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.
where to check the actual diversity factor?
ReplyDeleteSorry for the late reply.
DeleteYou can't find the actual diversity factor (DF). DF is an assume value to calculate the MD since the total MD need to be declared to the utility provider for billing purpose.
The more DF you apply (value reaching to 1) means that the total connected load (TCL)is equal to MD. Practically, it would not happen since you might not using all the loads (TCL) in one time. Furthermore, declaring the TCL=MD will end up you need to pay higher meter deposit (depend on certain utility provider).
Dear sir(s),
ReplyDeleteWe have two no. Power transformer of 10/12.5MVA and load connected is about 5000kw daily. but we have two separate energy meter (Actrus make) on each transformer but problem is that during billing the energy consumption is about 3000kwh monthly from both the transformers. But individual Maximum demand is about 45500 KW & 6500 kW respectively. Our contract demand reserved was about 10400 KW.
Question here is, should we have sum up the individual MD (i.e. 4500 + 6500 = 1100kW) for billing which is not found logic as actual consumption is 3000kwh only??
hai...sorry for the late reply.
Deletethe billing calculation might differ based on electrical provider at certain country.
as for Malaysia, the billing will be calculated based on MD and KWh usage. i've done some calculation on how to calculate the electricity bill as per link below;
http://miorzaini.blogspot.com/2010/11/transfering-electrical-load_22.html
hopes it moght help you.
Hi Mr Mior.
ReplyDeleteThis post really interest me.
Could you tell me the power rating of 5 pin 63A industrial power socket. I've search in the internet and cant find any clue.
Thanks.
Sorry for the late reply..
DeleteI assume, you mentioning about 3Phase system(since you mentioning a 5 pin socket)
The simplest way, you can use this formula to calculate the power (P)=(sqrt 3)X Voltage X Current X Power Factor.
P= 1.732(415V)(63A)(0.85) = 38,491W @ 38.5kW
But...assuming you need to calculate the MD for equipments that using the 3phase 63A, you need to consider the Diversity Factor (DF). The DF is subjective and it depend on the designer itself.
Lets look into these 2 scenarios.. (1)Load for Air Handling Unit (AHU), (2) Load for sump pump (used only during rainy days)
Scenario 1: Total MD = Power X DF = 38.5kW X 0.9 = 34.65kW
Scenario 2: Total MD = Power X DF = 38.5kW X 0.1 = 3.85kW
Scenario 1: I'm considering out of the total power of 38.5kW, the AHU using 90% of it and the AHU will contribute 34.65kW for overall MD since the AHU are fully operated.
Scenario 2: I'm considering the pump will only contribute 3.85kW for overall MD. This is to consider that not everyday is a rainy day and even its raining..the total power consume is only about 10%.
hopes I'm answering you..
Mr Mior,
DeleteYour explanation is outstanding. So, I assume that I have to know the load that will be used for the socket?
1 more thing, sir. How did you get 250W power rate for SSO 13A when 230 X 13A = 3.12kW.
Thanks.
It a rule of thumb..most of designer taking 200W or 250W per 13A SSO.
Deleteexample
1 no. 13A sso = 250W
2 nos. 13S sso = 500W
3 nos. 13A sso = 750W...and so on..
Dear Sir,
ReplyDeleteI have 1 MVA power installed and my total connected load is 2061.30 KVA, is this acceptable or what is the standard connected load for 1MVA.
Thanks
Hello Sir,
ReplyDeleteWould like to know how to determine the socket Watts in calculation for TCL and MD
Draw a S.L.D of main panel for a hospital, showing meter position.
ReplyDeleteEssential loads are:
1) Equipment load 100 KW
2) Critical load 500 KW
3) Life AID Safety load 400 KW
4) NON-Essential load 200 KW
5) Other service load 200 KW
Calculate and suggest size of transformer, size of main cable, capacitor bank, and calculate the
capacity of emergency load having above first three mentioned loads is supplied by emergency
generator .????
Sir, your concerns are underlying in our design calculations
ReplyDeleteTERBAIK. mudah faham tuan
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