What Is An Electric Load?

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Is the electrical load anything to do with weight? Will a big electrical load make my electrical cables sag and maybe come loose?

Electrical load refers to anything in an electrical circuit that adds resistance. It can be a light bulb, a washing machine in a residential setting or a motor in an industrial setting. Electrical load does not physically make your cables sag, but it does make them heat up, and this is why the electrical load is vital to calculate.

Contents

What is the purpose of electrical load?

The electrical load is a component found in an electrical circuit such as a device like a washing machine or a motor in an industrial application.

The component in the circuit converts electrical energy (power) and converts it into another form of energy, such as heat or light from a bulb.

Electrical loads can be found around your home from the tumble dryer that converts power into heat and motion.

How do you calculate the electrical load of a house?

Using an electrician, the load calculated needs to be accurate and have electrical load diversity incorporated into the circuit design.

You can use purely just maths and ohms Ω law to calculate how much current is needed in amps to overcome resistance in the circuit, such as an appliance.

You will need to imagine a parallel circuit with 3 resistors in the circuit, but all parallel meaning the power to each circuit will be uniform.

The voltage going into the circuit is a constant source to designate Vs for the voltage.

You think that the UK voltage is 230-240 volts but test the outlet, and it’s likely 240 volts. Plus, for this example, it’s easy to divide.

Each resistor has a value of 20R1. 80R2 and 60R3 by a simple calculation, you can now find out the current in each resistor and add that to your total load.

{"backgroundColor":"#ffffff","type":"$$","code":"$$I1=Vs/R1=240/20=12A$$","font":{"family":"Arial","color":"#000000","size":11},"aid":null,"backgroundColorModified":null,"id":"1","ts":1651586086955,"cs":"F09RBs15xqgG4C2cP4GTjw==","size":{"width":217,"height":16}}

{"type":"$$","backgroundColorModified":null,"backgroundColor":"#ffffff","id":"5","code":"$$I2\\,=\\,Vs/R2\\,=\\,240/80\\,=\\,3A$$","aid":null,"font":{"color":"#000000","family":"Arial","size":11},"ts":1651586394372,"cs":"gKadUtjjDQxhXMS6mJBImg==","size":{"width":226,"height":16}}

{"type":"$$","code":"$$I3\\,=\\,Vs/R3\\,=\\,240/60\\,=\\,4A$$","backgroundColorModified":null,"backgroundColor":"#ffffff","id":"6","aid":null,"font":{"size":11,"color":"#000000","family":"Arial"},"ts":1651586438050,"cs":"iQUqAzOAXKqJKu6J5ZnwNQ==","size":{"width":226,"height":16}}

You then simply take:

{"type":"$$","code":"$$I3\\,=\\,Vs/R3\\,=\\,240/60\\,=\\,4A$$","backgroundColorModified":null,"backgroundColor":"#ffffff","id":"6","aid":null,"font":{"size":11,"color":"#000000","family":"Arial"},"ts":1651586438050,"cs":"iQUqAzOAXKqJKu6J5ZnwNQ==","size":{"width":226,"height":16}}

19amps for this circuit which is the resistive load.

Use the on-site guide

The 18th edition on-site guide has a wealth of knowledge incorporated into the book. You can find a section where all amps are expressed in a typical residential circuit, which saves a lot of time and effort listing everything in an excel sheet.

It is worth creating an excel sheet for a typical residential setting such as a 2 bedroom house, 3 bedroom house, or 4 bedroom house, so you know pretty much before you arrive on-site what the load will be.

What is the difference between kW and kVA?

The difference is that kW is the actual power in the circuit which is the power being converted into a useful working output. On the other hand, the kVa is known as the apparent power. The apparent power is the available power you have to work within a circuit.

What is the general formula for calculating the total load in kW and kVA?

