Powered Ventilation
 

Permanently installed with regard to an engine means that it is securely fastened to the boat’s structure and the necessary wiring, piping and controls are connected and secured to the boat in accordance with the applicable USCG regulations. See Title 33 CFR Part 183, Subpart I, Electrical Systems and Title 33 CFR Part 183, Subpart J, Fuel Systems. The use of the term "permanently installed" is to highlight that the engine is not portable or easily removed from the boat and to differentiate it from "portable equipment".

The term gasoline engine with a cranking motor is used to indicate that the gasoline engine can be started from a location that is remote from the compartment where it is permanently installed. An engine without a cranking motor (starter) requires the presence of a person at the engine location in order to start the engine. Presumably, any dangerous conditions such as liquid fuel or vapors being present at the engine location would be detected by odor and/or sight and remedied before the engine is started.

This section of the regulation addresses boats that have a permanently installed engine with a cranking motor in a compartment. To comply with the regulation one of the following alternatives must be satisfied:

• The compartment must be open to the atmosphere, as defined in 183.605.
• There must be an exhaust blower system installed to ventilate the compartment in which the engine is installed. An exhaust blower system consists of one or more blowers with ductwork and terminal fittings attached to the ducts.

TABLE II - 183.610

Net compartment volume is the result of subtracting the volume of permanently installed items such as the engine(s), fuel tanks, equipment and accessories from the total compartment volume of the compartment. A discussion of the items that may or may not be included, and suggestions for accounting for engines and fuel tanks appears as part of the discussion under 183.605 of this guideline.

The regulation is not specific about compartments that adjoin a compartment which qualifies as open to the atmosphere. The following discussion presents acceptable ways of handling this problem but they are not necessarily the only ways.

A compartment adjacent and connected to a compartment that is open to the atmosphere may be considered open to the atmosphere if:

The total of all open areas directly exposed to the atmosphere from both compartments is at least 15 square inches for each cubic foot of the combined net compartment volumes.

Long narrow compartments should have openings at each end or along the sides if they are to be considered open to the atmosphere.

See Figure 4 for diagrams of connecting compartments.

REMOVABLE ENCLOSURES

Fabric weather enclosures are not airtight and must be opened in order to enter the boat. Upon entering, any gasoline vapors present should be detectable by means of their odor. If an open compartment is covered by removable fabric weather enclosures, the enclosure may be ignored. The actual ventilation openings should remain outside of the weather enclosure. Snap-in bulkheads, such as motor well curtains, are not weather enclosures and may require the enclosed compartment to be ventilated.

FIGURE 4 - Connecting Compartments Qualifying as "Open to the Atmosphere"

SCREENS AND LOUVERS

If openings to a compartment are screened or louvered, the area of the opening is the aggregate net open area of the screen or louver. The compartment volume is determined by the average cross section of the compartment in square feet and multiplied by the length of the compartment in feet. This computation will give the compartment volume in cubic feet. For an irregular compartment, the volumes of portions of the compartment may be computed separately and then the volumes combined to get the total compartment volume. To get the net compartment volume, subtract the volume of the installed items as referred to in 183.605.

The net volume of adjoining compartments may have to be added to the engine compartment volume. The following rules apply:

ADD - If the area of openings between compartments is more than 2% of the area of the separation structure; i.e. bulkheads, stringers, frames, etc.

DO NOT ADD - If the area of openings between compartments is equal to or less than 2% of the area of the separation structure; i.e. bulkheads, stringers, frames, etc.

The total net volume of the engine compartment and all other connecting compartment volumes are required to be ADDED. See Column 1 of Table 183.610. These volumes are used to determine the required rated blower capacity and the blower system output. See Columns 2 and 3 of Table 183.610.

RATED BLOWER CAPACITY - TABLE 183.610 COLUMN 2

The air flow capacity rating (Fr) of blowers is determined by one of the following procedures:

• AMCA Standard 210-74, Figure 12 or UL Standard 1128. The UL Standard is specifically for testing marine blowers. See the appendix for the reference.
• This information may be found in the information supplied by the blower manufacturer.

BLOWER SIZE SELECTION

The total rated capacity of the required blower or blowers (Fr) is based on the net compartment volume (V) as specified in Table 183.610. One or more blowers may be used to provide the required capacity. Figure 5 is a graph of rated blower capacity versus net compartment volume.

Example 1: The net compartment volume of an engine compartment in a boat is 20 cubic feet (Below 34; See Table 183.610).

The required rated blower capacity is 50 cubic feet per minute.

Normally one blower will satisfy the requirement for this compartment.

Example 2: The net compartment volume of an engine compartment is 100 cubic feet (34 to 100 cu. ft.; See Table 183.610).

The required rated blower capacity is 150 cubic feet per minute. (1.5 x 100 = 150)

Two blowers could be used to satisfy this requirement - one rated at 100 cubic feet per minute and one rated at 50 cubic feet per minute. One 150 cubic feet per minute blower would satisfy the requirement that Fr = 1.5 V. Blowers with higher capacity ratings than the minimum may be used.

Example 3: The net compartment volume of an engine compartment is 800 cubic feet (over 100 cu. ft.; See Table 183.610). The rated blower capacity required in this installation is 500 cubic feet per minute (800/2 + 100 = 500).

One, two or more blowers may be used to satisfy this requirement. Using readily available marine blowers, two 200 cubic feet per minute blowers and one 100 cubic feet per minute blower might be selected. Blowers with higher capacity ratings than the minimum may be used.

FIGURE 5 - Rated Blower Capacity 
 

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