I dont believe this is a Memorial Day tradition, but a small rural town
had a big dinner cooking for the whole town. For a reasonable price,
you could get a complete meal with all the fixings an dessert too.
One problem. Many women in town converged on the town's community
center building, all equipped with an electric roaster filled with food.
They plugged in roaster after roaster, and had to move several of them
after tripping some breakers. They finally got them all working. There
were around 25 roasters total, but not all were plugged in at once.
However they did manage to plug in about 15 of them. Then they plugged
in a half dozen huge industrial sized coffee pots, cranked up the walk
in freezer for the ice cream, turned on all the lights in the large
dining room, and since it was a hot day, they turned on the air
For awhile, everything worked fine. Right when the people were coming
in to eat, the place went dark. No lights, all the roasters went off,
the air conditioning went off, the water stopped flowing from the sinks
(well pump), and everyone was eating in the dark. Minutes later the
fire department arrived with a large generator. The generator failed
after 3 minutes of use and although the gas engine still ran, it would
not put out even one volt of power.
About that same time, the electrician arrived, several neighbors whose
homes are nearby came over and said they had no power in their homes.
OOPS!!!! The electrician confirmed that there was no power coming from
the pole to that building, nor to all the homes for a couple block area.
It was a hot day, as well, so lots of people were running Air
Yep, all those roasters and coffee pots and ACs and other stuff, roasted
the pole transformer.
It took the power company about an hour to arrive, and another 20
minutes to locate the drivers of cars that were in the way of power
company's trucks. They finally got to the top of the pole, when one of
the workers began to remove wires, touched the transformer with his bare
hands and burned his fingers. (by this time the power had been off for
over one and a half hours, so it had cooled down some).
They removed the 25 KVA transformer and replaced it with a 37.5 KVA
When I got home, I did some figuring. Those roasters (most are old),
consume about 14 amps each. Those huge coffee pots are not much less.
So, lets just use round figures and say they averaged 12 amps per unit.
15 roasters, and 6 coffee makers is 21 devices. That works out to a
draw of 252 amps at 120V AC. Add to that the freezer, the AC, the
lights, and then add all the stuff that was running in homes along that
It's no surprise that the transformer failed.
Now comes a question.
How many amps can a 25 kva (kila volt amps) produce without overloading?
(at 120 volts AC. single phase). I did some googling and found some
complex mathematic formulas. I could not find a simple chart. Math is
not really my best subject....
Therefore how many amps can a 25 kva transformer safely handle.
What about the replacement 37.5 kva. And how about a 15 kva (which is
what supplies my house).
Thanks in advance!