Insulation resistance

[pushrod]

If insulation resistances get too small, and before it goes bang, do you get milliamps leaking into earth and if so at what sort of MΩ does this start to happen?

 

[davelerave]

0.5 megohm would be 1/2 a milliamp -leakage can accumulate on paralleled circuits and electronic ballats etc.


eventually trip an rcd if circuit is protected


water heating appliances can leak much more if not rcd protected

 

[pushrod]

Doh!!! Hadn't thought of actually calculating it.

cheers

 

[davelerave]

never did myself til u mentioned it

would be great if i could remember all the theory when i'm actually working

 

[pushrod]

never did myself til u mentioned it

would be great if i could remember all the theory when i'm actually working

you should have kept quiet i thought you had cleverly done 240 V ÷ 500,000 Ω =0.48mA

Do you know how the paralleling up of circuits increases earth leakage?

 

[davelerave]

paralleling reduces IR-therefore increases earth leakage


1megohm in parallel with 1 megohm = 0.5 megohm

 

[pushrod]

paralleling reduces IR-therefore increases earth leakage


1megohm in parallel with 1 megohm = 0.5 megohm

cheers , was just wondering if there was something else in addition to that, that i was missing

 

[davelerave]

the overal installation l IR will reduce when circuits are added -and of course there's appliances on top of that

there's varying degrees of low/high IR and faults on circuits obviously as well