# Extension cord will harm treadmill? **URL:** \ **Category:** Factual Questions\ **Created:** [January 29, 2017, 9:32pm UTC](https://boards.straightdope.com/t/extension-cord-will-harm-treadmill/778530 "2017-01-29T21:32:28Z")\ **Posts on this page:** 11\ **Page:** 2
**Author:** ![K2500](https://avatars.discourse-cdn.com/v4/letter/k/f6c823/32.png) [@K2500](https://boards.straightdope.com/u/K2500)\ **Post date:** [January 31, 2017, 12:53am UTC](https://boards.straightdope.com/t/extension-cord-will-harm-treadmill/778530/21 "2017-01-31T00:53:58Z")
A four foot extension cord is unlikely to burn the house, or the machine, down(or up I suppose). Name plate current ratings for consumer goods are unreliable at best, but conservatively at least. Home air compressors are the world’s worst at this, or so I’ve noticed. I’ve never owned a treadmill but if it’s like most appliances the cord should be pretty easy to change for one that’s four feet longer, depending on your apptitude. Changing the cord would eliminate the extra connection point, which is a common point of failure for cord and plug devices. Longer cords in multiple sizes are available with molded ends. ---
**Author:** ![watchwolf49](https://avatars.discourse-cdn.com/v4/letter/w/e9c0ed/32.png) [@watchwolf49](https://boards.straightdope.com/u/watchwolf49)\ **Post date:** [January 31, 2017, 1:39am UTC](https://boards.straightdope.com/t/extension-cord-will-harm-treadmill/778530/22 "2017-01-31T01:39:08Z")
> [@Alley\_Dweller](#): > > But then if I plug the treadmill into an outlet in my living room, the electricity has to run through 30 feet more wire than if I plug it into an outlet in my kitchen. Do I have to concern myself with this? > > What difference does it make if the wire the electricity runs through is inside the wall (house wiring) or outside the wall (extension cord) when the wire is the same gauge? The problems occur at the connections … the wires in your wall have no connections (or there better not be) … all the connections should be in the boxes where they are always accessible … and connections here are tight, complete and professionally installed … The problems with extension cords is where they plug into each other and/or the wall … just them lil’ prongs don’t always make a great connection and that’s where the heating problems occur … in the OP’s case, his 12 gauge extension cord should be fine … but where he plugs in the whimpy 16 gauge power cord for the machine is where it will heat up … perhaps dangerously so if these plugs are worn some … ---
**Author:** ![Crafter\_Man](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/crafter_man/32/458_2.png) [@Crafter\_Man](https://boards.straightdope.com/u/Crafter_Man)\ **Post date:** [January 31, 2017, 1:44am UTC](https://boards.straightdope.com/t/extension-cord-will-harm-treadmill/778530/23 "2017-01-31T01:44:07Z")
> [@Melbourne](#): > > Another problem with long thin extension cords with multiple junctions, is that there may be too much voltage drop during the start-up, when the motor draws 5-10 times as much current. This can, in extreme cases, cause the motor to burn out. True, but it is usually only a problem with long extension cords. Let’s say you have a 120 V device that draws 10 A. And you want to power it with a 100 foot extension cord. What gauge wire should the extension cord be? Since you’re pulling 10 A, you can safely use a 12 gauge, 14 gauge, or 16 gauge extension cord. But as you mentioned, there is another issue that must be considered: voltage drop along the cord. Assuming T = 70 °C and doing the math we discover: Using a 12 gauge extension cord, the voltage at the load will be 116.2 V (3.2% low). Using a 14 gauge extension cord, the voltage at the load will be 114.0 V (5.0% low). Using a 16 gauge extension cord, the voltage at the load will be 110.4 V (8.0% low). The threshold is 5%. So a 12 gauge extension cord would work fine. A 14 gauge extension cord would be marginal. A 16 gauge extension cord could be bad… the voltage would be 8% low at the device. The device could be damaged, depending on what it is. ---
