The first step is to develop a consistent plan of control for heat-using equipment throughout the facility. Decide whether to control heating operation at the plant, at the end-use equipment, or in some combination of these two.

Each approach has advantages and disadvantages:

• minimizing steam consumption by turning off the end-use equipment. You can install shutdown controls on each item of end-use equipment. From an overall efficiency standpoint, this method is good because each piece of end-use equipment can shut down in accordance with its individual heating requirements.

The major disadvantage of this method is the expense and maintenance of having separate controls at each item of end-use equipment. The boiler senses the disappearance of heating load when the end-use equipment shuts off.

Boiler output falls as the end-use equipment shuts down, and no separate boiler plant controls may be required. However, this method does not eliminate the energy consumed to keep the boiler system warmed up, to replace distribution system losses, and to operate boiler plant auxiliary equipment. To avoid these losses, you need additional controls to shut down the boiler plant itself.

• minimizing steam consumption by shutting down the boiler plant. At the other extreme, you may shut down the boiler system, which will shut down all the equipment served by the system. This method is much less expensive than installing individual shutdown controls on the end-use equipment.

This method wastes some energy unless all end use equipment operates on the same schedule. For example, if the boiler plant serves radiators, operating a boiler to provide heat to one room keeps every radiator in the facility working.

Another disadvantage of this method is that it does not stop the energy consumption of non-heating components of end-use equipment, such as the fans in fan-coil units.

• minimizing steam consumption when end-use equipment operates on a variety of schedules. In situations where some end-use equipment operates on a shorter schedule than the boiler plant, you can provide separate shutdown controls just for the equipment that operates on shorter schedules.

For example, you might install such controls for the administrative spaces in a hotel, while the guest rooms have heating available continuously or seasonally.

• minimizing steam consumption using different control criteria. You can use different methods of shutdown for the boiler plant and the end-use equipment. For example, you might shut down enduse equipment with timeclocks and shut down the boiler plant with an outside air temperature sensor.

There may be many ways to distribute shutdown control of heating within a facility. Your objective is to make the boiler plant respond efficiently to the range of conditions that may occur, including the operating schedule of heating equipment, outside temperature, etc., and to satisfy the constraints of cost, reliability, and maintenance requirements.

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