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NORA Oilheat Technicians Manual

Steam heating systems Just like hot water boilers, steam boilers are heat exchangers that use the heat from the flame to heat water. A key difference is that steam boilers are only partially full of water, so that when the water is heated it turns to steam and expands by 1,700 times. It is this expansion that pushes the steam into the heating system. All we have to do is get the air that is in the system out of the way and the steam will rush in. Additionally, it takes a lot of energy to turn water into steam. And, when that steam turns back to water, it releases a lot of energy. Thus, the steam can provide a lot of heat to the residence. Steam pressure The job of steam pressure is just to Chapter 13 Heating Systems Removable Head Chapter 13—Heating Systems 13-15 Part III overcome the friction that steam meets as it works its way around the system. We have to supply enough pressure back at the boiler to overcome the system piping friction. The pressure needed is remarkably low, less than 2 PSI. Raising the pressure higher than two PSI will cause problems because steam is a gas. When you raise the pressure on a gas, you compress it. When you compress steam, it takes up less space. It also begins to move more slowly. It takes longer for high-pressure steam to get out to the radiators than it does for low-pressure steam. Also, high-pressure steam, since it’s more tightly packed, will take more water out of the boiler than low-pressure steam. This can lead to low-water problems back at the boiler. Figure 13-19: Electric zone valves Securing Screws (2) Cover Retaining Screw Shaft Removable Head Valve Body Assembly radiation. Figure 13-19 shows zone valves. They can also be of the nonelectric type installed on each piece of radiation. Combinations of these two types can be very effective and provide positive, efficient and inexpensive total comfort control.


NORA Oilheat Technicians Manual
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