Determining the amount of load to assign to a particular circuit breaker, has always been a challenge to most people. As an electrician, this is the aspect of the work you need to know well enough. The reason is that for you to make a good installation work the circuits should be appropriately loaded with loads. Sometimes in installation, you find out the circuit breaker cut/tripped OFF, even when there is no fault. This is as result of overloading a particular circuit. And to avoid the issue of overload, we need to share and load our electrical load properly. What I mean by electrical loads are consumable electrical appliances, ranging from electric bulbs, tv sets, AC, and others.
some elementary calculations to be familiar with in loading the circuit breaker.
To perfectly load shade the loads well, we need calculations based on the type of load we are having. This calculation is not far from the basic electricity calculation we have been familiar with. Which are the ohms laws. Which in summary is I =V/R. Where I am the current in Amps. V is the voltage in Volts. And R is the load resistance in ohms. When calculating the power, we make use of the formulae, P(watts)= V(volts) × I(Ampere).
the miniature circuit breakers inside the distribution board are always rated in ampere. The work of the breaker is only to cut off when there is an excess current from the line maybe as a result of a short circuit of overload.
The miniature circuit breakers have different ratings, like 10A, 15A, 20A, 25A, and so on. So even from the rating of the circuit breaker, we observe that breakers used for lighting points should be different from the ones used for sockets or water heaters.
The miniature circuit breaker’s main work is for the protection of our electrical work. The ones for lighting points, sockets, and water heaters are already specified but our work is to make sure not to overload during installation. Another thing we should consider is what they called diversity factors.
calculating/estimating the suitable circuit breaker for our installations.
During the installations, we choose and merge some loads before assigning them to a particular breaker. In the electrical installation, some electrical loads share their circuit breakers while some don’t. For instance, the power circuits like electric water heaters and cooker units are not sharing a circuit breaker. So during the installation work, they are connected separately to their breaker.
Draft out the loads to be connected to the miniature circuit breaker and multiple them by their power factor. The load is drafted out in Watts. So now using the power formula, P(watts) and V(volts) are known. The V is the operating voltage we are using. It is either 120v or 240v depending on your country’s operating voltage.
so making the I(A) the subject formula in other to determine the current the circuit will draw during operation. Find the circuit breaker rating that is closer and above the calculated value and make use of it for the circuit.