I got an email today about a fire rated door that would not reliably close with the closer adjusted to provide 5 pounds of opening force. I did a post on opening force for accessibility a while back, but it’s important to note that fire-rated doors are not required to open with 5 pounds of force. This is clearly stated in the accessibility standards. Appendix A of NFPA 80 includes the following paragraph which recommends a size 3 closer for a 3′ interior door. The spring size on most newer closers is usually adjustable in the field, and some LCN closers include a gauge which indicates the spring size as you’re adjusting the closer.
A.22.214.171.124 Adequate spring power is essential for hydraulic door closers to close a fire door with sufficient force to overcome the resistance of the latching mechanism. However, too much spring power causes opening resistance and makes it difficult for the handicapped, the infirm, and young children to open doors. Closers are classified in sizes from 2 to 6, with an increased closing force for higher numbers. Generally, a size 4 minimum closer should be used on exterior fire doors and a size 3 minimum closer should be used on interior fire doors. Door widths greater than 31⁄6 ft (0.97 m) exterior and 31⁄3 ft (1.02 m) interior, parallel or single lever arm applications, and abnormal air pressures usually require an increase to the next size. A combination of these factors could necessitate an increase of two sizes. Individual manufacturer recommendations should be consulted. Spring hinges should be adjusted to achieve positive latching when allowed to close freely from an open position of 30 degrees.
Photo courtesy of LCN Closers.