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Circuit breakers and fuses are used in virtually every electrical system, and inverters are no exception. If you are going to install a 2000W inverter for instance, make sure you have the right circuit breaker to protect your appliances.
A 2000 12V watt inverter requires a 250A circuit breaker and a 2/0 AWG size wire. You cannot use a smaller wire because the circuit breaker carries excess current during a surge and could damage the inverter.
How to Calculate Circuit Breaker Sizes for Inverters
The calculations are straightforward. And they are applicable whether you run the inverter from 120V AC or 12V/24V battery banks, at 2000 watts or other sizes.
Inverter current output x 1.25 = circuit breaker size
If you prefer a fuse, use this conversion:
Inverter current output x 1.75 = fuse size
You can increase the fuse multiplier to 2.5, though the inverter should be fine with 1.75.
If you have a 2000 watt inverter like the Voltworks Power Inverter running off 120V AC, its current output is 16.6A and you need a 25A circuit breaker.
First we need to find the inverter current or amp output. We do that by dividing the watt load by the voltage.
Use the watt load, not the inverter capacity. If you load 1500 watts into the inverter, use that instead of 2000 watts.
2000 / 120 = 16.6
Now multiply this by 1.25 to get the circuit breaker size:
16.6 x 1.25 = 20.75
You could probably get away with a 20A breaker, but for safety go with the next largest circuit breaker size which is 25A.
Some More Calculations
Now suppose you want to run the inverter with a solar array and batteries. The steps are the same but this time you use the battery voltage, which can be 12V, 24V or 48V.
Most 2000W inverters use 24V so assuming you have that:
2000 / 24 = 83.3
83.3 x 1.25 = 104.1
Round off 104.1 amps to the nearest breaker size of 110A.
If you have a 2000W 12V system, the process is similar.
2000 / 12 = 166.6
166.6 x 1.25 = 208.25
Round that to the nearest available size which is 225 or 250A.
Repeat these steps for any inverter size you want to use. You can also use these same process if you have a 48V or 220V / 230V electrical system. If you are looking for a 24V battery to pair with your inverter, we recommend the Ampere Time LiFePO4 Deep Cycle Battery as it works great with these systems.
Keep in mind that circuit breakers should only be used for 80% of their capacity. So the maximum load for a 20A breaker is 16 amps for example. Follow this rule for your breakers and fuses at all times.
Fuses vs. Circuit Breakers For Inverters
A fuse and circuit breaker have the same purpose, protect the wires from excessive heat. Without a fuse or breaker, the wires could overheat and start a fire. So which is better, a fuse or circuit breaker?
Fuses are cheaper and easier to install. However you can only use it once. Circuit breakers cost more but you can use it repeatedly and has a higher capacity.
A fuse consists of a wire encased in glass. If the inverter has a sudden power surge the fuse container is going to break. If it is hot enough the wire will melt too. However the circuit is going to be disconnected. If your inverter blows a fuse you have to replace it with a higher capacity to handle the voltage.
A circuit breaker does the same thing, disconnect the inverter from the main power in case of an overload. However a breaker lets a current go from the lower to upper terminal to a strip.
If the current is above the safety threshold, the breaker stops the current. Unlike a fuse, the breaker does not melt or blow up. You can reset the breaker and use it again.
So Which is Better?
A circuit breaker costs more than a fuse but it is more effective. And unlike a fuse you do not have to buy a replacement every time there is a sudden voltage spike.
Whether you use fuses or circuit breakers make sure the inverter cable size is the right one. And if you do blow a fuse or the breaker goes off, find out what caused it.
Resetting the breaker or replacing the fuse is just one step. Check the inverter for possible damage or issues.
Do not overload the inverter even if you have a breaker. Make sure the inverter – and the rest of your electrical system – is running smoothly and without overloading.
How to Install a Circuit Breaker on an Inverter
If your home runs on solar power, you can easily connect a circuit breaker to the inverter. The following assumes you have some experience installing electrical components. Consult an electrician if you do not feel comfortable handling these wires.
Shut off the circuit breaker main power. Turn off the inverter power button too. If you have not already, turn off and disconnect any appliances or load on the inverter.
Remove the screws from the circuit breaker plate. Get the breaker you want to plug into the inverter. Use a screwdriver to remove the panel side cover.
Connect the cables to the inverter output. If you are using a 2000 watt inverter, use a 2/0 AWG wire. Other inverter sizes are going to need different wires so check the instructions.
Press the probes of a multimeter to the bus bar. If you shut off the main power there should be no voltage. If there is, check the breaker main power.
Remove half an inch insulation from the cable that connects the breaker and inverter. Set the wire onto the breaker neutral ground bar with a screwdriver.
Look into the circuit breaker rear panel. Find the breaker you chose and connect the wires. If you followed the steps above the inverter will run.
But if the breaker is not working or the system displays error messages, check the wiring as something could be loose.
Put the breaker panel back and turn the switch on. Power up the inverter. Run a test to see if the system is working.
These are general and simplified procedures to installing a circuit breaker. Your solar power system may have other components and require more steps.
Inverter Circuit Breaker Buying Guide
Before you buy, check the specifications of your inverter. If you are going to buy cables for the solar panels, look up its requirements too. Make sure to check the local building codes and regulations in your area. They determine what type of circuit breaker or fuse you can install.
Breakers and fuse sizes are measured by amperage. The breaker / fuse size required by a 2000 watt inverter is going to depend on its current output.
The amperage determines how much current the breaker permits before it disconnects the inverter. As we mentioned earlier, breakers should only handle up to 80% of their rated amperage. If you need more power, get a larger breaker.
Arc fault circuit interrupting breakers can tell the difference between harmless and risky arcs, and will shut off power if it is the latter. Arcing can happen in solar panels and inverters. A breaker should have this feature so it can turn off the power in case the arcing is dangerous.
Ground fault circuit interrupting (GFCI) breakers trip off or cut power in case of overloading. In addition, a GFCI breaker also disconnects power if there is a ground fault. This feature is essential for locations that will probably be wet like basements or garages.
If you are on a grid tied solar system, the inverter is going to run on 120V. A typical single pole circuit breaker will be fine.
A 2000W inverter should be fine with a 25A or 30A breaker. But this assumes you will be using the breaker for light to medium powered appliances only. You need a double pole circuit breaker to run a washing machine and other high powered appliances.
Modern inverters have safeguards built in, but it never hurts to have a circuit breaker in place. Once installed you can have peace of mind knowing your system is safe from any power surges.
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