pscc, pefc and pfc

[hodaire]

got a submain feeding a consumer unit, bit unsure with the pscc, pefc and pfc

pscc would be voltage / resistance of live and neutral cables plus the ze
pefc would be voltage / zs

how do i get pfc, is this just the highest of the 2 readings?

if i was fitting a 3 phase board pscc would it just be 400 / resistance of live and neutral cables plus the ze but pefc would still be 230 / zs?

 

[ezzzekiel]

pfc is the higher of pscc or pefc which would be the same on a pme

 

[zupos40]

got a submain feeding a consumer unit, bit unsure with the pscc, pefc and pfc

pscc would be voltage / resistance of live and neutral cables plus the ze
pefc would be voltage / zs

how do i get pfc, is this just the highest of the 2 readings?

if i was fitting a 3 phase board pscc would it just be 400 / resistance of live and neutral cables plus the ze but pefc would still be 230 / zs?

Pefc - Prospective earth fault current is measured between line and earth (with all bonding in place) if you have a 3 lead tester connect Green to Main earth at MET black to incomming neutral on main switch and finally red to incomming line on main switch then measure using a PFC tester on 20kA range.

Pscc - Prospective short circuit current is measured between Line and neutral - connect bothe the green lead and the black lead to the neutral, then finally the red lead to the line and again measure using a PFC tester on 20kA range.

which ever is the highest of either Pefc or Pscc are recorded on the test sheet as the PFC prospective fault current for that installation.

If you do not possess a PFC tester than do the test a described above but use an ELZ tester and calculate the both the Pefc and Pscc.


Where pefc = measured voltage L-E / measured impedance L to E

Pscc = measured voltage L-N/ measured impedance L-N

again whic ever the highest record as your PFC

 

[NoSparks]

Don't forget, "For three-phase supplies, the maximum balanced Prospective Short-Circuit level will be, as a rule of thumb, approximately twice the single-phase value."