A double pole double throw switch is _not_ a safe design for a transfer switch
an inductive load that causes arcing on the opening contacts can result in
connecting both sources together or one source onto a fault. A panel that has
pairs of switches tied together can connect both sources to the load if one
switch or the link fails, with no opportunity to verify that the disconnect
occurred before the connect occurred. Neither protect against trying to
synchronise the source network a long way out of phase with the load network
Iggy's solution requires that one source is isolated well before the other
source can be connected.
Oh, and I have, in my role as an electrical engineer, in the last year had to
refuse to connect UL and CE marked equipment supplied by a major (Blue)
manufacturer because it was unsafe as assembled. When the installation
"engineer" claimed that similar equipment had been installed all over the
country, I had to state that it's use would be illegal in each of those
installations. I'm not that bothered about safety except where the lack of it
endangers people, then I get quite particular.
I'm coming in late on this, didn't see the original post but from
reading the replies I'm infering Iggy wants to use a couple of keyed
lock mechanical doohickies to prevent his genny breaker & mains
disconnect from both being "on" at the same time.
This is, everyplace I've ever been, perfectly legal as long as theres
only one key & it can only be withdrawn from the lock when the
doohicky has the breaker in the "off" position. I've had a number of
systems like this in sites where the feeds were physically seperated.
Now, that isn't to say I don't prefer a single changeover switch type
of deal, 'cause I very much do, but the keyed switchs are perfectly
acceptable if properly designed.
This has been discussed before somewheres on usenet, I remember
posting on it.
On Sun, 13 May 2007 14:43:04 GMT, Howard Eisenhauer
Yes, a "Kirk Key®" interlock is legal - but ONLY where access is
restricted to trained and responsible personnel like at power plants
and industrial buildings. People who know what will happen if they
screw up, and that they'll be held fully to account for it.
It is too easy to deliberately bypass that type of mechanical
interlock and cause a backfeed, as easy as unbolting the front panel
of the switchboard that the interlocks are secured to and operating
the circuit breakers out of sequence. Takes only seconds.
And there are too many fools who are ready and willing to do it out
of total and deliberate ignorance of the consequences.
For residential and light commercial/industrial applications where
the transfer equipment is not secured and can and will be operated by
untrained personnel, it HAS TO BE type accepted for that use. That
calls for a pre-packaged automatic or manual transfer switch of some
sort that has failsafes against backfeeds, and eliminates any "Kirk
Key®" type systems from consideration.
Unless you want to be up for multiple counts of Murder 2 for
backfeeding the utility service and killing a few workers on the line
gang, out trying to restore power after the storm...
--<< Bruce >>--
Not at all - a person properly trained in electricity theories,
construction codes and the like would know the risks involved, and if
he did cause a backfeed into the utility system anyway and someone
dies, Murder 2 (done deliberately but with no premeditation) would be
a reasonable charge to level.
Though I'd bet most career prosecutors would charge it as Murder 2
just so they could plea-bargain it down to an easy Manslaughter.
IANAL, but even 120VAC is a potentially lethal voltage. And when it
kicks backward through a transformer and is suddenly boosted to 5KV to
35KV or more, then it's really easy to "reach out and touch someone."
And I have personal knowledge of how massive screw-ups of this
magnitude can and do happen, but please DAMHIKT. Let's just say it
wasn't pretty, and leave it at that.
--<< Bruce >>--
I am both an electronics technician and a licensed electrician, so I think
I have had a bit of training in electricity theories.
That is absolute bullshit.
Don't get me wrong, I believe in doing things right. In fact, I have a
proper transfer switch on my own home. But why must this transfer switch
conversation always disintegrate into such childish nonsense?
Nope. It's called, 'reckless disregard for others resulting in the death of
someone'. In many states that fits the statute of murder. In NY it's not
called Murder-2 since that is 'premeditated' while Murder-1 is 'causing the
death of a law enforcement person while committing a felony act'. In NY it
would be manslaughter in the first-degree.
All it would take is an accident and the DA being able to prove that you 1)
had the prerequisite knowledge yet 2) choose to deliberately ignore the code
requirements and that 3) your actions resulted in the death.
Let's be careful making legal judgments.
Making a mistake while trying to do a good job is not reckless.
"Reckless" in this context would be, for example, deliberately
connecting the generator to utility side as an experiment.
That's true. But the other poster is talking about blatently ignoring the
code requirements and claims to be an electrical engineering type.
So, in his situation, he is dancing on the edge of 'reckless disregard for
human life'. He knows the risks, he knows it's against the code, he knows
it could put someone else in jeopardy, yet he's talking about willfully
doing it anyway. He may 'get away with it' several times and even be lulled
into a false sense of safety. But if there is an accident, he can't claim,
"I didn't know any better."
Now, if he was just some amateur Joe, with a 'suicide cord' and didn't know
any better, then that would not necessarily be 'reckless disregard'. But
that ain't what the other poster said.
Are you a lawyer in real life or do you just play one on the Internet? If
the former, can you provide us a link to a comparable case?
Frankly, I am tired of the silliness that always results from these transfer
Although I would never advise someone to use a generator without a
listed transfer device (and that can be a breaker interlock if it was
tested on that panel by a NRTL) but I agree, these threads get silly.
Your puny little generator will not handle "the grid" for more than a
few miliseconds. When it hits the locked rotor of your neighbor's AC
units it will trip out. Linemen are not going to die since they have
procedures that assume NOTHING is dead until they prove it and then
they short it out. I suppose if you did have a very localized failure
you might light up a neighbor but the power company is likely to do
that too when they restore power.
