Extension cords are a convenient way to bring power to where you need it, but they can also be a potential fire hazard if not used properly. Believe it or not, one of the main safety considerations when using an extension cord is the length of the cord.
The longer the cord, the more resistance it has and the more heat it will generate. This is why most extension cords are only rated for a certain number of hours of use. Once that limit is reached, the cord will start to overheat and could potentially cause a fire.
Extension Cord Time Limits
Does OSHA actually provide a limit as to how many hours you can use an extension cord? Technically, no. People often ask how many hours an extension cord can be used for before it becomes unsafe, but the answer to that question is not as simple as you might think. There is no one answer to the length of time you can use a power extension cord, as it will always depend on multiple factors. These include the appliance being used, and whether or not the cord is designed for heavy-duty or general purpose use.
It's important to be aware of how much power your extension cord is rated for and to not exceed that. If you need to use a longer cord, make sure to get one that is properly rated for the length you need.
If you're not sure, take into consideration the length of your extension cord.
Short-Length Extension Cords
If you are using an extension cord anywhere between 3 to 50 feet, most likely you are using a short-length extension cord. The rule of thumb is that the shorter the cord, the higher the amp rating can be. This is due to the fact that there is less copper wire in a shorter cord.
For heavy-duty use on an appliance being powered by a short extension cord, you should give the cable a break every few hours. If you are using a lower amp rated extension cord for general purposes, you may be able to get away with not unplugging it as often. General purpose cords are much safer to use, but of course they will only power up small appliances.
Medium-Length Extension Cords
An extension cord that is 50 to 100 feet long is considered to be a medium-length extension cord. The rule of thumb for these types of extension cords is that for every additional foot in length, the amp rating should be decreased by 0.5.
This means that if you are using a 50-foot long extension cord that is rated for 15 amps, you should only use it to power appliances that require 7.5 amps or less. If you need to power something that requires more than 7.5 amps, you will need to use a shorter extension cord or one that is rated for a higher amp rating.
Long-Length Extension Cords
For an extension cord that is 100 feet or longer, the rule of thumb is to decrease the amp rating by 1 for every additional foot in length. This means that if you are using a 100-foot extension cord that is rated for 15 amps, you should only use it to power appliances that require 5 amps or less.
If these rules are followed for short, medium, and long-length cables, you should only need to give the extension cord a break every few hours. Extension cords can be used for hours at a time, but no extension cord is designed to run for an entire 24 hours. Many factors will determine how long an extension cord will last, but typically the longer the cord, the more chance it has to overheat. Longer cables should be checked and controlled for temperature more frequently than shorter cables.
Extension Cord Safety Rules
- You should always check periodically if your extension cord is getting warm to the touch. If it does feel warm, and especially if it feels hot, you should unplug the cord and give it some time to cool off.
- You should never use an extension cord as a permanent solution. That is NOT what they are designed for!! They are designed for short-term use only. If you need to power something on a permanent basis, you should have an electrician install the proper outlets and wiring.
- Never plug two extension cords together in attempt to create a longer cable.
Trusted by Professionals
Extension cords are a handy tool to have around, but it's important to use them safely. Be sure to always check the rating of your extension cord and never exceed that.
As you can see, the length of an extension cord can be a limiting factor in how long it can be used for. It is important to be aware of the amp rating of your extension cord and to not exceed that.
