What gauge wire for 30 amp circuit?

10 gauge wire is the correct gauge for a 30 amp circuit The length of wire-run should also be factored-in when deciding the correct wire size To get the right answers refer to the Wiring Codes or Regulations for your locality. (Town/State. ) As always, if you are in doubt about what to do, the best advice anyone should give you is to call a licensed electrician to advise what work is needed Before you do any work yourself on electrical circuits, equipment or appliances always use a test meter to ensure the circuit is, in fact, de-energized IF YOU ARE NOT ALREADY SURE YOU CAN DO THIS JOB SAFELY AND COMPETENTLY REFER THIS WORK TO QUALIFIED PROFESSIONALS.


Because of our ever increasing demand for electrical power in out homes, most new homes are being built with a minimum of a 150 Amp service and 200 is not uncommon. Many older homes still have 60 amp services and in rural locations it is still possible to find 30 amp services. It is important to understand the relationship between wire gauge and amperage.

To do this we will look at the original fuse. The original fuse was a piece of wire sized to melt when a specific amount of amps (current) was going through it, as shown in Figure 3. Figure 3 - The fuse element, on the left of the picture, is what is inside the cartridge.

The thinner the link between the caps the less amount of current (amps) that the link can handle before it melts, due to the heat. A piece of wire gets hot as it carries the current to your home or throughout your home. This is why a toaster, stove or hotplate works, current is sent through the wires and they get hot.

The thinner the wire, the hotter it gets when a specific amount of amps are flowing through it. Circuit breakers, as shown in Figure 4, perform the same function although they work in a different manner. They work in a similar manner to a thermostat.

As current flows through the breaker, a piece of metal warms and bends, when the bend reaches a point it mechanically trips the breaker to the "TRIPPED" position, which is between the "OFF" and "ON" positions. It may be noted that although circuit breakers are more convenient than fuses because they can be reset. Fuses react much faster to overloads and hence shut down a circuit faster than breakers do.


A #10 copper wire with an insulation factor of 90 degree C and a voltage rating of 300 volts has an ampacity of 30 amps.


10 gauge wire is the largest I like to use in home use. Depending on who you talk to and what code book you are looking at, the amount of current a 10 gauge wire can handle changes. I tend to think it can safely handle about a 30 amp breaker (and I think most code books fall in line with this).

You can add up the amps (12+15=27 amps) to get the total amps possible. This would mean that a 30 amp breaker with 10 gauge wire should work fine. However, check your currents to make sure that is the max that will be pulled.

Many items have a large start up current that can cause a breaker to trip if you aren't careful.


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