In heating systems, what does the term 'W.C.' stand for?

In heating systems, the term 'W.C.' stands for Water Column. This measurement is crucial as it indicates the pressure of the gas or air in a system, typically measured in inches of water column. It helps technicians understand the system's performance and efficiency, as it relates to airflow and pressure within heating appliances, such as furnaces and boilers. Knowing the water column pressure is essential for ensuring that these systems operate safely and effectively, as incorrect pressure levels can lead to inefficient heating or safety hazards.

The other options do not relate directly to heating system measurements or terminology and thus do not have the same relevance or application within the context of heating systems.