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# Selection guide for household circuit breakers in 2020

By：Nader Updated：September 09,2020 12:08PM

The air switch is used as a main power protection switch or branch line protection switch in the household power supply.

When a short circuit or overload occurs in residential wiring or household appliances, it can automatically trip and cut off the power supply, thereby effectively protecting these equipment from damage or preventing accidents from expanding; households generally use two-pole (ie 2P) air switches for main power protection. Single pole (1P) is used for branch protection; if the rated current of the air switch is selected too small, the air switch is likely to trip frequently and cause unnecessary power outages. If the selection is too large, the expected protection effect will not be achieved, so home improvement For air switches, it is important to correctly select the rated capacity and current.

General small air switch specifications are mainly divided into 6A, 10A, 16A, 20A, 25A, 32A, 40A, 50A, 63A, 80A, 100A, etc. according to rated current; then, how do ordinary families choose circuit breakers?

1. Calculate the value of each branch current

• Pure resistive loads, such as light bulbs, electric heaters, etc., can be obtained by directly dividing the indicated power by the voltage, the formula I=power/220v; for example, for a 20w bulb, the branch current I=20W/220=0.09A. Electric fans, electric irons, electric blankets, electric water heaters, electric heaters, rice cookers, electric frying pans, vacuum cleaners, air conditioners, etc. are resistive loads.
• Inductive loads, such as fluorescent lamps, televisions, washing machines, etc. The calculations are slightly complicated. Power consumption should be considered, and the specific calculations should also consider power factor. In order to facilitate the estimation, the author gives a simple calculation method, that is, general inductive loads. It is sufficient to indicate that the calculated power of the load is doubled. For example, indicate that the branch current of a 20W fluorescent lamp is I=20W/220v=0.09A, which is doubled to 0.09A*2=0.18A (than the exact calculated value of 0.15A , 0.03A more)

2. The total load current is the sum of the branch currents; if you know the branch current and the total current, you can select the branch air switch and the main switch air switch, the main fuse, the main electric meter and the specifications of each branch wire, or the check calculation has been designed Whether the specifications of these electrical components meet the safety requirements;

3. In order to ensure safety and reliability, the rated working current of electrical components should generally be greater than 2 times the required maximum load current; in addition, when designing and selecting electrical components, the possibility of future increase in electrical load should also be taken into account. Need to leave a margin;