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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?

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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
    Commented Feb 8, 2023 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
    Commented Feb 9, 2023 at 3:51
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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
    Commented Feb 9, 2023 at 8:09
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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
    Commented Feb 9, 2023 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
    Commented Feb 9, 2023 at 15:18

3 Answers 3

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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.

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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.
    – user20574
    Commented Feb 9, 2023 at 9:00
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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
    Commented Feb 9, 2023 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
    Commented Feb 9, 2023 at 14:22
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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
    Commented Feb 9, 2023 at 20:02
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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
    Commented Feb 10, 2023 at 14:10
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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.

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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.

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    Wonder what they expect people in small houses to do? Plug it into their neighbours.
    – crip659
    Commented Feb 8, 2023 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
    Commented Feb 8, 2023 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
    Commented Feb 8, 2023 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
    – user20574
    Commented Feb 9, 2023 at 9:05

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