Another Generator Grounding Question

[ceb58]

JW, I admire your tenacity and I have no argument that you are technically correct here. I have had these same arguments about these installs. I just don't know what the practical solution is here. The NEC, UL and the manufacturers need to come up with a practical solution.

They have. Install it as a separately derived system.

 

[texie]

They have. Install it as a separately derived system.

Really? Show me a resi grade manual or auto transfer switch with a switched neutral.

 

[templdl]

Now there's something I can agree with.

But the manufacturers must realize that the is an issue. When I worked as a sales and applications engineer I went to as many code and electrical safety forums as I could so that I would be able to relate to my customers. I often think that those who design and manufacture products don't have a clue about what the real world application problems are.
When I worked for a transformer manufacturer I never understood why my design engineers always put a grounding stud on the outside of the terminal enclosure of a NEMA 3R transformer. You use conduit with the wires inside the conduit, run an EGC inside the conduit and have a ground stud out side the terminal compartment.

 

[ActionDave]

They have. Install it as a separately derived system.

What is it about a SDS that makes it better/safer than a non-SDS?

 

[goldstar]

The opening sentence in UL-FTCN states the following :

This category covers internal-combustion-engine-driven generators rated
15 kW or less, 250 V or less, which are provided only with receptacle outlets for the ac output circuits.

Does that mean that I can use this portable unit as a non-separately derived system ?

http://www.electricgeneratorsdirect.com/Generac-5735-Portable-Generator/p2685.html

Aside from the KW rating it meets ALL the requirements listed in FTCN. I don't see any technical difference in the way it's built when compared with smaller KW units. If you click on the "specs" tab you'll see that the neutral IS bonded. Would this be a safe and Code compliant installation if I didn't transfer the neutral ?

 

[goldstar]

But the manufacturers must realize that the is an issue.

This is the point that I've been trying to make all along. It would be one thing if only one manufacturer made a product that wasn't Code compliant but they've all seemed to have hopped on the band wagon. I'm not disputing what UL-FTCN states but CH and Sq D all make their own interlock kits that they claim are UL recognized devices. Reliance and Gen-Tran are pushing transfer panels out the door that they claim are UL recognized. People are making home "how to" videos like this one appealing to unsuspecting HO's

http://www.youtube.com/watch?v=2y1EhVQqjiw .

Walk into any supply house, HD or Lowe's and they're pushing generator transfer products. Is it possible that ALL these companies are incorrectly telling consumers that these are Code compliant installations and the only ones correct are those few who are not performing portable hook-up installations because they read UL-FTCN ?

 

[templdl]

This is the point that I've been trying to make all along. It would be one thing if only one manufacturer made a product that wasn't Code compliant but they've all seemed to have hopped on the band wagon. I'm not disputing what UL-FTCN states but CH and Sq D all make their own interlock kits that they claim are UL recognized devices. Reliance and Gen-Tran are pushing transfer panels out the door that they claim are UL recognized. People are making home "how to" videos like this one appealing to unsuspecting HO's

http://www.youtube.com/watch?v=2y1EhVQqjiw .

Walk into any supply house, HD or Lowe's and they're pushing generator transfer products. Is it possible that ALL these companies are incorrectly telling consumers that these are Code compliant installations and the only ones correct are those few who are not performing portable hook-up installations because they read UL-FTCN ?

Unless there are knowledgeable people at Lowe's, HD, etc such as former licensed electricians they most likely are following the manufacturers lead with the assumption that the manufacturer knows what they are doing.

 

[goldstar]

Unless there are knowledgeable people at Lowe's, HD, etc such as former licensed electricians they most likely are following the manufacturers lead with the assumption that the manufacturer knows what they are doing.

Exactly, but it's not just HD & Lowe's. I walked into one of my supply houses the other day and there were 30 amp power cords and power inlet boxes sitting right out in the open like a super-market for EC's and unsuspecting customers to grab at will. There were also CH panel covers with built-in interlock kits on display. I'm not saying this is right. All I'm trying to point out is that there's a multi-million dollar generator marketing campaign that's been going on for several years now. Manufacturers have been pushing these products out the door in record #'s and it will grind to a halt if and when they are forced to recognize UL-FTCN. Who's going to win in the long run - UL or the multi $$$ marketing campaign ?

