The standard door closer operates by using fluid in a rack-and-pinion spring-loaded piston mechanism. When the door is opened, the arm assembly rotates a geared spindle that moves a gear driven piston, compressing the main spring and forcing fluid into the area where the piston originally was. The result is the door closer builds up spring pressure as the door is opened. The farther the door is opened, the greater the amount of spring pressure. The location of the door closer and arm assembly determine the maximum opening.
NOTE: Most door closers are pre-loaded during installation, so the closer exerts spring pressure even when the door is closed. This way there is sufficient pressure to close and latch the door even though the arm assembly cannot rotate any further.
When the opened door is released, the built up spring pressure moves the gear-driven piston, rotating the geared spindle and causing the door to swing back towards the closed position. At the door open position, the fluid is on the side of the closer cylinder where the piston has moved out of and the expanding spring pressure wants to return the piston. When the door is closed, the spring has expanded, the piston is at the rest position and the fluid is on the spring side of the closer body. When there is sufficient spring pressure, the door closes and the lock's latching mechanism engages, securing the door.
The fluid in the door closer is designed to control the speed at which the closer arm assembly rotates during opening and closing. Without the fluid, the spring would expand rapidly and the door would slam. There are several types of door closer fluid. Most door closer fluids have the consistency of lightweight oil. Depending upon the manufacturer and the application, door closer fluids are available for extreme weather conditions, and fluid types can vary by the function of the door closer.
In a closer where the door is closed, almost all of the fluid is in the area containing the main spring. As the door is opened, this spring compresses and the fluid is forced around the piston through two or more portholes into the other side of the piston. The adjustable valves control the flow of the fluid. Depending upon the door closer; there can be a closing valve, latching valve, backcheck valve, delayed action valve, etc. The location of each channel's openings and the valve determines the functionality, as the piston moves from the closed to the open and back to the closed position.
Each valve controls the rate at which the fluid flows from one side of the piston to the other. The fluid flow rate controls the rate of spring expansion. Controlling the fluid flow permits the closer to operate smoothly.
The functionality of the modern rack- and-pinion type of door closer operates on average at approximately two-thirds efficiency. This means that for every three pounds force exerted on a theoretically frictionless door, only about two pounds of force affects the opening and closing. In the real world, when we add in butt hinges and door alignment friction, rack and pinion door closer efficiency drops even more.
The reason that the efficiency of the door closer is important is that federal and state laws determine the maximum force permitted for operating a door. Years ago, there was a federal law of eight pounds for operating an exterior door. The federal law was struck down; however, a number of states had and still have their own accessibility laws. Most require a minimum of eight pounds.
California Building Code (CBC) 2001 and 2007 in section 1133B.2.5, can be read as the effort to operate an exterior door shall not exceed 5 pounds. However, this code section does not appear to address an exterior entrance where multiple door leafs are provided at one location. Check with your local authority having jurisdiction (AHJ) before installing a door closers on an exterior door.
Interior doors have a five-pound minimum opening force required by federal law. The exception is interior doors labeled “in the means of egress” must close and latch. National Fire Protection Act (NFPA) 101 paragraph 18.104.22.168.5 states that a door must have 30lb/sf. maximum opening force to put door in motion and 15lbsf. maximum opening force to reach required width. However, California Building Code (CBC) places a maximum of 15 pounds opening force. The interior doors that are not “in the means of egress” must be five pounds.
Important: The operating force restrictions are tested on the moving door at approximately three inches from the closed position and measured 30 inches from the hinge.
If you are from a state that has different operating requirements, please let me know and I will include the information in the magazine. Thanks.
To improve closing efficiency, Norton introduced the Cam Action Door Closer. The Norton 2800ST Series Grade 1 Door Closer uses a cam lobe operating mechanism. Unlike the gear-driven piston type closer, the cam lobe closer, according to Norton, “is more efficient, between 70 and 80 percent, providing up to four pounds closing force for a five pound opening force.” The Norton 2800ST series is equipped with a size one through six adjustable power spring . The spring adjustments can provide operating force sufficient for any required pound setting.
The Norton 2800ST Series Cam Action Door Closers are designed to operate on maximum door weight of 250 pounds. For interior door applications, the maximum door width is 54 inches.
The Norton Cam Action Closers uses an egg-shaped cam lobe that takes the place of the geared spindle. There are two spring-loaded pistons, one on each side of the cam. The stronger, main spring is compressed by a piston as the door is opened. The second piston has a light spring that keeps the piston's roller against the cam even in the open position. Fluid flow controls the speed of movement.
The cam rotates slightly less than one half of a revolution, giving a maximum door opening for standard applications of not much more than 110 degrees. This results in about one-half inch total movement of the main piston. This is approximately one-third the distance traveled by a standard rack-and-pinion type door closer piston. To accommodate this shorten closing cycle, the cam action door closer operates using more accurate fluid control.
