Reminder: Never connect a generator to home wiring without transfer switch

Mel Beckman mel at
Mon Aug 30 19:20:01 UTC 2021

> The point that several brought up is that doing so is not only a bad idea, but that it simply won't work 


I’ve had this scenario play out several times:

DIYguy: Check out my new generator! It’s big enough to power the whole house!

Me: You run extension cords from the generator to all your devices then?

DIYguy: No need! I built this special “suicide cord” I read about online in a prepper forum. I just plug that into any wall outlet and it powers the whole house!

Me: Um, you haven’t tested this, have you?

DIYguy: Sure. I fired up the generator and plugged the dryer into it. Works a treat!

Me: No, I mean your special cord. Have you tested that?

DIYguy: Hey, if it'll power the dryer, it’ll power my whole house. No need to test!

Me: Ok, first of all, that’s not a “suicide cord”. That’s a “homicide cord”. Second, …

The problem with this scenario is that the DIYguy never finds out that it won’t work, at least not until the trial. :)


> On Aug 30, 2021, at 11:25 AM, Jay Hennigan <jay at> wrote:
> On 8/30/21 10:46, Aaron C. de Bruyn via NANOG wrote:
>> While they were waiting for a few more trucks to arrive with a replacement pole, I got to ask them a few questions.  They said it's standard practice for them to ground on both sides exactly for the reason that someone might accidentally connect a generator.  They open the nearest switch on the upstream side, test to make sure the line is dead, install grounds on all the wires, then test the downstream side and attach grounds to all the wires, effectively making the work zone an isolated segment.
> I don't think anyone participating in this forum was remotely close to suggesting that anyone connect a generator to home wiring without a transfer switch in place. It's stupid and dangerous.
> in the vast majority of power outage scenarios. Unless the outage is on your service drop or on your pole pig, the impedance of the neighborhood or city downstream of the outage as reflected through the transformers will vastly overwhelm any portable generator capable of being connected with a "suicide cord" by several orders of magnitude.
> The other point is that, assuming that the utility is following their safety protocols, the utility worker is going to ground the load side as well as the incoming feed specifically to prevent backfeeding the grid from a miswired generator.
> Yes, never connect a generator to home wiring without a properly installed transfer switch.
> Yes, the utility workers should ground the load side to avoid being killed in the event that someone does so.
> Yes, if the utility follows all procedures correctly, and you happen to connect your miswired generator at the exact instant that the utility worker removes the ground after making the connection, and said worker grabs the conductor with bare hands, and there's a path to ground through the worker's body at that instant, that worker is probably going to die. The probability of this happening is somewhat greater than that of winning the lottery, but if they're on a pole in the middle of a storm working on overhead wires, the odds of their being struck by lightning are also worth considering.
> It's a warning worth repeating, but probably not to this extent.
>>    This is NANOG -- I'm sure that we've all followed a set of steps
>>    perfectly and still managed to redistribute BGP into the IGP, or
>>    apply an ACL and lock ourselves out of a box, or types "show run"
>>    and watched the router randomly reboot. 
> Don't forget the classic "switchport trunk allowed vlan" vs. "switchport trunk allowed vlan add".
> -- 
> Jay Hennigan - jay at
> Network Engineering - CCIE #7880
> 503 897-8550 - WB6RDV

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