RCBO not restting

[sparkside1]

Hi all

Have a problem with a Wylex 32A Type C RCBO that has tripped to a utility room and heating plant room to a west London mid terraced house.
It will not reset even with all loads removed. I tried swapping the line and neutral conductors to an adjacent same rated RCBO and the same happened. I tested the ring between L-N at the utility sockets and incoming spur to the plant room and was 0.42 ohms. I only had time for a quick look on xmas eve and will return on Monday to carry out further tests. But not having had many issues with RCBO's I need some advice on how to test these devices properly and what the possible causes could be. There is no history on this fault as the property is vacant and the problem miraculously appeared!

Cheers

 

[trev]

Well he got 0.42 ohms from something. Could have been anything of course, no mention of whether that was a continuity reading, IR, Ze, Zs....nothing.

 

[telectrix]

give the guy a bit of slack, lads. he's said it's his boss's house. boss has probably asked him to have a quick look. most likely on his way home for a freebie. he's had a quick look and is now seeking pointers. which he's had. now let him go back, find the fault and, hopefully, report back as to what it was.

 

[trev]

An approximation of it can be calculated but I'll acknowledge that you got me there. Now, what gave you this 0.42 ohms reading.

 

[telectrix]

Trev..tell me bud, how do you get a Zs value from a dead circuit exactly? Read my posts before commenting
The job is not a freebie the boss pays for it.
I have calibrated testers.

Telectrix..spot on for getting it

can see trev's point , though. you stated a 0.42 resistance reading, but did not explain very well. face to face, you'd have had a reply 0.42 ohms what? on a forum, it's difficult to see what you mean without a full explanation. my irish grandmother might have known, being the seventh daughter of a witch, but otherwise it's guesswork.

 

[Geordie Spark]

Second income? Are you a comedian Murdoch? This is the boss's house.

Oh dear oh dear!! :laugh:

I can feel your embarrassment from here!! :yesnod:

 

[Geordie Spark]

can see trev's point , though. you stated a 0.42 resistance reading, but did not explain very well. face to face, you'd have had a reply 0.42 ohms what? on a forum, it's difficult to see what you mean without a full explanation. my irish grandmother might have known, being the seventh daughter of a witch, but otherwise it's guesswork.

You know since reading that I have come to the conclusion that YOU may be (very) distantly related to Tidyboiler!!

Now THAT'S scary!!

 

[sparkside1]

The 0.42 ohms reading was the highest reading taken between cross connected L and N and measured at the furthest point which was a spur for a gas boiler. I dodn't get a chance to take an R1+R2 or IR test. My tester is a megger mft1720 by the way.

 

[Geordie Spark]

give the guy a bit of slack, lads. he's said it's his boss's house. boss has probably asked him to have a quick look. most likely on his way home for a freebie. he's had a quick look and is now seeking pointers. which he's had. now let him go back, find the fault and, hopefully, report back as to what it was.

... and it's Christmas - the season of good will & all that so cut the poor sod some slack.

Next week, Christmas will be just a distant memory and you can rip him a new one then!!

 

[TJ Anderson]

The 0.42 ohms reading was the highest reading taken between cross connected L and N and measured at the furthest point which was a spur for a gas boiler. I dodn't get a chance to take an R1+R2 or IR test. My tester is a megger mft1720 by the way.

Are you saying that you cross connected L&N? What were you hoping this test would tell you in relation to this fault?

 

[Octopus]

Sod the Christmas cheer.

Half baked op, no real constructive answers, we may as we'll be passing in the wind.

 

[davesparks]

Trev..tell me bud, how do you get a Zs value from a dead circuit exactly? Read my posts before commenting
The job is not a freebie the boss pays for it.
I have calibrated testers.

Telectrix..spot on for getting it

Zs from a dead circuit is easy, you just use the alternative Zs testing method.

With the breaker open connect L to E at the far end of the circuit, test between the live and dead side of the breaker.

Simples!

As to how this could help you identify the fault, I am not entirely sure at the moment.


As far as your original post and the fault goes I would suggest that you did ask a bit of a daft question, you said the fault moved to with the circuit when you connected it to another RCBO so logically the fault must be on the circuit and not within the RCBO.
To properly test the RCBO you test it the same way you would a seperate RCD unit using the RCD test function of an MFT or a seperate RCD tester.


