Insulation resistance problem

[Videodoctor]

Firstly,ignore all the snide comments.You get a lot of it on here and its uncalled for.
Some people on here make out that you can only ask questions on here if you have years of experience and a shed load of qualifications. My opinion is that if you have to ask a question its because you don't know the answer and you have come here to pick everyone's brains.
Anyway onto your question.It does sound like something is still plugged in.An outside pond? Outside lights off a spur?
A surge protector adaptor can give very weird results.Also if you still have an rcd in circuit then it can affect the readings.ie spur off the house sockets but ending in an rcd in the garage.
Have you isolated the boiler?

Failing all this it sounds like you might have water under the floor and a joint box is sat in it or damp behind one of the sockets.Look for damp walls where there is a socket and take it off to look behind.As the good advice from previous posters,you need to split the ring and go from there. Good luck and come back to let us know if you find it.

 

[sparky1508]

Firstly,ignore all the snide comments.You get a lot of it on here and its uncalled for.
Some people on here make out that you can only ask questions on here if you have years of experience and a shed load of qualifications. My opinion is that if you have to ask a question its because you don't know the answer and you have come here to pick everyone's brains.
Anyway onto your question.It does sound like something is still plugged in.An outside pond? Outside lights off a spur?
A surge protector adaptor can give very weird results.Also if you still have an rcd in circuit then it can affect the readings.ie spur off the house sockets but ending in an rcd in the garage.
Have you isolated the boiler?

Failing all this it sounds like you might have water under the floor and a joint box is sat in it or damp behind one of the sockets.Look for damp walls where there is a socket and take it off to look behind.As the good advice from previous posters,you need to split the ring and go from there. Good luck and come back to let us know if you find it.

Thanks, I ended up doing the test with the conductors removed apart from the CPC. Will be back with more test results.
Thanks


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[davesparks]

Also are you saying that if CPC touched either neutral or line conductor it wouldn't create an imbalance between L and N therefore tripping the RCD. Also if L touched N that wouldn't cause a dead short therefore tripping the protective device. If I am wrong about these then clearly I don't have a clue. Just because I am uncertain of why I am getting low readings from an IR test you say I am incompetent.

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I am not saying that those situations wouldn't cause a fault, i am saying that the test results you have do not indicate that type of fault.

You have made no mention of a dead short in your posts, the lowest resistance I think you have quoted is 0.01M ohms, which is 10,000 ohms, simple maths will tell you that this is will not trip an RCD. A dead short would be in the region of zero ohms.

Nobody knows why they have a low IR reading until they have found the reason, my issue is that you don't understand what the test result actually means in real world terms.

 

[davesparks]

The whole reason I joined this forum was because I read a lot of posts and everyone seemed to be really helpful apart from a couple. So though I would join in. I've even joined in a couple of discussions here and there but the moment I ask a question I'm being called incompetent. All I want is advice not abuse and I've not once been shirty.

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If you ask a question which betrays a significant lack of knowledge or understanding then you have to expect to take some flak.
If you were on site with an electrician, bearing in mind you are claiming to be in the same trade, you would receive a heck of a lot worse a reaction.

 

[sparky1508]

If you ask a question which betrays a significant lack of knowledge or understanding then you have to expect to take some flak.
If you were on site with an electrician, bearing in mind you are claiming to be in the same trade, you would receive a heck of a lot worse a reaction.

If I were on site and said electrician knew I was fresh off the farm then I'm sure any half decent human being would understand that my knowledge isn't up to the same standard as someone who's been in the trade for some time. All this because I said I checked all sockets when clearly that wasn't the thing to do.

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[davesparks]

No not a trainee but just qualified and I expect you probably have low opinions of middle aged blokes doing fast track courses to try and change their life to be able to provide for their family but I personally don't worry about what people think of me. I paid good money to be taught something that I hope to get much better at. It's also my house that I'm testing so not wasting any ones time or Money. I may make some wrong decisions but isn't that why this forum is here? To help people like myself understand where we go wrong so we don't do it again. I totally understand if none of you want to help but just trying to learn more.
Thanks anyway

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I have an opinion about anyone doing a fast track course in this trade regardless of age or gender, there are plenty of other jobs out there which you could earn a fair wage at without placing your own life, and the lives of others at risk.

I have actually worked with three very different people who have all done fast track course and they were all making simple mistakes which could easily have cost them their lives, not through any fault of their own but a lack of proper education and a lack of understanding of some fundamental concepts. They had all paid good money to be taught something, and then only got taught a fraction of what they need to know.
Two of those people took the arrogant attitude of being qualified domestic installers and refused to accept help. The third realised her limitations and we worked together for 18 months and we still work together occasionally.

Never forget that electricity kills within a fraction of a second, and it's pretty damned hard to provide for your family from the afterlife.

Personally I have been knocked unconscious by a shock, and only survived thanks to an RCD operating. An apprentice died from a shock at the company where I served my apprenticeship, I don't think the two painters who were in the room below when his body came through the ceiling from the loft have ever really got over it.


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[sparky1508]

That's fair enough and I understand your point but you don't know me or my capabilities. If anyone has done any course and passed then they are qualified regardless of your opinion. I personally think I am quite capable that's why I have taken this route and believe me I know electricity kills. I have been taught enough to get by and hopefully in time I will learn more as all I want is to be the best I can be.

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[Octopus]

With readings like that I would be looking for a rcd socket or spur!

