Insulation resistance low

[sidekick]

Although insulation resistance of 26.9 ohms on a ring circuit and 22.5 ohms on a light circuit are with in limits, these are still low. What is the easiest way of finding and correcting the cause of the low reading?

 

[Des 56]

Before commenting
Is the wording in your post correct ?

 

[sidekick]

Sorry, Slip of the typing fingures. For Ohms please read Mega Ohms

 

[Des 56]

Sorry,but another question

Is this a hypothetical situation or are you thinking of finding and attempting to increase the readings on your installation

The insulation test result should be the whole of the installation with all circuits tested together
The reading should be one reading for all circuits



They are satisfactory readings for an installation
The comparison with readings that may be 200+ cannot be made because each installation has different equipment connected and results vary

Why do you think there is lower than expected readings ?

 

[jjjinx]

Des, isn't that for new installations where the supply isn't connected yet mostly, correct me if I'm wrong please?

I tend to test the circuits separately and given readings like that you need to take into account the age of the installation, whether theres any sign of vermin infestation or just plain old bad connections.

If its new wire that you've just pulled through then you may well have a problem as it should have exellent readings.

 

[Risteard]

Des, isn't that for new installations where the supply isn't connected yet mostly, correct me if I'm wrong please?

The Regulations and guidance refer to testing the installation as a whole, or if this is not practicable then the individual distribution boards as a whole. So I would say no, in general you should avoid insulation resistance testing the circuits individually and do the whole installation in one go where practicable.

Otherwise you will need to consider the effect of the resistances in parallel.