Cooling System - Westerbeke 7.6 KW BTD 60Hz 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
e,,"lernally from the fresh water to raw water by means of a heat exchanger; similar in function to an
automotive radiator. Raw 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 raw
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 raw water, and the raw water
carries the transferred heat over the side through the exhaust system. The fresh water and raw 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 following 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
engine. 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 where 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 the 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, e"'Pands sufficiently to split the heat exchanger and crack the engine block. A water/antifreeze
mi"iure of proper concentration will prevent freezing (see the 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
adding it to the cooling system.
43
WESTERBEKE GENERATORS