Code for "clearance" around a furnace

[Plasma1]

I ended up getting a 4 year old Trane from a neighbour and installed it in place of my old furnace. The Trane is wider than my last and the side of the unit is only 10.5" from one studed wall ( can be moved if have to). Both the front and back of the unit have about 30" of clearance. I haven't hook up the gas yet as I don't have a license so I'm just using the unit for A/C. What a difference from the 20 year old unit it replaced. The 'heating coils' looked fine on the old unit.

My question is what does the code say for clearance for the side of the furnace. A sticker on the inside the furnace says 2" on all sides.