Generators and E-stops

On a recent project, we have had some back and forth with the Louisiana State Fire Marshall (SFM) in regards to the requirements for an E-stop (Remote manual stop station). The following is a summary of occurrences.

The 2016 NFPA 110 requirements are as follows:* 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 in the premises where the prime mover is located outside the building. The remote manual stop station shall be labeled.

A. For systems located outdoors, the manual shutdown should be located external to the weatherproof enclosure and should be appropriately identified.

Due to the access not being restricted to the fence (public area), installing an emergency stop button with general public access was a concern. My first idea was to install an emergency stop at the ATS which is located inside the equipment room. The fire marshal didn’t agree. In the event of a catastrophe, locating a safety shutdown behind a locked door wasn’t considered as meeting the intent. Intent isn’t always written in a code book…

Reading further into the appendix section, the emergency stop only had to be located external to the weatherproof enclosure. Since it was an large open area on the second floor of a platform, my interpretation was that as long as the emergency stop was on the exterior of the sound proof enclosure, we were set – Right? Not exactly… The first plan was to locate the emergency stop on the first floor of the structure (generator was on the second floor of an open structure), approximately 6 feet horizontal and 7 feet below the generator location. The inspector didn’t agree on the proposed location.

To minimize all of the back and forth, I sent the inspector a drawing identifying a location at the very front of the structure approximately 30’ away from the generator and on the first floor. The inspector approved of the plan and everyone lived happily ever after – right? Almost… During the installation, the contractor installed an E-stop containing a normally closed contact. The wiring diagram for adding an E-stop to a Cummins generator identifies a normally open contact. Please keep this in mind when identifying emergency stop stations. A vast majority of the selection contains normally closed contacts.


In the event that someone figures out that there are some  generator controls at an automatic transfer switch, I’d like to offer a disclaimer that the controls at the auto transfer switch are designed to be used when the generator is in AUTO mode. If you can put the generator in RUN mode and still shutdown the generator remotely at the ATS, then you do have a remotely located emergency stop station. If the ATS controls do not stop a generator in RUN mode (which is likely the case), then you’ll have to add an emergency stop circuit directly wired to the generator.