There is no need for return air ducting – A marine AC unit is a bit like a vacuum cleaner in reverse, sucking air in and blowing the cooled or heated air through the delivery ducts to the air distribution grills.
The blower motor and rotary compressors are air cooled and do get warm, therefore it’s good to have the return air travel over these components enroute to the evaporator. There is no need to have the evaporator up against the return air grill, in fact it’s better to have the opposite – make sure the evaporator has at least 50-75mm of space from any bulkhead.
