Home circuitry is an important part of most DIY projects Safety should be the primary concern when working on anything with electricity within the home. It is recommended to always get a professional to do any work with electricity. Understanding the load you are subjecting your wires to and how much they can handle is crucial to installing circuitry safely in your home.
You can use a 12-gauge wire on a 15-amp circuit with room to spare. Generally, a larger wire supports higher loads and should be used when in doubt. The 14-gauge wire will also support a 15-amp circuit, but this is the wire’s upper limit and could increase the chance of overloading, making the 12-gauge wire a safer choice for a 15-amp circuit.
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We are examining at the best wire sizes for a 15-amp circuit in your home. We will also discuss which material to use for these wires and some of the best ways to install circuitry safely. Keep in mind that any type of electrical work should never be considered a DIY job with little basic knowledge of electrical work. Getting a professional to do any type of electrical work is necessary.
Wire Size for a 15-Amp Circuit
Working with circuitry in your home requires a good deal of planning, not just for the installation but also for the long-term effect it will cause. There is a good deal of effort that goes into laying down wires and connecting breakers and panels together.
Planning ahead as much as possible is wise when setting these systems up.
On the face of it, a 15-amp circuit will use a 14 AWG (American Wire Gauge) wire and then require a 15-amp breaker. The maximum ampacity a 14 AWG wire can support is 15 amps, so it will be able to handle this load. The breaker will ideally prevent an overload.
However, a 15-amp circuit is primarily used for lighting and small appliances. If this is the case for your 15-amp circuit, the 14 AWG wire will be able to bear the full load. The caveat is that unless you are sure that the load will remain below 15 amps, the 14 AWG wire is, at the least, limiting and, at the most, a potential fire hazard.
We also have an article on how many LED lights you can use on a circuit to give you an idea of the possible load requirements.
This adds a restriction to any possible future expansion along this circuit, limiting the possible outlets, appliances, and even lights that can be connected down the line.
When the load for the wire — the total watts being used by systems along it — grows beyond its capacity, it will overheat from the strain. This can lead to melting wires, damaged appliances, and even electric fires (source).
A Better Choice for the 15-Amp Circuit
Since an average 15-amp circuit is mainly for lights and small appliances, this overcapacity does not require much to be reached. Additionally, other factors can cause unforeseen strain on the wires.
This includes the length of the wire and the ambient temperature it is subjected to. Both can cause a wire to reach that overheat stage on less load than would normally cause it.
With this risk in mind, it might be the right move for you to upgrade your wire gauge to accommodate this potential for overloading.
The thicker wire can support a greater number of amps by supplying an easier, less resistant pathway for the electricity to flow. Therefore, electricians often recommend using the thicker 12 AWG wire for home installments.
Why Professionals Use 12-Gauge Wire
While a 14 AWG wire can support a load of 15 amps, there are several reasons the professionals recommend using the larger 12 AWG wire. A survey conducted on electrical contractors demonstrated an overwhelming 85% preference for the 12 AWG when it came to home wiring (source).
There are several reasons 12 AWG has become the wire size of choice for most contractors. The first and most essential reason is for increased safety. A thicker wire has a larger cross-sectional area and, therefore, more room for electricity to flow. The 12 AWG can support loads up to 20 amps without concern.
This increased capacity is linked to a decrease in resistance in the wire. With less resistance in the wire, there is less heat created from the electricity flowing through.
Heat increases the excitement of the electrons flowing through the wire and, subsequently, increases resistance even further. As we mentioned already, excess heat can also lead to wires melting and even electric fires.
Linked to the capacity available along the different wire sizes is the number of possible outlets that can be attached. Regardless of load, a 12 AWG can support a greater number of outlets along a single branch.
According to copper.org, a survey suggested that 8.4 average receptacles were allowed for a 14 AWG, while up to 10 were permitted for the 12 AWG.
