Reducing Arc Flash I/E At Fire Pump Controllers

Question: What are you guys recommending to reduce incident energy levels on fire pump controllers fed directly from the secondary side of utility transformers?

Answer: Can’t be done. This is a common practice but is very illegal in most cases. NEC is very specific in that overload protection (ie, overload relay) is eliminated and short circuit protection only remains. I have no idea why and I’ve had multiple fire marshals actually try to tell me that fire pumps get ZERO protection which is utterly false. In most cases the short circuit protection on the primary side is NOT sufficient to protect the branch circuit on the secondary side. And that’s the answer to your problem…short circuit protection (e.g. a MCP aka magnetic-only circuit breaker or simply a fuse) with the instantaneous trip point set below the arcing current fixes the problem and is 100% legal, and in most cases such as what you describe where it’s a huge Code violation, it also fixes that issue. READ MORE.