Insulation Resistance Testing Ring Circuit

[applesandppears]

Hello All,

I am to install some extra sockets for a customer on a relatively new build.

The insulation resistance test.

I tested at 250VDC between line conductors connected and earth and obtained a reading of 1.10 ohms (not megaohms)

Does this reading seem likely that a piece of equipment has not been disconnected?

Any thoughts?

 

[Guitarist]

Are you actually an electrician?

 

[44ALLAN]

Probably your Mp3 player in your lug lol

 

[applesandppears]

please don't blast me (too much!)

I know its simple, just asking for some help

any thoughts?

 

[Megavolt]

Have you disconnected everything before testing

 

[Englishman]

Something plugged in or a spur turned on by sounds of it, but if you can't work it out, then tbh, I have no idea what you're doing with either a tester or the trust to do someone's electrics:

 

[Des 56]

Hello All,

I am to install some extra sockets for a customer on a relatively new build.

The insulation resistance test.

I tested at 250VDC between line conductors connected and earth and obtained a reading of 1.10 ohms (not megaohms)

Does this reading seem likely that a piece of equipment has not been disconnected?

Any thoughts?

It's cused by a poor standard of wind up content

 

[telectrix]

circuit was working with the RCD holding in, therefore no earth leakage, so your reading can only be due to you doing it wrong.

 

[applesandppears]

thanks

its a large house and couldn't access all areas today. Though if i can't access everything surely a test between live conductors and earth is acceptable?

But why would this be so low? how do PIR soft tests give out acceptable readings with connected components?

If this was a PIR it would fail miserably?

 

[Geordie Spark]

Hello All,

I am to install some extra sockets for a customer on a relatively new build.

The insulation resistance test.

I tested at 250VDC between line conductors connected and earth and obtained a reading of 1.10 ohms (not megaohms)

Does this reading seem likely that a piece of equipment has not been disconnected?

Any thoughts?

Aye, My thought is that maybe you should be in the Trainees' Section.

 

[applesandppears]

thanks

A load connected would cause a low resistance (going through the component)

As indicated in GN3 an acceptable method if you can't connect equipment is to test between live conductors (live and neutral) connected together and earth.

If i did this how can it be so low. This is so stupid but i'm blank and any help would be appreciated

 

[trev]

If this was a PIR it would fail miserably?

What would you say to that question mate?
What reading would/should you expect?
What could be the possible reason/s for the low reading?

 

[funkymonkeytwo]

There goes that flat screen tv !!

 

[trev]

This is so stupid but i'm blank and any help would be appreciated

I'm working on the assumption that it's a blonde moment, we all have them at times

 

[telectrix]

he said in his OP that he linked L and N and tested to E. PME earthing, reading through supply??????? dis. circuit completely then test.

 

[applesandppears]

I would say this guys a numpty but needs a kick up the --- with some help?
I would expect a high resistance reading greater than 2 mega ohm, certainly not under 1 mega ohm?
Possible reasons for this would include damaged insulation, or a load connected.

Though my (clearly inferior!) brain can't see why is you have a live and neutral at the same potential difference going to earth then there should be a high resistance reading unless the voltage is arcing through line conductors to earth?

Shall I just stick the probes to my brain to stimulate it maybe? 1kV!

 

[applesandppears]

trev - yes it is possibly the blondest moment i've had for a few years. I'll die my hair back after i've cleared this up!

telectrix - thank you!

Considering the installation is relatively new (2004 good condition, visually) it seems very likely be that PME on the TN-C-S supply.

In anyones experience could it be damage anywhere? as this low resistance would surely cause a form of arcing on a 32A?

 

[danzor]

Neon on a spur sir?

 

[Silly Sausage]

An IR tester with a resolution of <1 ohm.

Interesting!

 

[derek preece]

An IR tester with a resolution of > 1 ohm.

Interesting!

He must be using one of those new testers given to 5wws that combine R1+R2 testing with an IR test plus Ze probably.