Another reason to consider 12 AWG wiring is the distance involved. The longer a wire, the more energy is required for the electricity to flow through it. This can result in a drop in voltage, which results in damage to systems using that power.
A wider channel for the electricity to flow, and a decreased resistance along this channel, means there is less chance a voltage drop will occur over longer distances.
The only downsides of using 12 AWG over 14 AWG is the price and the flexibility. The former does cost more, mainly because it is thicker and requires more material to manufacture.
This thickness also makes it less flexible than 14 AWG and, therefore, slightly harder to install neatly around objects and corners. These are hardly downsides, though, when compared to the benefits.
The Best Type of Wire for Your Home
By this point, is it clear that 12 AWG wiring is the preferred option for wire size. However, the material of the wire also plays a factor. When it comes to electric conductors, there are two primary choices: copper and aluminum.
Copper, in general, is the preferred choice for home wiring for several reasons. The first of these comes down to resistance once again. Copper has a specific electrical resistivity of 100, while aluminum sits at the 160 mark (source).
Like with the 12 AWG wire, this means that electricity can flow more easily through copper than it can through aluminum. It leads to a cooler operating temperature and, subsequently, even less resistance along the wire.
To compensate for this, aluminum wiring needs to be notably thicker than copper. Not only does this lead to stiffer cabling but also more joints required along a circuit.
The latter point is simply because there is less wire length in each spool due to the increased thickness, meaning the wires need to be carefully attached together more often to run the required length of the circuit.
These joints can be a point of weakness along the circuit. This leads to the next benefit of copper wire: thermal expansion. Copper is less likely than aluminum to expand relative to the heat involved. Expansion and contraction can cause damage to the wiring, especially at the connecting joints.
Copper is also far more resistant to corrosion, especially due to oxidation. While wires are insulated to protect against corrosion, this can still be a concern in the long run.
The same applies to water, where copper is again the preferred choice because it does react when in contact with moisture. Aluminum, on the other hand, does react with water, which can cause problems.
Another benefit of copper is that it is easier to work with. This relates to the fact that copper wire will be thinner than the aluminum wire but also that it is less brittle and, therefore, more malleable for specific situations. It is also easy to solder, making it simpler to connect and repair.
Again, like with the 12 AWG, this better performance comes at an increased cost. However, with these benefits, it is certainly worth the initial costs for better long-term reliability and efficiency.
Word of Warning when Working with Electricity
It is no secret that electricity can be dangerous. However, it is often even more hazardous than you might expect. A current of around 75 milliamps running directly through your heart can cause ventricular fibrillation (source).
This can cause your heart to stop pumping blood properly and restrict oxygen to the brain. As a point of reference, there are 15 000 milliamps in a 15-amp circuit.
Circuit breakers and grounding tools do offer some form of protection against electrical surges and overcurrent. These are largely to protect the entire system, though, and often do little to help against the smaller shocks that may occur.
Always utilize insulative gear and ensure there is no moisture or wetness around the cables and electric panels.
Ultimately, it is always advisable to contact a professional electrician when working with circuitry around your home. They have the tools and experience to navigate these risks in the best possible way. Safety must be your primary concern when working with anything electrical.
Consult An Electrician
An article such as this cannot cover all eventualities and codes that apply in all countries and all local municipalities.
For this reason, as well as for the safety of you, your family, and your home, it is best to consult with a local electrician before any type of electrical work.
When electricity is concerned, a little bit of knowledge can be deadly, and it is not worth taking the risk simply to save a little money.
Final Thoughts
Any type of electrical work should never be considered a DIY job with little basic knowledge of electrical work. It is recommended to always get a professional to do any work with electricity. There are several important factors to consider when you install your own circuitry. For a 15-amp circuit, the best wire size is 12-gauge because it offers several benefits over the smaller 14-gauge.
Copper wire is overwhelmingly the most popular material to use in your wires. Overall, make sure you are taking the necessary safety precautions when dealing with electricity.
