How to Get Furnace Sizing Right

September/October 2007
A version of this article appears in the September/October 2007 issue of Home Energy Magazine.
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September 02, 2007
Canada has developed a furnace sizing protocol that uses actual gas meter readings to size replacement furnaces.
Residential furnaces work best when they are properly sized. A furnace that is too large will cycle on and off quickly, with some inefficiencies of operation. This can cause the rooms farthest from the furnace to remain cool and can cause furnace chimneys to deteriorate, due to excessive condensation. It can also cause some furnace controls or parts to break down sooner than expected. Furnaces that are undersized may not keep the house at a comfortable temperature in the coldest parts of the winter. It will take much longer for an undersized furnace to bring a house back up to temperature after the thermostat has been turned down for a period (such as night setback or vacation).

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