Please clarify/settle a portable generator question

[IndyXJ]

With the recent ice storms in Indiana, there was a run on generators and the discussion thereof. I don't have one(yet). Someone I know says you can avoid "backfeeding" by just turning OFF the main breaker and only turning on the breakers for the appliances you need(of course if your generator can handle it).

In my research, I don't think that is a good idea either. When I get one, I don't intend on doing that, but wanted you guys to let me know if this is really safe or not. I know you can get special breaker boxes(for lack of a better term) installed to isolate a generator from the grid.

Keyword is safety, not what some neighbors cousin's dad did 5 years ago or stories like that, lol!

Thanks!

 

[Sniggs]

You need an Isolator - Hire a qualified electrician to do the work. You will probably need permits and an inspection too.

 

[old_man]

I'm an electrical engineer. The problem is one of safety. You really wouldn't want there to be any possibly way someone could flip that breaker and cause problems. Will it work, yes. Do I recommend it, no.

Personally I would do it and have done it, but I am a trained professsional and you should never try what you read about at home.

 

[IndyXJ]

Yeah, like I say, I'm not personally going to, but wanted everyone's take.
Luckily, I didn't lose any power and life was good last week. However, it's put power and heating during emergencies to the front of my mind.

 

[Jeepman401]

If you loose power often, go for the isolation switch. Other than the cost, there is no reason not to.
I am with old man, Done it several times, but I know the risks, and I accept them. If you are even the slightest bit uncomfortable about it, electricity is not something you want to mess with.

 

[BarFlyFisherman]

The problem is the NEUTRAL line.

The service disconnect does not separate the neutral line from the utility company. The neutral passes through the service entrance panel without a breaker. The utility's incoming neutral & the site's neutrals are actually connected together on the neutral bus bar.

An automatic transfer switch breaks the connection between the 2 incoming hot conductors AND the neutral conductor. The service entrance conductors are routed through the meter, then to the transfer switch, then to the service entrance panel.

Then like 3 giant parallel teeter-totters, the poles of the transfer switch move from the utility company inputs to the generator's inputs.

The National Electric Code (NEC) states that a utility company must also inspect any back-up generator installation, to ensure the safety of their personnel.

Plugging or wiring a generator into a buildings circuitry without the proper disconnect in place, can kill a utility company worker by back feeding the neutral circuit!

 

[RCP Phx]

The problem is the NEUTRAL line.

The service disconnect does not separate the neutral line from the utility company. The neutral passes through the service entrance panel without a breaker. The utility's incoming neutral & the site's neutrals are actually connected together on the neutral bus bar.

An automatic transfer switch breaks the connection between the 2 incoming hot conductors AND the neutral conductor. The service entrance conductors are routed through the meter, then to the transfer switch, then to the service entrance panel.

Then like 3 giant parallel teeter-totters, the poles of the transfer switch move from the utility company inputs to the generator's inputs.

The National Electric Code (NEC) states that a utility company must also inspect any back-up generator installation, to ensure the safety of their personnel.

Plugging or wiring a generator into a buildings circuitry without the proper disconnect in place, can kill a utility company worker by back feeding the neutral circuit!

Wrong on almost everything!

 

[WB9YZU]

I'm an electrical engineer. ...

Personally I would do it and have done it, but I am a trained professsional and you should never try what you read about at home.

You are an Electrical Engineer, or a Journeyman Electrician?

The latter is a trained professional qualified to perform the wiring, the 1st is not Just teasing.

RCPX: Yah, that doesn't ring true here either. IIRC, Neutral is grounded at the pole and at the house panel.
The idea is to transfer the hots from the outside service to the generator. Ground is handled at the main service panel.

I don't know about inspection, but it probably wouldn't be a bad idea.

 

[Ivan]

The power company is going to ground lines on thier side anyway, before any repair work commences. If you have a generator runing at the time, that is not separated from the grid; it will simply trip off once it senses the power company's grounding.

