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Troubleshooting a Hot Water Boiler - Gas Fired Boiler Repair

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Boiler Components
Gas Fired Boiler

Main Components of a Gas Fired Boiler

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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 temperature
  • Gas Valve and Burners - Combustion assembly that heats the water chamber
  • Combination Pressure / Temperature Gage (Tridicator) - Monitors water temperature and pressure
  • Water Feed Valve - Controls water flow to boiler
  • Pressure Reducing Valve - Automatically maintains correct water pressure at about 12-15 psi
  • Air Vent - Automatically purges unwanted air from hydronic system
  • Expansion 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 system
  • Pressure Relief Valve - Relieves high water pressure

    Hot Water Return Side:

  • Circulator - Electric pump that circulates water through the system
  • Drain Valve - Valve that opens to allow draining the boiler.
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