I’ve received this question a couple of times lately…What is the maximum holding force allowed for an electromagnetic holder (or other automatic-closing device)?
Automatic-closing doors are fire doors which are held open under normal operation, and release automatically during a fire to allow the door to close and latch. An automatic-closing door will typically be equipped with either a) a door closer and a wall- or floor-mounted electromagnetic holder, or b) an automatic-closing unit which incorporates the closer and electronic hold-open into one product.
NFPA 101 – The Life Safety Code, requires automatic-closing doors to be able to be closed manually, but the code does not include any prescriptive information to define what an acceptable amount of manual force would be. The NFPA 101 Handbook states: “The manual method might involve tugging on the door leaf to cause its release. Therefore, magnetic devices with significant holding forces that are not easily overcome by a deliberate tug on the door leaf cannot be used.”
But what’s a “deliberate tug”? This might vary from one AHJ to the next, and there’s a fine line between having enough holding force to overcome the closing force of the closer and keep the door in the open position, and still being able to close the door manually with a tug. When I was working in the Boston area, one of the end users used electromagnetic locks with a 600-pound holding force to hold open fire doors. For their application – high-traffic facilities open to the public and prone to vandalism – it was important for the facility to maintain control of the position of the doors. But they certainly couldn’t be closed manually with an average person’s tug.
I did some digging, and I think I found an answer that at least helps to establish a guideline – in the BHMA standard A156.15 – American National Standard for Release Devices – Closer Holder, Electromagnetic, and Electromechanical. In this standard, there are several references to a hold-open intensity between 10 lbf and 40 lbf:
5.3.7 Adjustable Hold-Open Intensity Test
Setup: Mount door closer for 90 degrees of hold-open.
Test: Open door until closer engages hold-open. The force required to manually release the door from hold-open shall be between 10 lbf (44 N) and 40 lbf (178 N). (Not applicable for free swinging models.)
Anybody disagree with a 40-lbf maximum?
I’ve been so busy that I forgot to wish iDigHardware and our community a Happy 8th Birthday! It’s hard to believe that there has been something door-related to write about every weekday for the last 8 years – and I haven’t come close to running out of topics.
If you have questions or topics I haven’t addressed yet, feel free to leave a comment or drop me a line any time.
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