Which issue can cause sidewall-vented mid-efficiency oil furnaces to function poorly?

Improper vent location is a critical issue that can cause sidewall-vented mid-efficiency oil furnaces to function poorly. These types of furnaces rely on a specific venting configuration to ensure that exhaust gases are safely expelled from the living space and that fresh air is drawn in effectively for combustion. If the vent is not located according to manufacturer specifications or local building codes, it can lead to improper airflow or backdrafting. This can not only diminish the efficiency of the furnace but also pose safety hazards, such as the potential for carbon monoxide entering the home. Proper vent location is essential for maintaining optimal performance and safety in oil-fired heating systems.

In contrast, while corroded pipes, incorrect fuel type, and small filter size can all lead to operational challenges, they do not directly relate to the inherent function of the venting system, which is crucial for mid-efficiency oil furnaces.