 

[Videodoctor]

I have been a qualified electrician for 30 years but hold back from posting on here because of the attitude of some of the members on here.Instead of trying to answer the person's questions,they harp on about not being qualified,electricity kills etc. Just because some people haven't the many years of experience doesn't give the members on here to ridicule first time posters asking simple questions.I would like to think that we are here to help and educate.Fault finding is one of the hardest things to master and 'yes' ,it take years of experience but we all had to start somewhere so give the guy a break and try and offer things he can try to find his fault.Rant over:furious3:

 

[davesparks]

That's fair enough and I understand your point but you don't know me or my capabilities. If anyone has done any course and passed then they are qualified regardless of your opinion. I personally think I am quite capable that's why I have taken this route and believe me I know electricity kills. I have been taught enough to get by and hopefully in time I will learn more as all I want is to be the best I can be.

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Well you are welcome to come out on a job with me and prove me wrong,

 

[Midwest]

Sparky1508, some of the replies you don't like, are probably not helped by the fact, that you do not indicate your qualifications or competency in your profile. You'll see members have gone there to have a look, including me. If you do display them, you might find the negatives a little less shared.

I find fault finding quite taxing, where others on here find it enthralling. As well as the many other helpful suggestions, may I suggest (following safe isolation of course) is removing (not disconnecting) all face plates, too see how many cables you have at each point. This might identify any errant spurs etc, you may not be aware of and indeed might reveal any possible faults, if it is a fault at all.

As davesparks finished his sentence with a comma, you make wish to take up his job offer or mentoring, as he does have a compassionate side which he tries to conceal at times, but indeed has a realm of experience to offer.

 

[sparky1508]

I was hoping to get help on here as I've seen in many posts he's very knowledgeable and always gives sound advice. I cant seem to find how to put my info on my profile but this is what I now have.
City and guilds 2393-10
City and guilds level 3 2382-15 regs
City and guilds level 3 2394 and 2395
City and guilds 2377-22.
All I want to do is learn that's why I'm on here and at home testing my own stuff before I go out and do it for real.

 

[sparky1508]

I am not saying that those situations wouldn't cause a fault, i am saying that the test results you have do not indicate that type of fault.

You have made no mention of a dead short in your posts, the lowest resistance I think you have quoted is 0.01M ohms, which is 10,000 ohms, simple maths will tell you that this is will not trip an RCD. A dead short would be in the region of zero ohms.

Nobody knows why they have a low IR reading until they have found the reason, my issue is that you don't understand what the test result actually means in real world terms.

Thanks dave, I realise now what you are saying but I was thinking if a conductor was just very close to another but not actually touching somewhere would that not be similar to having bad insulation or am I still being simple.

 

[bigspark17]

Cooker hood.?

 

[davesparks]

Thanks dave, I realise now what you are saying but I was thinking if a conductor was just very close to another but not actually touching somewhere would that not be similar to having bad insulation or am I still being simple.

It would have to be very very close for it to have a measureable resistance at 500V.

It would just act as a capacitor

 

[tony mc]

Do you have a alarm system connected to the RFC via a spur or a RCD FCU or socket?

Once you start to test in a methodical way as Davesparks as suggested things will become far more clear,I would definately mark the sockets once eliminated dont try and just remember them as you quickly get confused.

Lets hope you tested L/N on soft test on 250 v scale for obvious reasons.

I would suggest access to a tester which has a KOhm range as when testing on the Meg scale when it gives a 0.00 result you need to switch scale to find out exactaly what the reading is. Many MFT testers dont have a KOhm range !


If you get a very low reading then as a guide you can get a rough idea how far away the fault is using maths and cable resistance values!

Let us know how you get on lets hope its not unaccessible joint boxes!

 

[sparky1508]

Thanks for that. I have a fluke 1654b, not sure I it has a Kohm setting but will look into it.

 

[sparky1508]

Do you have a alarm system connected to the RFC via a spur or a RCD FCU or socket?

Once you start to test in a methodical way as Davesparks as suggested things will become far more clear,I would definately mark the sockets once eliminated dont try and just remember them as you quickly get confused.

Lets hope you tested L/N on soft test on 250 v scale for obvious reasons.

I would suggest access to a tester which has a KOhm range as when testing on the Meg scale when it gives a 0.00 result you need to switch scale to find out exactaly what the reading is. Many MFT testers dont have a KOhm range !


If you get a very low reading then as a guide you can get a rough idea how far away the fault is using maths and cable resistance values!

Let us know how you get on lets hope its not unaccessible joint boxes!

Thanks
No alarm connected.
Will do methodical as Dave suggested.
Forgive me for this but the only reason to test on 250v as far as I am aware is to protect sensitive equipment but I had every plug disconnected from the sockets and had nothing left connected. I know I don't need to unplug but just went round and unplugged everything anyway. Is there another reason I should test on 250v?

 

[telectrix]

Thanks
No alarm connected.
Will do methodical as Dave suggested.
Forgive me for this but the only reason to test on 250v as far as I am aware is to protect sensitive equipment but I had every plug disconnected from the sockets and had nothing left connected. I know I don't need to unplug but just went round and unplugged everything anyway. Is there another reason I should test on 250v?

you do this so that, even though you think all loads are disconnected there could be one left that you have missed.

 

[sparky1508]

So if there is still a load connected and I test at 250v would my reading be >200 Mohm meaning everything is good.