How do I determine furnace size?

The heating capacity of a furnace, also referred to as size, is measured in thousands of BTUs (British Thermal Units). Furnaces are rated by the input BTU’s, that is, the amount of fuel energy that goes into it when running. Different furnaces of the same input BTUs will have different output BTUs if the furnace efficiency ratings are different. Select a furnace for your home according to the output BTUs, as this is the actual heating capability of the furnace. You can easily calculate the output BTUs of a furnace according to the efficiency rating of the unit and the input BTUs – simply multiply the efficiency percentage by the input BTUs. For example, a 100,000 BTU furnace at 80% efficiency will produce 80,000 BTUs of heat output, whereas as 100,000 BTU furnace at 92% efficiency will produce 92,000 BTUs of heat output.

There is only one correct size furnace for your home.
You don’t want a unit that is too big, as it will turn on and off too frequently, be inefficient, and accumulate moisture in the heat exchanger which can damage the unit over time. And you don’t want a unit that is too small as it won’t properly heat the home. You want just the right size. How do you determine which one is just right? There are several ways you might go about determining the correct furnace heating capacity (or size) unit:

Manual J Load Calculation
This is the proper and scientific method as well as the most accurate. It is the method taught to HVAC technicians at school and recommended for use by professionals in the trade. It consists of taking information about your home’s constructions materials, insulation levels, sizes of rooms, etc, and then makes a calculation based on those to determine the appropriate heating and cooling requirements needed. The BTUs recommended by this tool should be close to output BTUs of the furnace you select. It should be noted, that while this is the most accurate approach for determining furnace size, according to a study by the US Department of Energy, less than half of heating and air conditioning contractors actually use Manual J Calculations to determine the proper size for heating or cooling equipment.

Compare your home to similar homes in your area.
Does you neighbor have the same size home as you? If he has a properly sized furnace, then the same size unit may also work for you.

Ask a contractor.
Most furnace professionals give free in-home estimates for installing new heating equipment during which they will recommend a unit size. While we don’t encourage using contractors for quotes if you don’t intend to hire any of them, a contractor familiar with the homes in your neighborhood will likely be able to give you an idea over the phone of what size you might need.

If you are replacing an existing furnace, look at what size you have.
If the unit you have now is the correct size for your home, replace it with the same size. How do you know what size you currently have? Look at the name plate on the furnace usually located somewhere inside the unit (remove service panel to find). Remember, furnaces are rated by input BTUs, but you will want to determine what the actual output BTU is (often also listed on name plate) when selecting the right size replacement unit.

How does a central air conditioner work?

When the household thermostat signals the air conditioning system to lower room air temperature, a whole sequence of events begins. The air handling unit kicks on, drawing room air in from various parts of the house through return-air ducts. This air is pulled through a filter where airborne particles such as dust and lint are removed-in fact, sophisticated filters may remove microscopic pollutants as well, then it's routed to air supply ductwork that carries it back to rooms.

Whenever an air conditioner is running, this cycle repeats continually.But how does that evaporator coil get cold in the first place? That happens through the magic of refrigeration. Every air conditioner has three main parts: a condenser, an evaporator and a compressor. With a typical "split system," the condenser and compressor are located in an outdoor unit; the evaporator is mounted in the air handling unit (which is often a forced air furnace). (With a "package system," all components are located in a single outdoor unit that may be located on the ground or roof.)

A refrigerant circulates through copper tubing that runs between these components. This refrigerant receives and releases heat as it raises and lowers in temperature, changing from liquid to gas and back to liquid.

The refrigerant is especially cold when it begins to circulate through the indoor coil. As the air handler pushes warm room air across this coil, the cold refrigerant absorbs so much heat from the air that it turns into a vapor. As a vapor, it travels to a compressor that pressurizes it and it moves through the outdoor coil, which jettisons the heat. A fan helps to dissipate this heat. The refrigerant then passes through an expansion device which converts it to a low-pressure, low-temperature liquid, which returns to the indoor coil. And so the cycle continues.

How should I operate my furnace?

OPERATING TIPS
How you operate your heating system will influence how much energy you use. The following tips will help lower your heating bill and ensure that your furnace functions safely and efficiently.