Every time there's a disasterous storm like Hurricane Irene, Super-storm Sandy, nor-easter snow storms on the east coast that knock power out for several days, that generator market increases in $$ exponentially. UL can publish all the directives it wants to but people will continue to wait in HD or Lowe's parking lots buying generators right out of the back of the semi. I don't see EC's walking picket lines in HD parking lots with signs protesting that these units should not be connected to premise wiring in the manner they are being sold. IMHO, I just don't see this market drying up because awareness of UL-FTCN was brought to this Forum.

Sorry, I'm off the soap box now.

 

[iceworm]

I'm not understanding the danger. Yes I understand the code and the UL. I definitely need some help here with the physics. I've got a few things that I'm not clear on - I'll stay to one item per post.

What is it about a SDS that makes it better/safer than a non-SDS?

I don't know. I work on/ specify/put in a lot of generation systems and they are all non-SDS. But they all are way bigger than a typical residential. Why the safety favors SDS at 15KW and below baffles me.

That 17kw unit goldstar referenced looked fine. Why not install as an SDS? I would remove the gen NG bond.

So what changes between 15kw and 17kw (the physics, not the code)?

ice

 

[iceworm]

... In a non-bonded genset that is being used as a temp power source for 120 volts and something happens to a winding then instead of 120 volts one could possibly have 240 volts supplying that 120 volt appliance. ...

jw - I'm completely baffled here.
Are you discussing using a generator with receptacles and the gen NG bond has been removed, to power cord and plug equipment?

If so, you are correct - it is not a good idea. However, I'm completely baffled how if "something happens to a winding one could possibly have 240 volts supplying that 120v appliance". Please explain how this could happen - I don't see it.

I'm thinking, since this has, "been documented", perhaps you could put up a sketch.

ice

 

[iceworm]

jw - I'm completely baffled here.
Are you discussing using a generator with receptacles and the gen NG bond has been removed, to power cord and plug equipment?

If so, you are correct - it is not a good idea. However, I'm completely baffled how if "something happens to a winding one could possibly have 240 volts supplying that 120V appliance". Please explain how this could happen - I don't see it. ...

Maybe I do see what you are saying:
With the NG bond removed, and one end of the 240V winding faults to ground, the neutral goes to 120V above ground and the other end of the winding goes to 240V above ground. The grounding conductor is still at ground (gen frame) potential. Is this what you are saying?

If so, that is true. Possibly (probably?) not dangerous until the tool and the gfci both fail. But still, not good to run with a hidden failure.

Is that it?

ice

 

[goldstar]

I'm not understanding the danger. Yes I understand the code and the UL. I definitely need some help here with the physics. I've got a few things that I'm not clear on - I'll stay to one item per post.


I don't know. I work on/ specify/put in a lot of generation systems and they are all non-SDS. But they all are way bigger than a typical residential. Why the safety favors SDS at 15KW and below baffles me.

That 17kw unit goldstar referenced looked fine. Why not install as an SDS? I would remove the gen NG bond.

I think you meant non-SDS if I'm not mistaken. I'm with you on this but let me see if I can clarify this for you based on what's been posted here so far and if I'm wrong someone please correct me. I'm not sure where UL came up with this edict but UL-FTCN states :

• This category covers internal-combustion-engine-driven generators rated 15 kW or less, 250 V or less
• which are provided only with receptacle outlets for the ac output circuits.
• The generators may incorporate alternating or direct-current generator sections for supplying energy to battery charging circuits.

When a portable generator (of the specified sizes BTW) is used to supply a building wiring system:

• The generator is considered a separately derived system in accordance with ANSI/NFPA 70, ??National Electrical Code?? (NEC) (They don't cite a specific section)
• The generator is intended to be connected through permanently installed Listed transfer equipment that switches all conductors other than the equipment grounding conductor.
• The frame of a Listed generator is connected to the equipment grounding conductor and the grounded (neutral) conductor of the
  generator. When properly connected to a premises or structure, the portable generator will be connected to the premises or structure
  grounding electrode for its ground reference. So, apparently, in order to be a LISTED unit a N-G bond must be factory installed. Removing that bond would void the UL listing. But when you plug in the 4-wire power cord isn't this connection already done for you ?
• Portable generators used other than to power building structures are intended to be connected to ground in accordance with the NEC. (Again, no specific section cited)

So what changes between 15kw and 17kw (the physics, not the code)?

That's the question I posed and I wish I could answer it for you. I see no difference in the way this unit is made as opposed to a 15 KW unit. Hopefully others more knowledgable will chime in on this.