For general fault finding I would strongly recommend an analogue insulation resistance tester, it is much easier to work with a needle than a digital display. It doesn't have to be expensive or even calibrated if all you are looking for is the yes/no/maybe rather than measured values.


(And just in case anyone is wondering, yes I have been reunited with my happy pills this evening)

 

[Geordie Spark]

Sod the Christmas cheer.

Half baked op, no real constructive answers, we may as we'll be passing in the wind.

I think you and Tony could be vying for the post of Official Forum Grumpy Git.

You won't find it an easy ride though ... he's had a LOT of practice

 

[telectrix]

apprentice grumpy, geordie. he's an apprentice grumpy. :ack2:

 

[Geordie Spark]

apprentice grumpy, geordie. he's an apprentice grumpy. :ack2:

Apprentice ..... as highly qualified as that ???

Not just a 5 Week Wonder Grumpy Git then???

 

[Darkwood]

Sorry Parkside you are reported for abuse... if you feel others have done the same to yourself then use the report symbol at the bottom L/H of the post in question (the triangle)...

Reacting with agressive and immature language is not on regardless whether suggestive or not!... this is in the public domain and free to view by anyone on the internet, so please respect anyone may read your replies.

 

[tazz]

Please note debate by all means, but any abuse or bad language directed at any member will not be tolerated.

 

[shanky887614]

do your normal continuity tests etc.

if it keeps tripping there will probably be a short or bad appliance connected somewhere

 

[trev]

or bad appliance connected somewhere

The first thing is to ensure no appliances are connected. They might not like 500 volts up em when the time comes.

 

[Geordie Spark]

The first thing is to ensure no appliances are connected. They might not like 500 volts up em when the time comes.

They don't like it up 'em Captain Mainwaring Sir .. they don't like it up 'em!!

 

[TJ Anderson]

The first thing is to ensure no appliances are connected. They might not like 500 volts up em when the time comes.

250V range. There would be very few occasions when I would be using 500v on fault finding!

 

[shanky887614]

id use my fluke dmm on continuity. it goes a lot lower than the continuity on a megger.

no need for a megger when fault finding

 

[trev]

250V range. There would be very few occasions when I would be using 500v on fault finding!

As a rule I always do the 250 test first but I often use 500 when fault finding. The thing is though, some may not have the sense to do a soft test first

 

[davesparks]

250V range. There would be very few occasions when I would be using 500v on fault finding!

Always use 500V for circuits operating at 240V AC, there's no point testing insulation resistance at a voltage less than the peak voltage of the supply.

 

[Darkwood]

Very good point brought by Davesparks.... if we have 230v RMS then peak voltage is around 320v so exactly what would an insulation test that isn't in excess of this proof because it may not show any issues or failed readings where a 500v would unless its very poor value.

 

[TJ Anderson]

Always use 500V for circuits operating at 240V AC, there's no point testing insulation resistance at a voltage less than the peak voltage of the supply.

On a new install / additions then definitely 500V. Not faulting on an existing installation unless you are absolutely 100% that all loads are disconnected and after 250V has shown clear. Like I said very rare I would use 500v outside new installation. To be honest, in this scenario 500V will provide no benefit over 250V and only the risk of damaging equipment which will give the OP another problem to deal with.

 

[TJ Anderson]

Very good point brought by Davesparks.... if we have 230v RMS then peak voltage is around 320v so exactly what would an insulation test that isn't in excess of this proof because it may not show any issues or failed readings where a 500v would unless its very poor value.

You have answered your own question there, the fault is present at 230v and is operating the RCBO, therefore higher than that is not required to trace the fault. I appreciate what 500VDC testing provides, but in the case of locating a fault that is tripping a 30ma RCD, 250VDC is adequate and with no risk.

 

[TJ Anderson]

id use my fluke dmm on continuity. it goes a lot lower than the continuity on a megger.

no need for a megger when fault finding

Good luck when you get an insulation fault!

 

[telectrix]

1000V kill or cure. shove it up 'em.

 

[PEG]

...Right! i have finally got it...the 0.42 is the duration our poor OP lasted,from original post,1.00 being a full day of 24 hours,corrected for temperature...:icon12:

 

[trev]

...Right! i have finally got it...the 0.42 is the duration our poor OP lasted,from original post,1.00 being a full day of 24 hours,corrected for temperature...:icon12:

Sigh.
Peg, he's already said what the measurement was all about mate. It was a completely pointless exercise as far as fault finding is concerned but never mind.
Actually, thinking about it maybe you've got more of a point.