Let me start by saying I know this is very dangerous and I don't plan
on doing it (I have a new generator and new uninstalled transfer
switch) so save your flames. I plan on installing my transfer switch
when I get some time in the next month or two.
I read a post suggesting that in a power outage, you could flip your
main breaker off to prevent anything going to the lines and killing a
line worker, and use a suicide cord from your generator to you clothes
dryer outlet (240 vac) and then your main panel would serve as your
switch for what circuits are using the generator--and that this would
power both 240 and 120 outlets.
As dangerous as this is, is this even possible?
Yes, but not recommended because of the potential danger involved (both
to the homeowner and to the line workers in the event someone forgets
to turn off the main). You would be limited by the size of the breaker
you are feeding through (in this case the clothes dryer), but it would
make your whole panel live just as if it were being fed through the
I had asked this hypothetical question a few years ago and glad you
mentioned the flames...LOL...Cause I sure got my fair share of those asking
that question.. One thing that was constructive in my replies is that even
with your main braker shut off, you may be still feeding power down the line
via the neutral wire....another constructive reply was to also ask in
alt.energy.homepower They are a very knowledgable group... Hope that was
of some help.... Jim
If the neutral isn't properly grounded at the service tap, it is forced back
up the line to the next good grounding point. Not a serious danger unless
people or equipment are connected in parallel to this defacto circuit. I
think it's possible that someone in an adjacent residence could be at risk
of getting a shock by being connected to both a good ground and the ground
terminal of an outlet, if the resistence to ground is greater at their
junction box. An example might be having one hand on a water tap and the
other on the metal case of an appliance with a 3-prong plug, and feeling a
tingle of current that originated from your neighbor's generator.
OK, I suppose that could be possible, but would not put out a heck of
a lot. Good grounding should exist anyhow, but I get your point.
This would only affect those on the same transformer, I would think.
... One thing that was constructive in my replies is that even
Most transfer switches do not switch the neutral wire anyway. However,
if your generator and your panel is properly grounded, it should be
almost impossible to energize the neutral enough to do harm, even
without a real transfer switch.
Having said that, obviously, a transfer switch is the only way to go.
Backfeeding an outlet is dangerous and violates the NEC.
Yes, it is possible......BUT only a person with your special
qualifications (beerguzzler50) should even THINK about doing
it, let alone actually TRYING to do it....... I think the
"I was drunk at the time" defense might actually work for you.
Sounds possible, and safe, unless you guzzle too much beer. You might
hang a big tag on the generator that says "Turn off the main breaker!"
That seems a very unlikely hazard, since it requires 1) a grid power
failure, and 2) a hot to neutral connection that doesn't blow your own
breaker, and 3) a neutral wire that doesn't end up attached to ground
somewhere outside your house.
For the added piece of mind, a generator/main selector switch is a modest
Power failures can result in stress and confusion that make things like
leaving the main breaker on a virtual certtainty at some point. Why take the
chance to save a few bucks.
Unless I'm mistaken, some 240V outlets do not have the neutral wire
connected to the mains. Only a ground wire, which is insufficient to power
the 120V circuits. This would result in 240 service only in the house
wiring, when feeding in from a generator.
You are partially mistaken. Some older 240v outlets indeed do not have a
neutral connection, however newer ones do (code change). Since the
ground and neutral are required by code to be bonded at the service
entrance panel you will get the same functionality even if you're
feeding an older dryer outlet with no dedicated neutral i.e. using the
ground as a neutral.
The ground on the circuit may be a gauge lighter wire than the main
conductors which would limit your circuit capacity if you had a large
generator (~7kw or larger), but most people doing a dryer outlet
backfeed will have 5kw or smaller generators in which case even a
reduced gauge ground on a dryer outlet has adequate capacity.
Additionally since not only are the ground and neutral requited by code
to be bonded at the service entrance panel, there is also a required
ground rod (or two) connection at the service entrance panel which makes
it all but impossible to backfeed any power down the line if the main
breaker is off. The additional grounding of the utility system neutral
every few poles provides yet another level of protection.
The true risks are 1. Forgetting to shut off the main breaker, and 2.
Forgetting the danger of the double-male "suicide" cord and proper
connection / disconnection sequences.
There is one very hugh assumption being made here in this thread.
It seems that everyone ASSUMES that all the houses that are going
to be backfeed, have wiring that is in TOTAL Compliance with the NEC,
and that if it was once in compliance, it is still in compliance, many
years later. Just what happens when the Ground Rod connection corrodes?
When was the last time you checked yours? What about the Neutral/Ground
bonding strap? what is the resistance across that today, in your house?
Do you even know? Seems like very big assumptions to "Me"....
I didn't assume anything, I noted the code requirements which mean that
there would have to be a significant number of violations/failures for
there to be a safety issue past the obvious forgetting to shutoff the
main or the suicide cord which I noted as well.
Remember that even if your ground rod is rust, you've still got a ground
within a couple utility poles unless it is your actual service drop that
is down. It is all but impossible to build any dangerous voltage
relative to ground on the neutral. Even forgetting to pull the main has
a 99.999% probability of killing any small generator or tripping it's
circuit breakers before any dangerous voltage could build on the utility
Additionally the utility crews are supposed to 1. wear their insulating
gloves, 2. check lines for voltage before handling, and 3. ground lines
before working on them. All of which puts the odds of killing a utility
worker with your temporary generator connection worse than the odds of
winning Powerball. The chances of killing yourself with the suicide cord
on the other hand are much better.
Reminds me of a accident we had while I was in the navy.
Old Gearing class destroyer with manual transfer to shorepower.
Someone forgot the other breaker and the shipboard distribution
When it recieved BOTH ship generator and shorepower.The hot oil from the
transformer took out half the electrical gang in the engineering
compartment.A 1/2 hour "all hands" firefight ensued after towards.
Had to rebuild all the shipboard generators a short time later.
I would do it in an emergency if there was an extended power outage, but
I'd probably pull the electric meter first to make absolutely sure I
wasn't backfeeding the power lines.
Yeah, I know about breaking the seal on the meter, but ya gotta do what
ya gotta do if it's really an emergency.
HomeOwnersHub.com is a website for homeowners and building and maintenance pros. It is not affiliated with any of the manufacturers or service providers discussed here.
All logos and trade names are the property of their respective owners.