What is the size of the fuse for the 1000W amplifier (detailed)

You receive the protection provided by an electrical fuse only if the rating matches the circuit or wiring system in which it is installed.

When this rating is higher than required, you get overcurrent damage to your speakers, and when it's lower, you permanently break the fuse wire and audio system circuit. 

Keep reading to find out the fuse ratings you need to install to protect your 1000W amplifier in your car or home.

Let's get started.

What is the fuse size for the 1000W amplifier?

For the 1000 watt audio amplifier in your car, you will need a fuse of about 80 amps to properly protect it. This rating is obtained from the formula I=P/V, which takes into account the power rating of the amplifier, the output power of the vehicle's alternator, and the efficiency class of the amplifier.

Although the car audio amplifier usually comes with an internal fuse to protect it from power surges, this protection does not extend to the external wiring of the speakers and the entire audio system.

This means you still need an electrical fuse to protect your entire amplifier system and wiring in the event of any power surge.

Usually, choosing a new electrical fuse should be fairly straightforward. You just pick one with the same model and rating as the old blown fuse box.

However, this becomes difficult if you do not have any indication of the rating or if you are installing a new amplifier in your car.

To help you fully understand how to correctly size an electrical fuse, we will explain what the three factors mentioned above are. We will also show you their place in the presented formula.

Amplifier power rating and efficiency class

The power of an audio amplifier is the output power that it emits when operating. When you look at your car's amplifier, you see the wattage rating in the specs. In our case, we expect to see a 1000W spec. Now there are other factors to consider.

Audio amplifiers usually fall into different classes, and these classes are characterized by different levels of efficiency in operation. The efficiency level of an amplifier is the amount of power it radiates in watts compared to its input power.

The most popular audio amplifier classes and their respective performance levels are listed below:

• Class A - efficiency 30%
• Class B - 50% efficiency
• Class AB - efficiency 50-60%
• Class C - 100% efficiency
• Class D - 80% efficiency

You first take these efficiency values ​​into account when calculating the correct power or power value to enter into the formula. How do you implement them?

Class A amplifiers are commonly used in low power circuits due to their inefficiency. This means you don't normally see them on 1000 watt systems.

You will most likely be dealing with class AB, class C and class D amplifiers due to their higher efficiency and safety in 1000 watt systems.

For example, for a 1000 watt class D unit with 80% efficiency, your amplifier's initial input power goes up to 1250 watts (1000 watts / 80%). This means that the power value you enter into the formula is 1250W, not 1000W.

After that, you keep 1000 watts for class C amps and about 1660 watts for class AB amps.

Generator output

When we calculate the fuse rating for amplifiers, we are actually calculating the current or current being sent by its power supply. In the case of a car amplifier, we are considering the current supplied by the alternator.

In addition, the ratings of electrical fuses are always indicated in amperage. If you see a "70" rating on a fuse, that means it's rated at 70 amps. Since the power characteristics of speakers are usually power values, the formula helps to make the appropriate conversions. 

A 1000W amplifier is always running a 1000W alternator, so we aim to convert that power to amps. This is where the formula comes in.

The basic formula for converting watts to amps is as follows:

Ampere = W/Volt or I=P/V where "I" is an amp, "P" is power, and "V" is voltage.

Determining the voltage supplied by an alternator is not difficult, as it is usually listed on the alternator specifications. On average, this value ranges from 13.8 V to 14.4 V, with the latter being more common. Then, in the formula, you store 14.4V as a constant voltage value.

If you want to be accurate in your estimates, you can use a multimeter to check the generator supply voltage. Our guide to diagnosing the generator with a multimeter helps with this.

Examples of Fuse Ratings for Amplifier Power and Class 

With all that being said, if you want to get a recommended rating for an amp, you must first consider its class and efficiency. You apply this efficiency factor to get the amplifier's initial input power, and then convert it to amps to find out how much current it's safe to draw.

1000 watt class AB amplifier

With a 1000 watt class AB amplifier you will find an initial input power that is around 1660 watts considering its 60% efficiency (1000 watts / 0.6). Then you apply the formula:

I = 1660/14.4 = 115A

The fuse size you use for class AB amplifiers will be close to this value. This is a 110 amp fuse.

1000 watt class C amplifier

At 100% efficiency, you get the same output power from Class C amplifiers as their input power. This means that "P" will remain at 1000 watts. Then the formula looks like this:

I = 1000/14.4 = 69.4A

By rounding this value to the nearest available value, you select a 70 amp fuse.

1000 watt class D amplifier

With an efficiency of 80%, 1000 watt class D amplifiers start with 1,250 watts (1000 watts/0.8). You then calculate the ranking using these values ​​in a formula:

I = 1250/14.4 = 86.8A

You are looking for a 90A car fuse.

What about different sized fuses?

500W class D amplifier

For a 500-watt amplifier, the principles remain the same. Instead of using 500 watts in the formula, you are considering class efficiency. In this case, 80% efficiency means you're using 625W instead. To calculate your rating, you then feed those values ​​into a formula.

I = 625/14.4 = 43.4A

Rounding that up to the nearest available rating, you're looking for a 45 amp fuse.

1000 W class D fuse in 120 V circuits

If the amplifier you want to fuse is used in your home and not in your car, the AC power supply for it is typically 120V or 240V. For 120V power supplies, you implement the values:

I = 1250/120 = 10.4 A. This means you are choosing a 10 amp fuse.

For 240 V power supplies, the following formula applies instead:

I \u1250d 240/5.2 \u5d XNUMX A. You round this number to the nearest available rating, that is, you choose a XNUMXA fuse.

However, in addition to all this, there is one more thing to consider when determining the fuse current rating safely.

Factors Affecting Fuse Rating

There are many factors involved in fuse sizing, and they either make the base rating higher or lower than what is determined by the formula.

Some of these factors include the sensitivity of the device that the fuse protects, the air conditioning systems available, and how the connecting cables converge.

When choosing a fuse, you should also consider its voltage rating, maximum short-circuit current, and physical size. The type of fuse used in the circuit mainly determines the factors to be considered.

In car amps, you use a car blade fuse, while cartridge fuses are mostly found in your home appliances.

Now, when determining the fuse rating, there is one important factor to pay attention to. This is a fuse rating issue.

Fuse derating

Derating occurs when the recommended fuse rating is changed to avoid unwanted blowout. The temperature of the environment in which you intend to use the fuse is an important factor influencing the final fuse rating.

The standard fusible wire test temperature is 25°C, which derates fuses by 25% from their normal ratings. Instead of using a 70A fuse for a Class C amplifier, you choose a fuse with a 25% higher rating.

This means you are using a 90A fuse. This dispersion may be higher or lower depending on the other factors mentioned above.

F.A.Q.

How many amps does a 1000 watt amplifier draw?

It depends on the voltage the amplifier is working with. The 1000W amplifier consumes 8.3 amps when operating in a 120V circuit, 4.5 amps when operating in a 220V circuit, and 83 amps when operating in a 12V circuit.

What size fuse do I need for 1200W?

For 1200 watts, you use a 10 amp fuse in the 120 volt circuit, a 5 amp fuse in the 240 volt circuit, and a 100 amp fuse in the 12 volt circuit. They vary depending on the amount of derating required.