The combustion efficiency of a non-weatherized oil furnace must be at least 75%. It uses a secondary heat exchanger to extract heat.
Condensing furnaces
A condensing oil furnace is a heating device that needs a source of oil in order to generate heat.
This device (condensing oil furnace) may use a secondary heat exchanger to extract more heat from gases.
The condensing oil furnaces exhibit a high efficiency ranging from 75% to 90+%.
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