Using the optional calculation method, four or more separately-controlled electric space-heating units are calculated at ___% of their nameplate ratings.

Using the optional calculation method, four or more separately-controlled electric space-heating units are calculated at ___% of their nameplate ratings.

• A. 20%
• B. 40%
• C. 60%
• D. 80%

Answer: (B)

When using the optional calculation method for electric space heating, you account for the fact that not all heaters will be on at the same time. For four or more separately controlled space-heating units, you calculate their load at 40% of their total nameplate ratings. This 40% reflects typical usage patterns and thermostat cycling, providing a realistic demand estimate without oversized feeders or panels. Using a higher factor would overstate the load, while a lower factor would understate it, so 40% is the standard value for this scenario.

When using the optional calculation method for electric space heating, you account for the fact that not all heaters will be on at the same time. For four or more separately controlled space-heating units, you calculate their load at 40% of their total nameplate ratings. This 40% reflects typical usage patterns and thermostat cycling, providing a realistic demand estimate without oversized feeders or panels. Using a higher factor would overstate the load, while a lower factor would understate it, so 40% is the standard value for this scenario.