• Set your thermostat between 68 and 70 degrees when you are at home. Turn down the thermostat when you are away or sleeping. Regularly lowering your thermostat temperature, by five degrees for eight hours every day will save about five percent on your heating bill. Use a programmable thermostat to adjust the temperature automatically, based on the time of the day and the day of the week.


• Leave the fan switch on your thermostat set to “auto” unless you have a specific need for additional air circulation. Some customers choose to operate their fan continuously to even out warm and cold spots in their home, or to provide extra air filtration which may be beneficial where occupants have health concerns. Setting the fan to “on” will cause it to run all the time whether or not there is a need for heating or cooling. Those extra hours of operation can add several hundred dollars to your annual electric bill. If you do need to run your fan continuously, install a furnace with an ECM. Running the fan year-round will cost only about $50.


• Clean or replace furnace filters as recommended by your contractor or as noted on your filter packaging. Filters may need to be replaced as often as once a month.


• Be sure registers in occupied rooms aren’t blocked by furniture or draperies.


• Have your furnace tuned up every other year unless the manufacturer indicates otherwise. The contractor will test the efficiency, adjust the air and fuel flow, inspect the fan, and clean the unit.


• Install carbon monoxide detectors on every floor with a bedroom. Carbon monoxide detectors are not a substitute for properly maintaining your combustion appliances, but provide added protection against carbon monoxide poisoning.

What are some tips on reducing air conditioner’s load?

You can reduce the load on your air conditioning system with a few simple measures. First, be sure to clean or replace your furnace filters per the manufacturers recommendations. To reduce heat gain, pull drapes or shades over sun-facing windows. Stir up breezes using a whole-house fan or ceiling fans; or circulate air using the "Fan Only" setting on your heating system. When possible, minimize mid-day activities that add humidity to the air, such as washing and drying clothes, showering, and cooking.

What do I look for in a central air conditioner?

If you're thinking about buying a new central air conditioner, there are a few factors you should consider. Because buying and installing an air conditioner is not a do-it-yourself project, these are things you should discuss with a qualified air conditioning contractor.

First find out whether your house can readily accept an air conditioning system. Installing one usually only makes sense if a house is being newly constructed or has a forced-air heating system that the air conditioner can piggyback on--retrofitting ductwork is simply too expensive in most cases. Even in a home with usable ductwork, a standard central air conditioning system will typically cost from $3000 to $6000 installed. Because the cost depends upon so many variables, the only way to pinpoint it is to get bids. Be sure to get at least three from contractors.

Central air conditioners run on electricity for the compressor, blower, and fan. In some hot climates, where an air conditioner must run frequently, this can push energy costs sky high. The amount of electricity needed to run a central air conditioner depends on two things: cooling capacity and efficiency.

Cooling capacity
Manufacturers produce air conditioners in a variety of sizes, typically measured in "tons" or "BTUs per hour." A BTU (British Thermal Unit) is a common unit used for measuring heat output, equal to the amount of energy required to raise one pound of water one degree Fahrenheit. One ton equals 12,000 BTUs/hour-a term derived from the amount of energy required to melt 1 ton of ice in a day.

With air conditioners, bigger is not necessarily better. For one thing, the larger the capacity, the more a unit will cost; output is directly related to cost. Also, it's critically important to pick a size that is appropriate for the house. An air conditioner that is too small can't keep up with load requirements on a particularly hot day. One that is too large will cycle off and on too frequently, doing a poor job of dehumidifying the air, which degrades comfort. In fact, it's better to slightly undersize an air conditioner than to oversize it. Also, the air flow into and out of rooms must be carefully balanced to insure efficient operation of the system. These factors, as well how well a house is insulated, how it's used by your family, the climate and more must be taken into account when selecting and designing your system. That's why you should consult a qualified air conditioning contractor.

Efficiency
To reduce wasted energy, there are minimum efficiency standards for air conditioners . Every unit is given an efficiency rating, called a SEER (Seasonal Energy Efficiency Rating). This is listed on the yellow Energy Guide label posted on each unit. It's very important to look at these ratings-the higher the number, the more efficient the unit and the lower the cost to provide a given amount of cooling.

