Another Generator Grounding Question

[don_resqcapt19]

02 (C) Grounded Conductor Bonding. A system conductor that is required to be grounded by 250.26 shall be bonded to the generator frame where the generator is a component of a separately derived system.

05 (C) Grounded Conductor Bonding A system conductor that is required to be grounded by 250.26 shall be bonded to the generator frame where the generator is a component of a separately derived system

08 (C) Grounded Conductor Bonding. A system conductor that is required to be grounded by 250.26 shall be connected to the generator frame where the generator is a component of a separately derived system

11 (C) Grounded Conductor Bonding. A system conductor that is required to be grounded by 250.26 shall be connected to the generator frame where the generator is a component of a separately derived system.

If we go all the way back to the 1993 cycle we find similar wording but every one of the cycles all the way back to the ?93 in the FPN/IN clearly state that a generator that fits the description outlined in A and B is to be connect to a premises wiring as a SDS.

250.34 (A) & (B) relieves the requirement to connect a stand-alone generator to earth but C in all the code cycles state that the conductor that is required by 250.26 to be connected to earth is to be connected to the frame of the generator. The frame of the generator is the earth connection.

If a stand-alone generator is connected to a premises wiring system as a SDS the connection to earth takes place through the bonding conductor between the generator and the premises equipment. All metal in the premises wiring is bonded to the grounding electrode conductor at the service equipment of the premises wiring system thus the generator is also connected to earth.

Many try to use the reference in (C) to say ?if we float the neutral then the generator is a non-SDS?, but by doing so causes the other receptacles mounted on the frame to be non-code compliant and have the ability to become very dangerous. When the neutral is disconnected from the frame the devices mounted there upon are protected only from overcurrent and not protected from ground fault.

The GFCI devices will clear a ground fault on the load side of the device but will do nothing to stop a fault on the line side or clear a hot EGC. This is accomplished only through bonding the neutral to the frame.

All of that is fine and good, but under the current code there is no way to have a grounded system without a connection to a grounding electrode. This was an unintended consequence of the change in the definition of "grounded". Until this is fixed the use of a portable generator to supply "premises wiring systems" requires a connection to a grounding electrode.

 

[Wilmon Culley]

Wilmon Culley

Wilmon Culley

I am using an interlock switch to disconnect the MAIN when generator is in use. The neutral is not switched....only the hot feeds. I have a Briggs EXL8000 which has a bonded neutral. I am setting it up not far from my utility inlet.

Question: To solve any grounding issues, couldn't I simply connect a ground wire of suitable gauge from my generator ground nut directly to my existing service grounding rod? If this is the case, I should not have to reconfigure my generator to a floating ground.....I would think. (???) Am I missing something? I really do not want to manipulate the generator if possible.

Its like a garage not connected to the house. Even though the equipment grounding conductor goes from the garage sub panel to the service you still drive a ground rod at the unit connected to the generator frame.

 

[jwelectric]

250.34 Portable and Vehicle-Mounted Generators.
(A) Portable Generators. The frame of a portable generator shall not be required to be connected to a grounding electrode as defined in 250.52 for a system supplied by the generator under the following conditions:
(1) The generator supplies only equipment mounted on the generator, cord-and-plug-connected equipment through receptacles mounted on the generator, or both, and
(2) The normally non?current-carrying metal parts of equipment and the equipment grounding conductor terminals of the receptacles are connected to the generator frame.

As many electrodes of all eight types can be connected to a portable generator. There is nothing to prevent this from happening.

Should a portable generator be connected to a premises wiring system as a SDS the connection to the electrode will take place through the service equipment via the bonding of the frame of the generator and the metal of the premises wiring.

If the generator has overcurrent devices mounted there upon then the earth connection will take place through the EGC run with the feeders. See 702.11 for more information

 

[don_resqcapt19]

250.34 Portable and Vehicle-Mounted Generators.
(A) Portable Generators. The frame of a portable generator shall not be required to be connected to a grounding electrode as defined in 250.52 for a system supplied by the generator under the following conditions:
(1) The generator supplies only equipment mounted on the generator, cord-and-plug-connected equipment through receptacles mounted on the generator, or both, and
(2) The normally non?current-carrying metal parts of equipment and the equipment grounding conductor terminals of the receptacles are connected to the generator frame.
...

