Kohler 20--2800 kW manual City Water Cooling, Cooling Tower

The engine water pump can be used to circulate water through the remote radiator providing that the vertical distance from the engine water pump does not exceed the engine manufacturer’s recommendations. The allowable static head may range from 17-50 feet (5.2-15.2 m). Consult the Specification Sheet for the unit. This is important because greater height will result in excessive head pressure on engine components, causing problems such as leaking water pump seals. The piping between the engine and remote radiator must be sized for a maximum of 2 psi (0.141 kg/cm2) pressure drop at the rated flow of the engine water pump. A vent line from the engine to the radiator may be necessary to purge air from the cooling system.

When either horizontal or vertical distances exceed the above limitations, a hot well tank or heat exchanger and auxiliary circulating pump as shown in Figure 4-10 should be used. The circulating pump should always be wired in parallel with the remote radiator fan so that both will operate whenever the generator set operates.

Heated water is forced by the engine pump into the “hot” side and then is drawn off by the auxiliary pump and forced into the radiator. After circulating through the radiator, coolant flows back to the cold side of the well where it is removed by the engine water pump. Head pressures are thus isolated from the engine. Pressure can also be isolated by installing a heat exchanger between the engine and remote radiator.

With the radiator at a remote location, it is easily overlooked each time the generator is serviced. For this reason, low water alarms, or automatic “make-up” controls are often included in these systems. Antifreeze is required if the radiator is subject to freezing temperatures.

Shutoff valves should be located between the engine and cooling system to allow for isolation of both systems. This will eliminate the need to drain the entire system during service.

To determine radiator size and air requirements check the Specification Sheet for your model. The amount of air required to ventilate the generator set room or enclosure determines the size of the air inlet and outlet—a ventilating fan is usually necessary as generator heat loss as well as engine heat loss must be dissipated.

4.9 City Water Cooling

These systems utilizes city water and heat exchangers for cooling and are similar to remote radiator systems in

that they require less cooling air than unit-mounted radiator systems. Refer to Figure 4-11 for a view of some of the elements of a typical installation.

The heat exchanger the effects of city water (lime deposits, corrosion) to one side of a heat exchanger which is relatively easy to clean or replace, while engine coolant circulates in a closed system similar to a radiator system.

It allows better control of engine temperature, permits the use of antifreeze and coolant conditioners, and is suited to the use of an engine block heater as a starting aid.

Water inlet and outlet connections are mounted on the generator set skid and isolated from engine vibration by flexible sections. If the generator set is vibration- mounted to the skid and the skid is bolted directly to the mounting base, no additional flexible sections are needed between connection points on the skid and city water lines. If the generator set skid is mounted to the base with vibration isolators, flexible sections must be used between connection points on the skid and city water lines.

A solenoid valve mounted at the inlet connection point automatically opens upon start-up of the generator set, providing water under pressure from city mains for engine cooling. This valve automatically closes when the unit shuts down. Be sure that the solenoid valve is located upstream of the supply flexible connection. An additional customer-supplied valve may be used ahead of the entire system to manually shut off city water when servicing the generator.

4.10 Cooling Tower

In warm, dry climates, a cooling tower may be a suitable source of generator set cooling water. A typical system is shown in Figure 4-12. This is a variation of the city water cooling with heat exchanger. The engine system usually includes the engine water pump, a heat exchanger, a surge tank, and the water jacket of the engine. The raw water system consists of the cooling tower, a raw water pump, and the tube portion of the heat exchanger. Raw water is circulated through the heat exchanger tubes to absorb heat from the engine system which is circulated around the surrounding shell of the heat exchanger. The heated raw water is directed into a pipe at the top of the cooling tower and sprayed down into the tower to cool by evaporation. Since some water is constantly being lost by evaporation, the system must include provision for “make up” water.

18 Section 4 Air Requirements TP-5700 7/93