The APR Controls are classified by refrigerant and the maximum amount of modulation. Thus an APR-410-1 gives 1.5 tons of modulation on an R-410A system. Please note that the capacity listed on the APR is the modulation capacity not the system capacity. 100% modulation is NEVER acceptable. Example: a 3.5 ton system could not use the APR-410-3 (3.5 tons of modulation).