Your Heating System

No matter what fuel you use, the heat it creates is distributed throughout your home in one of three ways: hot water, steam or warm air. The basic operation of these systems is described below. The two most common methods, hot water and warm air, are illustrated with diagrams.

How Heating Systems Make Heat

Your thermostat (1) has a sensor which measures room temperature. When the temperature drops below your thermostat setting (or you raise the level above the room temperature), it sends a signal to the controls (2) on your burner (3) to get into action. A fuel pump (4) draws oil through a filter (5) to your burner. It turns this oil into a fine spray, mixes it with air and ignites it in the combustion chamber (6), causing the chamber to get very hot. What happens next depends on the type of system you have:

  • If you have a Hot Water (hydronic) System (upper right), water circulates around your boiler’s (10) flue passages. A circulator (11) pumps the hot water through radiators, baseboards or through pipes in the floor (radiant heat). An expansion tank (12) adjusts to varying pressures.
  • If you have a Warm Air System (lower right), air absorbs heat from your furnace’s heat exchanger (7) or hydronic coil. A blower (8) sends this air through ducts (9) to heat your home.
  • Steam Systems work similarly, except steam is generated and rises to the radiators (no circulators are needed). A low water cut-off prevents damage to the boiler by shutting it down in case water levels drop too low. In all systems, the combustion emissions go up the flue (13), never mixing with either the air or water going through your house.