61009 rcbo max zs 1667ohms?

[beatboaby924y]

Doing some testing today and came across something I was hoping to get cleared up.

The maz zs of a c type 16amp 61009 is 1.44 ohms on table 41.3 however on table 41.5 it states that a 30ma 61009 under 32amp can have max zs of 1667ohms.

Would you write on test sheet maz zs 1667 ohms and that as long as result is under the 1667 then its ok? Because the recorded result I got was 1.76 ohms which fails first table but is ok in the second one. Confusing lol

Thanks in advance.

 

[Leesparkykent]

Whats the earthing arrangement?

 

[beatboaby924y]

Its a tn-s.

 

[GEOFF S]

Doing some testing today and came across something I was hoping to get cleared up.

The maz zs of a c type 16amp 61009 is 1.44 ohms on table 41.3 however on table 41.5 it states that a 30ma 61009 under 32amp can have max zs of 1667ohms.

Would you write on test sheet maz zs 1667 ohms and that as long as result is under the 1667 then its ok? Because the recorded result I got was 1.76 ohms which fails first table but is ok in the second one. Confusing lol

Thanks in advance.

Its your choice, either comply. But if you designed to meet the 1.44 then id be looking as to why its exceeded the value.

Cheers

Cheers

 

[Andy78]

What does "doing some testing" comprise ? periodic testing or initial verification ?

Using a RCD as fault protection in a TN-S would be my personal last course of action.

 

[Sintra]

What does "doing some testing" comprise ? periodic testing or initial verification ?

Using a RCD as fault protection in a TN-S would be my personal last course of action.

Exactly. On a TN system the 30mA part of the RCBO is for additional protection.

 

[Engineer54]

It seems from other threads on the same subject, that if conducting an EICR where you are testing an existing electrical installation you can, if the circuit does not comply with the current ADS limitations use the RCD's 1667 ohms as compliance (possibly with a remark being made in the appropriate section of the report). If however you are testing a new installation, then ADS requirements must be complied with whether or not an additional protection device (RCD) is provided.

Personally, i don't particularly agree with that stance as i know, maybe more than some here, just how unreliable RCD devices can be over a period of time....