A 4110 with AVB (advance variable back check) would be recommended. Using a SCUSH (Spring Cush) arm will also help minimize shock to all door hardware.
To correctly answer this question, we need to know how much more force is required to get the door closed. They could try turning the Rod & Shoe over (short side of shoe towards the hinge), or they...
The size 6 handed closers will have the most (strongest) closing force. The 4016 (pull side), the 4026 (top jamb push side) or the 4116 (push side parallel arm) have the highest closing force.
The LCN closer fluid "Liquid X" will perform without variation between:
-30° F to +120° F - for manual closers.
+35° F to +120° F - for electrical closers and automatic operators.
At around ...
The pneumatic operators are designed to function with an input air pressure to the 7901/7902 Series control box of 80 (min) 100 (max) PSI, and an output pressure of 60 to 80 PSI to the pneumatic (2...
If an Size 1 (ADA) closer is set to 5 lbs. opening force, it will only have about 3 lbs. (60/70%) closing force. If the closer will not close against air pressure, but the ADA requirements have to ...
24 volt version draws 90 mAmps (0.090A).
120 volt version draws 30 mAmps (0.030A).
See here for the LCN catalog sheets that contain this information (page 2 of 48).
The minimum top rail required to mount a 4110 closer is 5-1/8" measured from the stop of the frame.
If the top rail is less than 5-1/8" the 4110-18 drop plate is required.