemn it at the first attempt"
They say"should have gone to a differnent school"
I say " steady on i'm sensitive you know"