Chapter 8 - Hydronic Systems

Abstract

Hydronic systems are systems that use water or steam as the heat transfer medium. This chapter discusses the systems where water-heated and/or water-cooled equipment provide most of the heating and/or cooling. In some buildings, these systems use low-pressure steam instead of hot water for heating. The performance is similar to hot water systems with higher outputs due to the higher temperature of the steam. However, control in these steam systems is generally inferior, due to the fixed temperature of steam. Because of their ability to produce high output on an “as-needed basis,” hydronic systems are most commonly used where high and variable sensible heating and/or cooling loads occur. The very simplest water heating systems consist of pipes with hot water flowing through them. The output from a bare pipe is generally too low to be effective, so an extended surface is used to dissipate more heat. The radiator emits heat by both radiation and convection. These water heaters can be controlled by varying the water flow or by varying the water supply temperature. These hydronic heating systems do not provide any ventilation air from outside. When water systems are in use, ventilation requirements can be met by opening windows, window air conditioners, or separate ventilation systems with optional cooling.