 

[kastein]

I'm an electrical engineer. The problem is one of safety. You really wouldn't want there to be any possibly way someone could flip that breaker and cause problems. Will it work, yes. Do I recommend it, no.

Personally I would do it and have done it, but I am a trained professsional and you should never try what you read about at home.

Fully agreed. I would only do something like this if I absolutely had to have power for some reason - to keep a ghost containment grid operational, maintain life support, keep the water pipes in the house from freezing, microwave hot wings during the super bowl, etc. If it was just to watch the news or keep the heat at 65, no way.

If this is done, you should always lock out the breaker. Most good breaker panels I have seen have a way to put a padlock on them while the main breaker is off which keeps it from being turned back on. The lock should be clearly flagged with a tag explaining why the breaker is locked off and who to ask before unlocking it.

The problem is the NEUTRAL line.

The service disconnect does not separate the neutral line from the utility company. The neutral passes through the service entrance panel without a breaker. The utility's incoming neutral & the site's neutrals are actually connected together on the neutral bus bar.

An automatic transfer switch breaks the connection between the 2 incoming hot conductors AND the neutral conductor. The service entrance conductors are routed through the meter, then to the transfer switch, then to the service entrance panel.

Then like 3 giant parallel teeter-totters, the poles of the transfer switch move from the utility company inputs to the generator's inputs.

The National Electric Code (NEC) states that a utility company must also inspect any back-up generator installation, to ensure the safety of their personnel.

Plugging or wiring a generator into a buildings circuitry without the proper disconnect in place, can kill a utility company worker by back feeding the neutral circuit!

I am sorry but you have absolutely no idea what you are talking about. SPOBI.

The neutral line is grounded to a 10 foot copper plated pole jammed into the ground (or equivalent) at the panel in the house. It is also grounded at the pole.

 

[Boatwrench]

I am sorry but you have absolutely no idea what you are talking about. SPOBI.

The neutral line is grounded to a 10 foot copper plated pole jammed into the ground (or equivalent) at the panel in the house. It is also grounded at the pole.

Could it possibly be that MA and AZ have different electrical codes? or the age of the house?
There isn't a copper rod jammed into my house in Petaluma, CA built in 1981, but my former house in San Francisco remodeled in 1990 had a rod.

 

[kastein]

He's referencing NEC, which is the national electric code... what I took issue with was his explanation of what could happen, which is somewhere between "a glorious work of fiction" and "completely wrong."

 

[Matthew Currie]

this question has come up a few times, and as I understand it, a transfer switch will also often not disconnect either neutral or ground. Nor, as far as I know, do the legal down-stream emergency circuit transfer boxes you can get at Home Depot, etc. I gather that problems with neutral will occur if your installation is incorrect and the neutral and ground are tied together incorrectly, but otherwise, it's the hot that needs to be isolated. I may still be wrong on this, having heard it both ways, but that's the way I heard it last from sources that seem reliable.

Interestingly, if you dig deeply into the Square D catalog, you'll find interlocks that are designed specifically to allow a backup generator to be backfed through a sub breaker adjacent to the main. One presumes that if Square D is selling these as "backfed generator" interlocks, they're acceptable. It appears that my breaker box is compatible with these, and if so, that's what I'm going to do when I get the chance. Move a couple of breakers around, put a 30 in the designated space for the generator, and backfeed happily ever after.

I have at times backfed through my dryer outlet, and it works very well. But of course, to do this one must be absolutely thoroughly, "do-or-die" certain to disconnect the main first.

on other topic: I can't picture a code-legal service without a ground rod. I have seen a house in which that was omitted. Before I married my current wife, she lived in a new house whose electrician had omitted the ground rod. It very nearly electrocuted her when she did the laundry, and fried the submersible pump.

 

[RCP Phx]

Ground rods are one of many types off "grounding electrodes" used in a "grounding electrode system",but they are not required.You are required to have a grounding electrode to connect to the neutral conductor at each "service" or "separately derived system".Generators can be a "separately derived system" but are not required to be.The type of transfer switch used will determine whether you tie the generators neutral to the service neutral.

