high pfc reading

[simbin]

can anyone out there throw up any ideas as to why i got a high pfc reading of 15.2 ka on a domestic installation??

 

[IQ Electrical]

can anyone out there throw up any ideas as to why i got a high pfc reading of 15.2 ka on a domestic installation??

A low Ze perhaps?

 

[Amp David]

Thats some low Ze reading

 

[IQ Electrical]

What was Zs at the consumer unit?

 

[simbin]

zs at consumer unit came up at less than 0.01

 

[IQ Electrical]

Well there's you answer, it's that chap Ohms again!

Your Zs is probably so low as a result of a low Ze plus parallel paths from protective bonding conductors.

If your consumer unit is to BS60439-3 or BS5486-13 and you have a BS1361 fuse at the DNO supply then you can use 16kA as the short circuit rating of your protective devices.

 

[simbin]

iq i thank you!

 

[Deleted member 9648]

I've never come across a PSC/Ze anything like that on a domestic...are you sure your meter is reading correctly?

 

[Sparky Ninja]

I've never come across a PSC/Ze anything like that on a domestic...are you sure your meter is reading correctly?

Same here.

Mathmatically the numbers make sense, but theoretically, on a domestic, those numbers dont seem plausible.

Is the supply transformer in the basement or something?

 

[IQ Electrical]

I tested a caretakers house recently where the DNO transformer was literally in his garden inside a metal cage, that had a rather large PFC too!

Our test meters are pretty poor at measuring such miniscule values of impedance so where accuracy is imperative, a known resistance can be incorporated into the circuit (R2 lead for example) to lift the test meter into it's sweet spot.
Another way is to use the transformer impedance if you can read the rating plate.

 

[ezzzekiel]

Same here.

Is the supply transformer in the basement or something?

lol lol

 

[gamblor6]

ive come across this, can you take the 1361 16ka as the max? surely the 6ka 60898s are first to come in to contact with the fault. plus parallel paths surely are removed when testing for ZE. any info on this would really help.

 

[IQ Electrical]

ive come across this, can you take the 1361 16ka as the max? surely the 6ka 60898s are first to come in to contact with the fault. plus parallel paths surely are removed when testing for ZE. any info on this would really help.

Check out BS60439-3 UK Annex ZA.

Parallel paths removed for Ze but should be present for Zs at the cu and for PFC

 

[gamblor6]

nice one mate just looked it up an it checks out

 

[IQ Electrical]

nice one mate just looked it up an it checks out

It's a good one to remember, but only applies in domestic situations with single phase supply, BS1361 supply fuse of 100 A or lower.