To get the required wattage rating for the subpanel, multiply the total wattage (from the square footage and appliance calculations) by 1.25 to obtain the adjusted load. The National Electrical Code requires this safety modification, which acts as a buffer for voltage loss on the feeder circuit. This will ensure that enough power is available for all appliances being fed from the panel.

The next step is to divide the amperage of your circuit by the number needed for the subpanel. For example, if the circuit is 20 amperes, then you would need a 220-volt, 30-amp breaker in the main panel. If you have a 200-volt system, then you would need a 2,000-watt generator instead. Be sure to select a generator with **at least twice the expected demand** for **this calculation**. Also make sure it is listed as approved for outdoor use.

You can also use **an electrical power calculator** to determine how many amps you need for your subpanel. These tools are very accurate and will tell you exactly how much power you need for your application. However, be aware that using a higher amperage than recommended may overstress your wiring and cause it to fail prematurely.

If you are unsure about how to calculate **the correct subpanel size**, or want to save some money, our software automatically generates the correct requirements based on your building information.

Subpanel Circuit Breaker Sizing and just round up to the next bigger breaker size. For example, if the load calculation results in 48 amps, you should safeguard the circuit with a 50-amp breaker. Subpanel feeder circuits are 240-volt and need a double-pole circuit breaker. The other two circuits can be 120 volts so they use standard single-pole breakers.

The main purpose of the subpanel breaker is to protect the wiring inside the panel from damage if electricity goes wrong. If you install a subpanel but don't have **enough space** for a full-size breaker, then you will need to use **a miniature breaker** or a breaker adapter. These devices allow you to use smaller breakers than those approved for normal household current; however, they are still designed to carry enough power to energize an adequate number of outlets to serve **their protective function** in case of a fault.

There are three types of subpanel breakers: magnetic, thermal, and electronic. Magnetic breakers use the metal parts inside the breaker box to create a magnetic field that interrupts the flow of current through the conductor it surrounds. This means that the breaker must be closed to work properly. Thermal breakers work by detecting heat generated by excess current flowing through a wire and immediately opening the circuit when it does. Electronic breakers use sensors and microprocessors to detect any voltage on the line before opening the circuit.

Watts divided by volts equals amps, according to a simple math. After you've estimated this, it's only a matter of adding roughly 10% to the figure and selecting the closest fuse to match. If you need a 3, 5, or even 13 amp fuse, this is a more exact way than simply guessing.

The first thing you need to know is the wattage of the lights in **your installation**. This is measured in watts, which is the amount of power that flows through each light bulb. Knowing the wattage of your lights will help you choose the correct size fuse for any overload condition. For example, if one string of lights is consuming **15 watts** and another is using 20 watts, a single 20-amp fuse will not be enough to protect your home because the first set of lights will continue to burn out one by one until the overloaded circuit breaks.

Determine the sub's "watts RMS" rating. Then multiply the number of subs by their RMS rating to get their overall RMS rating. You must ensure that the amp you select will not deliver more than the entire RMS rating of the subsystem. For example, if your system is rated at 20 RMS and you choose an amp that delivers 25 RMS, you will damage your speakers quickly.

Once you have the total RMS rating of your system, you can find out how many watts of equipment you need by dividing the total by 2.1 (the average value for amps with a DC output). For example, if your system is rated at **20 RMS**, you would need an amplifier that outputs about 40 watts RMS to cover all of your speakers.

The best way to decide on the wattage requirement of your system is by using a speaker impedance load chart. These charts are usually included in the user's manual or website for your speaker manufacturer. They show the relationship between input voltage, output power, and loading for each speaker type. You should use an impedance load chart when choosing an amplifier because it takes into account the loaded sound pressure levels and power ratings of **your components**.

For example, if you were to buy a 10-watt per channel amp, then you would need a system with a total of 20 watts RMS to cover your speakers.

400 watts RMS each sub equals 800, thus 150 percent (ideal) equals 1200 watts. If 1200 watts (RMS) is what you're looking for in an amp, look for it. Otherwise, find one that fits your budget.

The amount of power that an amplifier can produce depends on how many amperes it draws when powered up. So if you drive two 12-volt vehicles with **your amplifier**, you'll need **a 2000-watt amp** to start them both off at **the same time**. A 500-watt amp would be enough to start just one car.

Most cars today are driven only once or twice a week so you'd want a 200-300 watt amp to start them both off at **the same time**. A 100-200 watt amp would be sufficient to start one car while another car was being driven safely down the road.

Amps are measured in amps passing through them; therefore, the more amps an amp passes, the hotter it gets. Thus, you should use low current drivers in **a high power amp** to keep it from getting too hot. The tester below will tell you if your amp is large enough.

You should always match the load being driven by your amplifier to the capacity of the amp.