That is in conflict with the definition of "grounded" and the requirement for the generator output to be a grounded system. A change in the section you cited needs to be made before you can say that the output of the generator, under the conditions in 250.52, is a grounded system. There is nothing in 250.52 that says a generator installed per that section can supply a grounded system. They just missed making that change when they took the words "or other conductive object that serves in place of the earth" out of the definition of "grounded".

If you connect it to a building as a SDS, then you will have a connection to the building grounding electrode and can have a code compliant system.

 

[GoldDigger]

Its like a garage not connected to the house. Even though the equipment grounding conductor goes from the garage sub panel to the service you still drive a ground rod at the unit connected to the generator frame.

But you do not bond the neutral to that grounding electrode at the garage. You just add that electrode to the grounding system by connecting it to the EGC at the ground bus of the sub panel or the EGC of a single branch circuit if that is what you have.

Sent from my XT1080 using Tapatalk

 

[goldstar]

The cord plugs into the inlet at the house but it originates at the generator on terminals. This generator can be installed either as a SDS or as a non-SDS

Sorry, just jumping back into this thread after being away for a few days. Ok, I can see your point here. I misread the slide. Question (and please bear with me as I may not be thinking out of the box) with respect to 702.7(C) signs (FYI, we here in NJ are not on 2014 NEC yet). For who's benefit is the sign being placed? If it's the original installer, doesn't he already know that ? If it's the building owner or HO, would they know the difference ? Judging by the amount of times this topic has been discussed and argued about (just in this Forum alone - and BTW, thanks for the education) I would venture to guess that the vast majority of electricians throughout the US don't know the difference.

If the generator has receptacles mounted on the frame then those receptacles must comply just as any receptacle installed in the building. The EGC of that receptacle must be bonded to the neutral for a low impedance fault clearing path. Generators such as the one below are dangerous if the neutral is not bonded to the frame as anyone using the generator as a stand-alone unit would have no fault clearing path and could possibly end up holding something in their hand that has a potential of 240 volts.

I guess this is the part that I'm having trouble with. If the generator shown below is a UL listed product then the EGC and neutral have to be bonded to the frame. There is no "if the neutral is not bonded to the frame" scenario unless a HO bought some rusted bucket of bolts at a garage sale, in which case I would not be installing their power inlet port.

The big problem with understanding the requirements outlined in the NEC is that a lot of people think of a portable generator as being one such as in this post and cannot imagine a portable generator as in the post above. Both generators are portable but the one in this post is the one outlined in FTCN.

I hate to keep bringing this up, but take a look at the 8 portables being marketed on the first page of this website http://www.electricgeneratorsdirect.com/quick_search.php . Only 2 have GFI receptacles mounted on the frame and none have GFI protected 120/240 volt receptacles. Are you saying that all this will disappear with the advent of the 2014 NEC ?

 

[texie]

Sorry, just jumping back into this thread after being away for a few days. Ok, I can see your point here. I misread the slide. Question (and please bear with me as I may not be thinking out of the box) with respect to 702.7(C) signs (FYI, we here in NJ are not on 2014 NEC yet). For who's benefit is the sign being placed? If it's the original installer, doesn't he already know that ? If it's the building owner or HO, would they know the difference ? Judging by the amount of times this topic has been discussed and argued about (just in this Forum alone - and BTW, thanks for the education) I would venture to guess that the vast majority of electricians throughout the US don't know the difference.
I guess this is the part that I'm having trouble with. If the generator shown below is a UL listed product then the EGC and neutral have to be bonded to the frame. There is no "if the neutral is not bonded to the frame" scenario unless a HO bought some rusted bucket of bolts at a garage sale, in which case I would not be installing their power inlet port.



I hate to keep bringing this up, but take a look at the 8 portables being marketed on the first page of this website http://www.electricgeneratorsdirect.com/quick_search.php . Only 2 have GFI receptacles mounted on the frame and none have GFI protected 120/240 volt receptacles. Are you saying that all this will disappear with the advent of the 2014 NEC ?