On Tue, 15 May 2007 22:43:36 -0400, firstname.lastname@example.org wrote:
I'd rather see some silliness, as long as the subject is fresh in
your mind when you go to hook up a generator - it's always the
preferred attitude over death-ness.
The trick is where the primary line feeding your transformer goes
physically open, so you aren't trying to backfeed "the rest of the
grid" you are only energizing your own service transformer. If you
are the only house on that line there are no foreign loads to drag
down and stall your generator, but you're still boosting that 120V and
sending 5KV to 35KV back down that string of poles.
(Gee, why is our streetlight out at the highway back on?)
If the line crew is out fixing the downed circuits, they know that
the line is off from the feed end, they've already done the
Lockout/Tagout and ground bond cable safety procedures. It's dead,
they made sure of it.
But if they are too far away from your homestead to hear your little
generator chugging away, and they don't use the same level of caution
in checking, ground bonding and handling the supposedly dead load-side
power line that you are backfeeding...
"Don't worry about that line Charlie, it's dead..."
--<< Bruce >>--
Bullshit. When you get proper training in line maitenance techniques
you will agree the whole argument that reappears every two months for
the last ten years is bullshit.
and why? All because some amateur thinks he can beat the law and save
a few bucks and wants somebody here to back his scheme up so he can
feel smarter than the rules.
On Wed, 16 May 2007 19:14:29 -0500, "Solar Flaire"
Do me a favor, please. Drop the belligerence when I'm On Your Side.
I don't want the amateur to cockamamie the connections and create a
potential backfeed in the first place. The OP of this thread (Igor)
is a r.c.metalworking regular and will get "great ideas" like using a
set of Kirk Key interlocks he got for real cheap (or free) on a home
install, but will also abandon the idea when you prove your point as
to where the flaws are with them.
(I think that he already conceded on the idea a while back, but the
bickering^h^h^h^h^h^h^h^h^h discussion plays on...)
And I am aware of the precautions that the linemen need to make. I
normally don't touch anything over 480V, but I've seen the switch
tag-outs and the safety ground-out jumpers on the 34.5KV lines in the
area when they're adding a new service. We had a vehicle shear off
the pole that dropped our neighborhood at 2 AM, and took out three 5KV
feeders. I stood there watching them do all the substation lockouts
over the radio, and getting clearance to work.
But whenever you develop safety equipment or work procedures that
are meant to be "Idiot Proof", Mother Nature rises to the challenge
and develops a craftier idiot. There are ways to screw up Just Right
and create a backfeed that doesn't stall the generator set or trip out
And there are always linemen that don't follow every rule in the
book to the letter every single time, be it through fatigue (working a
week of 20-hour days during an ice storm or other disaster will do
that...), inattention, lack of ground-out cables on hand, or just
plain apathy since "That never happens."
And that's when the million-to-one potential exists for somebody to
touch a "dead" line and ground at the same time and get nailed.
--<< Bruce >>--
Or they might walk across the street, overtired and the boom will fall
on the neighbour's nailgun and fire a framing nail through the
lineman's heart and kill him too.
I have to agree with you, whatever it was now...LOL.. The best one was
everybody is sick of the "is it OK to bypass safety if I do it this
way ot that way?" question. Have a good one!
And yet, linemen do get electrocuted while working on lines. One can sit
smugly back and say, "It's because they didn't follow procedures." But they
are still dead.
there is story that a back feed killed someone in Flomonton AL. They
specifically mention backfeeding from a home generator.
http://blog.constructionlawblog.net/archives/004368.html (sixth paragraph)
FEMA seems to think there is a risk to 'unwary utility lineman'
Cayman Islands Health Service Authority seems to think wiring a generator
improperly is a risk.
Team Florida seems to think you could be, "... responsible for the
electrocution of a lineman."
So, is one life enough to stop calling it 'bullshit', or do should we google
for some more?
Just about every utility in the country will tell you that an improperly
connected generator can be an electrocution risk for their linemen. Yet
some arm-chair wannabe's still think it's 'bullshit' because they took a
Saturday afternoon course on wiring at a big box store and bought a book.
I don't know which is worse, the one's that don't know any better and are
just trying to avoid paying a professional, or the 'experts' that 'know
better' and 'would never leave the mains breaker shut'. They know there's a
risk, but talk themselves into believing, "It could never happen. I won't
make that mistake. Besides, linemen are supposed to be properly trained."
Tell it to the widows and children...
Do a web search, ask your utility, go to a professional lineman's forum and
ask them what they think of the idea. Ask *them* if the whole idea of a
backfeeding generator killing someone is 'Bullshit'.
I have, and it is bullshit, to use trained linemen as an excuse.
You profess to have so much vast knowledge of electrical systems and
utilities. Ask them yourself.
Utilty workers have the lowest compensation rates of any profession.
there is a reason for that. Oh yeah, I forgot the US is about 30 years
behind in safety measures according to the trainers training in most
states. This may not apply there.
It would seem to me that if your power is off you actually are not connected
to "the grid". How much of the distribution sysetm is dead but still
connected to your house is often an unknown variable. All of the pros and
cons of every conceivable type of situation have been mentioned many times.
There are no new arguments for either position.
I think it is just a matter of whether you want to do the correct, legal,
and safest thing or not. Some people even stop at stop signs when no other
cars are present. Others do not. Neither group is likely to change its
I have to agree with you on that one!
It all starts with "if the lineman has complete disregard of....."
"Then the child reaches out and touches the 115kV lne that was backfed
from the home generator"
Our HV lines, especially the 500kV lines are always within easy reach
so we can connect our appliances.
Fuck! people. It is illegal and stupid to shortcut the safety stuff.
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.