Pyro Cable Tripping RCD

[tony mc]

my megger only goes up to 450v.

nope trips straight away. its so strange because there are three runs of pyro on the left of the hall doing it, and one run on the right of the hall.

i think i will just replace it anyway because, i'm guessing theres a chance it will get damp and trip again anyways even if i did dry it. now that you have said that i'm always certain that it is a damp issue. but would damp cause a dead short???

What sort of megger do you have which only put out 450v on a IR test ?

 

[Deleted member 26818]

I'm assuming that these four bad legs, are in fact two lengths of cable linking between three socket-outlets.
If so, could you inform us of the state of play at the midle socket-outlet?
Is it damp or corroded, do the two links into the socket-outlet run together, are they damaged?

 

[Golden_Boy]

yep and once i dry it out. who's to say it wont happen again in a week or two???

You make the ends off properly .... Simples...

 

[sl1210]

like i said i have disconnected all of the socket faces and it still trips, so can't be the socket/spur plates.

tony mc i've got a megger mft1710 and only IR tests at 250v and 500v, so to answer your question no it doesn't test at 1000v.

tony its all very well you saying i should look at my testing method without actually giving me any advise on what you would do?

like i said i've identified where the first leg is, disconnected it and done a 450v IR Test??? as soon as i reconnect the line to the db it trips.

 

[Golden_Boy]

like i said i have disconnected all of the socket faces and it still trips, so can't be the socket/spur plates.

tony mc i've got a megger mft1710 and only IR tests at 250v and 500v, so to answer your question no it doesn't test at 1000v.

tony its all very well you saying i should look at my testing method without actually giving me any advise on what you would do?

like i said i've identified where the first leg is, disconnected it and done a 450v IR Test??? as soon as i reconnect the line to the db it trips.

Can you please tell us EXACTLY whay readings you are getting on these cable runs. If IR tests show low readings what are they? DEAD SHORT means nothing.... We are here to help but need more information as to the readings you are getting...

 

[sl1210]

o ohms

 

[telectrix]

try your tester on continuity. a reading of 0 meg. on a IR test could be several kohms. you need about 8 kohms or less to trip a 30mA RCD.

 

[MDJ]

i'm sure its damp too

Na can't see that, if the pot and seal were fitted properly and they obviously were due to the age of the circuit damp probably won't be the reason, you could stick a pyro under water and run over it with a steam roller and it will still work, also I very much doubt 4 legs are down, that seems almost impossible, unless alterations have been carried out by someone not familiar with MICC.

 

[Deleted member 26818]

Is it actually four legs though?
If you have a length of cable and damage one end, both ends would read as being damaged.
The OP appears to state that this is a single circuit supplying sockets.
It could be that the cable goes into the side of the first socket, then out the other side to th next socket.
Or it could be that the cable is run up at ceiling height and there are drops down to each socket.
One loop in and one loop out.
It may be that a pair of cables to a socket have been damaged, and the OP is reading it as four damaged legs, when in fact it's just two damaged cables.

 

[Knobhead]

Well having had a read through his previous started posts, I'll leave you gentlemen to it.

 

[hasel5]

nevera truer word spoken tony

 

[Golden_Boy]

o ohms

You cant have "0" ohms unless the short is exactly where you are measuring from.... I give up..

 

[GLENNSPARK]

why dont the O/P seperate each leg.....and test em individually rather than just goin round...n round...n round....
and stop using `extention leads` to test with...or any other crappy lashups like that....

 

[trev]

Was just about to suggest that Glenn, it's the only way. Work your way round the circuit leg by leg and you'll find your problem. You've probably gone round and round in circles and are now in the process of disappearing up your own backside, we've all been there and done it. As others have said, it's bar nigh impossible for 4 lengths of pyro to all go down at the same time.

 

[Deleted member 26818]

As others have said, it's bar nigh impossible for 4 lengths of pyro to all go down at the same time.

Reminds me of the Jubilee line extension.

 

[vjsmarwick]

i am still guessing that the problem has been caused by someone not knowing what they were doing and they have tried to tighten the pots a very big no no as we who know knows. and no i am not 50 yet lol but getting there faster every year!!!!!

Or another possibility is its a 4 core pyro and its just one length that is damaged and he is just not explaining it very well ????

 

[Guest55]

Reminds me of the Jubilee line extension.

why ? what happened there spin ?

 

[Guest55]

theres no shame in admitting you have no experience in pyro , its a dying skill that isnt taught anymore as its only used in a handful of building types.
i'm old enough to have been at college when it was still a practiced technique but its been over 6 years since i did any work on micc and i dont have , nor intend buying , the expensive tools to work with the stuff , and as such i avoid it like the plague.
i'll take fp200 any day as i know i can fix it in 2 minutes flat rather than fanny about for hours with blow torches and sealing putty.

 

[vjsmarwick]

well i would take pyro over fp200 any day and don't need expensive tools to make off the ends needs must when they are not available

 

[richy3333]

theres no shame in admitting you have no experience in pyro , its a dying skill that isnt taught anymore as its only used in a handful of building types.

Yeah but when you get some of the cantankerous posters on this forum combined with the fact that most sparkies are not overly eloquent with the typed word you can see why people are reticent to post or don't explain themselves as well as needed, and then you go around in circles trying to fathom out the fault/issue.

I still maintain prayer is you greatest weapon in resolving this problem...