Some of the points to ponder - as in regards to SCA figures are:

  • When dealing with a Multi-Customer used Transformer, and the KVA size needs to be increased a significant level (such as upgrading a 300 KVA 3.0%Z Transformer with a 500 KVA 1.2% Z Transformer), this might skyrocket passed the limits of a Series Rated system's capability (or even a system without Series Rating in place, but with MCCB's which just made the original minimum KAIC),
  • Increasingly higher Induction Motor loads at any point[s] in the system - either from other Tenants, or within the Client / Tenant of concern. Such Motors being placed in the "End Load Sides" of Series rated systems, being of 10 HP or more with highly Dynamic loads connected to their shafts, contributing a high level of SCA into the system,
  • An inexperienced or "Cut-Throat" installer whom installs equipment which is incompatable to the Series Rated system, or falls below the minimum KAIC Rating at a given point. These installs may be done by persons both unaware of the consequences and unconcerned with the results, or be installed by a person with good intentions whom is willing to try and save the Client money (not a "Cut-Throat" person!).


These are a few things to get threads started and possibly burning [Linked Image]

Like to see some feedback.

Personally, I try to use these instances in mind when designing a Client's Power System. Also am a stickler to design selectively!
Can't even count how many times I have heard questions from persons in the field asking why the Subfeeder main, or as far as the Main breaker or Main Fuse[s] tripped / blew when someone Ground Faulted a Branch Circuit. This is another thing to consider when planning a Power System's setup and equipment coordination.

Scott S.E.T.

Scott " 35 " Thompson
Just Say NO To Green Eggs And Ham!