Replacement Gas Boilers
Installing a new high-efficiency boiler can save energy and dollars while improving comfort in your home.
Boilers that are well-maintained can last as long as 30 years. However, the life of a boiler can be severely shortened by poor maintenance. If your boiler is very old or has not been well maintained for many years, you should consider replacing it with a new high-efficiency boiler. Gas boilers are much less expensive to operate, and will save you money all winter long.
The Annual Fuel Utilization Efficiency (AFUE) rating indicates what percentage of the energy in the fuel is converted into usable heat. A new high-efficiency boiler will have an AFUE rating of 87% or greater while older boilers typically have AFUE ratings from 60% to 75%. If your boiler has not been well maintained, then its efficiency is further decreased.
Annual fuel reduction can be calcualated as follows:
% Reduction = AFUE of new unit / AFUE of new unit - AFUE of existing unit
Energy-Efficient Improvements
New high-efficiency boilers incorporate one or more of the following improvements to increase their AFUE.
- Power Burners - A power burner mechanically mixes gas and air and injects the mixture into the combustion chamber. A small motor is used to drive a blower which draws in combustion air from the surroundings. The air and gas are mixed and injected at line pressure. A positive pressure is produced inside the combustion chamber insuring proper draft through the boiler. Since these burners closely control the air/fuel mixture, they tend to be very efficient.
- Many new systems use a ceramic "hot surface igniter" which eliminates the pilot altogether. The igniter is energized electrically and quickly attains a very high temperature. When the gas valve opens, the gas is ignited by coming into contact with the hot surface igniter.
- Electronic Spark Ignition - Electronic spark ignition systems ignite the pilot light only when heat is demanded. An electrode is positioned on the pilot burner to provide an electric spark through which the gas will pass. When the device is energized, the electrode will create a spark until the pilot is ignited. The pilot will in turn ignite the burner. Electronic spark ignition improves the AFUE of a boiler by eliminating the consistently burning pilot flame.
- Vent Dampers - Boilers lose a considerable amount of heat up the flue. An automatic vent damper will prevent heat from escaping up the chimney when the main burner is off. By preventing the escape of heat during the "off" cycle, a vent damper can also increase the furnace's operating efficiency by minimizing "cold" starts. At the beginning of each "on" cycle, the unit's efficiency gradually increases until it reaches steady-state. The time needed to reach this point is reduced as a result of the vent damper. Vent dampers can also help to retain humidity in the building by reducing infiltration.
- Recuperative/Condensing Boilers - Recuperative/condensing boilers recoup most of the heat from the flue gases. This is accomplished through the addition of a secondary condensing heat exchanger. So much heat is extracted that the water vapour in the gases condenses, giving them the name condensing boilers. The exhaust gases from these type of boilers have lower temperatures and can be vented horizontally, eliminating the need for a chimney.
How to Proceed
Contact your heating service company to do a thorough evaluation for you. They should be able to estimate how efficiently your existing boiler is performing, its useful life, and whether replacing it with a new, properly sized, high efficiency unit makes sense.
