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

[grsthegreat]

What I have found is several blogs/message boards for utility linemen. To a T, they expect homeowners to be idiots and blame any injuries on poor training by the employer of the lineman or lack of discipline in not following proceedures. One that they refer to in '05 says a homeowner came past them and fired up a generator while the lineman was working on a line he was told was grounded out. It wasn't grounded out, and they never proved any homeowner fired up a generator. The line may have touched something else. Regardless, it wasn't grounded out while he was working on it.

from Pensacola News Journal

07-16-2005, 07:31 PM
from Pensacola News Journal

Published - July, 14, 2005
Probable electrocution 3rd storm-related death
Sean Smith
@PensacolaNewsJournal.com ADVERTISEMENT


Generator safety precautions
Customers using generators during an outage should never use a generator in an enclosed or partially enclosed space. Generators can produce high levels of carbon monoxide very quickly, which can lead to illness or death.

Do not connect portable generators to household electrical wiring. This could cause serious injury to you and power employees working on the lines.

Connect only essential appliances -- such as freezers and refrigerators -- directly to the generator.


In the wake of Hurricane Dennis, a Georgia lineman working to restore power in Flomaton, Ala., near Century likely died of electrocution, officials said Wednesday.

Ronnie Allen Adams Jr., 41, of Winterville, Ga., an employee of Pike Electric Inc. of Mount Airy, N.C., was found by co-workers slumped over in his bucket truck as he worked on Jackson Street about 4:55 p.m. Tuesday, the Flomaton Police Department reported.

Co-workers attempted cardiopulmonary resuscitation until firefighters and emergency medical crews arrived minutes later. A Baptist Lifeflight helicopter arrived at 5:21 p.m. and flew Adams to Jay Hospital, where he was pronounced dead, Flomaton police said.

Dr. Andi Minyard, medical examiner for Northwest Florida District 1, said the preliminary cause of death was high-voltage electricity.

The lineman's death is being investigated by Flomaton police, Pike Electric and Alabama Power, which was contracting work to Pike to help with storm relief.

"We are deeply saddened by this death, and our sincere condolences go to the families," said Michael Sznajderman, spokesman for Alabama Power.

It was the third storm-related death in the area since Hurricane Dennis struck Sunday. Two people were suspected of being killed in the Pensacola Bay Area by carbon monoxide poisoning stemming from improper use of portable generators.

The cause of Tuesday's incident is under investigation, but the improper use of a generator has not been ruled out, police said. Improperly installed generators can become dangerous for linemen working to restore electricity, Alabama Power and Gulf Power officials said.

Some homeowners have been plugging the generators through their meter boxes or into the house to provide electricity to appliances. That can send electricity back outside and energize lines that are supposed to be dead, Sznajderman said.

 

[grsthegreat]

When the NEC requires ground fault protection and you have an alternate power supply, you must switch the neutral. If you have a service larger than 1,000A, the NEC requires ground fault protection at the main service disconnect. If the generator neutral grounding runs via a solid connection to the main service neutral and the generator experiences a ground fault while feeding the load, the main service disconnect will open. This will not disconnect the arc fault from the generator, and coordination will be lost.

If the neutrals of the two sources are separately grounded, you must switch the load neutral conductor to the source feeding the load, per 230.95(C) FPN No. 3. Ground fault current will return only to the source from which it originates, providing for coordination of the ground fault protection scheme.

It’s not always necessary to separately ground the generator neutral conductor, but if you do, you may need to switch a load neutral along with its phase conductors when transferring loads between power sources, particularly when you use ground fault protection. The NEC requires ground fault protection for 480/277V, 3-phase, 4-wire, wye-connected services rated 1,000A or more, but it’s optional in other configurations that don’t include ground fault protection.

 

[buickanddeere]

What I have found is several blogs/message boards for utility linemen. To a T, they expect homeowners to be idiots and blame any injuries on poor training by the employer of the lineman or lack of discipline in not following proceedures. One that they refer to in '05 says a homeowner came past them and fired up a generator while the lineman was working on a line he was told was grounded out. It wasn't grounded out, and they never proved any homeowner fired up a generator. The line may have touched something else. Regardless, it wasn't grounded out while he was working on it.

Given the number of home brew jacklegg home owner Cobb Jobs that Linemen find . They are well within their rights to refer to 99+% of home owners unknowing and dangerous .

 

[buickanddeere]

I was told never to switch neutral. If that neutral part of the switch failed, you would get all kinds of odd voltages on your two legs, depending on loads.

If the generator neutral is bonded , the neutral has to be switched to avoid flowing neutral current through the ground system.

 

[Industrial Toys]

Why would you want a neutral bonded at the generator?

I actually don't even use a neutral on my gensets, but use a transformer set up as an autotransformer, so the generator will always be balanced AND I could take full load off either side on 110 without any issues.

 

[aczlan]

Why would you want a neutral bonded at the generator?

I actually don't even use a neutral on my gensets, but use a transformer set up as an autotransformer, so the generator will always be balanced AND I could take full load off either side on 110 without any issues.

If you use a generator as a stand-alone generator, it needs to be bonded then.

Aaron Z

 

[CobyRupert]

Why would you want a neutral bonded at the generator?

I actually don't even use a neutral on my gensets, but use a transformer set up as an autotransformer, so the generator will always be balanced AND I could take full load off either side on 110 without any issues.

If you have it as "standalone" generator, (or a switched neutral; i.e. a separately derived system) somewhere the neutral needs to be grounded (set to 0 volts, earth) that way 240V is divided evenly into 120V (L1 to neutral) and 120V (L2 to neutral). If Neutral wasn't grounded to zero someplace, (a "floating neutral") the 240V would get split based on what loads are turned on/off. So you may end up with 150V on one leg, and 90V on the other.

 

[CobyRupert]

If someone with a redneck connection doesn't flip the main and powers their house from their generator connected into a branch circuit, unless their little Honda can reverse-power the whole neighborhood, town, utility grid, etc.. it's unlikely a lineman is going to get injured.

Although that depends on how isolated the utility line being worked on is. If line just feeds one home on the end of a road, and only that line is being worked on (isolated), a genny at that home might be able to energize the line and not stall/trip out.

 

[coldsteelva]

If someone with a redneck connection doesn't flip the main and powers their house from their generator connected into a branch circuit, unless their little Honda can reverse-power the whole neighborhood, town, utility grid, etc.. it's unlikely a lineman is going to get injured.

Although that depends on how isolated the utility line being worked on is. If line just feeds one home on the end of a road, and only that line is being worked on (isolated), a genny at that home might be able to energize the line and not stall/trip out.

I don't believe the problem is the amount of power the generator is putting out, BUT if the lineman upstream is working on a line and there are one or even two transformers (which usually step down power) between your home and the lineman - those transformers in reverse will now step-UP the voltage. I am no electrician, but I always thought this was where the risk was introduced. Voltage causes burns, but it only takes .1 to .2 amps to stop your heart.

 

[laurencen]

our generator is a 15Kva, I have a transfer switch from the main panel that goes to a 16 breaker 50Amp box, this box powers furnace, water pump and specific lights and plugs, the transfer is manual and isolates this panel to either use line voltage or generator

I am amazed how many use a small gen set and connect using the wall plug outlet, all it takes is forgetting to throw the main breaker