Furnaces

Central heating systems have a primary heating appliance, such as a furnace, typically located in your basement or in the utility room. All furnaces consist of four main components: 1) burners that deliver and burn fuel, 2) heat exchangers, 3) a blower and 4) a flue that acts as an exhaust for gaseous by-products. Depending on your situation, region and needs, you can choose from heating systems running on either gas, electric or oil as fuel, or a hybrid packaged system that can use two fuel types.

Combustion gases are generated by the burners in your furnace and passed over a heat exchanger. Air from your home then blows across the heat exchanger to be warmed. It is then blown through a system of ducts to distribute throughout your home.

During warm seasons your heating system works with your central air conditioner. Air is cooled as it’s blown over your air conditioning unit’s cooling coil, often attached to the exhaust of the furnace, and then sent over the same air ducts throughout your home.

Furnaces are rated by the Annual Fuel Utilization Efficiency (AFUE) ratio, which is the percent of heat produced for every dollar of fuel consumed.

Like the miles-per-gallon rating on your automobile, the higher the AFUE rating, the lower your fuel costs. All furnaces manufactured today must meet minimum AFUE ratings. If your furnace is 10 – 15 years old, it very well may fall below the current furnace minimum and you are wasting energy.

This doesn't mean that you should only select a furnace based on its AFUE rating. The efficiency rating is just one factor to consider when looking for a new furnace. Furnaces use electricity to run fans and motors. The amount of electricity used varies greatly depending on the type of furnace. Be sure to check electricity usage prior to making a purchase decision.

Two-stage heating means the furnace gas valve assembly has two levels of heat output: high for cold winter days and low for milder days. Since the low setting is adequate to meet household heating demands 80% of the time, a two-stage unit runs for longer periods and provides more even heat distribution. Longer, low-capacity operation run time has many advantages:

Consistent Comfort
Two-stage heating eliminates the temperature swings associated with standard furnaces, regulating temperature to within as little as one degree of the thermostat setting.

Quiet Operation
Two-stage furnaces start in the first (low) stage, when the amount of heat required is lower, instead of reaching full capacity all at once. That means there's no sudden "kick" or blast of air.

Improved Air Filtration
Low speed operation allows your filters to capture more contaminants (because air is continually passing through them), so you can breathe easier.

Efficient Performance
Because the furnace operates mostly in its lower capacity first stage, it burns less fuel than a standard furnace that always runs at full capacity, and shuts off when the heating demand has been met.

The term "variable speed" refers to the furnace's indoor blower motor, which moves at different speeds to precisely control the flow of heated and cooled air throughout your home. Better airflow control has several benefits:

Electrical Efficiency
Variable speed motors can actually save you money on your energy bills, as they consume less electricity than standard motors.

Heating Efficiency
Variable speed technology also means you will gain heating efficiency or AFUE.

Zoning
Variable speed motors are excellent for zoning, which allows you to customize your comfort in different areas of your home and control your energy bills.

Air Quality
A variable speed motor can also help clean the air in your home. When the fan is in continual operation (indicated by the "fan" setting on your thermostat), the motor will continue to slowly circulate air, allowing filters to capture more contaminants.

Humidity Control
A variable speed motor combined with a humidifing sensing thermostat allows you to control the amount of humidity in your home for improved indoor air quality and comfort.

Furnace technology has advanced significantly in recent years, raising concerns over chimney use. As a result of changing technology, many existing masonry chimneys aren't able to meet the specific demands of new furnaces.

There are several reasons for a furnace not being compatibility with an existing chimney. First, the size of the chimney can be an issue. Modern, higher-efficiency furnaces transfer more heat into your home and less heat up the chimney than older, less-efficient units. While this means more efficiency for your energy dollar, it also means that the existing chimney might be too large for the new furnace. The result could be improper draft ventilation of flue products and possibe condensation problems inside the chimney.

Other considerations include chimney height and location, proper lining and condition of the chimney. Building codes must also be kept in mind to ensure proper draft in the chimney for adequate ventilation.

Your qualified heating and cooling contractor can help you determine if a separate flue system is needed or if existing chimney ventilation will work.

Modern furnaces are designed to provide more even and efficient heating than past furnaces, which can impact both how your system operates and what you notice about your system.

To better regulate temperatures and airflow, modern furnaces move more air over the heat exchanger than older furnaces. The air that comes out of your furnace registers may not seem as warm as the air from your old furnace, but overall airflow is improved. Better airflow means higher comfort.

Additionally, new furnaces are designed to integrate with high efficiency air conditioners, so furnace blowers are more powerful to accommodate add-on cooling. Since cold air is much heavier than warm air, your system needs an extra boost from the blower to deliver cool air throughout your home. If you have an older home, this performance boost could produce unfamiliar sounds because air duct systems were originally designed for heating only. To minimize sound levels, choose a variable speed product which automatically changes speeds to meet the airflow needs of both heating and cooling cycles.