Load list study is a calculation method to get a design capacity for electrical system. From this study we can get all electrical equipment rating, such us generator, transformer, bus bar rating etc. This study is just a simple calculation, we only add the load with their electrical duty (not the load rating).

For example:

Water well pump with rating 30kW, but only consumed 26.5kW electrical load. We choose the consumed load for our calculation (26.5kW)

Beside load rating, there also a load activity. In here we divide into three categories, there are continuous, intermittent, and standby. Load activity is needed to get the load contribution to our electrical system. We multiply the electrical duty, with some multiply factor (MF) depend with the load activity.

The calculation results are average load, maximum load, and design load. Average load is the normal power consumed in our system. Maximum load is the normal load, with the operation of largest standby unit. Design load is the equipment design rating.

Step by step:

1. Prepare all load, at least their power rating, consumed load rating, and load activity.

2. Classify all load into their load activity in different column.

3. Summary all load in each load activity.

4. Calculate the load with this formula

Average load (AL)          : (Summary continuous load) + (MF for intermittent load)x(Summary Intermittent load)

Maximum load (ML)      : (AL) + 110%x(Largest standby unit)

Design load (DL)              : (MF for design load)x(ML)

MF for intermittent load usually between 0.5-0.6

MF for design load usually between 110%-120% (spare for design)

Last, you’ll get the electrical equipment rating by considerate the design load.

CMIIW