There is a proposed TIA on this. Not sure if it has been passed. See here: http://www.nfpa.org/Assets/files/AboutTheCodes/70/ProposedTIA 1117_NFPA70.pdf

 

[jwelectric]

The signs are for service and emergency personal.
Wasn?t too long ago that the fire department let a commercial building burn to the ground because they couldn?t find the disconnect to kill power. I wouldn?t want to start spraying water on a live circuit.

There are many generators on the market today that are not listed therefore they don?t adhere to the UL standard. One can find two unlisted generators for every one listed generator. But one can also find 10 electricians that see no harm with installing these generators for every one electrician that refuses to install them.

I personally can?t see the advantage of connecting a power source to my home that can?t heat water while I watch TV but then again all the benefit I see in a TV is Sunday afternoon when there are 43 people turning left for a couple of hours. I keep telling the fine folks at my auto shop that I have seen a motor changed I less than 20 laps so why does it take them so long.

I have also seen 20 gallons of gas and four tires in less than 14 seconds so why does it take me 10 minutes to fill my tank. This just goes to prove that TV is bad so why hook a generator to my house just so I can watch one.

For most cases a cord will achieve what is needed for one of these small cracker boxes. For those with gas heat there is a male inlet with a two pole switch to connect a gas furnace. A cord for any appliance and light and save all those hundreds of dollars being thrown away to electricians who think they are doing something great.

Want a generator then spend the money for a real one. The generator at our local hospital would power anything one would need in their home. Better yet get a battery bank and an inverter. What most people don?t realize is that little generator will do more harm to the air we breathe in one hour than our car will in 10 hours. But some think that I am 62 and I will be dead and gone before it affects the air that much. Well I have four of the prettiest great grandchildren anyone has ever seen and I want the air they breathe to be pure and clean.

Hey I think I might be straying off topic just a little talking about going around in counter clock wise circles and my babies.

 

[electrofelon]

The EGC of that receptacle must be bonded to the neutral for a low impedance fault clearing path. Generators such as the one below are dangerous if the neutral is not bonded to the frame as anyone using the generator as a stand-alone unit would have no fault clearing path and could possibly end up holding something in their hand that has a potential of 240 volts.

But 240 volts to what (and Im not seeing the 240 instead of 120 volts situation either...)? I think it would have a hard time getting back to that other winding as it is an ungrounded system. I wont argue the code, but from a practical standpoint I think portable generators are pretty safe whether they be SDS, non sds, floating neutral, bonded neutral, whatever. Sure, anything you can think of has happened at least 27 times. I live off grid and use generators often. I have been in a well I was digging 18 feet down using an electric jackhammer with a frayed cord sitting in the water, used all sort of bad extension cords wire nutted together sitting in the mud, ran all sorts of pumps with frayed cords (its that common phenomenon, just like how auto mechanics always seem to have the crappiest cars at home). The only time I had any issue was down in the well jack hammering I did get a tingle a few times, so I put a sled under the generator to give it a bit more isolation from the ground and that fixed it. I certainly dont do stuff like this for other people nor put pictures of some of the stuff I have at my house on the side of the van. JW, we may be content with little or no conveniences when the power goes out, but there are many who want to be able to cook a thanksgiving dinner with electric appliances when the power is out - I put a 30KW in for someone once literally to meet that requirement! Oh it was their camp too. Its crazy.

 

[jwelectric]

But 240 volts to what (and Im not seeing the 240 instead of 120 volts situation either...)? I think it would have a hard time getting back to that other winding as it is an ungrounded system.

There are documented cases of the equipment grounding conductor of portable generators becoming energized. When this happens there will be a potential of 240 volts at the 120 volt receptacle, 120 volts on the hot conductor and 120 volts on the equipment grounding conductor each from a different winding.

If the neutral is not bonded to the frame of the generator there is no fault clearing path for this voltage on the equipment grounding conductor.

Ungrounded simply means that the generator is not connected to earth. A connection to earth in no way makes the use of electricity safe. The earth connection does nothing for the flow of current through our systems. There is four reasons we connect our systems to earth and these four reasons can be found in 250.4(A)(1).

Your story of the cords reminds me of a buddy of mine from high school. After his second tour in Nam he returned home and lived for 10 years. Every time he got drunk and this was increasing toward the end he played a very dangerous game that took 10 years for him to lose. It is sad that he left the way he did but the worst part is those he left behind.

