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Old 08-04-2014, 08:34 AM   #31
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transfer switch for generator for whole home power?


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Originally Posted by clw1963 View Post
One unsafe act leads to another IMO
The vagueness and generalization of that statement has no meaning in the context of our discussion.

Would I be correct to say that the general consensus is that back feeding a panel is ok so long as you install the breaker interlock device?

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Old 08-04-2014, 08:53 AM   #32
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transfer switch for generator for whole home power?


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...Would I be correct to say that the general consensus is that back feeding a panel is ok so long as you install the breaker interlock device?
Put it this way, a legally installed interlock device prevents "back feeding" by isolating generator input from the utility as would a transfer switch. Legally means a listed interlock for the panel and code compliance. They are listed when the manufacturer proves to UL that their interlock functions correctly with the panel in which it is installed. Some jurisdictions do not permit use of interlocks, primarily because they depend on user manipulation of circuit breakers to assure that the connected load does not exceed the rating of the generator. The original proposal to connect a 120v generator to a 240v panel does not comply in any way.
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Old 08-04-2014, 09:30 AM   #33
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transfer switch for generator for whole home power?


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You can successfully drive 60mph in a 25mph zone, but there are REAL risks. Speeding and back feeding are ILLEGAL in all communities. Do you expect someone else to write you a book when the information is available everywhere?
It would be better if I didn't have to decode your sarcasm but from what I'm getting, your answer is no.. Its just a procedural issue that can cause the unsafe condition..

Got it...

Oh.. and I should add that I don't think your analogy seems to fit.. Speeding is dangerous because it shortens the required reaction time to both internal and external events which are not within your circle of influence.

A more accurate analogy would be the industry (OSHA) standard procedure of chocking the wheels of a vehicle. Failure to do so will cause a dangerous condition to exist. Of course, there's no interlock for that...
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Old 08-04-2014, 09:45 AM   #34
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transfer switch for generator for whole home power?


Good, I hope you got it. The sarcasm was due to your demand that someone prove to you why it's wrong and therefore illegal. Volumes of information about the subject can be found on this forum and others.
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Old 08-04-2014, 10:24 AM   #35
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http://www.qsl.net/kc5qhh/backfeeddangers.pdf

Focuses on suicide cord use but has some points to make.

I do not condone this method. Just hazards are pointed out.

Last edited by clw1963; 08-04-2014 at 10:27 AM.
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Old 08-04-2014, 10:56 AM   #36
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...Its just a procedural issue that can cause the unsafe condition..

Oh.. and I should add that I don't think your analogy seems to fit...
Both scenarios involve a human decision to act contrary to what is right and involve risk that the decision maker can perform in a manner that they believe makes it safe for them to act as they do. Again IMO
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Old 08-04-2014, 11:35 AM   #37
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Both scenarios involve a human decision to act contrary to what is right and involve risk that the decision maker can perform in a manner that they believe makes it safe for them to act as they do. Again IMO
Thank you for your opinion.. and thank you for staying civil with it.. While sarcasm has its place(s), I don't think this conversation should be one of them.

One interesting facet is that the use of an interlock seems to garner acceptance and even some applause... And yet, if you look at that PDF file you posted a link to, the interlock does absolutely nothing to reduce the risk of issues 3, 4, 5 and 6..
It only reduces issues 1 and 2... Which would lead me to understand why the interlocks are not compliant everywhere.

Would you agree?
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Old 08-04-2014, 01:10 PM   #38
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transfer switch for generator for whole home power?


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One interesting facet is that the use of an interlock seems to garner acceptance and even some applause... And yet, if you look at that PDF file you posted a link to, the interlock does absolutely nothing to reduce the risk of issues 3, 4, 5 and 6..
It only reduces issues 1 and 2... Which would lead me to understand why the interlocks are not compliant everywhere.

Would you agree?
Understand how the interlock works before you make your observations.

3 is a non issue. You don't use a cord with male plugs on both ends. You put an "inlet" on your residence - it has the male end, on the house side. The interlock breaker isolates it from the mains when not in use.

You merely connect your transfer cord, with a female end going to the house and a male end to plug into your generator.

4 is not an issue. A circuit breaker will function either direction.

5 and 6 refer to your "backfeeding" and not a properly installed interlock. All circuits will be protected by the same breakers you use every day on municipal power. All grounds are tied in as well.

