120V Lamps on 240V?

[Roby]

My neighbor the (um) electrician tried backfeeding his house through a 240V
receptacle in the garage. The generator is a real old-timer: open frame
with cotton cloth insulated wire in the windings. The three-wire output
from the alternator is terminated at a three-position terminal board,
unmarked and no terminal is grounded to the frame.

Neighbor *guessed* how to connect this to the house ... never bothered to
check voltages with a multimeter. Immediately after starting up the
generator, he observed that the lights were "real bright". So he shut down
and ran a wire from the generator frame to a piece of conduit driven into
the ground. Alas, the second startup was like the first and quickly
aborted and declared an unsolvable mystery.

Neighbor went into the house, noticed smell of burning insulation
everywhere. He filed a claim with his insurance company for damage due to
an electrical surge: microwave oven, VCR, two televisions, cordless phone,
clock radio, control transformer in furnace, etc. The refrigerator and two
freezers were not damaged.

My guess is that he misconnected the genny, putting 240 on one side of the
service and zero on the other. The three coldboxes were lucky to be on the
zero volt side. But would a light bulb operated at 200% rated voltage just
become "real bright" and survive a couple of brief tests or become an
instant flashbulb?

Roby

ps: This guy really is an electrician ... or at least has been selling his
time as such for about 20 years. Seldom gets additional work from old
customers though.

 

[Roby]

He is a WINNER.... Darwin would be proud. You should send
this in to the awards committee.


whatta guy.


you got it


Whats his billing rate and what region of the country...
enquiring minds want to now.

Phil Scott

He works cheap (which is why he gets work at all); midwestern US.
A sample: you can save a wire by just running hot and neutral to a
grounding receptacle ... and then connect a jumper between the neutral and
ground terminals at the receptacle. It's amazing (scary, really) that this
sort of thing goes on.

Roby

 

[Roby]

Well that neighbor, if really an electrician, is a real dim bulb for a)
not marking the generator leads before connecting it, and b) not figuring
out what happened the first time he fired it up.


If he had swapped the neutral and a hot, half the devices would get 240
volts and the other half would get 120 volts, not zero. (assuming it
is a 120-0-120V generator. Is it? Might be anything if that old)

Ooops ... you're right about the volts! I don't know what it really is/was.
He put it back in storage; will likely try again someday. I wish I didn't
live right next door!

 

[Beachcomber]

I don't really know if 'railroad' bulbs exist(ed), or if they were designed
for 60 volts, or if photographers really did use them.

I used to have some old 60 V. bulbs that were originally from an old
AT&T Telephone test board at one of their abandoned Long Lines
Microwave Facilities. These were standard Edsion based incandescent
bulbs that came in different colors (yellow and red). Not sure
exactly what they were used for but they did exist.

Beachcomber

 

[TimPerry]

alas, unless he actually dies he just doesn't qualify for a Darwin. killin'
someone else don't count.

 

[TimPerry]

awww shit. I thought we had a winner there.

http://www.darwinawards.com/

he might qualify for an honorable mention:

The stupidity displayed by the participants
in the following tales stops short of the ultimate
sacrifice, but we salute their spirit and innovation

 

[crugera]

I once inadvertently put nominal 230v on a 110v light bulb. It was very
bright for about 2 seconds before dying. Did not go "pop" just died.

 

[JohnR]

|>My guess is that he misconnected the genny, putting 240 on one side of the
|>service and zero on the other.
|
| If he had swapped the neutral and a hot, half the devices would get 240
| volts and the other half would get 120 volts, not zero. (assuming it
| is a 120-0-120V generator. Is it? Might be anything if that old)

And 120 volts to the 240 volt loads.

If he picked up some surplus military generator, it could be a 416Y/240
model. It might be reconfigurable to 208Y/120.


| If the first is true, the incandescent bulbs, assuming a rated lifetime
| of 1000 hours, would last about 1/4000 of that, or about 15 minutes if
| brand new. Assuming, of course, the 12th power relationship, if true,
| works at the extreme of doubled voltage.

I did that many years ago to a 60 watt bulb. It lasted about 20 minutes.
Another bulb lasted about 20 seconds. The former could have been one of
those "130 volt" bulbs intended for longer laster in hard to reach places.
The latter could have been a cheapie.

Oh, and the 240 volts was gotten from one of those travel transformers
in reverse. It may have been sligtly less than 240 volts.

Probably much less. Those are usually rated 50 watts. The over driven bulb
draws more current and pulls down the voltage.

At the melting point of tungsten, those mathematical relationships are no
longer valid!
John
http://ka9wgn.ham.org/ |

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