What value

[Farmelectrics]

Ok so we no that for are insulation resistance tests 1 M ohm is the acceptable value well greater than that is but how do work out say for a 6 amp b type breaker how low would your reading have to go before it takes the breaker out

 

[Richard Burns]

Just think that if a reading of 0.007 Mohms is the value to trip a 30mA RCD then the resistance values to trip an MCB that requires about a thousand times more current will be a thousand times smaller.

 

[Zebra Stripe]

Come on, you've got nearly 2000 posts - are you asking what insulation resistance value would one expect to measure for a 6amp B type MCB to disconnect? Disconnect in what time scale? - geological??

 

[Lucien Nunes]

but how do work out say for a 6 amp b type breaker how low would your reading have to go

I am increasingly worried by the reluctance of electricians to use Ohm's law because similar questions keep popping up. Maybe there is a whole generation of them out there who don't know that voltage, current and resistance are somehow related. Like a whole generation of butchers who don't realise that meat comes from animals.

R=V/I.
EN60898 MCB should trip within 1 hour at 1.45In
R=230/ (1.45*6)
=26Ω

Or for the multiplicationally disinclined: 0.000026 MΩ.

 

[Farmelectrics]

Thank you Lucien