 

[electrofelon]

There are documented cases of the equipment grounding conductor of portable generators becoming energized. When this happens there will be a potential of 240 volts at the 120 volt receptacle, 120 volts on the hot conductor and 120 volts on the equipment grounding conductor each from a different winding.

If the neutral is not bonded to the frame of the generator there is no fault clearing path for this voltage on the equipment grounding conductor.

Ungrounded simply means that the generator is not connected to earth. A connection to earth in no way makes the use of electricity safe. The earth connection does nothing for the flow of current through our systems. There is four reasons we connect our systems to earth and these four reasons can be found in 250.4(A)(1).

Your story of the cords reminds me of a buddy of mine from high school. After his second tour in Nam he returned home and lived for 10 years. Every time he got drunk and this was increasing toward the end he played a very dangerous game that took 10 years for him to lose. It is sad that he left the way he did but the worst part is those he left behind.

I would argue that in general we are obsessed with grounding electrical systems. There is one very big disadvantage of grounded systems and that is that it makes it much easier to get a line to grounded conductor shock. I am not making a blanket statement that every system would be better off ungrounded, but if you take away all the voodoo about system grounding, ungrounded system have there place and can be safer. As you know there are certain systems in the NEC that are required to not be grounded, and it a common practice to use an isolation transformer when working on certain equipment. I am not sure how floating neutral generators are typically set up, probably the EGC on the receps is bonded to the frame which is isolated from neutral? I would argue that if the EGC were not bonded to the frame and just floated there in space, it could be safer and avoid the situation you describe. I'll be fine, I never drink when I am using frayed cords around water

 

[qcroanoke]

I really hate to bump this back to the top but here goes:

The generator I have has a bonded neutral. It is not UL listed because it does not have GFI protected receptacles.
I looked it up on Big Blue's website and searched through the questions about the generator (because I was just curious to know) and this is 1 of 10 responses to the questions of "Is the neutral bonded in this unit and what type of transfer switch is needed?"

Hello,
The best transfer switch to use for a portable generator is one with a switching neutral. This is because the neutral on the generator is bonded to the ground. You can use a Briggs & Stratton manual transfer switch model number 071014.
Thank you for your question.
Posted by
Troybilt

FYI that transfer switch is $489.00
click here: http://www.amazon.com/Briggs-Stratton-71014-Discontinued-Manufacturer/dp/B000OAJQCE

 

[goldstar]

Did you happen to notice that it stated that it was discontinued by the manufacturer ?

 

[qcroanoke]

Did you happen to notice that it stated that it was discontinued by the manufacturer ?

Yes, just wanted to let everyone know what it looked like.

 

[goldstar]

OK. You should probably use one of the panels listed on this page : http://www.reliancecontrols.com/x-series-panel-link.aspx

 

[qcroanoke]

OK. You should probably use one of the panels listed on this page : http://www.reliancecontrols.com/x-series-panel-link.aspx

Or cut the bond loose in my generator...........

 

[goldstar]

Hello again. Sorry but I couldn't just let this topic go without doing some more research. I wanted to find out why the PG market was fluorishing and why more EC's weren't installing these units as SDS's. I wrote a letter to PGMA (Portable Generator Manufactures Association) inquiring as to the UL listing of portable generators, the manufacturing of these units to applicable UL standards and the use of these units as SDS's. I received a phone call from a representative who told me that in March of 2009 Underwriters issued UL 2201 - Standard for Portable Engine-Generator Assemblies http://www.ul.com/global/eng/pages/...ndards/catalogofstandards/standard/?id=2201_1 . He told me that irrespective of the fact that UL issued this standard, none of the manufactures began building units to those standards and the vast majority are not doing so to this day. In addition, if you look at the portables listed on sites like EG Direct you'll be hard pressed to find any of them UL Listed. You will find safety brocures like this one fron UL http://www.ul.com/global/documents/noteworthy/stormsafety/UL_Operating_Portable_Generators_v4.pdf advising of the safe operation of portable generators but not much more.

