Furnaces
In most American homes, the primary heating system is a furnace fueled by oil, natural gas, or electricity. The furnace usually is regulated by a thermo stat, which you set to the temperature you want maintained in your house. As the air cools off, it ‘informs” the thermostat that more heat is required. The thermostat in turn “informs” the furnace, and the furnace kicks on. As the air in your house warms up, it informs the thermostat that no more heat is needed; the thermostat passes this information on to the furnace, and heat production ceases. As the air cools down again, the cycle is repeated.
The success your furnace has in converting the potential heat in its fuel into actual and usable heat is called its combustion efficiency.
There are oil, gas, electric, and coal furnaces. If you don’t already know what kind you have, take a look at it. An oil furnace has a motor, pump, and blower and has to have a fill stem somewhere for oil deliveries; and you surely know if you’re getting oil deliveries! A gas furnace has no pumps or motors, but has a pilot light and gas pipes feeding in from outside. An electric furnace has many wires, but no pilot light. and a coal furnace has coal stored in a large hopper.
On a daily basis, all you need to know about most heating systems is how to turn the thermostat up and down. Even if a furnace gets worn or clogged, it may continue to work. Its efficiency, how ever, will be impaired—it is burning more fuel, yet heating less well. Your furnace should be checked annually.
Doing a furnace checkup may not be your idea of an entertaining home project—and in fact, for the most part, you should leave that task to a trained professional. Assuming that your furnace is not presently in need of a major over haul (if it is, get it done without equivocation, or your living room will be very chilly come December when your furnace breaks down completely), a general tune-up will cost you about $80 to $90, and will probably save you at least the cost of the minor adjustment in unused fuel. It could even save you twice that amount.
If you don’t know when your furnace was last inspected and can’t find out (if, for example, the previous owners of your house moved to Tahiti and left no forwarding address), you can safely assume that it needs at least a bit of cleaning in early fall. Call in a service person to inspect it at that time, and you’ll find out exactly what your furnace needs. Most furnaces are pretty solid creatures, and it is unlikely that you will have to spend much.
Furnace Maintenance
Since the combustion efficiency of electric furnaces is very high (almost 100 percent), there is basically no way to improve on the service yours pro vides except to have it checked periodically, according to the manufacturer’s instructions.
Gas- and oil-fueled furnaces, how ever, are another story. Their combustion efficiencies rarely exceed 80 per cent; frequently they drop toward 60 percent or even lower. Most of the lost heat simply slips up the flue; flue gas temperatures ordinarily fluctuate between 350° F and 700° F where they leave the furnace.
Even though maintaining your furnace is one of those tasks that’s best done by an expert, it pays to be as prepared as you can—you should be able to discuss a few specific items with your ser vice person. (For some suggestions on how to work effectively with contractors, see “What to Look for in a Contractor”)
Electric furnaces require little in the way of servicing, but at each checkup, gas and oil furnaces require both a draft test and a stack temperature test. A draft test checks the amount of air that’s drawn into the furnace to mix with its burning fuel. If the draft is too great, heat is lost up the flue unnecessarily; if the draft is too small, the fuel won’t burn completely. The stack temperature test determines how much heat your furnace is losing up the flue (all furnaces lose some). If your stack temperature is too high, you may need to have your furnace burner adjusted, or your heat ex changer cleaned.
+ Old furnace maintenance: In addition to the tests noted above, an oil furnace should have a smoke test and a CO test. The smoke test determines whether your furnace is burning its oil efficiently. If it isn’t, there will be a heavy residue on the inside of the furnace. This residue insulates the heat exchanger surfaces and diminishes the useful heat produced by your system. The C02 test gauges the quantity of air mixing with your oil for combustion. Too much air will cause a larger fraction of the heat to go up the stack, rather than into the house. Too little air will produce smoke and also reduce efficiency.
At each visit, the maintenance person should change the oil and air filters and clean the oil burner—combustion efficiency will improve, and you may realize immediate savings. The service person should also adjust and clean the thermostat contacts in your house, and the heating elements in the furnace, if necessary. The draft regulator, oil pump, electrical connections, and the fuel/air ratio all should be checked and adjusted, if need be; oil leaks should be spotted and corrected.
+ Gas furnace maintenance: With a gas furnace, have the maintenance person check and adjust all valves and regulators, the air supply nozzle, and the thermostat contacts in the house. Baffle and burner housings, as well as burner bottoms, should be cleaned; and , of course, filters should be replaced (unless you plan to take on this job your self).
+ Coal furnace maintenance: Few people use coal-burning furnaces these days; and since the recent increased interest in coal production concentrates on industrial and research developments rather than on home heating, coal-burning furnaces are not likely to gain enormous popularity in the near future. How ever, if you already have a coal-burner, it should be cleaned and adjusted at the end of every heating season. Make sure that the stoker is cleaned and adjusted, and that the inside of the coal screw and the hopper are oiled, to keep them from rusting.
