Furnace improvements :
The following recommendations can be used to reduce the effects of an existing , mid-efficiency or high efficiency
furnaces that are over sized.
Have your heating contractor adjust the fan limit switches in your furnace to increase the time that the furnace
blower fan operates. It is possible to adjust the default setting of the limit switches to allow the furnace blower
fan to start circulating warm air sooner after the burner turns on, and to continue circulating warm air after the
burner turns off. The additional electricity consumed to run the furnace blower fan longer is recovered quickly in
the additional heat that can be extracted from the furnace's heat exchanger. The furnace blower fan should turn on
at 50o C, and to turn off at 33o C.
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Have your heating contractor increase the blower fan speed. By increasing the blower fan speed it is possibleto take more heat from the furnace's heat exchanger, increasing the efficiency of the furnace. Some things
to be considered when having your blower fan speed increased:
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for conventional and mid-efficiency furnaces if too much heat is extracted from the furnace's heat exchanger,condensation may occur in the chimney. Also chimney liners must be installed.
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increasing the blower fan speed increases the speed of the air passing through the ductwork which in somehomes can lead to problems with static noise from pressure.
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extracting the heat from the furnace's heat exchanger faster will reduce furnace run times even more.•
To reduce the electrical consumption of the furnace, the blower fan motor can be replaced with a direct current(DC) motor. The energy savings from these motors will usually pay for the cost of having them installed in less
than five years. This is an especially good idea if the furnace blower fan is used with an air-conditioning system
or used to continuously circulate the air in the house.
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To improve the comfort in rooms further from the furnace, seal and insulate all the accessible ductwork. Usingmastic or aluminum-backed duct tape the joints of the duct work can be sealed to ensure that the air arrives
where it is intended. Insulating the ducts can ensure that the air arriving in the rooms furthest from the furnace is
still warm, increasing the amount of heat delivered to the room.
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Increase the adjustable run time setting (sometimes called span or dead band) of your thermostat to increase thefurnace run time. If your thermostat does not have an adjustable run time setting, you may consider replacing it
with a programmable thermostat that allows for this type of adjustments. The run time setting determines how
much of a temperature swing is allowed around the desired temperature before the furnace turns on or off. As
each brand of thermostat deals with the adjustable run time setting differently it is impossible to state how large it
should be set. It is recommended that the span setting be set as large as possible without causing comfort problems
in the household, due to increased temperature fluctuations. Combustion motors FAQ.