r1 + r2 calculations

[ohthatshowyoudo]

ANY HELP ON THIS LADS APPRECIATED!!
ok haveing tested a 230v 50hz circuit 100mtrs protected by (mcb 16a type c max ZS 1.44) (20a contactor) feeding (4 x 400w sodium floods)... the readings were as follows ..(cpc r1+r2 = 1.47ohms) Ir=>1999 (Ze = 0.01ohms) pfc 6.00 ka/ are my calculations correct in checking shock risk.... Zs = Ze+r1+r2=ohms so Zs= 0.01 + 1.47 = 1.48ohms over so fails..
i also wanted to check the design calculation for this circuit and my mind is frazzeld as to what table and page in regs i can find the r1 + r2 milohms/per mtr calcs for 6mm swa

any help plz

 

[KEVINDOE]

Hi,
Are you able to take a Zs reading with your meter ?

 

[Electricalserv]

How can you have a ze of 0.01ohms and a pfc of 6 KA?

 

[topquark]

I thought it was a "wind up" so ignored it! Sorry if it's not.

 

[ohthatshowyoudo]

Hi sorry about the confussion but yes these were the readings i took and i should have noted the if = Uo-ze was not correct i have just started testing so was puzzled by these results. and wanted to start from scratch and calculate the design from installed equipment. i will be doing another earth loop at at distribution. and yes i am able to take Zs at end of circuit but wanted to get full understanding of readings i have so far... again sorry for my lack of knowledge but i am new to this game and would like help.

 

[KEVINDOE]

I think your pfc would be 23Ka if your Ze is correct at 0.01 ?

 

[Sparky Ninja]

If=Uo/Ze

Zs=Ze+(R1&R2)

Are you carrying out the Ze correctly?

 

[morph]

pfc could be a value other than 23KA , pefc would be 23KA though

 

[topquark]

I think your pfc would be 23Ka if your Ze is correct at 0.01 ?

With 230V nominal voltage that's correct JemmaJones.

 

[topquark]

pfc could be a value other than 23KA , pefc would be 23KA though

Picky

 

[morph]

Picky

ha ha
was a bit , got to be done to keep alert from time to time

 

[Sparky Ninja]

pfc could be a value other than 23KA , pefc would be 23KA though

PFC can be 23KA, unless PSC is greater than PEFC

 

[ohthatshowyoudo]

Hi jemma jones
i will be looking at testing circuit again and getting new results. but please can you advice on the correct calculation for compliance and correct table for the shock risk so i can do design calculation from chair..... then when i have correct confirmed results i can cross referance these results.. at the moment i am in the dark the installation has been designed and they have not provided any test results or schematics. i am just struggling finding the r1 + r2 values for 6mm swa and the temp values for correction

 

[morph]

PFC can be 23KA, unless PSC is greater than PEFC

yes , thats why i said "could"

 

[topquark]

ha ha
was a bit , got to be done to keep alert from time to time

Must admit to doing the same with those that should know better ... I think the main thing there was they had there collective head around how to calculate what the PFC (PEFC) was. At least JemmaJones did.