Sizing a Gas Furnace and Central Air Conditioner for your Home

We want to be clear on sizing – we don’ttremendous amount of time trying to convince
care what size furnace you currently havepotential furnace buyers to purchase smaller
because almost all gas furnaces are considerablyfurnaces. We do this because we know the
oversized. Oversized furnaces use more fuel,buyers will be more comfortable and save money
reduce home comfort and wear out faster thanon their energy bills with a properly sized furnace.
properly sized furnaces. Why, because they cyclePlease remember there is no gain for heating and
too often - they’re constantly going on andair conditioning specialists to sell you a smaller
off. This cycling increases stress on the heatfurnace; we just want your furnace to work
exchanger and simply reduces the life of theefficiently and comfortably. Also, a performance
other components because of the frequency ofguarantee assures you that your furnace will not
their operation while at the same time wastingbe undersized.
gas.Sizing an air conditioner is a fairly simple process.
A properly sized furnace is critical to systemSome HVAC service contractor’s use what is
longevity and personal comfort. How do you sizeknown as a manual J load calculation to determine
a furnace for a house - there are a couple ofthe air conditioner size that a home requires. While
ways. Some contractor’s use what is knownthis is a good way to size an air cooling system
as a manual J load calculation to determine thefor a house under construction where all the
size furnace a home needs. While this is a goodinsulation values and the tightness of the home
way to size a system for a house underare known, it can be fairly inaccurate when cooling
construction where all the insulation values and theexisting structures. The best way to determine
tightness of the home are known, it can be fairlythe correct air conditioning system size for your
inaccurate on existing structures. Otherhome is to access how well the old system
contractors rely on their years of experience inworked. If your old system did the job in cooling,
the business. This method is probably the mostyour new system will do the same job more
suspect and will usually result in an over sizedefficiently.
system.If you are unsure of your central air
When determining the size of your furnace,system’s size, simply look at the nameplate
compare three critical aspects of your home: theon the outdoor AC unit. Almost all air conditioner
square footage, the age, and the configuration.manufactures put the Btu rating in the model
The configuration is defined as ranch, two story,number. One ton of cooling is equal to 12,000
bi level, slab – with or without a basement, orBtu’s. Most units start at 2 ton, or 24,000
contemporary. Using this data we can calculatebtu’s and increase in half ton increments,
the anticipated heat loss of your home andskipping 4-1/2 ton.
choose a furnace that will maximize your comfortSometimes you have to do a little detective work
and minimize your utility cost. One other factorto find the Btu number because there is no set
that can help size your furnace, believe it or not,location within the AC model number and it varies
is your air conditioner. Our program can take theby manufacturer. If you can’t figure it out,
size of your central air conditioner and calculatecontact a heating and cooling specialist with the
the size of the furnace your home needs usingnumber and see if they can provide you with the
some fairly simple mathematics.system size.
Heating and cooling specialists often spend a