+ Heat pump maintenance: If you have a heat pump: change the filters every three months; always leave the temperature at one setting; and have the pump checked annually by a professional service person. Usually, you can buy a maintenance service contract from the pump’s manufacturer, which will save you considerable trouble should some thing go wrong later on.
+ Wood and combination furnace maintenance: If you are one of those rare individuals who heat their homes with a wood furnace or have one of the newer combination furnaces, be sure to check with the manufacturer about an appropriate maintenance program. At least be sure all moving parts are cleaned and oiled, and replace filters as they become dirty.
Heat Pump: Summer vs. Winter. The heat pump is an automatic
heating and /or cooling device, which uses a liquid refrigerant and has components
similar to those of an air conditioner. Essentially, the heat pump refrigerates
the out doors and pumps the heat it picks up in this process into the house.
In summer, it reverses the process. Heat pumps cost 15 to 20 percent more
than convention-
Furnace Filters: Changing a furnace air filter is an easy and inexpensive job you can do your self. The purpose of a filter on any
forced- air furnace is to keep dust, soot, and other airborne grime out
of the air that blows into your living room. Air has more trouble passing
through the dirt- laden filter; therefore, your furnace has to work harder
when the filter gets dirty. So change your furnace’s air filter at /east
a couple of times during the heating season, and as often as every month
if you live in a dusty area or if your furnace has to work long hours. If
your central air-conditioning unit circulates through your furnace filter,
you may have to replace the filter during the cooling season as well as
during the heating season. The expense of a new filter—a dollar or two,
depending on the size—will quickly be made up in lower energy bills. and it will save strain on your furnace in the long run, too.
It isn’t hard to change a furnace air filter. If, after reading the following paragraph, you still have questions about how to do it, ask your furnace service person to demonstrate the process during his or her next routine visit. Then you too can do the job, and with confidence.
To replace a filter:
1. Turn off your thermostat.
2. Locate the metal panel that covers the filter on the furnace, near the blower.
3. Remove the panel and slide the filter out.
4. Slide the new filter in, according to the air-flow directions marked on it. (Be sure, of course, that the new filter is the correct size for your furnace.)
How a Furnace Works
• Forced-air systems: Most forced-air furnaces work on the same principles. An outer covering (the part you see) protects an inner shell known as a heat exchanger. This is where fuel is burned. In gas, oil, and coal fired furnaces, the air inside the heat exchanger itself is vented outside the house through the flue pipe, so its noxious fumes never enter your living space. When the heat exchanger reaches a certain temperature (predetermined by the manufacturer), blowers suck air from the return ducts into the outer covering of the furnace. There, the air is warmed by the heat exchanger. Then the blowers blow the newly warmed air into your living space through the supply ducts.
If you have a gas furnace, ask your service person or utility company representative to show you how to relight the pilot light if it blows out. Furnaces manufactured by different companies may require different procedures. In general, though, here’s what to do if your gas furnace isn’t working:
1. Turn the pilot light switch to off.
2. Wait for any lingering gas fumes to disappear. Then turn the switch to pilot.
3. Hold a match to the nozzle, and push the red reset button. Hold the but ton down for the length of time required by the manufacturer—usually 30 to 60 seconds.
4. Release the reset button.
5. When the pilot light stays on, turn the switch to on.
If you have a gas-fired wall heating- unit, use the same procedure.
General Furnace Schematic
• Pipe-heating systems: In an air sys tem, the furnace heats air which either rises to, or is blown to, the home’s living spaces through ducts. In a water or steam system, the furnace heats water in the boiler which is then pumped as water or steam through pipes to radiators or baseboard heaters. But essentially, the mechanism is the same: the furnace heats air or water which is then distributed to the desired space.
• Heat recovery unit: In a properly maintained furnace, the gases that escape into the stack generally range between about 350° F and 700° F. If the temperature falls below about 300° F, the gases will leave water vapor in the flue, which can rust the vents, and may also fail to burn off some noxious components. But if the temperature rises above 700° F, a lot of useful heat is simply being wasted. Much of this heat can be recovered through the use of a heat recovery unit.
Some heat recovery units clamp onto the flue pipe; others are inserted in the flue gas duct. In either case, heat is extracted from the stack, instead of being sent up into the sky.
By itself, a heat recovery unit will not reduce the amount of fuel you burn. But it will make more of the heat your fuel generates available to you. Of course, it will be effective in inverse proportion to the efficiency of the furnace: as the stack temperature drops, so does the amount of heat that can be recovered by a heat-recovery unit. You can use the recovered heat by directing it into your heat distribution system and sending it on its way through your house. Typically, a heat recovery unit will cost $200 to $300 installed, and save about 6 to 10 percent in fuel expenditures, paying for itself in three to six years. In some areas, however, heat recovery units are not permitted by building codes, so you should be sure to find out about your local code before you buy such a device.
Next: Radiant Heating; Wall Heaters; Heat Distribution