If a fixed electric space heater has a demand factor of 65%, what percent should be added to the heating circuit if the central air-conditioning unit has a demand factor of 100%?

If a fixed electric space heater has a demand factor of 65%, what percent should be added to the heating circuit if the central air-conditioning unit has a demand factor of 100%?

• A. 50%
• B. 75%
• C. 100%
• D. 125%

Answer: (C)

In electrical design, the demand factor is an important consideration when calculating the load requirements for different types of equipment. The demand factor accounts for the likelihood that not all appliances will be drawing power at their maximum rated capacity simultaneously.

In this case, the fixed electric space heater has a demand factor of 65%. This means that, when calculating the load for a circuit, only 65% of the heater's total capacity needs to be considered for the maximum load requirement. Meanwhile, the central air-conditioning unit operates at a demand factor of 100%, indicating that it will be drawing its full load when it is in operation.

To properly size the heating circuit in conjunction with the air-conditioning unit, you add the effective demand of the fixed heater (which is calculated at 65%) to the full demand of the air-conditioning unit (100%).

When you combine these scenarios, you need to account for the fact that the electrics may peak during severe usage conditions. Therefore, to adjust for the difference in demand factors, it makes sense that you take the full heating requirement from the heater and add the entire capacity of the air-conditioning unit, effectively treating it as 100%. This leads you to conclude that the total demand on the heating circuit with the