How much current is appropriate for a 3kw household electric water heater

In the nearby industrial zone, there is a mechanical maintenance master named Lao Wang, who usually helps various factories to repair mechanical equipment. With many years of experience, sometimes when encountering some circuit problems, he would take on the task without hesitation, and he always fixed it. Over time, he won the praise and trust of the bosses of various factories, and the bosses no longer needed to hire electricians in the factory, and let him do the work for them. This made Lao Wang forget that he is just an amateur electrician, and his main job is mechanical repair. Now, Lao Wang has made money, bought a new house, and is renovating it. Thinking that he is the "electrician" who is famous in various factories, he can just do the laying of pipes and wiring at home by himself. Isn't this a piece of cake! Yesterday, an old electrician friend came to visit his home. He happened to see Lao Wang wiring his home. Seeing that Lao Wang had put in 1 square wire, the friend asked him why the wires for household appliances were placed in the electric water heater. Lao Wang said: A new 3KW household electric water heater, a famous brand, Head & Shoulders. Seeing Lao Wang showing off with a beam of joy, the electrician friend was confused and asked Lao Wang: Why do you use 1 square wire for your 3KW water heater? Lao Wang answered fluently: We are all "electricians", who doesn't know that a kilowatt current is 2A, and my 3KW water heater is only 6A, so 1 square is more than enough. The electrician friend couldn't help laughing and told Lao Wang to replace the wires with copper core wires of more than 2.5 square immediately. Avoid unnecessary losses in the future! In addition, he strongly recommended that Lao Wang buy an electrician's manual and read it carefully, because face slapping is not important, safety is the most important!

How much current is required for 3KW power?

Let's take 1KW as an example. First, we need to see whether the appliance is powered by 380V or 220V. Secondly, we need to see whether it is an inductive load or a resistive load.

Three-phase asynchronous motor

The first case: 380V power supply 1KW power inductive load (such as a three-phase asynchronous motor) The calculation formula is as follows: current = power / (voltage * root 3 * power factor) = 1000W / (380 * 1.732 * 0.8) = 1.9 (approximately equal to 2A)

Three-phase heating rod

The second case: 380V power supply 1KW power resistive load (such as a three-phase heating rod) The calculation formula is as follows: Current = power / (voltage * root 3) = 1000 / (380 * 1.732) = 1.51 (approximately equal to 1.5A)

Single-phase asynchronous motor

The third case: 220V power supply 1KW power inductive load (such as single-phase asynchronous motor) The calculation formula is as follows: current = power / (voltage * power factor) = 1000W / (220 * 0.8) = 5.68 (approximately equal to 5.7A)

Electric kettle

The fourth case: 220V power supply 1KW power resistive load (such as a single-phase water heater) The calculation formula is as follows: current = power/voltage = 1000W/220 = 4.54 (approximately equal to 4.5A) The electric water heater of Lao Wang’s house above belongs to the fourth case. The electric water heater of 220v power supply 3KW has a working current of about 13.5A. Normally, our single-strand copper wire 1 square can carry 6A current, 1.5 square can carry 10A current, and 2.5 square can carry 15A current (the above single-strand copper wire safety current carrying capacity is reduced by some on the manufacturer’s design current). Therefore, it is safe and durable to choose 2.5 square copper wire! In addition, when we choose wires, in addition to considering the actual current of the electrical appliances, we must also distinguish whether it is copper wire or aluminum wire. The materials are different, and the current carrying capacity of the same wire diameter is also different. Copper wire has a higher current carrying capacity than aluminum wire. It also depends on whether it is single-strand or multi-strand. Generally, multi-strand wires have a higher current carrying capacity than single-strand wires.

Single and multi-strand copper wire and aluminum wire. Have you learned how to calculate the current based on the power and choose the appropriate wire?