Quite a few questions about battery back-up were asked during my webinars last week, so I think this is a good time to clarify this issue and also to get some feedback from you. Here are the Quick Questions for today’s post:
Is it acceptable by code to provide battery back-up for an electromagnetic lock? What about other types of electrified hardware?
This is an issue that is not specifically addressed in the model codes, so the answers depend somewhat on the interpretation of each Authority Having Jurisdiction (AHJ). I am not an AHJ, so this is the way I’m interpreting the code requirements but someone else may have a different view. I’d love to know what you are hearing in the field, and if you’re an AHJ, please weigh in by leaving a comment!
This topic was addressed in my very first Decoded column for Doors & Hardware magazine (more than 100 columns ago!). The article talks about NFPA 72 – Fire Alarm Code, and how it addresses electrically-locked doors. The code has been updated since then, but I think the intent remains the same. From the 2019 edition of NFPA 72:
21.10.3* Secondary power supplies of fire alarm control units shall not be utilized to maintain means of egress doors in the locked condition unless the fire alarm control unit is arranged with circuitry and sufficient secondary power to ensure that the means of egress doors will unlock within 10 minutes of loss of primary power.
A.21.10.3 A problem could exist when batteries are used as a secondary power source if a fire alarm control unit having 24 hours of standby operating power were to lose primary power and be operated for more than 24 hours from the secondary power source (batteries). It is possible that sufficient voltage would be available to keep the doors locked, but not enough voltage would be available to operate the fire alarm control unit to release the locks.
According to the model codes, electromagnetic locks are required to unlock upon loss of power; mag-locks released by a sensor are also required to unlock upon fire alarm activation. My interpretation, based on what I’ve heard from AHJs and others, is that if an electromagnetic lock has back-up power, it must be the same back-up power that powers the fire alarm system.
In my opinion, this would not apply to access-control doors that allow free egress at all times. For example, if a door has a reader on the outside and a lever handle or panic hardware that allows egress, independent battery back-up for the electrified hardware (separate from the fire alarm system) would have no impact on egress. But for mag-locks, delayed egress locks, or controlled egress locks that have back-up power, the same system should provide back-up power to the fire alarm. This ensures that the doors will release upon fire alarm activation, as required by the model codes.
Remember, some AHJs or local codes may have different requirements. Some AHJs do not allow battery back-up for electrified hardware AT ALL, and some don’t even have it on their radar or check to see how the system functions. It’s always best to get approval from the local code officials before the system is installed.