Low IR

[sivoodoo]

Im getting Low IR readings between live conductors and earth on a ring main what would be a some reasons for this, Ive had a look to see if theres anything plugged in, but should this matter between live and earth?

Thanks

 

[Mark.W]

Depends on what the ring is serving. If it's a kitchen then look for the small things like neons and the electric ignition on some cookers. Burglar alarms have also been mentioned before.

 

[sivoodoo]

Even though Im only testng between line conductors and earth, I didnt think there was a load when this method was used?

 

[Mark.W]

What were your readings?

Could possibly be a nail/screw through a wire.

 

[sivoodoo]

readings were:

7M Ohms. Probes placed at Live on the mcb screw to earth at the earth bar.

 

[Mark.W]

What about Neutral / Earth?

7M ohms is low but still within the regs....

You're just going to have to investigate. Start by splitting the ring in half and taking a reading of each leg (you'll probably find one half is ok and the other gives a low reading again), then split the half that has the low reading and test each leg again, carry on splitting and testing until you find which part of the cable is faulty.

Hope this helps

 

[thepurple1]

If its an old installation then 7Mohms is ok

 

[zupos40]

7M suggest to me that insulation has been damged some where, nail or may be fixing screw in one of the outlets, I had dampness in the wall cause a similar problem, as prievoiusly said you best split ring in half and investigating, may be first unscrew all socket front and see if reading improves, tested a house recently and found cable insulation had deterated such that ring read 2.1 M replaced cable reading went upto 100M, it is possible to overload the ring and for a cable to deterate, there were no since of damage, it was not near centraling heating pipe or any other reason other then age and possible overloading.

Let us now how you get on.

 

[andekoch]

If old instalation then 7M is likely, have often seen 2-3M on old wiring (talking grey sheath with B&R conductor insulation), age and possible overloads most likely.
As said 7M is within regs so no prob but warn customer that it is low and there might be a problem that needs further investigation. Cert allows for comments, use it.

 

[brs73]

i've had some circuits recently where it was impossible to unplug everything so i done a test between live and neutral together and earth at 250v. i lot of circuits were reading 0.00ohms.
what types of equipment would cause this.
i also had the same readings on lighting circuits where i couldn't remove all lamps/transformers?

 

[oldtimer]

Also watch out for the central heating as I got caught with the switched fused supply being spurred off the ring and yep Intruder alarms plus smoke heads dont help