Shorted Hots together

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Old 11-13-19, 11:13 PM
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Unhappy Shorted Hots together

Feeling like a right moron here...

Background - decided we needed a generator. Got a Champion with 120V output on a NEMA outlet. Have a convenient unused dryer socket in garage, direct to distribution box a few feet away. Has both live/hot legs in it. Perfect for a simple cable to connect the one live from the generator to the two hot wires in the outlet. Made up a cable, plugged in to test, flipped breaker and of course... bang! Main breaker trips, house in the dark.

So I turn off all circuits and wait a few mins, put main breaker back on and tentatively try low power circuits. All breakers engage but only one live phase is working. Expecting I need a sparky, and planning to wire fridges etc to the live phase, unexpectedly within a minure, the other phase comes back too.

I've checked all voltages on both phases, no sign of damage, no smell of burning. It all seems fine. We are on SCE and have a smart meter and a grid tied solar inverter. the only thing I've not attempted is re-trying the dryer socket. And yes, I removed my idiot wire!

My questions to those of you with more experience and less moron'ness:
a) does the utility company meter sense a short and then returns power one phase at a time?
b) will there be any lasting damage that I should get a pro to look for?

Thanks
 
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Old 11-14-19, 04:01 AM
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The installation is not safe. You need an interlock to prevent power backfeed onto the utility lines. You are also using what is called a suicide cord.
 
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Old 11-14-19, 05:56 AM
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You haven't turned on the generator yet.

The suicide cord you made up shorted both hots of the 240 volt system to each other, as you described. In this case the result was tripping of the main breaker.

In reality, much more than 200 amps flowed for an instant before the breaker tripped. I am not sure how the utility power system reacted to it. I do not know of any component that would cause a delay of return of power on one leg if your house is fed by one pole transformer.

If your house is fed by two pole transformers (actually there might be three but only two of them supply your house) then the short circuit in your house may have caused delay components further upstream to trip out one of the pole transformers for several seconds. In this case you would probably have 208 volts instead of 240; the 120 volts would still be about 120.

With the proper interlock or transfer switch, and proper connection of the generator, it would have been okay for the 120 volt generator to power both legs but you would not be able to let the 240 volt utility power come in and short itself out.

There are a few pieces of equipment, mostly for laboratory use, where there may be two cords with (male) plugs coming out. But you should never construct, possess, or use a cord with male plugs at both ends.
 

Last edited by AllanJ; 11-14-19 at 06:18 AM.
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Old 11-14-19, 09:53 AM
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Many smart meters allow the power company the ability to shut your power off if you don't pay the bill. That means there is a switching relay inside the meter. That may been jolted.
 
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