The spindle has an internal spline to time the arm instead of an external square or hex. A splined spindle offers more positional options for preloading the closer and allows for lower setting when the door needs to meet low opening force requirements such as American's with Disabilities Act (ADA). The purpose of pre-loading a closer's arm is to provide sufficient spring pressure at the end of the closing cycle for the door to close and latch or to keep the door closed when there is no latch mechanism.
The Norton 2800ST Series Grade 1 Door Closers are designed to operate by using a slide track mechanism. Unlike a standard arm assembly having a main arm and secondary arm, the slide track mechanism requires only the main arm. The slide track replaces the secondary arm.
The Norton cam closer uses two different styles of slide tracks. One is designed for the pull side of the door. The mounting holes in this track are on the sides so it can be mounted on the face of the frame. The other slide track is designed for the push side of the door. The mounting holes are in the groove of the track so it can be mounted to the bottom of the jamb. For either application, the closer is always mounted to the door and the slide track is always mounted to the jamb. Slide tracks are available with or without Hold Open.
For Pull Side Applications, the track is mounted onto the face of the jamb with the screw holes located at 1-5/8 inches above the bottom of the jamb. A minimum ceiling clearance of two inches is required above the top of the door.
Mounting the Norton 2800ST Series Door Closer requires more exact measurements. For example, there are four maximum degree of opening angles (85, 90, 100 and 110 degrees), each having a different distance from the center of the hinge or pivot. The distance the slide track is from the hinge/pivot edge of the door determines the maximum opening of the door.
I was invited to the installation of the Norton 2800ST Series Cam Action Door Closer onto a solid core wood door requiring a 100-degree maximum opening. This chosen door was in a high traffic corridor. According to the instructions, a 100-degree maximum opening locates the first hole for mounting the track at 5-1/8 inches from the centerline of the hinge. The installation provides information on installation up to a maximum of 110 degrees. For opening requirements greater than 110 degrees, contact the Norton factory.
For this installation, sex bolts were used to secure the door closer onto the solid core door. Because the door's core appeared to be compressed saw dust, using wood screws was not an option.
Four 3/8-inch diameter holes were drilled in order to sex bolt the closer body to the face of the door. We used four ¼-inch machine screws and metal sex bolts.
The slide track was mounted using a 13/64” (#7) diameter drill bit and a 1/4-20 tap to thread the screw holes in the 18 gauge metal jamb.
Once the closer and slide track were mounted onto the door, the arm was attached to the splined shaft. The splined shaft was inserted into the top of the closer having a five degree pre-load on the arm at the closed position. Pre-loading helps the door latch and close.
The final step is to attach the arm assembly to the slide block in the track assembly. Slide the arm stud into the slide block and secure by pushing in on the retainer clip until it is flush with the slide block.
Adjust the operation of the closer by setting the closing power control using a 5/8-inch diameter socket or wrench. Power increases in a clockwise direction. Once the door closes with sufficient force, adjust the closing cycle using the latch speed valve to (increase in a counterclockwise direction) to control the door speed in the Latch range (final five degrees). Then adjust the closing speed valve to (increase in a counterclockwise direction) to control the door speed in the Sweep Range (from opening to the final five degrees). Both the latch speed and the closing speed valves are adjusted using a 4mm hex wrench.
Note: Never back the adjustment valves all the way out. The oil will pour out and the closer will no longer function properly.
Test the operation of the door closer using a door gauge. To test the operation of a door closer, mark an “X” onto the closing face of the door at thirty inches from the hinge. Begin to measure the closing force at about six inches and check the force at three inches from the closed position. Make sure this adjusted and measured force required meets your local authority having jurisdiction and code requirements.
The Norton 2800ST Series Cam Action door closer is equipped with adjustable backcheck . The purpose of the backcheck is to slow and eventually stop the opening of the door in the last 10 degrees or more of the opening cycle. A backcheck should never be used in place of a proper doorstop. Remember: Never close a backcheck valve completely as this can result in damage to the door closer and/or hardware.
If the door closer slide track is equipped with optional hold open, it is possible to adjust the hold open power. This is accomplished by turning the adjustment shaft in the end of the slide track nearest the hinges. The provided 9/64-inch hex wrench is rotated clockwise to increase holding power.
A plastic cover comes standard with the Norton 2800ST Series Cam Action Door Closer. For security applications, a metal cover will be an available option. Contact the Norton factory for details. These door closers and slide tracks are available in all Norton standard and custom painted finishes. Contact the factory for availability of plated finishes.
For more information, contact your local locksmith wholesaler or Norton Door Controls, 3000 Highway 74 East, Monroe , NC 28112 . Telephone: 800-438-1951. Fax: 800-338-0965. Web Site: www.nortondoorcontrols.com.