**Author:** ![Mangosteen](https://avatars.discourse-cdn.com/v4/letter/m/6a8cbe/32.png) [@Mangosteen](https://boards.straightdope.com/u/Mangosteen)\ **Post date:** [January 31, 2017, 1:44am UTC](https://boards.straightdope.com/t/extension-cord-will-harm-treadmill/778530/24 "2017-01-31T01:44:54Z")
Does it help to unplug the treadmill after using it to allow the cord to cool down? I use it 3 times a week for about 36 minutes each time. Should I keep it unplugged when not in use? ---
**Author:** ![Crafter\_Man](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/crafter_man/32/458_2.png) [@Crafter\_Man](https://boards.straightdope.com/u/Crafter_Man)\ **Post date:** [January 31, 2017, 1:51am UTC](https://boards.straightdope.com/t/extension-cord-will-harm-treadmill/778530/25 "2017-01-31T01:51:29Z")
> [@Alley\_Dweller](#): > > But then if I plug the treadmill into an outlet in my living room, the electricity has to run through 30 feet more wire than if I plug it into an outlet in my kitchen. Do I have to concern myself with this? > > What difference does it make if the wire the electricity runs through is inside the wall (house wiring) or outside the wall (extension cord) when the wire is the same gauge? Indeed, the _entire_ length of wiring between the device and the home’s transformer matters. In my example above, I assumed (for simplicity’s sake) the voltage at the receptacle is regulated at 120 V. This is not true, of course. A more thorough analysis would also include the length and gauge of the Romex wiring in the walls. In buildings were there are very long runs of wiring, the electrician will increase the gauge of the wiring (to an appropriate size) to keep the voltage drop to less than 5% at maximum current. And there is the issue with temperature. It can get complicated… ---
**Author:** ![jnglmassiv](https://avatars.discourse-cdn.com/v4/letter/j/f07891/32.png) [@jnglmassiv](https://boards.straightdope.com/u/jnglmassiv)\ **Post date:** [January 31, 2017, 2:04am UTC](https://boards.straightdope.com/t/extension-cord-will-harm-treadmill/778530/26 "2017-01-31T02:04:54Z")
> [@Mangosteen](#): > > Does it help to unplug the treadmill after using it to allow the cord to cool down? > I use it 3 times a week for about 36 minutes each time. > Should I keep it unplugged when not in use? IF the cord is getting warm, it will only do so when the device is in use and, most likely, when under significant load. For a treadmill, this is primarily during that initial few seconds as it comes up to speed. Unplugging the cord will not help anything powered down cool off. There may be other safety reasons to unplug it that aren’t related to any electrical hazards like, say, a cat or child accidentally turning the thing on. Go get an appliance cord from the hardware store and rest easy. Folks use these for thirsty things like microwaves and air conditioners all the time. If you’re really concerned, feel the cord after a normal workout session. It may be warm but shouldn’t be hot. Further, feel the blades on both cords and see if they’re hot. Thinking about it, I’d make sure that the connection at the wall isn’t too loose, either. It should take a solid push to insert and a similar tug to pull out. The guy upthread using 200 feet (too long) of daisy-chained (insertion loss at each plug) cords for a chainsaw (high load device) is exactly the irresponsible behavior that compels manufacturers to say to never use extensions of any kind. ---
**Author:** ![K2500](https://avatars.discourse-cdn.com/v4/letter/k/f6c823/32.png) [@K2500](https://boards.straightdope.com/u/K2500)\ **Post date:** [January 31, 2017, 3:00am UTC](https://boards.straightdope.com/t/extension-cord-will-harm-treadmill/778530/27 "2017-01-31T03:00:24Z")
It’s a four foot cord, no need for VD calculations or ambient considerations. A four foot cord for a treadmill mill? It’ll work fine. ---
