PFC Reading

[simbin]

I did a test yesterday on a new build i've been working on & got a reading of 4.8 kA for PFC. Any ideas why such a high reading, i was expecting lower. Ze was 0.05

 

[Darkwood]

I can only assume the substation is very close hence the very low resistance as well as been a tncs at a guess, dont worry about it your mcb's will be 6k or 10k rated so no further measures need to be taken unless your on 3ph.

 

[simbin]

all breakers are 6k, single phase.

 

[Darkwood]

all breakers are 6k, single phase.

Sounds ok to me then, for future ref if it was above the breaking capacity of your fusing devices then they would either need replacing for higher rated if this cant be done then a device installed upstream (e.g. hrc fuse) which usually have breaking capacities between 16k and 80k.

 

[andekoch]

I did a test yesterday on a new build i've been working on & got a reading of 4.8 kA for PFC. Any ideas why such a high reading, i was expecting lower. Ze was 0.05

Why were you expecting a lower value? V=IR so 230V/0.05ohms = 4.6kA and 240/0.05=4.8kA so this is the reading I would expecting for so low a Ze.

As long as this is lower than the mcb rating you are ok, as said current mcb's are generally 6kA. The problem is with old wylex wired fuses which are generally between 1 and 3kA (I think although not concentrating too much right now) depending on type and as this is generally not easy to determine you have to assume they are the lowest ie 1kA so a problem which neds to be recorded and pointed out to the customer.