1. What is "AFUE"?
Annual Fuel Utilization Efficiency. In a general sense, it is a measure
of the amount of heat that you actually get inside of the home compared
to the amount of heat that is being used by the system. As an example,
a 100,000 BTU, 80% AFUE gas furnace will provide 80,000 BTU's of heat
into the home if it runs for one hour. The other 20,000 BTU's of heat
will go up the chimney as products of combustion.
2. How important is AFUE?
least efficient gas furnace available today has a AFUE of 78%. All
furnace manufacturers today build two efficiency ranges of gas
furnaces. Their standard gas furnace will be between 78%-81% efficient
(called "80% AFUE") and their high efficiency gas furnace will be
between 90%-96% efficient (called "90% AFUE). To be practical, most
homes will have some factor that will justify one efficiency range or
the other. In very few homes are both efficiency ranges equally
The 80% AFUE gas
furnaces require some type of masonry or metal vertical chimney. A home
with an existing chimney is usually a candidate for the 80% AFUE
furnace. A home that currently has no chimney (ie, existing heat pump
home that may be switching to natural gas) or a home that has a very
old defective chimney, probably would be the best candidate for a 90%
AFUE gas furnace. Other factors also play into the choice.
3. What air conditioner works best with a gas furnace?
efficiency air conditioner (or heat pump) will operate with a gas
furnace. There is no one type or efficiency that is "better". In most
parts of the country the heating system runs more than the air
conditioner and is, therefore, the more expensive item to operate. For
this reason, We recommend that your choice of a furnace is more
important than the air conditioner. You will benefit from purchasing
the best, lowest operating cost, gas furnace. If this stretches the
budget, then purchase the more standard model air conditioner.
4. What is a "ton" of air conditioning?
ton of air conditioning is 12,000 BTU. A BTU is short for British
thermal unit and is the amount of heat that will raise or lower one
pound of water by one degree Fahrenheit. It is important to note that
actual capacity is not constant and will change based on outdoor or
indoor temperature. The published rating of a unit is based upon
capacity when the outdoor temperature is 95 degrees F. and the inside
temperature is 80 degrees F.
some manufacturers may call their unit a 3 ton system even though it
only delivers 34,000 BTU. Another manufacturer may be offering 37,000
BTU's with their 3 ton unit.
5. Should a thermostat be set to "auto" or "on"?
the thermostat is set to "auto", the fan operates only when the
temperature requires it (whenever the cooling unit or heating unit is
running). When set to "on", the fan operates all the time. You may want
the fan to run all the time to do its best possible job of filtering
6. What is the difference in a Manufacturer's Limited Warranty and an Extended parts and labor Warranty?
limited warranty covers specific parts (i.e. compressor, coil,
electronics, etc.); therefore, it is limited by the language in the
warranty. Extended warranties are generally purchased in addition to
the equipment. Extended warranties cover all parts and may also include
the labor for the service call. An extended warranty protects you for
unexpected and unbudgeted service calls for the duration of the
warranty. Be aware that no warranty includes maintenance, shipping
costs, and related parts (parts not provided by the manufacturer). Most
labor warranties do not include labor for diagnostics. Most of the
better manufacturer's now require proof that routine maintenance has
been performed on the equipment. If a contractor offers a labor or long
parts warranty, you should remember that it is only good as long as the
dealer is in business.
7. What is the difference between manufacturers products?
you are probably aware that most manufacturers market their gas
furnaces under several different brand names. Often these furnaces are
identical. Carrier markets under several brand names including Bryant.
Rheem markets under the name Ruud. American Standard markets under
their own name plus Trane. The list goes on and on. The differences
between truly competing gas furnaces can be significant. The thickness
of the metal used for the equipment jacket (quietness), the thickness
of the heat exchanger (quality), the construction of the inner parts of
the furnace (quietness), quality of the internal components, warranty,
insulation, packaging, availability of parts-all are areas where a gas
furnace can be made into a quality product or just a commodity.
8. My gas furnace is no longer heating properly. What is the most likely problem?
of our "replacement" gas furnaces are sold because the old furnace
developed a crack in the heat exchanger. The crack is seldom visible to
the untrained eye. Sometimes it is not visible to the most experienced
technician but he is able to make a judgement call based upon the
operation of the system. Maybe the pilot light keeps going out. Maybe a
safety switch sometimes cuts the furnace off. Then the homeowner resets
the furnace and it seems to work for a few days. Both of the above
could be due to a cracked heat exchanger. As the "crack" gets larger,
the chance that the furnace will malfunction becomes much greater. If
the homeowner fails to see the symptoms, eventually a technician will
be called for repairs.
9. What is a cracked heat exchanger?
heat exchanger is the area of the furnace where "heat" is
exchanged-from the fire at the gas burner to the air that is recycled
into the home through the duct system. The heat exchanger is sealed so
that the products of combustion from the gas burner never come into
contact with the air that goes back into the home. When a "crack"
develops, the seal between the two sides has broken and the products of
combustion (including carbon monoxide) can mix with the air going into
10. When do I know it's time to replace my system?
the system starts giving more problems than seem cost-effective to fix,
particularly when major components such as the gas valve or heat
exchanger fail. When faced with major repairs, consider that a new
system will eliminate costly repairs and will save money on your
monthly power bill because of the increased efficiency. The average
life of a gas furnace is 18-20 years. We recommend that any gas furnace
over 12 years old only be repaired as a last resort. The newer models
are so much more efficient that often they will help pay for themselves
with the fuel they save.
11. Should I keep running my old system until it wears out or replace it sooner?
newer equipment usually is more energy efficient than older central air
conditioning or heat pump systems, you may actually save money by
replacing your old system before it wears out. In some cases, the money
you save in reduced utility costs might pay back your purchase price of
a new system years earlier than you might think.
12. What is the best type of system to meet all indoor comfort needs?
best system depends on many variables, including family size, house
location, design, and utility costs. The optimum indoor comfort system
might include high efficiency air conditioning, high efficiency
heating, high efficiency air cleaning, air purification, and
13. What about having my ducts cleaned?
outlets and registers should be cleaned as part of your regular home
cleaning routine. It's the filter in the system, and to a lesser degree
the grilles and registers at the duct outlets, that collect most of the
dust, and therefore need changing or cleaning.
usually don't require cleaning, especially if filters are kept clean,
You can occasionally check ducts by removing a few registers and
inspecting the ducts from the inside with a flashlight. I have never
seen a heat pump duct system that needed cleaning. I have never seen a
properly operating gas or oil furnace duct system that needed cleaning.
I have only seldom seen a gas furnace duct system that could have
benefitted from cleaning, and never a system less than 30 years old.
Many oil furnace duct systems could benefit from cleaning if the oil
furnace has ever "cracked", malfunctioned, or been in use over 30
companies have invested in special "duct cleaning" equipment and often
offer specials just to keep their cleaning crew busy. Of course, you
can find dust inside of your ducts but your money might be better spent
on purchasing a high efficiency air filter-that would keep the ducts
super clean in the future.
14. Should my home be humidified?
depends largely on your personal needs. Humidification is definitely
helpful in many homes during a 6-8 week period during the coldest
winter weather. In the coldest weather insufficient moisture in the air
often is responsible for such assorted problems as stuffy noses, sore
throats, more dust than usual, cracks and dried-out joints in wood
furniture, and static electricity. A good humidifier can cost
$350-$600.00. It will be used only during the winter months and you
will need to "clean and start" the humidifier in the fall. When spring
arrives, you must "drain, clean, and shut-down" the humidifier or it
could become a breeding ground for mold during the summer.