test form

[printer]

hi, TT system rod value 85 ohms, periodic test form has box for max Zs permitted by BS 7671, has box for R1 + R2, and has box for max measured Zs so far so good. however with all bonds connected Ze at board is 20 ohms max Zs for 6A b type breaker (used to be 8ohm now 7.67ohm). So reading on lighting is 21 ohms at furthest point so i`m putting max allowed in one box as 8 ohms or so, and max measured 21 ohms what are we supposed to put in? these two readings are contradicting each other, any help gratfully received

 

[RF Lighting]

Were there any RCDs in the installation?

 

[printer]

yes

 

[flyingsparks]

With a 30mA RCD you can have a max Zs of 1667 ohms.

 

[flyingsparks]

1667 divided by max touch voltage 50V = 0.029A or 30mA

 

[printer]

so is this value we put in the max Zs permitted by BS 7671 box?

 

[flyingsparks]

if its a 30ma RCD yes.

 

[printer]

cheers flyingsparks, just found it in regs page 50 table 41.5, thank you for your help

 

[luminaire]

1667 divided by max touch voltage 50V = 0.029A or 30mA