What if a circuits Max Zs is exceeded but the circuit is protected by an RCD?

[DefyG]

Could just be down to the RCD. Always find a difference in Zs before and after the RCD.
Measured one the other day 0.25ohms before the RCD, 0.85 ohms after the RCD resulting in a higher than expected Zs for the circuit.

 

[willy fixit]

By-pass the RCD and measure again! Or - r1 + r2 + Zdb (Ze)

 

[Zdb]

How much higher is slightly higher?

If only slightly then you may find that the Zs is still within the maximum permitted values stated by the manufacturers' instructions / data.

 

[Zdb]

Deleted

 

[Bobster]

0.1ohm is still likely in tolerance if you can alter the cmin factor a little.

Or look at manufacturer data for the MCB. BS7671 is sometimes overly cautious with the values it uses.