Wiring main box, DSC alarm

[dave11]

I'm planning to install a DSC 1832 hardwired system, with about 20 zones. Was planning to surface mount the panel on the sheetrock wall of a walk-in closet in the MBR, with all cables coming down from the attic inside a conduit that's also surface-monuted  I noticed the DSC panel box for the Powerseries comes with only 3/4 inch cut outs on top, though there two. Twenty cables of 4 conductor wire though is never going to fit through one 3/4 conduit, and I think would be tight in two of them. That's assuming that the 40% NEC rule on conduit fill isn't applicable here, which i'm still not sure about.
 
There's the really big hole in the back of the panel--is that what's meant to carry the majority of cables? If so, it seems like a lot of fishing down the wall.
 
What's the proper way to run a slew of cables to a surface mounted box in a living space?
 
Thanks.

 

[upstatemike]

What about using a punch or hole saw to enarge one of the 3/4 inch knockouts to 3 inches and then use a large PVC pipe to bring the wires down. You could also use a piece of square channel with a pop off cover to make it easier to add stuff over time. If you use the channel option don't forget to put some kind of bushing in the large hole you made so you don't cut into the wires with the edge of the panel box. 

 

[BraveSirRobbin]

I did that for my friend's Elk installation.  Just used a hole saw as upstatemike suggested and conduit via PVC.  I can't remember the size I was able to go up to with the PVC diameter.
 
You can also go behind the drywall and just cut a hole in your panel as well as I did for my old home as shown here.
 
Be aware that most get a large size enclosure for ease of installation and expandiability.