Furnace Pressure Switch Symptoms

Furnace Gas Pressure

• Gas-fired furnaces rely on a series of working components that ensure gas and air exchanges correspond with the manufacturer’s specifications. The furnace pressure switch regulates when gas releases occur and how gas materials enter a furnace’s heat exchanger compartment. Air exchange processes within the heat exchanger compartment enable gas combustion to take place. As furnace parts can vary in terms of pipe sizes and compartment size, a furnace switch emits gases at a pressure that allows for optimal furnace efficiency.

Furnace Backfires

• A furnace starts up when a system room thermostat sends a signal that room temperatures have dipped below a certain point. In response, the furnace pressure switch releases gas, which tells the ignition system to light the pilot flame. A furnace pressure switch includes a spring component that affects how much gas is released. Over time, a weakened spring can result in an increase in gas pressure. Furnace backfires occur when too much gas occupies the heat exchanger compartment before the pilot flame lights. With excess levels of gas present, the pilot and burners ignite in an uneven pattern that causes a loud backfire noise.

Burner Flame Patterns

• Symptoms of a furnace pressure switch problem may appear in the way the burners light up once a furnace turns on. A well functioning burner component will light up in a silent, orderly pattern shortly after the pilot flame lights. Normal burner flames have a bluish color and burn at even or similar heights. If the furnace pressure switch causes too much gas to flow, burner flames may appear yellowish, have yellow tips or flicker in a blue and yellow pattern. Irregular flame patterns hamper normal combustion processes involving air flow and gases. In effect, these conditions can reduce a furnace’s energy efficiency levels.

Heat Exchanger Damage

• The heat exchanger compartment consists of a metal cabinet that allows air and gases to circulate. When a furnace pressure switch malfunctions, the furnace works harder at maintaining temperature levels in the home. When this happens, the heat exchanger compartment may develop areas of rust and corrosion as a result of abnormal air, moisture and gas mixtures. In effect, yellow burner flames produce excess heat levels within the heat exchanger compartment. Excess heat levels place undo pressure on compartment walls and can potentially cause leaks or cracks to appear.