Oct 24, 2010

How To Calculate The Maximum Demand and The Total Connected Load?


One of the most basic electrical calculations that an electrical engineer should know is to calculate the Total Connected Load (TCL) and Maximum Demand (MD).

The one million dollar question: What is Total Connected Load and Maximum Demand?

Total Connected Load (TCL) is the mechanical and electrical load (in kW) that will be connected (or to consumed) for that particular area.

The Maximum Demand (MD) is the total kW that actually contributes the total power used in one time after applying the diversity factor based on the Total Connected Load calculated.

Example 1
Let say, your own bedroom is having 1no. 2hp air-conditioning split unit, 4nos. of single phase socket outlet and 1no. 2X36W T8 Florescent Tube.

I’m using the Excel program since I can easily manipulate all the values in case fine-tuning values need to be made in future.

Then, your Total Connected Load and the Maximum Demand will be as per above;


By looking into the figure above, the Total Connected Load and the Maximum Demand is 2.57kW and 1.36kW respectively.

How The Calculation Works?
1. The unit for TCL and MD is in Watt. Therefore, all the loads need to convert into Watt.
a) 2hp a/cond split unit = 2 X 746W = 1492W
b) 2X36W Flou. Fitting = (2 X 36W) + Ballast Wattage = 80W
c) 13A Socket Outlet = 250W (this is rather subjective since some engineer putting 300W/nos)
2. Determine the Diversity Factor (DF) for the respective load. The DF is the percentage of load that will contribute for the total of the Maximum Demand. For the above example, I’m expecting the split unit will contribute 6o% of the total MD, lighting will be 80% and socket outlet is 40%.
3. Multiply the Diversity Factor with the Connected Load to get the Maximum Demand.
4. Summing-up the individual MD to obtain the Total MD.

Why I Need To Calculate The TCL and MD?
By calculating the TCL, you’ll know the total load connected for a particular area and also you can determine the sizing of cables. But, the most important thing is by having the TCL, you can determine your MD. This MD will be declared to the utility provider for the purpose of meter deposit and utility bill.