PFC Calcs

[telectrix]

readings are fine. the 22.8Mohm is probably due to appliances still being plugged in.

 

[IQ Electrical]

If you're measuring PFC then forget Ohms, it won't be a true Ze value as bonding should still be connected.

Record the highest value as PFC.

On Ze you have to have parallel paths removed and you are measuring between line (s) and earthing conductor, highest value recorded.

Zs=Ze+(R1+R2)

 

[soar]

Your Ze is the test done with your main earthing conductor removed and as IQ note above you clip the disconnected earth and the LINE conductor on the supply side of your isolated switch and take the ohm reading

Your prospective earth fault current (PEFC) and your Prospective short circuit current (PSCC) is tested with the earth conductor re-connected to the MET. PEFC is done with clip to MET then to LINE and the Ka rating is taken. The PSCC test is between LINE/NEUTRAL and the Ka is taken, which ever is the highest is the value you take. Note on a TNC-S the chances are thje values will be near enough the same.

The Zs value for you lighting circuit is Zs = Ze + ( R1 + R2) so the PEFC and the PSCC should not come into the equation.

Sorry am getting myself mixup, i did disconnect the earth, so the value i got is 0.36ohm, 676amps, so this should record in form4 *2 and *3

 

[soar]

readings are fine. the 22.8Mohm is probably due to appliances still being plugged in.

So i should record this 22.8 M ohm in IR,L/E column *10, in sted of >200

 

[malcolmsanford]

If the 0.36 ohms is the ohmeric Ze value with the earth conductor REMOVED then yes that is the value you put on the form.

If 0.676Ka is the highest PFC value after you have RECONNECTED your earth and tested both PEFC and PSCC current then yes that is the one you put on the form.

 

[mart8235]

So i should record this 22.8 M ohm in IR,L/E column *10, in sted of >200

are you testing 2 separate circuits? upstairs and downstairs on separate circuits? if so then record 22.8Meg on downstairs and >200Meg on upstairs in relevant boxes.

 

[Nicktric]

PEFC is done with clip to MET then to LINE and the Ka rating is taken. The PSCC test is between LINE/NEUTRAL and the Ka is taken, which ever is the highest is the value you take. Note on a TNC-S the chances are thje values will be near enough the same.

Hi Malcolm,
can I just check 3 probe set up PEFC join earth and neutral probes then probe MET and line supply side. Then PSCC Neutral and earth probes joined, probe Line and Neutral supply side?

Cheers