Last edited by AandPDan; 08-04-2014 at 01:13 PM.
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Old 08-04-2014, 01:16 PM   #39
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I only posted that to share other risks involved. Everything has risks, as a lineman I can mitigate only so much and still accomplish my goal. But I've had 25 years of learning so hopefully my risks are less then the avg joe. That goes for anyone in a trade for a period of time. Yes an interlock won't cure all risks. It isolates upstream. It puts the risk locally on the decision maker and his conscience.

Back to the speeding scenario. If you're on a highway and a guy goes speeding by you, you're trusting in his ability to not affect your safe passage, somewhat. An interlock puts that driver on the other side of a wall, speeding to his hearts content. Now only his passengers are at risk and not yours.

We just seem to have different perspectives, as I often do with EEs. Especially ones that come on board from the aerospace industry. The things they think you can do in the field.

Last edited by clw1963; 08-04-2014 at 01:23 PM.
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Old 08-04-2014, 01:32 PM   #40
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...Would you agree?
Not exactly. A properly installed interlock through an inlet does not have any bare hot prongs, does not depend on live reverse tripping of the main, and does not interfere with circuit protection of individual panel circuits. It is nominally safe with 2 main risks. First, it depends on the panel main functioning correctly when manually opened. Second, and most important, it depends on the homeowner to open all CBs in the panel before connecting the generator and closing only those that can be supported by the generators capacity. A typical homeowner will not be completely aware of all load issues such as motor inrush. To that extent it is also not proper to depend on the generators own load protection CB.

A transfer switch installed to code will guarantee that there is no connection ever between the generator output, and the utility and its circuits must be limited so that all connected devices are within the power rating of the generator based on a load calculation.

Edit: Others beat me to most of this.
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Old 08-04-2014, 02:40 PM   #41
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We just seem to have different perspectives, as I often do with EEs. Especially ones that come on board from the aerospace industry. The things they think you can do in the field.
This has been a bit of a learning experience for me.. I didn't even know they made these interlock things... A very good idea.

As for me, I will continue to back-feed through the same circuit that I hook my welder and plasma cutter up to.
While I have always understood the dangers involved, and have controls in place to mitigate those issues, I will be sure to watch what I say in these forums when speaking with "Mr. Average Homeowner" from this point forward.

Thank you to all for your input..
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Old 08-04-2014, 05:52 PM   #42
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transfer switch for generator for whole home power?


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I will be sure to watch what I say in these forums when speaking with "Mr. Average Homeowner" from this point forward.

This should always be the case when posting.

And it's the reason why many people get riled up
over certain issue's of safety.
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Old 08-04-2014, 07:26 PM   #43
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transfer switch for generator for whole home power?


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As a licensed guy, what exactly do you find so dangerous about back feeding a breaker panel with a generator?

I'm guessing you're going to come back with "If you don't turn off that main breaker, etc etc etc.. " or some version of this....

Would that be about it? Or as an engineer who DOES NOT make a living dealing with residential applications, am I missing or overlooking something beyond the main breaker concern?
Very perceptive. In the unlikely scenario that no one else in the area has their main breaker on there is a slight chance that someone could get killed, ie. a lineman. More likely the generator will try and power up the whole neighborhood until it cuts off.
Unfortunately, not every homeowner is as smart as you are. Those are the people we (licensed guys) have to look out for. People will tell you, "Of course I'll do the safe thing!" When the time comes around again they forget all about it and turn around and blame you. All the safeguards and warning labels are there to try and prevent bad things from happening.
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Old 08-05-2014, 01:09 AM   #44
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transfer switch for generator for whole home power?


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Very perceptive. In the unlikely scenario that no one else in the area has their main breaker on there is a slight chance that someone could get killed, ie. a lineman. More likely the generator will try and power up the whole neighborhood until it cuts off.
I think you are understating the risk. It does not take a lot of volts on the secondary side of a 100:1 transformer to put dangerous and potentially lethal voltage up on the primary. Hopefully the crew has the grounds in the right places.
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Old 08-05-2014, 09:07 PM   #45
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transfer switch for generator for whole home power?


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This has been a bit of a learning experience for me.. I didn't even know they made these interlock things... A very good idea.

As for me, I will continue to back-feed through the same circuit that I hook my welder and plasma cutter up to.
While I have always understood the dangers involved, and have controls in place to mitigate those issues, I will be sure to watch what I say in these forums when speaking with "Mr. Average Homeowner" from this point forward.

Thank you to all for your input..
While you may understand the risks there might be a time that someone tries to connect the genset and does not know your process and grabs the energized end of the suicide cord and ends up dead.. Your family goes out to see why they don't have lights on yet and trip over the dead body. Do you think your method is foolproof?

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