Condition Of Insulation Of Live Parts

If your recent homebuyer / landlord report has flagged an issue for “Condition Of Insulation Of Live Parts” then you may be wondering what all this means?

Many other electricians fail to provide any real detail (or if possible, pictures) with their electrical reports. As such, it can often feel like Double Dutch to the person ordering the report. Read on for a breakdown of what this fault is, and the general causes behind it.

Give yourself a quick refresher on the basic construction of a cable before looking through this, CLICK HERE

This particular issue can be discovered one of 2 ways. Firstly, it can be visually inspected. Obviously this is simply viewing any breakdown to the insulation material of the cable. (part of an electrical report involves detailed inspection of accessible cables/sockets/switches/etc…)

The 2nd method is using sensitive test equipment, testing for something called “insulation resistance”

Insulation Of Live Conductors Readily Breaks Away

“Insulation Of Live Conductors Readily Breaks Away” would describe the issue where it has been visually confirmed.

This is a phenomenon mainly seen with older rubber insulated cables. Over years of use, current being passed through the cable and changes to the temperature have caused the rubber to deteriorate. What tends to happen, is whenever the cable is flexed (IE: a socket or switch removed), then large chunks of the protective insulation simply crumble away.

As seen above, once the insulation falls away, the live metal conductor underneath is exposed.

However this can affect more modern cable in certain instances. We have seen examples of this where the cable has got warm in the back of a light fitting (not melted), however it just makes the PVC insulation go brittle over time.

Another factor that can cause insulation to deteriorate is exposure to sun/weather. Although it would be rare to see unsheathed cores outdoors, it does happen and the inner PVC insulation will eventually deteriorate with exposure to both UV and also general harsh weather conditions.

Low Insulation Resistance Test Reading

Part of the testing for an electrical report involves testing for something called “Insulation Resistance”. In a nutshell, this test measures the condition of the insulation between whichever cables are under test.

It is tested with everything removed from the circuit (all sockets removed or light bulbs removed) as these can provide false readings on the sensitive test equipment.

The level of the “insulation resistance” is measured in Mega-Ohms, literally Millions of Ohms resistance. The cable must be over 1M Ohms minimum to pass the test (although anything lower than 2-3M Ohms would be regarded as faulty and investigated).

Low insulation resistance readings can be caused by a number of issues:

  • Extremely low readings indicate a dead (or nearly so) short between 2 of the conductors. Causes of this include physical damage to cables (rodent damage, drilled cable, melted cable), or potentially a loose wire that has caused a short. Loose wires would fall into a different category of fault as it is not related to the insulation.
  • The same issue affecting the old rubber insulated cables (where the insulation breaks away, as above) is the cause of this. It gives low readings where the insulation has failed
  • There are some other issues that can cause this: Inexperienced testers can often find a fault similar to this by not removing loads from the circuit. Everything must be unplugged or disconnected (including switches with neon lights on) as these items give false readings

How is this item Coded on a Landlord / Homebuyer Report?

This issue would almost without fail attract a minimum of a C2 – POTENTIALLY DANGEROUS issue on a Landlord / Homebuyer Electrical Report.

If the cable is in an area where the breakdown of the insulation has caused the live metal conductor inside the cable to become visible (and potentially touched) then this would be an immediate C1 – DANGER PRESENT fault.

C1 – DANGER PRESENT faults indicate an immediate risk of injury (or even potential death). If your installation has a C1 fault, your electrician should make this safe before further testing occurs. Immediate remedial works must be completed before the installation can be used.

How to repair the issue?

Although the exact repair would depend on what is found to have caused this fault. If it truly is down to poor condition of the insulation (found either via thorough testing or else visual confirmation), then rewiring the affected section (or even the whole installation) is the only real solution.

If you want to learn more about FREE 18th Edition Inspection & Testing Training then head over to Electrical Assistance where a bunch of QS electricians have started a site about the finer points of inspection & testing

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