Refrigerant charge for air-conditioning instead cold-rooms

Hi friends,
By very simple explanation in cold-rooms we have smaller condenser and evaporator with smaller inside volume of evaporator instead air-conditioning system that needs large condensers.
But why we should charge cold room systems with more refrigerant instead air-conditioning system ?
For example we have 10 HP compressor in A/C system, usually we have to charge 0.8Kg ~ max 1 Kg / HP to make system full of charge but while this 10 HP compressor works for cold room we must charge more refrigerant to make it full.
Why ?

Sincerely yours.

http://www.generalcooltrade.com