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I just bought a killer electric chainsaw. Very powerful, fast and draws a FULL 15 amps. I keep tripping the 15 amp breaker at the box in the basement. It's a LONG run of extension cord (50' 10 guage) but its also some 80 feet to the panel so the wire is probably, what 14 gauge to the panel in my walls? Maybe that's whats tripping the breaker. I'm cutting BIG ROUNDS so the saw is working hard for like 2-3 full minutes and that's when the circuit breaker says, "too much". I have to take frequent breaks every 30 seconds to let the breaker cool before I can resume work.

The outlet at the side of the house has 2 15 amp circuits, one to each plug, like a kitchen in newer home construction. The outlet is GFI protected. Can I pigtail 2 male plugs and wire a single female to the males? That would give me 30 amps? I won't overload the extension cord. It's really heavy duty and I won't overload the wiring in the house, 2 15 amp circuits.

My home is finished and basement done, I can't run a new wire to the back yard. Please help.

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    I'm voting to close this question as off-topic because it isn't about home improvement. – isherwood Apr 14 '17 at 13:15
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    Isn't this a legitimate question that other people might have? I think we should keep it here (perhaps with some editing to make it clearer), and keep the answer that you absolutely cannot do that. – Mark Apr 14 '17 at 13:33
  • @Kris "There's no such thing as a stupid question"™. There are however crispy homeowners, who were too proud/afraid/stupid to ask. – Tester101 Apr 14 '17 at 14:02
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    This. This is why you don't finish basements. – Harper - Reinstate Monica Apr 14 '17 at 15:27
  • Treat the finished basement like a real electrician - a place that needs wiring done, and later someone (else, in their case) can patch and paint. – Ecnerwal Apr 14 '17 at 16:53
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No, you absolutely cannot do that.

For starters, they will be on different legs of your hydro connection. You will create a short circuit. There is 240v between the hot wires of those plugs. Even if they were on the same leg, it's still not allowed or advisable, because there is no way to make sure they share the load evenly. Either way, you'll end up damaging your circuit breakers by continually tripping them, or start a fire.

What you need is to run a new 15 or 20 amp circuit with appropriate gauge wire (which might be thicker depending on length of the run) outside. Since you know you'll be using long extension cords with it, I'd add the length of my longest extension cord when calculating the length of the run, and see if that makes you need to upsize the wire further.

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    "Hydro connection"? – isherwood Apr 14 '17 at 13:17
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    @isherwood OP must be from Canada. They call the electrical utility "hydro", I'm guessing because most of their power comes from hydroelectric? – Tester101 Apr 14 '17 at 13:56
  • @isherwood Yup, Canuck here. We call it hydro...dunno why, that's just what we do, eh? – Grant Apr 14 '17 at 17:30
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In addition to other reasons: when you wire two male connectors together you end up with an exposed energized male terminal after you plug the first one in, that is why they are called widowmakers. Do not do this; even if you are careful, someone else who is unaware of the danger might try to use it.

  • Yes I understand this and would use the setup ONLY for the odd time I'm using the saw at maximum power cutting large rounds. Small stuff, no problem, the saw does not run long enough to trip the breaker. I think a 15 amp circuit can give 17-18 amps for a few seconds. I need about 16 or 17 continuous over a minute or two. – Kevin Apr 14 '17 at 18:51
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What you're up against is the infernally small size of US electrical service - 1800 watts. European countries get between 3100 and 3600 watts at any random receptacle. However, Americans have an ace up our sleeve that'll let us bring up to 4800W to a receptacle.

Ganging both circuits to serve one receptacle is out of the question. It is a bad practice for a dozen reasons, unworkable due to GFCI, and utterly impracticable absent an isolation transformer rigged in a way that would really need engineering supervision (i.e. Your institution has a staff of electricians directly overseeing this setup, as such, I won't go into details.)

There are several ways to solve this.

Turn off the other loads on the circuit

Seriously. Are you 100% sure you know every outlet on the circuit and are ypu positive there aren't any other loads also burdening the circuit? Because if there are, it would explain everything.

Bigger cables the whole way

You have the right idea with a 10 AWG extension cord. You just need to go all the way back to the service panel with it, so you are not relying on that long run of skimpy 14 AWG built into the house.

More likely than not, there is a receptacle directly underneath your service panel. This is the electrician's outlet, when he wired the house, he "hot-wired" this receptacle so it was energized when nothing else was. And then he ran extension cords for his tools and lights. When he was nearly done, he punched it down into its own circuit breaker. Good chance it's 20A. That is a great receptacle to use.

Rewire the faraway receptacle for 240V; get a transformer.

