PFC test

[solavie]

when doing a PFC test on the lighting circuit, it keeps tripping the MCB type B . Also had problem with testing the fault current where I get trip on my meter. Using a Megger MFT 1552 for both test. Any suggestion as to why.

Thanks

 

[old dog]

the meter delivers a high current for a short period of time and will trip a 6amp type b
this is normal and not a fault you can calculate or use a type c for testing purpose
then replace your type b

 

[diditrain]

Why are you doing a PFC on a lighting circuit?

 

[old dog]

Why are you doing a PFC on a lighting circuit?

i assume he meant Zs

 

[solavie]

I have just changed the consumer unit and was doing all the nornal test. I thought that I had to do a PFC test to check the MCB capacity to withstand. I am fairly new in this field.

My Other problem was the ze where I keep getting trip on my MFT 1552. I can work it out but would really know why the meter trip. I was using the 3 test lead and setting the meter on no trip as suggested by the instruction.

Cheers.

 

[sparkswillfly]

pfc and pefc is done at the cu put the dial pfc use two leads red in red socket green or black in black socket(not no trip)socket test line and neutral for pfc line earth for pefc record highest of the two the ka resault should be lower than whats on the side of the breaker

 

[diditrain]

You would measure your PFC at the point where this would be at it`s highest level. i.e. the consumer unit.
When you know this value you check to see that the installed equipment i.e. fuses/mcb`s etc, can cope with this level of fault current.
If you are measuring PFC at the circuit extremity then the value would be lower. As old dog said you probably meant Zs.

How did you connect your test leads when you were trying to measure Ze

 

[solavie]

diditrain

Connected red lead to phase, green to cpc and black to neutral at ceiling rose. Set meter to Loop No trip. Then got trip on test meter but no trip at consumer unit.

 

[iceman]

hi wile i was testin pfc and pefc i got a reading of 3.5 on a TNC-S system would this be acceptable any help would be great cheers

thts testin pssc and pefc cheers

 

[Guest123]

Hi Iceman.

What was the Ze reading you had??

 

[iceman]

Ze 0.05 ;-)

Ze 0.05 cheers

 

[Guest123]

You must be right next to a sub-station or transformer. With a Ze that low then your PFC is fine in relation to it.

Cheers

 

[iceman]

there is a way to calculate it pfc if ya got ze and visa versa i thought normaly on a tncs system the pfc is 1600ka to work out ze im i rite in sayin ohms law 230/1600 = ze 0.14 with a readin of 3.5 would i do the same thing 230/3.5???

 

[Guest123]

Hi.

Yes, if you divide Uo - 230V by your PFC of 3500A you get 0.06. Your reading was 0.05 so this ties up fine.

 

[iceman]

i just know when i go for me assesment the guys gona ask me y we test for pfc and ze do all the breakers have to fall with in the pfc value???

would i record 3500Ka on both parts of the eic cert???