The minimum air flow in any panel is calculated as the sum of what components?

• A. The open circuit capacity of the largest fan only.
• B. The total capacity of the ventilation system.
• C. The open circuit capacities of all operating auxiliary fans plus 30% of the largest auxiliary fan's open circuit capacity.
• D. The sum of the returns and intakes.

Answer: (C)

The key idea is to determine the minimum air flow for a panel by combining the contributions from all auxiliary fans that are actually operating. You take the open circuit capacities of every operating auxiliary fan and add them together, then you also add 30% of the largest auxiliary fan’s open circuit capacity. This approach reflects how multiple fans share the load and accounts for the extra boost that the largest fan can provide, while also allowing for distribution losses and system dynamics.

Open circuit capacity means the airflow the fan could deliver with no resistance, so using these capacities provides a conservative estimate of what the panel can receive when all contributing fans are working. The 30% of the largest auxiliary fan’s capacity helps cover the fact that the biggest fan tends to drive a larger portion of the flow and that real-world ducting and resistances can affect distribution.

Why the other ideas aren’t correct: calculating with only the largest fan ignores the load contributed by other operating auxiliary fans; using the total capacity of the whole ventilation system may include fans or paths not feeding that panel and can overstate the minimum flow; and simply summing returns and intakes describes the physical flow paths rather than how to quantify the minimum panel air flow from the operating fan capacities.