America does have a standard for 240V and it's as good as Europe's. It's just rarely used. Doubling the haul voltage cuts current flow in half, and cuts haulage losses by 3/4. 15A at 240V transforms to 30A at 120V - more than enough. In fact 16 AWG extension cords would suffice if operating at 240V. The goal would be move the transformer as close to the work as practical, though your excellent 10 AWG extension cord will be perfectly adequate to haul 120V long distances, don't alter it.

Assuming the long-run receptacle you use is 15A, I'm not sure whether it's MWBC or not, it makes no difference. Cap the neutral, convert that circuit to 240V and stick NEMA 6-15 outlets there.

If it's dual 14/2 or 14/2/2, even better - those are two separate circuits, leave one 120V and make the other 240V by taping its white wire on both ends and connecting it to a 2-pole 240V breaker of same amperage. And fit a dual NEMA 5 and 6 receptacle - they make those. Likewise you would change the ends on an extension cord to NEMA 6.

Now for the 240 to 120 transformer. This is a little tricky. The cheapie step-up/down transformers are dodgy because they don't isolate, and the "common" side is presumed to be neutral. In North American 240V, both legs are hot, no neutral. On the other hand, these things come with a Schuko plug, which is non-polarized, so in Europe you never know which leg will be neutral.

A better choice is a true isolating transformer, such as a 2 KVA 240/480-120/240 transformer meant for small service installations. Jumper one side for 240 and the other for 120, obviously. Since this secondary is isolated, a single ground fault will not kill you. A GFCI on the output would be nice, though.

The ideal choice, hard to source in the USA, would be the 110V style of power used in UK construction sites. They use an isolation transformer, as I described in the last paragraph, but the 110V side has a center-tap, which they ground. As a result, even if the tool has a ground fault, it is only 55V from earth, which is not likely to be lethal. I don't think you could simply import a UK construction transformer, becuase they are made for 50-cycle operations.

  • Harper, my house does not have an extra 20-A "electrician's receptacle" below the panel. What percent of houses do have that? Around here during construction equipment is powered by a temporary service drop to a meter on a temporary post in the yard. – Jim Stewart Apr 17 '17 at 18:03
  • @JimStewart most that I've seen but I don't deal much with brand new houses. The temp service drop on the pole seems to be a recent idea. – Harper - Reinstate Monica Apr 18 '17 at 20:45
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Use an extension cord through a window to a 20-A circuit somewhere in the house.

Or get a gasoline generator that can deliver sufficient current to power the chainsaw.

EDIT I believe the Y connection of two circuits on the same leg to the same load would trip a GFCI. I made a neutral to neutral test connection in my garage and it tripped the GFCI.

I have a 20-A circuit with GFCI duplex receptacle in one wall of my garage. Nearby is another duplex receptacle on the same leg but a different circuit (15-A no GFCI). I plugged an extension cord into the GFCI receptacle and inserted a paper clip halfway into the NEUTRAL side of the female end of the cord. I brought the end of the extension cord up to the other wall receptacle and pushed the end of the paper clip into the NEUTRAL of the other receptacle.

The GFCI immediately tripped. No sparks, no drama, just tripped. I could test the hots the same way, but don't feel like doing it. Testing of the two hots with a VOM shows they are on the same leg (~0.1 V reading), but I'm not going to chance that I have not thought it through.

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    You never want to do this. Trying to run two circuits in parallel you cannot be sure that the wiring, connections, circuit breakers and voltage feed will be identical. As a result one circuit almost always ends up sourcing more power than the other. At high current that circuit will trip its breaker first followed soon by tripping the second breaker as it sees the full load on the second circuit. The only thing to do that is safe is to run a single circuit with a suitably sized wire through a single circuit breaker sized to match the capacity of the installed wiring. – Michael Karas Apr 14 '17 at 15:13
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    @JimStewart it would be ok if you were in Japan... At a nuclear reactor site... that just got hit by a tsunami... And the work is emergent... And the responsible electrican's team is overseeing... But for a random citizen to ding-dong such a setup, that's just a good way to kill somebody or burn a house down. Not least, the neutrals are not fused!! – Harper - Reinstate Monica Apr 14 '17 at 15:35
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    Why get a generator? Surely a gas powered chainsaw is cheaper. – Tester101 Apr 14 '17 at 16:00
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    @JimStewart Generators designed to be placed in parallel have extra work done to them to make sure they share the load equally. On modern ones that usually means extra control circuitry to make sure the generators stay in sync and make sure they start up together properly. – Grant Apr 14 '17 at 17:29
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    Getting a gas powered generator would defeat the purpose of getting an electric chainsaw. I want quiet as I'm in a residential neighborhood. To the other gentleman, I'd sure like to plug into (through a window) a 20 amp circuit. I don't have one that I know of. – Kevin Apr 14 '17 at 18:47

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