Wetroom Store - Network Wetroom Suppliers
This official sponsor may provide discounts for members

Discuss PFC test in the Periodic Inspection Reporting & Certification area at ElectriciansForums.net

S

solavie

Welcome to ElectriciansForums.net - The American Electrical Advice Forum
Head straight to the main forums to chat by click here:  American Electrical Advice Forum

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
 
CK Tools :) The professionals choice when it comes to Electrical Tools
This official sponsor may provide discounts for members

old dog

-
Arms
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
 
S

solavie

  • Thread Starter Thread Starter
  • #5
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.
 
S

sparkswillfly

  • Thread Starter Thread Starter
  • #6
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

-
Arms
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
 
S

solavie

  • Thread Starter Thread Starter
  • #8
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.
 
I

iceman

  • Thread Starter Thread Starter
  • #9
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
 
Last edited by a moderator:
G

Guest123

  • Thread Starter Thread Starter
  • #10
Hi Iceman.

What was the Ze reading you had??
 
I

iceman

  • Thread Starter Thread Starter
  • #11
Ze 0.05 ;-)

Ze 0.05 cheers
 
Last edited by a moderator:
G

Guest123

  • Thread Starter Thread Starter
  • #12
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
 
I

iceman

  • Thread Starter Thread Starter
  • #13
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???
 
G

Guest123

  • Thread Starter Thread Starter
  • #14
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.
 
I

iceman

  • Thread Starter Thread Starter
  • #15
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???
 
Last edited by a moderator:
Hi.

When you said mcb tripped, did you actually mean it physically tripped or the word " trip " came up on the screen, I just brought a 1552, having some teething problems, if you do not have a good connection during the " test time " it will come up trip, try again using clips or a better physical connection.
 
A

Andywyatt

  • Thread Starter Thread Starter
  • #17
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???
The breaking capacity of the MCB has to be greater than the PFC of the installation.
Yes you record your pfc and Ze of forms
Andy
 
Last edited by a moderator:
Z

zupos40

  • Thread Starter Thread Starter
  • #18
The breaking capacity of the MCB has to be greater than the PFC of the installation.
Yes you record your pfc and Ze of forms
Andy
Hope you do not mind but your statement is only partially correct.

With reference too G.N.3 if the Consumer unit complies with BS 5486-13 or BS EN 60439-3 and the consumer unit is supplied through a type 2 fuse to BS 1361:1971 rated at no more than 100A. It also states that the current rating of the devices do not exceed 50A.

I investigated the above statement and found that all CCU to BS EN 60439-3 are type tested using 16kA fault current, also main switch is tested as well, both closing and opening underfault whether C.B are 3kA 6kA or 10kA.

With reference to the BS1361 type II 100A cartridge fuse that it 'let through energy' (thermal energy that could cause damage to the cable insulation) which is 27,000 A2 S ( 2 represents squared) is less than the let through energy that 6kA mcb can withstand which is 29,700 A2 S, so the fuse will melt before damage can occur to Circuit Breakers thus complying with Reg. 434.5.1

So as long as K2S2 (2 representing squared) of the smallest conductor feed from the C.B. must be greater or equal to I2t (A2s) of the C.B. Reg 434.5.2

See page 76, 77 BS7671:2008.
 
Last edited by a moderator:
M

mikeymoo

  • Thread Starter Thread Starter
  • #19
If your using the probes to do the zs test, then use the croc clips instead. The smallest of movements whilst doing this test with the megger will display trip. If its rcd protected. use all 3 leads and plug red cable into no trip port on the side.
 
Last edited by a moderator:

ian.settle1

-
Mentor
Arms
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.
The MCB will tell you what short circuit current it will take no need to test it.

This is why before designing a installation you need to know the Ze and thus the PFC so as to make sure the correct MCBs or other protecive devices are fitted as if you fit 6KA MCBs and the PFC can be greater then if the MCB trips it may be damaged and need replacing.
 
W

wire the world

  • Thread Starter Thread Starter
  • #21
hi guys testing pfc on a tn_s systemgot ze = 0.09 doing the calculations means i have a pfc ov 24ka ish is this correct?????? mant thanks:cool:
 
M

m4tty

  • Thread Starter Thread Starter
  • #22
230/0.09 equals 2555.55555 so 2.555ka or 2555 amps so 6000A Breaker is fine
 
Wetroom Store - Network Wetroom Suppliers
This official sponsor may provide discounts for members

Reply to PFC test in the Periodic Inspection Reporting & Certification area at ElectriciansForums.net

SuperlecDirect - ElectriciansForums.net Electrical Suppliers
This official sponsor may provide discounts for members
Top Bottom