What is the demand factor for five household clothes dryers?

What is the demand factor for five household clothes dryers?

• A. 75%
• B. 65%
• C. 85%
• D. 100%

Answer: (C)

Demand factor is all about how much of the total connected load you actually expect to draw at peak. With multiple clothes dryers, you don’t get five devices all at full power at the same moment, so the peak demand is less than the sum of their rated loads. For five household clothes dryers, the standard practice is to apply a factor of 85% to the combined rating. So you size feeders or a service using 0.85 times the total of the dryers’ ratings. For example, if each dryer is rated 6 kW, the total would be 30 kW; applying 85% gives 25.5 kW, which is about 106 A at 240 V. The other options would imply either using the full connected load (no diversity) or applying too large a reduction, which isn’t consistent with typical NEC guidance for five dryers.

Demand factor is all about how much of the total connected load you actually expect to draw at peak. With multiple clothes dryers, you don’t get five devices all at full power at the same moment, so the peak demand is less than the sum of their rated loads. For five household clothes dryers, the standard practice is to apply a factor of 85% to the combined rating. So you size feeders or a service using 0.85 times the total of the dryers’ ratings.

For example, if each dryer is rated 6 kW, the total would be 30 kW; applying 85% gives 25.5 kW, which is about 106 A at 240 V. The other options would imply either using the full connected load (no diversity) or applying too large a reduction, which isn’t consistent with typical NEC guidance for five dryers.