2391-10 advice please

[ICE]

Hi All


Call me thick and poke me in the eye, I know this but for some reason can not drag the answer from the depths of my BRAIN.


how do I determine the max Zs for a 300mA RCD ? (what is the calc)

Cheers in advance


Mr Thicky

 

[iceman]

RA X I^n = >50 v touch voltage


50
----- = I^n
RA





50
---- = 0.3 so maximum will be 300mA
166


50
---- = RA
I^n


50
---- = 166
0.3


i think its something like this

someone please correct me if im wrong

 

[ICE]

is it not 50÷I∆N

50÷0.3=166Ω for a 300mA RCD

 

[iceman]

the equation is in the exam succes book 2391 states in there RA x I^n <50

50
--- = RA
I^n

50
--- = 1666
0.3

 

[ICE]

No,

1666Ω is max Zs for a 30mA 50÷0.03=1666Ω

166Ω is max Zs for 300mA 50÷0.3=166Ω

I Think

 

[iceman]

the maximum Zs for 300 mA RCD is 167 ohms