Where to read what type refrigerant your ac unit takes?

If you have a split unit - one with an outdoor condensing unit and an evaporator coil built into the furnace indoors, the refrigerant type will be shown on a label or engraved metal plate attached to the condensing unit. The amount of refrigerant will vary, depending on the diameter and length of pipe connecting the two units.

Most window air conditioners have an hermetically sealed refrigerant loop and cannot be recharged in the field, although they may also list the refrigerant type on a data plate somewhere.