Natural Gas furnaces are the preferred choice of home heating over electricity, oil or propane because of its cost efficiency. Mid-efficiency furnaces range from 78 to 82 per cent rating, while high-efficiency furnaces range from 90 to 97 per cent efficient. An efficiency rating (AFUE) means Annual Fuel Utilization Efficiency in which indicates how much of the heat produced by burning natural gas can be used to warm your home.

With an additional heat exchanger to recover more heat from the flue gases, you use about 30 percent less natural gas than regular furnaces while supplying the same amount of heat. The heat is also more evenly distributed creating a great comfort level. High-efficiency furnaces can also be direct vented through a wall, which allows a great deal of design and flexibility during installation.

High-efficiency comparisons

Dual-output or variable capacity burner can operate at a low or high capacity which adjusts automatically to changing temperatures. The dual-output burner can operate for long periods at a low output using less gas or switch to high output when the weather turns cold. This results in a more efficient and comfort level being maintained.

Sealed combustion models have a motorized fan or blower that draws the right amount of air to the burner. With this efficient burning it then pulls the hot gas through the heat exchanger at a constant rate, resulting in more heat recovery from the burning gas.

Some high-efficiency furnaces may have an energy-efficient motor for the furnace fan or blower. It is very noticeable how much less electricity, as well as gas, is used whenever the furnace is on.

Pulse Combustion Furnaces uses a different gas burning process. A spark igniter lights a tiny amount of gas mixed with air, creating the “pulse”. This activates a cycle of rapid burning (in tiny bursts), creating positive and negative pressure waves in the sealed combustion chamber. The pressure waves keep the cycle going as long as the heat is needed.

Conventional Natural Gas Furnace

High-Efficiency Condensing Gas Furnace

The difference between a mid-efficiency and a high-efficiency furnace, is the Secondary Heat Exchanger, which recovers additional heat from the warm vapour that is usually expelled.

Points to consider

When considering to buy a high-efficiency furnace a few options may determine as to which one is the right one for you. Your individual needs, budgets and lifestyles can reflect your choice.

Present Furnace Type Present Expense Gas Savings/Yr Connect/High-Efficiency
Mid-efficiency $900./year $  87.00
Conventional $900./year $219.00

The life expectancy of a furnace is 18 – 25 years depending on the type and quality of the furnace. The trend is to purchase a furnace that is a high-efficiency with options to lease or buy. All options must be considered when making this decision. This can only be done with time and research as to the right type of furnace for your needs.

Costs involved

On the average a Mid-Efficiency furnace would cost from $1,825.00 – $2,595.00 and a High-Efficiency may be in the range of $2,795.00 – $3,895.00. The difference of the two would involve the components of the individual furnaces and the efficiency rating. The repair costs for either type of furnace would typically run approximately $600.00 to $800.00 for a vent or motor or an ignition system, which are the main items that may experience a breakdown.

Check Your Furnace Fan

During routine maintenance work, burner controls are checked but often the furnace fan controls are not. They are separate controls that can result in potential fuel savings. Fan controls can be set improperly causing them to come on too late or shut off too early allowing some of the heat to escape up the chimney. For two speed fans adjusting is not required as they are running constantly during the heating season.

The standard operation of the fan controls is controlled by the room thermostat that only turns on the burner. Another thermostat senses the temperature in the furnace which is then activated at 150F. This circulates the heat through the duct work. When the house temperature reaches the desired temperature the thermostat turns the burner off, but the fans still run to circulate all the heat through the duct work. This continues until the air has cooled to a preset temperature of 120.

Research has shown that more heat can be extracted from the furnace if the fan comes on earlier and stays on longer. By lowering the fan-on temperature to 120 and the fan-off temperature to 90 this effect can be achieved. Depending on what type of furnace you have the controls will be found for gas – behind the front access panel above the pilot light valve and oil- on the outside. Before the adjustments are made the furnace should be turned off. When the fan stops it is safe to make your changes.

Steps for adjustment:

  1. Locate circular fan limit control (scale 50-250 with three pointers). The lowest pointer (fan-off temp.- set to 90 ), next pointer (fan-on setting -set to 120), highest pointer (safety limit – usually set at 200, this should not be changed).
  2. Hold dial firmly with one hand while moving the pointers with the other.
  3. Replace cover and reset the house thermostat. The air coming from the registers will not be as hot as before, but by blowing longer, it will deliver more heat.

This will also improve circulation and have a more even temperature throughout the home.