Gas Fitter Practice Test

What is the normal supply air volume for forced air furnaces in cfm?

1. 500

2. 600

3. 700

4. 800

The correct answer is: 700

The normal supply air volume for forced air furnaces typically falls within a range that aligns with the heating requirements of residential and commercial spaces. In practice, a commonly accepted guideline suggests that a furnace should deliver approximately 400 to 600 cubic feet per minute (cfm) of air for every ton of cooling it provides, but for heating, the standard is often closer to the 600 cfm mark per 100,000 BTU of input. Given that options presented include a value of 700 cfm, this value is most often associated with situations where there are increased heating demands or a larger space that needs to be warmed. The 700 cfm mark is advantageous as it allows for more effective distribution of heat throughout the space, ensuring a more consistent and comfortable indoor environment. Utilizing 700 cfm reflects a balance between airflow, efficiency, and effective heat transfer, which is crucial for ensuring that the furnace operates at optimal levels without excessive strain on the system. Thus, this choice takes into account the common practices and considerations in forced air heating systems, leading to its suitability as the standard for supply air volume in many scenarios.