Components of a Hot Water Boiler
The boiler is more complex than a forced air furnace
in that it has more parts, valves and controls. However gas-fired boilers are fairly reliable and most problems, when they do occur, usually relate to the expansion tank or water circulator pump(s).
Let's take a quick look at the major components of the boiler for a forced-water (hydronic) system:
Hot Water Supply Side:Aquastat - The thermostat that regulates the boiler's temperatureGas Valve and Burners - Combustion assembly that heats the water chamberCombination Pressure / Temperature Gage (Tridicator) - Monitors water temperature and pressureWater Feed Valve - Controls water flow to boilerPressure Reducing Valve - Automatically maintains correct water pressure at about 12-15 psiAir Vent - Automatically purges unwanted air from hydronic systemExpansion Tank - Critical component that allows expansion of water as it heats. There are two types of expansion tanks, the older larger style horizontal steel expansion tank and the newer smaller style diaphragm expansion tank.Flow Control Valve - Regulates flow of hot water to systemPressure Relief Valve - Relieves high water pressure
Hot Water Return Side:Circulator - Electric pump that circulates water through the systemDrain Valve - Valve that opens to allow draining the boiler.