The Home Tips website describes several types of central heating systems. A ducted air system uses an electric furnace to heat air, blowing the heated air through ducts to warm various parts of a house, while radiant heating systems use a central boiler to heat water inside radiators. Mechanical problems can plague heating systems, leading to uneven performance or outright failure.
Failure to Start
If a radiant heating system fails to start up, the pilot light may have gone out, according the Central and Underfloor Heating website. If the pilot light will not relight, the timer may have failed or the thermostat may register too low a temperature for the system to engage.
The Gas Guide website warns that water pipes in boiler-driven systems may suffer damage if their insulation fails to protects them from freezing temperatures. Drops in boiler pressure can suggest the presence of a leak. The Central and Underfloor Heating website advises turning the system off, draining it and replacing any damaged sections of pipe.
Radiators can sometimes makes knocking noises if the pipes have collected a certain amount of trapped air. According to the Gas Guide website, a lack of water in the heating system's water tank can also cause this symptom. If the water tank appears to perform normally, then you may have to "bleed" the radiator by opening a valve to allow the trapped air to escape from the pipes.
If a radiator seems to heat unevenly from top to bottom, sludge may have gathered at the bottom of the unit, according to the Gas Guide website. If flushing the radiator with water fails to fix the problem, or if multiple radiators share the same issue, then a blocked pipe or faulty circulating pump may require professional attention.
If a ducted air system warms the house unevenly, individual ducts may have air leaks at the joints, according to the National Resources Canada website, or they may lack sufficient insulation in colder parts of the house.
Central heating systems driven by a boiler can malfunction if the pressure level drops significantly. The Gas Guide website notes that small water leaks can gradually cause a drop in pressure over time, as can the removal of air from a bled radiator. If the pressure gauge on the boiler indicates a drop in pressure, adding water through a manual "filling loop" can correct the problem.