Insulation on the suction line is very important for two reasons. One being that this line will sweat if it is not insulated. The drops of water that are formed from this sweat will create water damage. Secondly, the pipe should be insulated so that is doesn't pick up any extra heat that the condenser will then have to remove. All the heat that the air conditioner absorbs should occur in the evaporator. For efficiency reasons, the only air that should be circulated through the ductwork should be treated air.

If you have a cartridge pump there are no couplers or oil ports.