Use gentle bends
Keep flexible duct fully extended and supported. A broad sweep loses less pressure and transmits less fan noise.
Marine Air Conditioning Ducting and Airflow
A marine air conditioner cannot deliver the capacity on its label if the blower is fighting a tiny grille, a crushed hose or three sharp bends. Design the air path before the cabinetmaker closes the locker.
01
Supply and Return Air in a Marine Air Conditioning System
Warm cabin air enters through the return grille, crosses a clean filter and cold coil, then leaves through the supply duct. The two openings must not face each other so closely that cold air goes straight back into the machine. That short circuit cools the sensor while the berth stays warm.
Warm cabin air→Large return→Filter + coil→Short duct→High supply
The precise minimum duct and grille area is model-specific. Use the installation manual for the exact unit; never shrink the opening because a prettier grille was easier to source.
02
Boat Air Conditioning Grille Placement and Duct Routing
A high supply helps cool air mix before it falls. Aim across the cabin rather than directly at a pillow. Put the return where luggage and cushions cannot cover it, and provide a real transfer path when one unit serves a closed cabin. A gap under a door may not carry the volume the blower expects.
Keep runs short
Put the unit near the space it serves. Long branches often need balancing and can leave the far cabin starved.
Necking down
A small decorative grille becomes a whistle and raises blower load. Free area matters, not frame dimensions.
Hot, wet voids
Insulate cold duct through warm lockers so its outer surface does not sweat onto wiring, liners or stores.
If two cabins share a unit, add control at the branches only after the main return path is adequate. Closing every outlet while the blower runs can freeze the coil and damage the fan.
03
Restricted Airflow, Duct Noise and Uneven Cabin Cooling
| Symptom | Likely air-side check | Useful next page |
|---|---|---|
| Strong noise, weak breeze | Blocked filter, undersized grille or collapsed duct | New or excessive noise |
| Ice on the coil | Return restriction, low fan speed or closed outlets | Freezing up |
| Controller satisfied, berth warm | Supply air recirculating directly into return | Short cycling |
| Locker exterior is wet | Missing or damaged duct insulation | Humidity and condensate |
Clean the filter and uncover the grilles first. If the unit still lacks airflow, compare every duct and opening with the manufacturer specification before assuming the compressor is short of refrigerant. Refrigerant work belongs to a licensed technician; the resources page explains how to verify the right source and licence.