The 3130 Series closer is UL listed- Fire Rated (UL-10C) for up to 3 Hr.   The Door and Frame Manufacturer needs to be contacted to verify their Door/Frame rating would not be ...
615R is not a door closer model number. It is a UL number for the Falcon SC Series closers.
Yes, the Falcon SC Series closers have a UL listing.
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 4000T Series closers have a maximum opening of 90°.
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 4110 Cush closer can be templated for 85°, 90°, 100°, and 110° maximum as standard templates. The 4110 if ordered by ST-3220 will allow templating to 135°
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.
LCN does not recommend this type of installation, and has never sold a coupler to do this.