Pfc ??

[sivoodoo]

Hi all,

Just measured Zs at socket outlets and I get a reading of 120 ohms, also the PFC is 2A.

I take it no earthing, the supply incomer has a green cable coming out of it after the cutout, which goes no where?

Customer has ordered a PME.

Could someone explain to me the PFC result, I am currently study the 2391 at college, but am as yet to cover Fault currents.

Thanks

Si.

 

[DanBrown]

Hi all,

Just measured Zs at socket outlets and I get a reading of 120 ohms, also the PFC is 2A.

I take it no earthing, the supply incomer has a green cable coming out of it after the cutout, which goes no where?

Customer has ordered a PME.

Could someone explain to me the PFC result, I am currently study the 2391 at college, but am as yet to cover Fault currents.

Thanks

Si.

To be honest mate, you should real know that by now, if your on 2391 inspection and testing.... Its near enough basics..

Anyway..
The fault current is the amount of current that is expected to flow in the event of a fault / short. Basically to calculate this, you divide the supply voltage by your Zs value. 230 / 120 = 1.91A (2A)
That is a total complete failure lol....
It sounds like the earth as you say is missing, and the reason for 120 ohms Zs suggests that it is finding a path back to Earth.. Through ground maybe..
Its not on a TT or anything is it??.

 

[old dog]

hi is there a met block (maim earth terminal) near the board?
have you taken a ze reading?
its hard to say what the problem without more info however at a guess and
this is only a guess it looks like the main earth conductor has been removed
from the met to take a Ze reading and not been reconnected

 

[Spudnik]

If the client has ordered PME then i assume its a TT.

If it is, then ideally your Ze could do with being under 100 ohms, but i dont see it being a huge problem at 120 as this would still bring the touch voltage well under 50V.

The only time to be a little concerned is over 200 ohms.

 

[sivoodoo]

Its an old back to back house,
The supply cable enters the house in the external cellar wall and into the cutout, There is a cut off Earth cable protruding from the supply after the cut out.
The supply goes back into the wall where it reamerges into the meter in an adjoining room.
Just before the meter the supply cable splits off an earth cable to the MET.

The meter must have been moved at some point, but why there is a terminated earth coming from one part of the supply is odd.

 

[Spudnik]

Tricky.

Not sure i understand the earth cable after the cutout?

They normally come out from the service head into an MET.

Im sure you already know this so, is there any chance you can post a pic sometime?

 

[sivoodoo]

Sure and thanks for the replies.