30yrs IBEW LU 640
15yrs IAEI Electrical Inspector

 

[Matthew Currie]

Ground rods are one of many types off "grounding electrodes" used in a "grounding electrode system",but they are not required.You are required to have a grounding electrode to connect to the neutral conductor at each "service" or "separately derived system".Generators can be a "separately derived system" but are not required to be.The type of transfer switch used will determine whether you tie the generators neutral to the service neutral.

30yrs IBEW LU 640
15yrs IAEI Electrical Inspector

So am I reading this more or less correctly: if I have a proper grounding electrode (earth ground, usually but not necessarily a ground rod) tied to the neutral of my main breaker box, and if I use a properly interlocked back-fed breaker in that same box as the input for my generator, it should be all right, since it is tied to the service neutral and the ground electrode?

 

[5-90]

I think I'm a bit at sea here myself - can someone clarify the following point for me?

Is or is not the "return" or "neutral" line the same thing as the "earth" or "ground?"

I've long been under the impression that they are different - which is why we can have two-prong (hot and return) or three-prong (hot, return, and ground) plugs and outlets for common 115VAC.

The "return" or "neutral" line is the split between the two 115VAC supply lines going into the house (both of the 115VAC lines are used when 230VAC is needed, like for a dryer or a welder - three prongs is hot/hot/return, and four prongs is hot/hot/return/earth,) so you either have a "hot" and a "return" (two prongs) or a "hot," "return," and "earth" (three prongs.)

Am I missing something here? Or did I just learn it wrong all those years ago? I just want to make sure.

 

[Matthew Currie]

I think I'm a bit at sea here myself - can someone clarify the following point for me?

Is or is not the "return" or "neutral" line the same thing as the "earth" or "ground?"

I've long been under the impression that they are different - which is why we can have two-prong (hot and return) or three-prong (hot, return, and ground) plugs and outlets for common 115VAC.

The "return" or "neutral" line is the split between the two 115VAC supply lines going into the house (both of the 115VAC lines are used when 230VAC is needed, like for a dryer or a welder - three prongs is hot/hot/return, and four prongs is hot/hot/return/earth,) so you either have a "hot" and a "return" (two prongs) or a "hot," "return," and "earth" (three prongs.)

Am I missing something here? Or did I just learn it wrong all those years ago? I just want to make sure.

On a 115 volt circuit, the neutral line, though it joins the ground at the service, is a current-carrying line in the circuit even though the potential to ground is zero, and this differentiates it from the ground in a three-wire line, which ordinarily carries no current. When using a two wire plug, both lines carry current, obviously, since that's the whole circuit. If the plug is polarized, then parts of the appliance in question can be part of the circuit but with no potential to ground. Once upon a time many AC-DC radios and TV's without transformers used the entire chassis as common ground without any isolation, so they, for example, require a polarized plug or you'd risk a shock when you touch the case.

In a 240 volt circuit such as a stove or dryer, the neutral line carries current only for any 115 volt accessories, such as the oven bulb, clock, timer, etc., or in the case of dryers usually, the motor. For the 240 volt portion, it's only the two hot lines that carry current. A four prong distinguishes between neutral and ground, so that the appliance can be safely grounded without sharing a line with the current carrying neutral, a very small but not zero risk.

 

[RCP Phx]

Very well said!Grounded conductors and grounding conductors serve completely separate functions.

On a similar note,weve had an influx of "Utility-Interactive" photo voltaic installations.We had a big meeting today to discuss issues,some of these are almost 1 Megawatt and the amount were seeing is growing!

 

[Sniggs]

You need an Isolator - Hire a qualified electrician to do the work. You will probably need permits and an inspection too.

Yeah. What I said.

 

[ECKSJAY]

Yeah. What I said.

lol stfu old guy