The minimum allowable SEER rating for new central air conditioners has been 10, but is to be changed to 13 in January, 2006. The most efficient models have SEERs of 15 to 17. When buying, watch the terminology. "High efficiency" models are actually those that meet the minimum SEER standard of 10. "Super-high" efficiency models have a SEER of from 11 to 12. "Ultra-high" efficiency models are 12 and over.

To achieve particularly high SEERs, air conditioners may have any number of energy-saving features: typically large coils for more efficient heat transfer and variable speed blower and fan motors to reduce electricity consumption. Programmable thermostats also help by offering precise control. Another energy-saving feature is a fan that stays on long enough to utilize residual cool air that remains after the compressor turns off. And some units have an indicator light that lets you know when the filter needs changing, which also boosts efficiency by insuring proper maintenance.

Do you need an ultra-high efficiency air conditioner? Not necessarily. If you live in a climate that requires little cooling during the year, it may not be worth the premium you'll pay for it. Or if your home isn't tightly insulated, all the gains of a premium model may not be worthwhile. On the other hand, where an air conditioner must run frequently during the year, a highly-efficient model will pay for itself in energy savings over a period of years.

One note about replacing an aging system: be sure to replace both the outdoor condensing unit and the indoor evaporator. Otherwise, if you just replace the condensing unit, potential gains of a higher-efficiency unit may be lost.

What do I look for when choosing an efficient furnace?

Select a furnace with an AFUE of 90 percent or higher.
The Annual Fuel Utilization Efficiency or AFUE measures a furnace’s overall energy performance. The higher the AFUE, the more heat you get for your heating dollar. In Ontario, Fill In The Blanks.

Select a furnace with multi-stage firing for the right size furnace for all heating conditions.
Your furnace must have enough capacity to meet your heating needs on the coldest day of winter. However, for most of the heating season, it will be more heating capacity than you need. Unlike a furnace with single-stage firing that is either firing at full output or completely off, a furnace with multi-stage firing can selectively turn some burners off when full furnace output is not needed. Multi-stage firing gives you the right size furnace for the majority of the heating season, and a reserve capacity to meet additional heating needs on really cold days or to recover from a temperature setback period. Multi-stage furnaces are usually equipped with another efficiency feature as well: an electronically commutated motor (ECM) that uses considerably less electricity to run the fan.

Select a furnace that uses electricity efficiently.
A gas furnace uses electricity to run the fan blower motor. Furnaces equipped with an ECM have lower annual operating costs and can save you $40 to $300 per year depending on how you use the furnace fan. An ECM will save the most if you run your furnace fan all the time. Multi-stage ECM furnaces not only save you money, they are usually much quieter and less prone to producing unpleasant drafts.

Your new furnace must be installed properly to ensure that it operates safely and efficiently.
The contractor should adjust the air flow so the furnace fan setting is matched to the ductwork and furnace characteristics. An improperly installed furnace can result in higher energy costs and a less comfortable home.

Do you have a furnace installed in your house? We would be glad to come by and ensure that your furnace is installed to work efficiently and safely.

What is Air Duct Cleaning?

Most people are now aware that indoor air pollution is an issue of growing concern and increased visibility. Many companies are marketing products and services intended to improve the quality of your indoor air. You have probably seen an advertisement, received a coupon in the mail, or been approached directly by a company offering to clean your air ducts as a means of improving your home's indoor air quality. These services typically -- but not always -- range in cost from $200 to $1,000 per heating and cooling system, depending on the services offered, the size of the system to be cleaned, system accessibility, climatic region, and level of contamination.

Duct cleaning generally refers to the cleaning of various heating and cooling system components of forced air systems, including the supply and return air ducts and registers, grilles and diffusers, heat exchangers heating and cooling coils, condensate drain pans (drip pans), fan motor and fan housing, and the air handling unit housing (See diagram).

