Interlock vs. throwing the main circuit breaker for generator powering a house

[buckeyefarmer]

This "issue" gets brought up and argued over at least once a year, it's only January and here it is already.

 

[aczlan]

Only works IF the generator is Hard Wired to the electrical service .

Huh? It will work just as well with a male outlet on its own circuit that you plug the generator into, or a whip that you plug into the generator.

Aaron Z

 

[LouNY]

I found an interesting pdf file on generators and the NEC;

https://www.mikeholt.com/download.php?file.../Generators...Standby...2014NEC.pdf

This pdf shows several permissible transfer switch wirings, most of which do not switch the neutral,
if it is switched there are several bonding and grounding requirement.
Article 702 of the NEC is the provision for standby generators that are not legally required or
mandated emergency generators.

Lou

 

[zzvyb6]

Depends if the generator has a floating or bonded neutral if the transfer switch also switches the neutral.
Only way a neutral is going to send power back to the utility is an incorrect installation.

Consider this: my neighbors a few doors down had a situation where a lightning strike shorted one leg of the 240v to the neutral underground. Lights became very bright, smoke from wall receptacles and after a short while, the entire house burned unto the basement. Because of the insurance delay, water in the basement froze and cracked and split the foundation. If the power had burned itself a disconnect, how would a standby generator without a neutral opening transfer switch reacted to this?

The reason I asked is because a few months ago, I had a 7600v underground line going from a pole to my on the ground transformer burn out and shorted to earth. If it had shorted to a neutral, my house could have been burned. The talk of neutral disconnect is new to this semi-annual discussion.

BTW; the DTE guys showed up here at 10 pm. used a 'thumper' to locate the short, dug it up spliced in a patch and restored power by 1:00 a.m. !

Meanwhile, there is a new device on the market that goes between the meter housing and the backing plate to be used for a home generator connection. What's your opinion of this technique?

 

[bcp]

Meanwhile, there is a new device on the market that goes between the meter housing and the backing plate to be used for a home generator connection. What's your opinion of this technique?

Sounds like a good idea. My electric co. won't allow it. I asked.

Bruce

 

[MossRoad]

Consider this: my neighbors a few doors down had a situation where a lightning strike shorted one leg of the 240v to the neutral underground. Lights became very bright, smoke from wall receptacles and after a short while, the entire house burned unto the basement. Because of the insurance delay, water in the basement froze and cracked and split the foundation. If the power had burned itself a disconnect, how would a standby generator without a neutral opening transfer switch reacted to this?

The reason I asked is because a few months ago, I had a 7600v underground line going from a pole to my on the ground transformer burn out and shorted to earth. If it had shorted to a neutral, my house could have been burned. The talk of neutral disconnect is new to this semi-annual discussion.

BTW; the DTE guys showed up here at 10 pm. used a 'thumper' to locate the short, dug it up spliced in a patch and restored power by 1:00 a.m. ! View attachment 588006

Meanwhile, there is a new device on the market that goes between the meter housing and the backing plate to be used for a home generator connection. What's your opinion of this technique?

I think I've seen those for about 10 years.

 

[grsthegreat]

Anyone have a link to the code that shows the neutral should be switched?

The neutral DOES NOT HAVE TO BE SWITCHED... unless your talking about a separately derived system...which the whole house is not. Residental transfer switches do not switch neutral. A UL approved interlock is aporoved to use as long as main breaker cannot be engaged when generator breaker is engaged.

There is a product that is mounted between a meter panel and the panel. Its called Generlink. Some utility companies up my way install them. They have 30 and i believe 50 amp versions. Its a nifty idea.

 

[JerryK]

I have been using the back feed method for using a generator since time began. I currently have a sliding face plate type interlock on my 200 amp barn panel. Any competent person can back feed a panel, but you have to admit there are those among us that do not pass this test 24/7, especially in the odd times the power seems to always fail. There are also times that you might not be around, and your significant other might attempt to get the juices flowing and get into trouble. So an interlock of some type is not a bad thing. Can't make things 100% safe, but the electrical code is written to try to reach that goal. I ...IS... a retired person that was once extremely well paid to do electrical work, so your results may vary.....

