Heat build up in retractable extension cords

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Srv52761

Srv52761

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In a woodworking forum I frequent a member is building a new shop and is now laying out his electricals. He intends to install several drops from the 10’ ceiling, he is asking for advice on layout.
Several members have suggested regular outlets with a 25’ retractable reel extension cord.

I feel like that is not a good idea. When I visualize that I see something like a 12 amp router or circular saw with a 6’ cord plugged into the 16 or 14 gauge extension cord, with only about 3’ or 4’ of the extension cord actually being splayed out.
So figuring the axle of the reel at maybe 8” diameter, with the diameter getting 3/4” bigger after every 3 wraps… that’s about ten wraps still within the enclosed reel… the equivalent of 20 current carrying conductors.
In conduit, we would have to derate the ampacity to 50% because of its reduced ability to dissipate heat. The reel would be even worse; each conductor has its own insulation layer, then every two ccc would have another insulation sheath around it. And, unlike conduit where the 20 conductors would travel away from any one spot, spreading out over about 21 feet; in the reel, the 20 conductors on the top of the axle would be 8” away from the conductors on the other side; all being contained in about 200 cubic inches of plastic).

I think a 25’ extension cord is fine when you have the bulk of the cord splayed out. But I think leaving the bulk wound up on most occasions is not wise.
Would you think there would be any issue or am I just being paranoid.
 
I would never spec a 16AWG cord reel for anything. For a residential use, 14AWG would be the minimum.

For a woodshop, going to tools, I don't see the issue? Usage of those tools is intermittent and not continuous. I don't see anyone using a router or table saw for more than a few minutes on/few minutes off. Plenty of time to cool down between uses.

I certainly wouldn't connect a continuous device such as a dust collector to it though.

Seriously, when was the last time you read about a cord reel causing a house fire? If they are as common as you fear, they'd be in the news everyday. As with anything in this world, you need to use it with some common sense. No, you don't wrap a 100' of 16/3 on a reel, then plug a 1500watt space heater in to it.

An experienced wood worker with enough smarts to design and build a shop should be a reasonable use. On the other hand, I wouldn't leave my wife alone in a room with a space heater and a 16/3 cord.
 
I have an extension chord for our garden. If I fully extend it I can operate it at 13A. If I limited it it reduces to 5A.
 
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Srv52761 said:
In a woodworking forum I frequent a member is building a new shop and is now laying out his electricals. He intends to install several drops from the 10’ ceiling, he is asking for advice on layout.
Several members have suggested regular outlets with a 25’ retractable reel extension cord.

I feel like that is not a good idea. When I visualize that I see something like a 12 amp router or circular saw with a 6’ cord plugged into the 16 or 14 gauge extension cord, with only about 3’ or 4’ of the extension cord actually being splayed out.
So figuring the axle of the reel at maybe 8” diameter, with the diameter getting 3/4” bigger after every 3 wraps… that’s about ten wraps still within the enclosed reel… the equivalent of 20 current carrying conductors.
In conduit, we would have to derate the ampacity to 50% because of its reduced ability to dissipate heat. The reel would be even worse; each conductor has its own insulation layer, then every two ccc would have another insulation sheath around it. And, unlike conduit where the 20 conductors would travel away from any one spot, spreading out over about 21 feet; in the reel, the 20 conductors on the top of the axle would be 8” away from the conductors on the other side; all being contained in about 200 cubic inches of plastic).

I think a 25’ extension cord is fine when you have the bulk of the cord splayed out. But I think leaving the bulk wound up on most occasions is not wise.
Would you think there would be any issue or am I just being paranoid.
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retirede said:
1cc377a689ef00bb4efa45c237b87191.jpg
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Heres a different approach with differing materials that works well for my customers shop fab areas, without expensive or cheap chord reels.

www.electriciantalk.com

Any ideas for mounting power and data to racks

Customer wants data / power stations at multiple stock / shelving racks I’m just curious on how you guys would do this. I don’t want to directly mount to rack because shelves move and they will need access to notches
www.electriciantalk.com www.electriciantalk.com
 
Srv52761 said:
When I visualize that I see something like a 12 amp router or circular saw with a 6’ cord plugged into the 16 or 14 gauge extension cord, with only about 3’ or 4’ of the extension cord actually being splayed out.
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You have the wrong cord reel in mind.

I installed 2 of these in a French Deli over a large table in the middle of the kitchen. They get used all day, every day. Been there 4 years with no issues - Screenshot_20230201_235937_Chrome.jpg12 gauge, 20 feet.

 
Flexible cords delivered in a roll on a reel or form of some kind often have a greatly reduced ampacity while tightly wound, even partially.
But commercial spring loaded retractible cord reels are most often designed to deliver the full nominal ampacity when fully retracted.
This can involve both using a heavier gauge wire than would be used for an open cord of the same ampacity, designing the cord reel itself to keep the cord adequately ventilated, or a combination of the two approaches.
If the manufacturer's documentation does not specifically state what the ampacity is when fully spooled, I would be inclined not to use that product partially or completely retracted.
 
I have a few in my workshop. They're 12 AWG with an integral 15A circuit breaker. All the UL Listed ones on the market now seem to include the overcurrent protection. If a reel is Listed I wouldn't worry about using it. I wouldn't install 14 AWG or 16 AWG reels (or unlisted ones) in a workshop.
 
BarryO said:
I have a few in my workshop. They're 12 AWG with an integral 15A circuit breaker. All the UL Listed ones on the market now seem to include the overcurrent protection. If a reel is Listed I wouldn't worry about using it. I wouldn't install 14 AWG or 16 AWG reels (or unlisted ones) in a workshop.
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The problem with those damn breakers is if you pop it, you're pulling out the ladder to reset it. Seems counter to the typical NEC requirement that stuff be readily accessible.

These are the ones I use. Open reel, and no stinking breaker.




images


I do have one exception. An older Craftsman with 14AWG wire and a triple tap on the end. It's the only one I've ever seen with the circuit breaker located on the female end and not the plug or the unit itself.
 
ActionDave said:
That damage didn't happen just because the cord was rolled up when it got used. Get Paul Harvey on the line, I want to know the rest of the story.
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Run a milk house heater for a few hours on that and see how hot it gets. I found one of those in an office 40 years ago. It hadn't failed yet but you could smell the plastic off-gassing and certainly couldn't touch it with bare hands.
 
VirutalElectrician said:
The problem with those damn breakers is if you pop it, you're pulling out the ladder to reset it. Seems counter to the typical NEC requirement that stuff be readily accessible.
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I've gotten pretty good at resetting them by reaching up with a piece of EMT or a 2x4. 😉

Per 240.10, Supplementary Overcurrent Protection is not required to be readily accessible.

The 15A breaker seems a reasonable value. The ampacity of these thermoplastic flexible cords is 25A for 12 AWG cord (Table 400.5(A)(1) for 2 current-carrying conductors). 15A is a derating to 60%. In a woodshop these should rarely have a continuous load; I use mine for routers and similar uses.
 
VirutalElectrician said:
Is that thing listed? The Amazon blurb doesn't mention UL or ETL listing.
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Yes it is, there is a UL sticker on the back side. It shows it is rated for 15A, 1875W and is 12ga wire, SJTOW, rated 105C. It says it has overload protection, but I can’t see a breaker so it might be a fuse in the female cord cap.

I would be fine with that.
 
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