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I bought a new surge protector and the included specification material says I need 30 feet between the outlet and the service panel. My situation is probably about 5 feet. The outlet I want to protect is on the first floor and almost directly over the service panel in the basement. The surge protector itself has a 6-foot cord.

Can I add a heavy gauge grounded extension cord (let’s say 25 feet of the same gauge as the house wiring) to satisfy this requirement?

Rohit Gupta
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    It would probably work, but goes against code to use an extension cord permanently. Find the 30ft an odd spec. – crip659 Feb 08 '23 at 19:21
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    Does anyone have a clue as to why that requirement might exist? I mean, I've got a surge protector _IN_ my panel at this point (though it's only promised to protect hardwired stuff, not plugged in electronics).... And there's another protecting the solar electronics which is maybe 10 feet, "manhattan distance", from the panel. – keshlam Feb 09 '23 at 03:51
  • Here is a link that pertains to your question. https://www.se.com/ww/en/faqs/FA370836/#:~:text=Issue%3A,and%20the%20electrical%20service%20panel. Good luck – Retired Master Electrician Feb 08 '23 at 21:07
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    The above link mentions a requirement of equipment being tested at a distance 10 metres (30 feet) from the panel. Which sounds like "The equipment is guaranteed to work at that distance, but not a lower one". Due to inductivity and capacitance of the cord, one should assume the surge will be less powerful at a greater distance, so it makes some sense to assume a protector that's rated for a 30 ft cord might get overloaded if the cord is shorter. – Guntram Blohm Feb 09 '23 at 08:09
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    @keshlam In-panel surge protectors generally work entirely differently from their plug-in cousins. A great many plug-in surge protectors will burn themselves out to protect your electronics. In-panel surge protectors try to send that excess voltage to ground. – Machavity Feb 09 '23 at 14:01
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    MOV surge protectors always work to short-circuit the excess voltage to ground. They often burn themselves out in the process of doing so if the surge is a large one; like fuses, they're best considered disposable components but should last a long time between failures. And yes, that applies to in-panel protectors too; that's why they have a status light that tells you when they're no longer providing protection. – keshlam Feb 09 '23 at 15:18
  • @GuntramBlohm: The size of a remote surge event the surge suppressor can clamp will be proportional to the resistance between the source of the event and the load being clamped. If the primary source of resistance between a surge source and the load is the 12ga or smaller wire connecting them, doubling that would double the size of a remote voltage surge event that the suppressor could clamp. To a surge suppressor, a 5000 volt surge on the end of a certain length of 12ga wire would look like a 2500 volt surge on a wire half as long. – supercat Feb 09 '23 at 17:27
  • Can you please post the make and model of your surge suppressor? A link to the manual would be helpful if you have it. – Freiheit Feb 09 '23 at 22:58
  • @crip659, How can building codes say anything about an extension cord if the extension cord is not attached to the building? (Unless, maybe that's what "permanent" means. Does "permanent" really mean, "attached to the building?") – Solomon Slow Feb 09 '23 at 23:23
  • @SolomonSlow It is more the amount/type of use. Temporary is when you use an extension to use a light to see in a dark corner/hole for five minutes. Permanent is using it to power the lights(stuff) in a room for a long time, maybe running it under a carpet(big no no). – crip659 Feb 09 '23 at 23:39
  • @SolomonSlow Not building code but electrical code. One of the others on here can probably point to the exact code number or google might help. – crip659 Feb 09 '23 at 23:55
  • @crip659, Suppose the inspector sees my toaster plugged in to an extension cord that runs along my kitchen countertop to an outlet 15 feet away. I get that _not_ having an outlet above the counter top every so-many feet along its length is a violation for which I can be cited. I get that there's a problem if I need the cord. But, as for the cord itself... Assuming I haven't _attached_ it to the wall, I'll just say, "It's not permanent. I put it away when I'm not using it. By the most _amazing_ coincidence, I was just getting ready to make toast when you knocked." Let him prove otherwise! – Solomon Slow Feb 10 '23 at 00:09

3 Answers3

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No! Never coil up an extension cord and put power through it! This happens. I know you didn't say "Imma coil it up" but what else were you going to do with it? Also most extension cords are a size or two smaller than in-wall wiring, which makes this heating problem more acute.

They want that length of wire so they can use the resistance of the wire to help tamp down surges. That means the device needs to shunt (short) far fewer amps to get voltage within limits which is easier on the surge suppressor.

But honestly, rather than run a bunch of wire in a straight line, I would run it in a tight coil around an iron core. Not me personally; I'd buy a transformer pre-made. Nothing suppresses surges like a transformer! They are tuned for 60 Hz and attenuate other frequencies, like the high frequencies seen in surges and spikes.