 

[check]

My electrician installed a 60 amp generator subpanel when we built the cottage back in 2002. Since we only had a 6500/5500 portable generator, we only put a certain number of important circuits in that subpanel. Of course it contains a simple mechanical device that forces you to shut off the power from the main panel while at the same time turning on the power from the generator that is plugged in outside. Very elegant, and very simple.

Now we have a 17 kW Propane standby generator, with an automatic transfer switch to power the whole house. However, if that generator ever fails, we can always plug in the portable one and still have power for essential circuits.

Despite the fact that the electricity company has upgraded huge amount of the infrastructure, we get regular power outages. Thank God for generators!

 

[MossRoad]

And one can always put twist-lock plugs on their furnace, well pump, etc.... and power things with extension cords in a pinch by just unplugging them and plugging them into the cords. Just run the cords through a window and close them up. Shove a towel in the crack if it's cold out or to keep the bugs out, etc... and keep the generator exhaust away from the house, not in a garage, etc....

There are so many deaths by carbon monoxide poisoning and generators each year. Be safe.

 

[Ford850]

Meanwhile, there is a new device on the market that goes between the meter housing and the backing plate to be used for a home generator connection. What's your opinion of this technique?

My electric company recommends these, sells them outright, and also sells them on payment plans added to your monthly bill. If you buy from them, they install it no charge.

 

[CobyRupert]

I found an interesting pdf file on generators and the NEC;

https://www.mikeholt.com/download.php?file.../Generators...Standby...2014NEC.pdf

This pdf shows several permissible transfer switch wirings, most of which do not switch the neutral,
if it is switched there are several bonding and grounding requirement.
Article 702 of the NEC is the provision for standby generators that are not legally required or
mandated emergency generators.

Lou

Ding ding ding! Winner.
Just as importantly, if neutral is not switched, do NOT bond neutral and ground at generator or transfer switch.
Most transfer switches do not switch the neutral. Yes they are legitimate.
IF the transfer switch switches the neutral, THAT is what makes the generator a “separately derived system” where the switched neutral now needs to be bonded to a separate ground electrode system associated with the generator, instead of associated with center tap of the utility’s transformer (which is what your panel/house ground is so that you get 120V & 240V)
Otherwise generator is not a “separately derived system”
NEC Article 250 (can’t remember exact paragraph, but it’s at the very beginning) gets into this.

Remember: the neutral and ground system can only be bonded at one location so that neutral (white wires) current doesn’t have a parallel path to travel on the ground (green wires) system. Otherwise, Ohms law says this will create a voltage on every grounded case. If you switch the neutral, you’ve remove this bond and have to establish a new one with the ground (ground rods and green wires); usually at the generator or transfer switch.

 

[turnkey4099]

well, since I'm the only one here. I'll be the one doing all the work connecting the generator and flipping the switches . I really don't see how they would help me.
I could see using something like these if there were many different people involved making connections and flipping switches. I have been doing it so long, it's as simple as getting in the truck, turning the keys to start the engine.

Uhuh, and I have had several experiences where asn automatic action learned over the years has failed me. Is it worth saving a few bucks if someone screws up just once and a lineman gets hurt? Guess who is going to pay then.

 

[turnkey4099]

it not only protects from back feeding,
but it protects your generator, as well, as if the grid comes back on and one flips the breaker on and the generator is still hooked up, most likely it is fried,

I had an example of human failure in a "fool proof" system. New maintenance man came in to do the annual test, somehow didn't follow the 'fool proof' system and kicked generator one stillconnected to the line. With both feeding the system it fried just about every electrical item in the jail...including the doors.

 

[MossRoad]

I had an example of human failure in a "fool proof" system. New maintenance man came in to do the annual test, somehow didn't follow the 'fool proof' system and kicked generator one stillconnected to the line. With both feeding the system it fried just about every electrical item in the jail...including the doors.