**Author:** ![watchwolf49](https://avatars.discourse-cdn.com/v4/letter/w/e9c0ed/32.png) [@watchwolf49](https://boards.straightdope.com/u/watchwolf49)\ **Post date:** [January 31, 2017, 3:12am UTC](https://boards.straightdope.com/t/extension-cord-will-harm-treadmill/778530/28 "2017-01-31T03:12:36Z")
> [@jnglmassiv](#): > > [snip] … The guy upthread using 200 feet (too long) of daisy-chained (insertion loss at each plug) cords for a chainsaw (high load device) is exactly the irresponsible behavior that compels manufacturers to say to never use extensions of any kind. Hey … I’m a trained professional … I knew _exactly_ what I was doing … it was just the one tree and I kept a sharp eye on matters … everything else is within 100’ and the 10 gauge cord works great … So, **Mangosteen** , just feel the cords after your workout … if there’s a heating problem you’ll easily note it … consider sliding the machine 4 feet towards the outlet as part of the workout … ---
**Author:** ![Melbourne](https://avatars.discourse-cdn.com/v4/letter/m/b5e925/32.png) [@Melbourne](https://boards.straightdope.com/u/Melbourne)\ **Post date:** [January 31, 2017, 11:07am UTC](https://boards.straightdope.com/t/extension-cord-will-harm-treadmill/778530/29 "2017-01-31T11:07:05Z")
> [@Crafter\_Man](#): > > True, but it is usually only a problem with long extension cords. > > Let’s say you have a 120 V device that draws 10 A. And you want to power it with a 100 foot extension cord. > > What gauge wire should the extension cord be? Since you’re pulling 10 A, you can safely use a 12 gauge, 14 gauge, or 16 gauge extension cord. But as you mentioned, there is another issue that must be considered: voltage drop along the cord. Assuming T = 70 °C and doing the math we discover: > > Using a 12 gauge extension cord, the voltage at the load will be 116.2 V (3.2% low). > Using a 14 gauge extension cord, the voltage at the load will be 114.0 V (5.0% low). > Using a 16 gauge extension cord, the voltage at the load will be 110.4 V (8.0% low). > > The threshold is 5%. So a 12 gauge extension cord would work fine. A 14 gauge extension cord would be marginal. A 16 gauge extension cord could be bad… the voltage would be 8% low at the device. The device could be damaged, depending on what it is. If it’s actually a 10A load for a 10A wire, then: Drawing 50 or 100A. As I said, at startup motors often draw 5-10 times the rated current. I would have guessed maybe a 500W motor, drawing 25 to 50 at startup. ---
**Author:** ![ftg](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/ftg/32/2801_2.png) [@ftg](https://boards.straightdope.com/u/ftg)\ **Post date:** [January 31, 2017, 1:21pm UTC](https://boards.straightdope.com/t/extension-cord-will-harm-treadmill/778530/30 "2017-01-31T13:21:35Z")
Again there’s damage to the cord and then there’s _damage to the treadmill_. Feeling the cord tells you _nothing_ about the extra strain that the treadmill motor is having for running at a reduced voltage. ---
**Author:** ![TokyoBayer](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/tokyobayer/32/13989_2.png) [@TokyoBayer](https://boards.straightdope.com/u/TokyoBayer)\ **Post date:** [February 3, 2017, 4:43am UTC](https://boards.straightdope.com/t/extension-cord-will-harm-treadmill/778530/32 "2017-02-03T04:43:10Z")
> [@ftg](#): > > Again there’s damage to the cord and then there’s _damage to the treadmill_. > > Feeling the cord tells you _nothing_ about the extra strain that the treadmill motor is having for running at a reduced voltage. Electric motors are rated to be used with a tolerance of voltages. If the OP has a good voltage from the wall, one additional connection and four feet isn’t going to cause the voltage to drop significantly, and would have much less effect than somewhere which has a low voltage from the power company. [Previous page](https://boards.straightdope.com/t/extension-cord-will-harm-treadmill/778530.md?page=1)