Remote Manual Stop Stations in Emergency Power Supply Systems

Q. Our fire inspector just gave us a pink slip because we didn’t have an emergency shut off for our generators. Is this valid?

A. Yes, if the inspector is citing NFPA 110, Standard for Emergency and Standby Power Systems.  NFPA 110, 5.6.5.6 states: “All installations shall have a remote manual stop station of a type to prevent inadvertent or unintentional operation located outside the room housing the prime mover, where so installed, or elsewhere on the premises where the prime mover is located outside the building.” An appendix item at A-5.6.5.6 suggests: "For systems located outdoors, the manual shutdown should be located external to the weatherproof enclosure and should be appropriately identified."

Recently, we performed a post-mortem on multiple generators located in a single room where an exhaust silencer exploded on one generator. The explosion occurred because an accumulation of unburned diesel fuel ignited in an improperly designed exhaust system.  When the explosion occurred, the wounded generator continued to run and filled the room with 400°F exhaust. This activated the sprinkler system, which watered down all of the generators.

When the technician on duty peered through the window into the generator room, all he could see was dense smoke and water accumulating on the floor, engines, control panels and alternator. A decision was made not to enter the room, which was now over 150°F, and "electric", to try and shut the engines down at the control panels. The technician also made the decision to turn off the fuel oil supply (FOS) valve, which was fortunately located outside the generator room.

Unfortunately, he also closed all fuel oil return (FOR) valves, which immediately disabled several engine components, resulting in diesel fuel now spewing from two of the engines. The fuel mixed with the water and flowed into the floor drains — and, from there, into the great beyond where the local EPA folks become involved. The generators continued to run until the fuel supply was depleted. Eutectic valves in the FOS may have helped, but that is a story for another time.

Remote manual stop stations have now been installed (one for each generator) in the switchgear room, and staff education programs put in place for maintenance and testing protocols.

This is just one example of the 37 EPSS "points of failure" often overlooked by designers and installation contractors.

Chisholm, president of MGI Consulting, Orlando, Fla., has provided emergency power supply systems (EPSS) consulting services and education to more than 1,500 health care facilities. He serves as a member of the National Fire Protection Association's Technical Committee responsible for NFPA 110, Emergency and Standby Power Systems and the Electrical Section of NFPA 99, Health Care Facilities. He also serves as a primary emergency power consultant to the U.S. Army Medical Department (AMEDD) and the Department of Defense.

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