Chapter 1 Hydronic System Components Figure 3 National Oilheat Research Alliance 5 Introduction A hot water heating system is made up of components that work together to provide and maintain comfortable temperature in a structure. A typical hot water heating system is shown in Figure 1. 1 Boiler—the boiler/burner combination is used to heat water which is then circulated through piping connected to a variety of terminal units (heat emitters), including radiators, convectors, baseboards, fan coils, radiant, indirect water heaters and others. Boiler nameplates (Figure 2) contain a significant amount of information; a typical boiler nameplate looks like this: Figure 2 Firing Rate This tells us the firing rate of the appliance, also known as the burner capacity. In this case, the boiler is rated for .75 gallons per hour (gph). It’s important to note that this is NOT the nozzle size. To determine the firing rate, fuel unit pressure must be considered. For example, if the pressure is 100 psi, then a .75 gph nozzle is correct; however if the pressure is 150 psi, a .60 gph nozzle is correct. DOE Cap. (Capacity) In this case, this unit is rated by the US Department of Energy at 91,000 Btus per hour capacity when fired at the specified burner input. This is also referred to as “gross output.” Net Rate (formerly I=B=R) This rating is used to select a properly sized boiler based on a heat loss calculation performed prior to installation, plus any additional load, such as domestic hot water. It includes a 15% allowance for piping and pick-up losses. The term pickup losses describes the energy required to heat the boiler and piping before the system contributes any heat to the home. 2 Pressure Relief Valve—The pressure relief valve protects the boiler from over-pressurization. If the pressure rises to the system’s maxi
NORA Advanced Hydronics
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