TT tripping issues

[rich.250]

Or there was a fault there all the time, and now you have an earth path..... LOL

 

[itchy]

The inlet comes through the floor And the wall the box is now on is a bare stud with all new cables for te rewire just hanging around and not connected to anything.
My tester doesn't ramp unfortunately... But I'm wondering if the sockets at fault as the chargers and radio are used daily and were operating ironically from the board that's been moved.
Will have to wait til Monday to have a proper look. But just thought it such an oddity that I'd post the issue to see if anyone had encountered it before!!

 

[tony mc]

Hi Itchy.

I am a little confused It is the RCD that is tripping with only one radial cct installed as you mention changing a 16A mcb for a 32 A .

So to confirm its the RCD not the MCB tripping.

If it is the RCD the ROD IMO will have nothing to do with it as long as upstream you line neutral and earth are seperate.

I take it on you radial cct the dead tests are all good especially the IR tests making sure the RCD will hold.

 

[itchy]

Yeah the mcbs don't trip, just the rcds. The only reason we moved the radial from 16 to 32 was to quickly eliminate the mcb. (tut tut!!).
The cable came straight out the box to a socket approximately 2' away. Cable not through walls or clipped at the time.
Didn't get a far as an ir test. Nobody living there and it was a Friday afternoon... You can guess the rest!
I'm pretty certain it's a simple problem, although as we've had everything tested pretty much, it would appear at the moment it's not.
If there was a l/n imbalance it would have had the issue before though?

 

[tony mc]

It is going to be either a L/E or N/E imbalance as that is what the RCD coil is detecting.

Once you IR the cct i would imagine you will locate your fault if you test between the above with your continuity meter I guess you will see a reading less than 7666 ohms !

 

[itchy]

Yeah true. I'll report the findings on Monday!!

 

[Engineer54]

IR tests would have been my first test to perform, even before energizing this temporary power outlet!! ...lol!!

 

[Deleted member 9648]

Cant believe a single socket radial tripping an RCD with nothing else connected would need an electrician to contact a forum for advise....5 minutes to sort with a tea break in the middle.

 

[topquark]

Dumb question, are you sure what you are using to draw current (extension/tool combo) doesn't have an earth fault and the RCDs are just doing their job? If so then I'd say you've got the neutral bars connected arse about face!

 

[Deleted member 9648]

Cant believe a single socket radial tripping an RCD with nothing else connected would need an electrician to contact a forum for advise....5 minutes to sort with a tea break in the middle.

Sorry...sarcasm not really called for...(it's been a rubbish day)....getting my coat now.

 

[itchy]

I don't mind sarcasm! I'm recently qualified and not really dealt with tt systems before. I'm not making excuses for not having a wealth of experience... Forgive me or not, no shame in asking questions on a forum?! Whether I was concentrating on something that I thought was a problem else where instead of just doing what I 'should' have been doing is just a learning curve for me surely?!
Thanks for the advice anyway, constructive criticism never goes amiss ;-)

 

[rich.250]

It is going to be either a L/E or N/E imbalance as that is what the RCD coil is detecting.

Once you IR the cct i would imagine you will locate your fault if you test between the above with your continuity meter I guess you will see a reading less than 7666 ohms !

I would go with neutral/earth as it doesn't trip until a load is applied

 

[tony mc]

I don't mind sarcasm! I'm recently qualified and not really dealt with tt systems before. I'm not making excuses for not having a wealth of experience... Forgive me or not, no shame in asking questions on a forum?! Whether I was concentrating on something that I thought was a problem else where instead of just doing what I 'should' have been doing is just a learning curve for me surely?!
Thanks for the advice anyway, constructive criticism never goes amiss ;-)

IMO I would not worry to much re TT systems once your Ra and RCD protection is in place.

Once you start testing its the same as TN systems with higher live ZS values depending on Ra and bonding paths.

Sometimes on 5 X RCD testing depending how high your Ra is the tester can abort the test when the touch voltage reaches 50v. (Something to be aware of) also many have tested with the test instrument set up at 25v for touch voltage which again can abort on 5 X RCD test.