Harper - Reinstate Monica
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    what's with the USA's wimpy extension cords? I've run 2000W vacuum cleaners through partly coiled extension cords and they barely get worn. Because ours are made properly. – user253751 Feb 09 '23 at 09:00
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    @user253751 you can buy 12awg extensions cords anywhere (I've replaced all of mine with 12awg), they're just expensive, so most people go for things like the 16awg – Brian Leishman Feb 09 '23 at 13:11
  • barely get warm* (typo) – user253751 Feb 09 '23 at 13:11
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    @user253751 Extension cords in the US vary greatly. You can buy them from 18ga to 14ga, but the difference between them is up to 3A between gauges. Very few people need a true 14ga extension cord. – Machavity Feb 09 '23 at 14:22
  • 30 ft is nowhere near long enough to make coiling/spooling a given. – R.. GitHub STOP HELPING ICE Feb 09 '23 at 17:09
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    @user253751 Europe has the same problem. Multiple conductors grouped tightly, and their inability to cool. Ampacity ratings *assume* the level of ambient cooling that will be available. **Extension cords can be 1 size smaller** than same-ampacity in-wall wiring - they're presumed to be in open air and not packed in insulation. That only makes them more vulnerable to coiling overheat. When wires are grouped, NEC 310.15(B)(3)(a) proscribes an ampacity derate to address the cooling limitations of grouping - coiling is grouping. – Harper - Reinstate Monica Feb 09 '23 at 20:02
  • I once did some IT consultancy work for a small community charity in Bristol, UK. The office was cold. They ran a 3 kW convector heater via an extension cord on an encased reel, partly unreeled. Local government provided the office and paid the utility bills. Someone remarked that it 'smelled funny' after being in use for an hour or two. I investigated and found that the black rubbery outer covering of the reeled cable had melted and merged into a contiguous mass. After disconnection I put my hand on that and it was pretty hot. They'd been using it like that for about 2 years. – Michael Harvey Feb 09 '23 at 21:19
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    @user253751 the thing is, a lot of equipment has relatively fixed power requirements. Which means that US uses twice the amperage. Which means four times the heat created in a resistor (`P = I**2 * R`), so the problem is simply much more prevalent than any place that uses 230V. – jaskij Feb 10 '23 at 14:10
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    @R..GitHubSTOPHELPINGICE: I wonder how hard it would be to design a cable with a thin positive-temperature-coefficient sense wire and a protection circuit that would sound an alarm and cut power in case the cable was overheating, so as to allow a cable to be safely used when coiled for intermittent or low-current loads, or uncoiled for use with higher current loads. – supercat Feb 10 '23 at 22:23
  • @supercat: Well, they can't even be bothered to incorporate fuses, so ... – R.. GitHub STOP HELPING ICE Feb 11 '23 at 14:02
  • Given that the amount of current a cable can safely carry when stretched in free air could be double the current it could carry if bunched up in a confined space, I don't think a circuit breaker that was set for a fixed amount of current would either have to trip in some cases where a wire could have carried a certain amount of current indefinitely, or pass through sufficient current to overheat in some cases, meaning a breaker sized to prevent the latter would result in nuisance trips. – supercat Feb 11 '23 at 16:55
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If you wish to follow good practices for wiring, and meet the spec, it's quite trivial to manage.

Run 30 feet of building cable (NM, AC, MC) (not coiled up, not an extension cord) out and back along the basement ceiling (properly attached) or floor joists or wall on your way from the service panel to the outlet 5 feet away. Basically take a 12-1/2 foot detour out and back again, or out 10, over 5, back 10 - whatever is convenient.

The smart move would also be to (additionally) install the type of surge suppressor that goes right in the panel itself and is actually intended to take lightning-related surges (though nothing really survives a direct strike...) as opposed to depending on a piddly one by itself. That is, a "Type 1 or Type 2" surge suppressor. The ones that drop into 2 adjacent breaker spaces are quite handy if your panel isn't full.

Ecnerwal
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The risk of having the surge protector close to the service panel is less than the risks created by plugging it in to an extension cord. Use it as-is. It will be fine. The requirement for a minimum 30 foot distance is relatively new. There is a small risk created by the short wiring, it's true. However it has never been recommended to use a power strip or surge protector on an extension cord.

KMJ
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    Wonder what they expect people in small houses to do? Plug it into their neighbours. – crip659 Feb 08 '23 at 19:26
  • Even with my long(65ft) house, with this spec I would only have 10ft at one end to use protectors, of course this is the end I don't need them. – crip659 Feb 08 '23 at 19:57
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    I solved this by just putting a Type 2 whole-panel protector in at the service entrance. Now I buy cheap power strips and don't care if they have a good surge protector or not. – KMJ Feb 08 '23 at 20:59
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    @crip659 they expect them to use them and then lose the lawsuit when their equipment is damaged by a surge – user253751 Feb 09 '23 at 09:05