These are louvered, passive, engine room suction air vents.
The SSV version has a frame that is highly polished 316 stainless steel and a plain anodized aluminum grill. The vent's model number relates to the number of engine horsepower for which the vent is suitable.
Several vents may be combined to provide the square inches of free air flow required by a given engine.
Vents are typically split evenly between starboard and port sides of the hull.
These vents are designed to open directly into the engine room and do not require collector boxes to port the air through ducts.
Optional "Dorade style" rain and spray catching plastic baffles are available for each size of vent. See Accessory Products, below.
Heavy on the technical side...
A marine diesel requires both combustion and cooling air to function properly.
The volume of combustion air required is approximately 2.66 cu ft/min per horsepower for a naturally aspirated engine. This works out to about 0.63 sq in of passive vent per horsepower.
The volume of cooling air required to dissipate radiated engine heat trapped in the engine room is typically about the same as the volume of combustion air.
Engines that ingest hot air burn fuel less efficiently than those that ingest cool air. (The chemistry of combustion is such that the hotter the reactants are, the slower the reaction will proceed.)
Therefore, the hotter the engine room, the more fuel you burn for the same energy output. In addition, heat shortens the service life of engine room mechanical gear, soft goods (hoses, belts), and electrical systems. An overly hot engine room can even be cause for voiding the engine or genset’s warranty.
The design of Vetus engine room air suction vents is based on these parameters.
The Model numbers of the vents relate to the number of engine horsepower for which they are suitable.
When designing an engine room, it is necessary to determine the size of the engine room air vents required. Both combustion and cooling air must be taken into account.
A boat with a 60 hp engine will require two louvered Model 60 air vents (1 starboard/1 port) for a total of about 75 sq in of air flow (0.63 sq in per hp x 60 hp = 37.8 sq in for combustion, and another 37.8 sq in for engine room cooling). A size 60 air vent provides 37.3 sq in of air flow area.
This same airflow can also be achieved using four Type 30 vents (2 starboard/two port) for a total of 76 sq in of air flow.