If not properly installed, maintained, and operated, these components may become contaminated with particles of dust, pollen or other debris. If moisture is present, the potential for microbiological growth (e.g., mold) is increased and spores from such growth may be released into the home's living space. Some of these contaminants may cause allergic reactions or other symptoms in people if they are exposed to them. If you decide to have your heating and cooling system cleaned, it is important to make sure the service provider agrees to clean all components of the system and is qualified to do so. Failure to clean a component of a contaminated system can result in re-contamination of the entire system, thus negating any potential benefits. Methods of duct cleaning vary, although standards have been established by industry associations concerned with air duct cleaning. Typically, a service provider will use specialized tools to dislodge dirt and other debris in ducts, then vacuum them out with a high-powered vacuum cleaner.

In addition, the service provider may propose applying chemical biocides, designed to kill microbiological contaminants, to the inside of the duct work and to other system components. Some service providers may also suggest applying chemical treatments (sealants or other encapsulants) to encapsulate or cover the inside surfaces of the air ducts and equipment housings because they believe it will control mold growth or prevent the release of dirt particles or fibers from ducts. These practices have yet to be fully researched and you should be fully informed before deciding to permit the use of biocides or chemical treatments in your air ducts. They should only be applied, if at all, after the system has been properly cleaned of all visible dust or debris.

Note: Use of sealants to encapsulate the inside surfaces of ducts is a different practice than sealing duct air leaks. Sealing duct air leaks can help save energy on heating and cooling bills.

What should I expect from an Air Duct Cleaning service provider?

If you choose to have your ducts cleaned, the service provider should:

Open access ports or doors to allow the entire system to be cleaned and inspected.
Inspect the system before cleaning to be sure that there are no asbestos-containing materials (e.g., insulation, register boots, etc.) in the heating and cooling system. Asbestos-containing materials require specialized procedures and should not be disturbed or removed except by specially trained and equipped contractors.
Use vacuum equipment that exhausts particles outside of the home or use only high-efficiency particle air (HEPA) vacuuming equipment if the vacuum exhausts inside the home.
Protect carpet and household furnishings during cleaning.
Use well-controlled brushing of duct surfaces in conjunction with contact vacuum cleaning to dislodge dust and other particles.
Use only soft-bristled brushes for fiberglass duct board and sheet metal ducts internally lined with fiberglass. (Although flex duct can also be cleaned using soft-bristled brushes, it can be more economical to simply replace accessible flex duct.)
Take care to protect the duct work, including sealing and re-insulating any access holes the service provider may have made or used so they are airtight.

When should I consider getting my air ducts cleaned?

You should consider having the air ducts in your home cleaned if:

• There is substantial visible mold growth inside hard surface (e.g., sheet metal) ducts or on other components of your heating and cooling system. There are several important points to understand concerning mold detection in heating and cooling systems:


• Many sections of your heating and cooling system may not be accessible for a visible inspection, so ask the service provider to show you any mold they say exists.




• You should be aware that although a substance may look like mold, a positive determination of whether it is mold or not can be made only by an expert and may require laboratory analysis for final confirmation. For about $50, some microbiology laboratories can tell you whether a sample sent to them on a clear strip of sticky household tape is mold or simply a substance that resembles it.


• If you have insulated air ducts and the insulation gets wet or moldy it cannot be effectively cleaned and should be removed and replaced.


• If the conditions causing the mold growth in the first place are not corrected, mold growth will recur.




• Ducts are infested with vermin, e.g. (rodents or insects); or


• Ducts are clogged with excessive amounts of dust and debris and/or particles are actually released into the home from your supply registers.

Other Important Considerations...
Duct cleaning has never been shown to actually prevent health problems. Neither do studies conclusively demonstrate that particle (e.g., dust) levels in homes increase because of dirty air ducts or go down after cleaning. This is because much of the dirt that may accumulate inside air ducts adheres to duct surfaces and does not necessarily enter the living space. It is important to keep in mind that dirty air ducts are only one of many possible sources of particles that are present in homes.

Pollutants that enter the home both from outdoors and indoor activities such as cooking, cleaning, smoking, or just moving around can cause greater exposure to contaminants than dirty air ducts. Moreover, there is no evidence that a light amount of household dust or other particulate matter in air ducts poses any risk to health.