Insulation Resistance on new ring.

[South Spark]

We've installed a new ring - ring continuity was fine but Insulation resistance while well outside the limits was 50-60 M ohms.Obviously as a new circuit it should be perfect. Took it in half - both halves still at 50-60 M ohms, then again still the same. Thinking we might have a dodgy roll of cable we took off all the sockets and connected it all up with wagos - perfect insulation resistance.

Exchanged the sockets for new ones and the same problem is recurring - any ideas?

 

[Plonker 3]

You don't have a neon on a FCU unit or other load somewhere when you yet with all points connected do you?

 

[telectrix]

damp sockets?

 

[Sharpend]

This new ring recently plastered over? Usually find that IR rises slowly if you keep your meter on it, this is usually damp as tel has indicated, leave it a couple of weeks with heating on to dry out room then measure it. Probably find that if has increased in value.

 

[cobrauk]

He did say it was fine after removing the sockets so its not damp.

I have had dodgy cable insulation before now, that cheap *hit cable they bringing in has very thin insulation and pressure in the box can be whats happening, I would remove all the sockets from the wall check again if OK then reconnect and test after fitting each one until you find the one or ones causing you the problem

 

[Plonker 3]

How can it be e cable, if as the OP says they have disconnected all the sockets and replaced them with wagons and the readings are alot better?

 

[iamelectric]

i know the IR value should be a lot higher being a new circuit but its well over the 1M-ohm min and you have checked the cable so theres not really a problem

 

[South Spark]

Ok - all cable tested Ins res came out fine - as soon as a new batch of sockets were put on it dived to 3 M ohms. That's outside the limit obviously but a real mystery. Zs, RCD checks out fine so we'll liven it up and see if the IR results are any better in a couple of days.

When the sockets were hanging out but connected IR results were higher - connecting the socket to the back box seems to be what caused the issue.

 

[telectrix]

squashed cable?

 

[Richard Burns]

Sockets stored outside before / after purchase, so got a bit damp?

 

[Marvo]

while well outside the limits was 50-60 M ohms.

I wouldn't stress, 50-60Mohms is very high especially if you were using 1000v test voltage. I certainly wouldn't waste time trying to localise a problem that isn't a problem. At best I'd take another reading if you're still there in a day or two, at worst I'd ignore it entirely if I had better things to do.

 

[yellowvanman]

Have you done an insulation test on the individual sockets?

Had a similar problem this week with a lighting circuit and JBs. Found one JB had a insulation resistance of 0.9Mohm between 2 terminals!

 

[brucelee]

Hi mate will be the damp from the plaster had the same problem few yrs back have learned my lesson since then

did the same as you split in halves it increases , remove sockets and use wagos and perfect readings the moisture in the plaster is in contact with the back box and your flying earths to the back boxes or the socket screw completes the circuit
held test button on and the readings rose
I then had a idea to test from 1 of the back box earth terminals with one lead and the other lead on the wall near socket
in different points and the readings were all over the place big differences from 1 cm to the next


Just leave it a few weeks fire it up and the heating in the house and test again in a few weeks the readings will have risen which is what i found, since then as long as the readings are higher than1M/Ohm it complies but its less than 2 M/ohm then I would start investigating
I would just test again in a few days or weeks time and record the values on the test sheets job done leave the socket fronts off slightly to help with any moisture inside

 

[Lou7]

Did you sort out the problem?