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High PFC

Hello,
I’m looking for help interpreting readings at a single-phase domestic CU, TNC-S. V= 241.6
Ze = 0.06Ω, main switch open, main earth disconnected.
I’ve taken the PFC readings twice now.
  1. PEFC = 2.2kA, PSC =4.0kA

  • PEFC = 2.7kA, PSC =6.0kA

These readings were from the supply side of the closed main switch with main and supp. earth connected. I took one set of PSC readings direct from the (6kA) RCBO’s of which the highest was 5.9kA.
Seems a large difference for a combined earth and neutral.
Main fuse is BS1361 type 2 so no problems there but before I spend £300 plus for 10kA breakers am I missing something here?
Thanks for any comments,

Pete


Parents
  • If Ze = 0.06 Ω, then at 241.6 V, PEFC = 4.03 kA so I don't know where the 2.2 kA value comes from. With a TNC-S system, PEFC should of course equal PSSC because the route is the same except between the service head and the DB.


    Were you using the same method for both readings? (2-lead v 3-lead)
Reply
  • If Ze = 0.06 Ω, then at 241.6 V, PEFC = 4.03 kA so I don't know where the 2.2 kA value comes from. With a TNC-S system, PEFC should of course equal PSSC because the route is the same except between the service head and the DB.


    Were you using the same method for both readings? (2-lead v 3-lead)
Children
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