Anyone who has ever spent a night tossing and turning in a cold house as a result of a busted heating system will never look at that particular equipment the same way again. It's as unpleasant as being stranded on a dark and lonely road when a car quits. But it may not take outright failure to make homeowners examine how their home is heated. It might be the system's noise or the fact that it simply doesn't work all that well. Being uncomfortable and annoyed all winter is a pretty compelling reason to consider the options for fixing or replacing it.
Then there's a fuel bill that lays waste to household finances. Let's say you have a boiler or furnace with 80 percent efficiency that produces a monthly gas bill of $279. About $56 of that has fueled nothing more than wasted heat that has gone up the chimney. Regardless of what prompts you to take a second look at your house's heating system, or perhaps the first look, you do need to be conversant with what makes it tick. Here are the basics.
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How Your Heating System Works
Heat Highway
Producing heat is easy. Getting it where it needs to go is the hard part.
* Hot Water
Water is the ideal heat-transport vehicle. A small pipe filled with hot water carries as much heat as a large air-filled duct, and it fits far more easily between studs and joists. In most houses that use hot-water systems, the pipe carries water at 120 to 180 F to baseboard convectors that consist of a piece of copper tube running through a row of sheetmetal fins. This sets up a convective heating loop as air is pulled in at the base and flows out the unit's top. Newer radiant-heat systems use plastic tubing routed in a serpentine pattern. Usually this is installed under wood-frame floors, or it is encased in concrete.
* Forced Hot Air
A forced-air heating system is simple and versatile. By connecting a humidifier, air cleaner or evaporator cooling coil to the duct system, a homeowner can completely control the indoor air's temperature, humidity and cleanliness. Air in these systems moves at about 700 ft per minute through the house in rectangular ducts, typically made from galvanized 30-gauge sheet steel. Some systems use round ducts connected to the main rectangular trunk, while other houses have flexible, round insulated ducts connected to an insulated trunk. In all cases, the joints in the duct system need to be meticulously sealed to prevent air leaks and energy loss.
What Goes On In a Heating System is Amazing
* Oil Burner
About 7 percent of U.S. homes heat with oil, collectively consuming about 7 billion gal of fuel a year. Modern burners atomize the oil by pumping it at about 100 psi to a tiny brass or steel nozzle that turns it into a spinning, cone-shaped spray pattern consisting of about 55 billion droplets. The spray is ignited by a 20,000-volt arc produced by a pair of burner electrodes. The result: a clean-burning flame of 2200 to 2600 F.
* Condensing Boiler or Furnace
A small but growing number of the nation's homes have condensing boilers or furnaces--both more than 90 percent efficient. In these appliances, flue gas condenses in a secondary heat exchanger, releasing usable energy. The flue gas and condensate are routed to the outdoors via plastic pipe. The equipment gains further efficiency by using unheated outdoor air for combustion, rather than conditioned indoor air.
Safety First
Keeping the heat on is important. So is knowing how to shut the system down in an emergency.
* Boiler Shutoff Valve
Stops water flow to the boiler and to valves or other devices downstream. (It is the first of several valves and devices on the boiler's feed line.)
* Burner Emergency Switch
Cuts power to a gas- or oil-burner circuit.
* Main Shutoff Valve
Controls gas flow from the meter to the building for maintenance or emergencies. The valve is turned with an adjustable wrench.
* Propane Tank Service Valve
Controls gas flow from the tank to the building for maintenance or emergencies.
* Circuit Breaker
Provides a means to automatically or manually cut power to heating-equipment circuits.
Roy Berendsohn has worked for more than 25 years at Popular Mechanics, where he has written on carpentry, masonry, painting, plumbing, electrical, woodworking, blacksmithing, welding, lawn care, chainsaw use, and outdoor power equipment. When he’s not working on his own house, he volunteers with Sovereign Grace Church doing home repair for families in rural, suburban and urban locations throughout central and southern New Jersey.
