Mike Dolt Enterprises
Mike Dolt Enterprises
User: rowelelectrical, Location: Connecticut
Asked on: Monday, May 2, 2011 at 1:16 pm EDT
Answered on: Tuesday, May 14, 2024 at 4:52 am EDT
Question: HI,Im doing a load calculation for a unit in a multifamily dwelling building. My question is, if i use the calculation method on 280.82 which is the first 10KVa and 40% remainder on loads for calculating the units main service, and when i have the total loads for each unit using this method of calculation, is it still right to use table 220.84 for calculating the building's service knowing i have used the 10KVA and 40% remainder on calculating the service for each unit? the building has 15 units so I have to use 40%.Appreciate all you advise.Thanks,
Yes, it is still correct to use Table 220.84 to calculate the building's service after using the method in 280.82 to calculate the unit main services.Here's why
The method in 280.82 provides a convenient way to estimate the service requirements for individual dwelling units in multifamily buildings. It considers the typical load characteristics of these units and provides a simplified approach to calculating the service size. Table 220.84, on the other hand, provides a method for calculating the service size for the entire building. It takes into account the total load of all the units in the building, as well as the diversity factor that reflects the fact that not all units will be using their maximum load at the same time.* The use of the 10kVA and 40% remainder method in 280.82 does not invalidate the use of Table 220.
84. This method is simply a means of estimating the load for each unit, and it is still necessary to take into account the total load of all the units when calculating the building's service size.
Therefore, to calculate the building's service size, you should
1. Calculate the main service for each unit using the method in 280.
82.2. Determine the total load of all the units in the building.
3. Use the total load and the appropriate diversity factor from Table 220.84 to calculate the building's service size.
In your case, since you have 15 units in the building, you would use a diversity factor of 40%. Flag for review