Cooling System - Westerbeke BCD 4.4KW Operator's Manual

COOLING SYSTEM
Description
Westerbeke marine diesel generators are designed and equipped for fresh water cooling. Heat produced
in the engine by combustion and friction is transferred to fresh water which circulates throughout the engine.
This circulating fresh water cools the engine block and its internal moving parts. The heat is transferred ex-
ternally from the fresh water to sea water by means of a heat exchanger, similar in function to an automo-
tive radiator. Sea water flows through the tubes of the heat exchanger while fresh water flows around the
tubes; engine heat transferred to the fresh water is conducted through the tube walls to the sea water which
is then pumped into the exhaust system where finally it is discharged overboard. In other words, the engine
is cooled by fresh water, the fresh water is cooled by sea water, and the sea water carries the transferred
heat over the side through the exhaust system. The fresh water and sea water circuits are independent of
each other. Using only fresh water within the engine allows the cooling water passages to stay clean and
free from harmful deposits. The two independent circuits and their components are discussed in the follow-
ing paragraphs.
Fresh Water Circuit
NOTE: Refer to paragraphs A and B in this section for the recommended antifreeze and water
mixture to be used as the fresh water coolant, and for information on filling the fresh water
system.
Fresh water is pumped through the engine by a belt-driven circulating pump, absorbing heat from the en-
gine. The fresh water coolant circulates through the engine's block absorbing heat, then passes through
the thermostat into the exhaust manifold, to the heat exchanger wher.e it is cooled, and then is returned to
the engine block through the suction side of the fresh water circulating pump. When the engine is started
cold, external fresh water flow is prevented by the closed thermostat (although some fresh water flow is
bypassed around the thermostat to prevent exhaust manifold from overheating). As the engine warms up,
the thermostat gradually opens, allowing full flow of the engine's fresh water coolant to flow unrestricted to
the external portion of the cooling system.
A. Fresh Water Coolant (Antifreeze) Mixture.
A freshwater and antifreeze mixture should be used year-round in the cooling system. Water, when it freezes,
expands sufficiently to split the heat exchanger and crack the engine block. A water/antifreeze mixture of
proper concentration will prevent freezing (see page 47 for an antifreeze/water mixture chart).
Use soft water with few impurities, such as tap water (potable water) or rainwater. Never use hard or foul
water. Use of hard water or water containing impurities will lead to the collection of scale in the engine and
heat exchanger which will reduce the cooling system's efficiency.
Antifreeze of poor quality or without rust inhibitors will cause corrosion within the cooling system. Always
use antifreeze which is compatible with aluminum cooling system components and is made by a reliable
manufacturer. Never mix different brands of antifreeze.
Make sure that the cooling system of the engine is well cleaned before adding antifreeze. Recommended
antifreeze for year round use is ZEREX or PRESTONE with rust inhibitors.
In order to control the concentration of the mixture, mix the antifreeze and freshwater thoroughly before ad-
ding it to the cooling system.
Westerbeke Generators
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