Calculation of Load in KW :

  • 1 phase = V×I×p.f×10^-3
  • 3 phase = √3 V×I×p.f × 10^-3

Calculation of Load in KVA :

  • 1 phase = V×I×10^-3
  • 3 phase = √3 V×I ×10^-3

Why is the motor rated in kVA, not in kVA?

The power factor is unknown from the power generator and the transformer; they are rated in kVA.

However, the motor is different. It has a stated power factor on its nameplate; hence electric motors are rated in kW and not kVA

What is considered an electrical load?

An electrical load is any component in a circuit that consumes power or energy from the circuit. This is termed the “load”.

In a domestic setting, the “load” can be a light bulb or a washing machine or anything in between, which is used in a domestic setting.

What causes the most load in my home? 

Here are the top five energy-consuming home appliances?

  • White goods such as washing machines, dishwashers and anything else that uses a water heater in an appliance.
  • Tumble dryers use constant high amps
  • Cold appliances, your fridge freezer is responsible for using approximately 12% of the average household electricity bill
  • Cooking, most ovens are electric and have gas hobs. The electric oven is a large user of electricity
  • Consumer electronics 
  • Lighting

Can a DIY enthusiast calculate the electrical load for a house and rewire the house?

There are some nuances to calculating the electrical load and cable sizing. For instance, what size cable would a DIY enthusiast use on a kettle? The kettle is fast boiling and is only switched on for a few minutes. Do you use a 6mm cable, or will a lesser cable suffice?

How will the DIY enthusiast compensate for the power diversity in a washing machine? When it starts, it cycles. It uses a lot of power, then the power drops off, then increases, then drops off again.

It’s best to let a qualified electrician calculate the power load on a circuit.

A DIY enthusiast can’t rewire a house. Rewires are covered under part P of the building regulations and are notifiable to the building department in your local area for inspection.

How do you calculate amperage load?

Volts to amps calculation with ohms

Then current/in amps (A) is equal to the voltage V in volts (V) divided by the resistance R in ohms (Ω)

{"type":"$$","code":"$$I3\\,=\\,Vs/R3\\,=\\,240/60\\,=\\,4A$$","backgroundColorModified":null,"backgroundColor":"#ffffff","id":"6","aid":null,"font":{"size":11,"color":"#000000","family":"Arial"},"ts":1651586438050,"cs":"iQUqAzOAXKqJKu6J5ZnwNQ==","size":{"width":226,"height":16}}

So

{"backgroundColor":"#ffffff","type":"$$","backgroundColorModified":null,"code":"$$amp = volt / ohm\n$$","aid":null,"id":"3","font":{"family":"Arial","size":11,"color":"#222222"},"ts":1651610835882,"cs":"his/Su67GRnyKmbwKrdE9g==","size":{"width":124,"height":16}}

Or

{"font":{"size":11,"family":"Arial","color":"#222222"},"backgroundColor":"#ffffff","aid":null,"code":"$$A = V / Ω\n$$","type":"$$","backgroundColorModified":null,"id":"4","ts":1651610892684,"cs":"VKgtsNl9ADP7Yvpzx7H3/w==","size":{"width":68,"height":16}}

Example

What is the current flow of an electrical circuit with a voltage supply of 30 volts and a resistance of 10Ω?

According to ohm’s law, the current I is equal to 30 volts divided by 10 ohms:

{"backgroundColor":"#ffffff","aid":null,"type":"$$","id":"6","code":"$$I = 30V / 10Ω = 3A\n$$","backgroundColorModified":null,"font":{"size":11,"family":"Arial","color":"#222222"},"ts":1651611030778,"cs":"iY+d0xBFkgZJgQ8Pc9RjmA==","size":{"width":144,"height":16}}

Who should calculate electrical loads?

It’s a no brainer for most people. You need a qualified, competent electrician to undertake this job, the calculations may not be difficult if you just left school, but they are a little intimidating for most.

A qualified electrician knows these calculations and knows their own name, so you will know the load calculations will be correct.

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