Now, again I'm not saying that jwelectric was wrong in his position on this, but my position all along has been that a massive portable generator market exists and is alive and well. Either the individual manufacturers or the PGMA or both have launched these enormous marketing campaigns to sell their generators to HO's that do not want to go for days without electricity. A market that was not highly visible before major storms knocked out power for days. IMHO, in order for that marketing campaign to work PG manufacturers, as well as generator accessory manufacturers, had to come up with products for sale to HO's that did the job and were reasonably priced. Now, again IMHO, if we become required to install a 3-pole manual transfer switch along with a separate main lug breaker panel, the cost will more than likely discourage the vast majority of HO's to part with those $$$. I'm sorry, but I just don't see that market disappearing any time soon.

I will continue to do more research and when I get more responses I will post them here.

 

[qcroanoke]

Hello again. Sorry but I couldn't just let this topic go without doing some more research. I wanted to find out why the PG market was fluorishing and why more EC's weren't installing these units as SDS's. I wrote a letter to PGMA (Portable Generator Manufactures Association) inquiring as to the UL listing of portable generators, the manufacturing of these units to applicable UL standards and the use of these units as SDS's. I received a phone call from a representative who told me that in March of 2009 Underwriters issued UL 2201 - Standard for Portable Engine-Generator Assemblies http://www.ul.com/global/eng/pages/...ndards/catalogofstandards/standard/?id=2201_1 . He told me that irrespective of the fact that UL issued this standard, none of the manufactures began building units to those standards and the vast majority are not doing so to this day. In addition, if you look at the portables listed on sites like EG Direct you'll be hard pressed to find any of them UL Listed. You will find safety brocures like this one fron UL http://www.ul.com/global/documents/noteworthy/stormsafety/UL_Operating_Portable_Generators_v4.pdf advising of the safe operation of portable generators but not much more.

Now, again I'm not saying that jwelectric was wrong in his position on this, but my position all along has been that a massive portable generator market exists and is alive and well. Either the individual manufacturers or the PGMA or both have launched these enormous marketing campaigns to sell their generators to HO's that do not want to go for days without electricity. A market that was not highly visible before major storms knocked out power for days. IMHO, in order for that marketing campaign to work PG manufacturers, as well as generator accessory manufacturers, had to come up with products for sale to HO's that did the job and were reasonably priced. Now, again IMHO, if we become required to install a 3-pole manual transfer switch along with a separate main lug breaker panel, the cost will more than likely discourage the vast majority of HO's to part with those $$$. I'm sorry, but I just don't see that market disappearing any time soon.

I will continue to do more research and when I get more responses I will post them here.

Thanks! As you stated just because UL has a standard on portable generators it doesn't mean they have to be built and installed to it.

 

[iceworm]

Thanks! As you stated just because UL has a standard on portable generators it doesn't mean they have to be built and installed to it.

Nope. Sure doesn't.

There is nothing unsafe about connecting a generator to a house as a non-sds. One must remove the generator N-G bond. As long as the gen is connected to the premisis wiring, there are no faults that can make 240v magically appear across a 120V receptacle.

Now if one wishes to disconnect the gen from the house and use as a portable gen, (edit) using the 120V receptacles, without installing the N-G bond, that is a different matter. This falls under the catagory of, "Any equipment improperly installed or used outside of the design specs may well have unknown failure modes". There is nothing anybody can do about that.

There is an additional danger if installing in NC. The solution is to purchase a 15.1KW gen. This will make it safe to install.

ice

 

[tankdriver]

Nope. Sure doesn't.

There is nothing unsafe about connecting a generator to a house as a non-sds. One must remove the generator N-G bond. As long as the gen is connected to the premisis wiring, there are no faults that can make 240v magically appear across a 120V receptacle.

Now if one wishes to disconnect the gen from the house and use as a portable gen, (edit) using the 120V receptacles, without installing the N-G bond, that is a different matter. This falls under the catagory of, "Any equipment improperly installed or used outside of the design specs may well have unknown failure modes". There is nothing anybody can do about that.

There is an additional danger if installing in NC. The solution is to purchase a 15.1KW gen. This will make it safe to install.

ice

Why would mfgs not install a switch where you could select bonded neutral, or floating neutral(or bonded, non-bonded)l. Where you could select what you needed? Does not seem like it would be hard to do.