insulation resistance

[ericmark]

swift2, it's nothing to do with whether the cable has been at operating temperature or not.
Insulation resistance is measured between two conductors. Nicking the insulation of one, or even both, will make no difference. In fact as BAS has said you could remove the insulation completely and the conductors will still be insulated by the air gap between them. However nicking the insulation and then letting the cable get damp and dirty will allow current to flow through the dirt, which will reduce the insulation resistance.

This is spot on it's not the damage you find but where dust and moisture have gathered. In a dry house you may never detect a fault.

 

[ban-all-sheds]

swift2, it's nothing to do with whether the cable has been at operating temperature or not.
Insulation resistance is measured between two conductors. Nicking the insulation of one, or even both, will make no difference. In fact as BAS has said you could remove the insulation completely and the conductors will still be insulated by the air gap between them. However nicking the insulation and then letting the cable get damp and dirty will allow current to flow through the dirt, which will reduce the insulation resistance.

Another reason for air-spaced conductors - nothing to trap dirt & damp, and any dampness will dry out through natural ventilation and the warming effect of the cable being used.

Nothing for mice to chew on either.

I could be onto a winner here - where's the number for Dragon's Den?