Here is a question for someone from an electric company.
There was a question on here about using a generator if the power goes
out. This got me thinking about something. Lets say that your
generator is incorrectly installed and is accidentally sending power
OUT of your house. Any building that is hooked to the same
transformer will get power from your generator. However that would
only be a few neighbors.
My question is what happens on the opposite side of the transformer?
The standard home transformer is dropping a very high voltage,
something like 5000 volts, down to (center tapped) 240/120 volts.
So, if you are backfeeding a generator into the secondary windings
(240 side), will the transformer increase the voltage to 5000, or
whatever it is, in the primary? Knowing how a transformer works, I
would assume it would. But do they have some sort of circuit built
into these transformers to prevent this from happening?
Also, what would happen if you were backfeeding and the electric
company turned their service back on? I would assume that the home
generator would be destroyed...... but I could be wrong....
Any body running a generator should read their instructions, know what
they are doing before turning it on , Or hooking it up. Not following
recomended startup procedure can mess up apliances and your generator.
This means turning off your Main Breaker First. Even with a transfer
switch this is common sense. and is safer.. Also if you are not using
a voltage controled unit check output voltage before using it . Ive
seen them not calibrated putting out 150 - 300 burning out
apliances . just because its new doesnt mean anything.. And dont
backfeed your house, it wasnt designed that way , wiring problems not
previously known can ruin your generator or worse
That means you don't know when power comes back on. We got ours back at
12:15am this morning.
Is there any way, without significant expense, to safely wire a buzzer to
the line side of the main breaker? You could put a switch on it, so it was
only potentially energized during an outage.
Regarding your comments about damage from generators; the company that just
put my new furnace in says that during a major ice storm a few months ago
they had the electronics burn out on 3 new furnaces by generators; and it is
not covered by warranty. I figured it was an inadequate sine wave, but I
suppose it could also be improper voltage or frequency.
Hi Wade . Your Idea of a buzzer or light would be a good idea. I
was just trying to point out cheap generators can make a mess of your
house, When I called Generac about my new 5500 watt " Home Power Plus
Unit" because it put out 135 they said ' WE dont recomend that unit for
sensitive electonics" and Lowes sold it With a free power transfer
system.. Well It doesnt say it on the box or in the manual... Well what
the hell... Most everything has sensitive electronics inside these
days.. So i returned it and got their better model . I never
thought about sign wave, What is it , how do you measure it , what
effect does it have on electronics? A friend of mine
blew out a 4 day old tv , he returned it no problem, but said his new
generac 3000w was putting out apx 150. And it blew in 10 minutes. I
know someone else who likes the way his generator makes his lites burn
Brighter. And he goes through expensive tvs apx every 4 years.. They
dont tell you this stuff on the box or in instructions. Its BS , Alot
of people will be buying generators now , and causing even more
problems. Youd think the News people would spend 5 minutes educating
people on this , A 500$ generator could cause alot of damage
quickly..If you are not careful on load issues.. I think the generator
cos should be liable for missinformation..
The obvious is you shouldn't do it. However, if you did, my
guess is that all of the neighbors still have significant load
on their lines and the transformer should work perfectly well in
reverse, therefore putting a huge load on your generator. It
probably will merely stall out ... unless it's a HUGE generator.
You're correct in your assumption, you'd be developing high voltage on the
line side of the transformer. You'd probably be violating code if you did
that and potentially (pun intended) liable for whatever injury or deaths
your careless actions caused.
On your last point, the genny would probably be spared if it has circuit
breakers on its output. They'd probably open when the power came back on.
AFAIK any municipal electrical code will require the installation of a
"transfer switch" along with an emergency generator, which disconnects the
site's wiring from the mains and connects it to the generator's output.
The safe way of making a temporary hookup to a portable generator to keep
a fridge or a few lamps runnning off it is to use extension cords from
those appliances which are then plugged into the female output receptacles
on the genny.
Just my .02.
BTW, anybody know what procedures the repair crews use to keep from
getting fried if someone decides to hook their genny up while they're in
the middle of repairing the lines. Do they put big shorting jumpers on
"cold" lines to make sure they stay "dead" until they're through and then
remove them carefully before they throw the power back on?
Jeff Wisnia (W1BSV + Brass Rat '57 EE)
"If you can keep smiling when things go wrong, you've thought of someone
to place the blame on."
Linemen have been killed from backfeeding. There is nothing in the
transformer to prevent it from occurring. The owner of the generator could
be held responsible for any death, injury or damage caused and it is their
responsibility to install the proper transfer gear.
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