What is the largest heat loss from an oil appliance attributed to?

The largest heat loss from an oil appliance is attributed to the burner on cycle. During this cycle, the appliance is actively heating, and while it is performing its primary function, significant thermal energy can be lost, particularly through the exhaust gases that exit the flue. The efficiency of fuel combustion and the design of the flue system play critical roles in how much heat is retained versus lost.

When the burner is operational, it generates heat not only for the space being heated but also in the form of waste gases that carry heat out of the system. If the burner is not operating efficiently, or if there are issues with the flue that can cause inadequate venting, this can further exacerbate heat losses during this cycle.

In comparison, other sources of heat loss, such as through walls or ductwork, typically represent losses that occur continuously over time or during periods when the system is not actively heating. While these can also contribute to overall inefficiencies in an oil heating system, the cycle of the burner itself tends to be the most significant source of heat loss when it is actually engaged in heating.