Sounds like an inside job.....



( Sorry, I've always wanted to say that. )

 

[buickanddeere]

Huh? It will work just as well with a male outlet on its own circuit that you plug the generator into, or a whip that you plug into the generator.



Aaron Z

. Where are you doing the switching and placing the locks to prevent energizing the male plug prongs ?

 

[buickanddeere]

Consider this: my neighbors a few doors down had a situation where a lightning strike shorted one leg of the 240v to the neutral underground. Lights became very bright, smoke from wall receptacles and after a short while, the entire house burned unto the basement. Because of the insurance delay, water in the basement froze and cracked and split the foundation. If the power had burned itself a disconnect, how would a standby generator without a neutral opening transfer switch reacted to this?

The reason I asked is because a few months ago, I had a 7600v underground line going from a pole to my on the ground transformer burn out and shorted to earth. If it had shorted to a neutral, my house could have been burned. The talk of neutral disconnect is new to this semi-annual discussion.

BTW; the DTE guys showed up here at 10 pm. used a 'thumper' to locate the short, dug it up spliced in a patch and restored power by 1:00 a.m. ! View attachment 588006

Meanwhile, there is a new device on the market that goes between the meter housing and the backing plate to be used for a home generator connection. What's your opinion of this technique?

The larger high current version of the Gener-Link works very well.

 

[buickanddeere]

Consider this: my neighbors a few doors down had a situation where a lightning strike shorted one leg of the 240v to the neutral underground. Lights became very bright, smoke from wall receptacles and after a short while, the entire house burned unto the basement. Because of the insurance delay, water in the basement froze and cracked and split the foundation. If the power had burned itself a disconnect, how would a standby generator without a neutral opening transfer switch reacted to this?

The reason I asked is because a few months ago, I had a 7600v underground line going from a pole to my on the ground transformer burn out and shorted to earth. If it had shorted to a neutral, my house could have been burned. The talk of neutral disconnect is new to this semi-annual discussion.

BTW; the DTE guys showed up here at 10 pm. used a 'thumper' to locate the short, dug it up spliced in a patch and restored power by 1:00 a.m. ! View attachment 588006

Meanwhile, there is a new device on the market that goes between the meter housing and the backing plate to be used for a home generator connection. What's your opinion of this technique?

if properly bonded and grounded a breaker would have tripped

 

[buickanddeere]

The neutral DOES NOT HAVE TO BE SWITCHED... unless your talking about a separately derived system...which the whole house is not. Residental transfer switches do not switch neutral. A UL approved interlock is aporoved to use as long as main breaker cannot be engaged when generator breaker is engaged.

There is a product that is mounted between a meter panel and the panel. Its called Generlink. Some utility companies up my way install them. They have 30 and i believe 50 amp versions. Its a nifty idea.

Of the generator痴 neutral is bonded . The transfer switch is supposed to switch the neutral to avoid running current through the ground system .

 

[MossRoad]

....I have been doing it so long, it's as simple as getting in the truck, turning the keys to start the engine.

I'm of your same mindset, as in I backfeed my house when I need to. And I do it from a sub-panel in my garage, which feeds back to the house. So I have to kill the main breaker outside under the meter, kill the main breaker in the house panel, etc... before doing the generator hookup in the garage.

However, as I get older, and hopefully wiser, I'm leaning towards being a bit safer, and if I can take a risk out of the equation, especially since it's so cheap to do now, I should do it. Accidents happen. I forget things once in a while. It's just not worth it when I can put a lockout on it for well under a hundred bucks.

We put one on my in-law's breaker panel and wired a "real" generator outlet onto the outside of their house. It works great.

And as far as it being as simple as getting in the truck, turning the keys.....

How many times have we read about people driving right through a store? These are people that have been driving for years, yet they have a brain freeze and BOOM.

https://www.lohud.com/story/news/lo...-many-drivers-crash-into-buildings/362650002/

So I figure I'm not infallible. It could happen to me. So why do it anymore when the safety system is so good and so cheap?