 

[jwelectric]

jw - I'm completely baffled here.
Are you discussing using a generator with receptacles and the gen NG bond has been removed, to power cord and plug equipment?

If so, you are correct - it is not a good idea. However, I'm completely baffled how if "something happens to a winding one could possibly have 240 volts supplying that 120v appliance". Please explain how this could happen - I don't see it.

I'm thinking, since this has, "been documented", perhaps you could put up a sketch.

ice

A winding shorts to the neutral of a non-bonded generator and there will be 240 volts on the 120 volt receptacles. This is why UL mandates that a generator that has devices mounted on the frame are to have the frame bonded to the neutral.

The generator linked to earlier in this thread would be required to be installed as a SDS because the frame is bonded to the neutral

When the neutral is bonded to the frame and the generator is installed as a NON-SDS then there is a parallel path for the neutral current

 

[iceworm]

I think you meant non-SDS if I'm not mistaken. ...

yes, thank you

... I'm with you on this but let me see if I can clarify this for you based on what's been posted here so far and if I'm wrong someone please correct me. I'm not sure where UL came up with this edict but UL-FTCN states :

First, I'm not advocating non-compliance with man's law of the land.

I'm pretty sure I have a clear understanding of the code and the UL and I think I know why they came up with it. I just don't see the physics behind the danger of non-compliance - unless one counts standing in front of an inspector that has a head of steam up and a gagged pressure relief, as a life threatening event.

:rant: (The Inspector)
(Me) or maybe :rotflmao: (depends on the day)

ice

 

[iceworm]

jw - I'm completely baffled here.
Are you discussing using a generator with receptacles and the gen NG bond has been removed, to power cord and plug equipment?

If so, you are correct - it is not a good idea. However, I'm completely baffled how if "something happens to a winding one could possibly have 240 volts supplying that 120v appliance". Please explain how this could happen - I don't see it.

I'm thinking, since this has, "been documented", perhaps you could put up a sketch.
ice

A winding shorts to the neutral of a non-bonded generator and there will be 240 volts on the 120 volt receptacles.

So you did not like my translation of your statement. Okay.

This is where I need a sketch - or a better explanation. There is no physics I know of where a generator winding failure would put 240 volts between the hot and neutral on a generator mounted 120V receptacle. I respectfully request an explanation of how this could happen.

ice

 

[iceworm]

jw -
There are several issues in this thread. I respectfully request to discuss them separately. if for no other reason than it will make it easier on me.

Item 2 of your post:

...The generator linked to earlier in this thread would be required to be installed as a SDS because the frame is bonded to the neutral ...

No it wouldn't. As I stated in the post where I said it would be okay to use as a non-SDS, I also said one needs to pull the bond. Not only is this safe, it meets the code, and the UL does not apply - over 15kw. :thumbsdown:

ice

 

[iceworm]

Item three of your post:

...When the neutral is bonded to the frame and the generator is installed as a NON-SDS then there is a parallel path for the neutral current

Your right. let's discuss the danger of non-compliance. I am personally against any MGN installations. Let's look at the codes:

As previously noted, it has been okay to re-bond the NG at outbuildings. And then there is the history of range and dryer connections using the neutral for the equipment ground - unless you had a mobile home or subpanel - then you couldn't. Now it is not okay for any installation - what changed?

And, of course, there is the issue of under NESC it is proper, recommended, and safe to have multiple NG bonds. But under the NEC it is illegal and unsafe to have multiple NG bonds. Good to know the electron are smart enough to know which side of the Service they are on.

Then there is my personal favorite piece of moronic code: Outside transformers must have a second NG bond. Huh??

Probably only somewhat dumb for residential - however since I work industrial, and most all sites have a ground grid, this practice guarantees problems with solidly grounded Wye systems.. It mandates any neutral current is split between the ground grid and the neutral conductor. This one looks far deadlier than any 15kw residential gen connection with an NG bond in the gen and a 2 pole switch.

I do not advocate non-compliance.
I do not advocate any MGN systems.

I do advocate non-SDS generator installations.

I do advocate the NEC and UL getting together and actually talking.

And as others have said or alluded to:
I do understand the issue of a small cord and plug generators used for residential power outage temporay generation are also likely to be used for other cord and plug free standing applications. It is not a good idea to have a small residential grade generator that has the NG bond removed for the house temp power and have to have it installed for free standing use.

I do advocate mfgs marketing an inexpensive, 3 pole, residential grade, manual transfer switch.

And one of my own mis-spoken peices of wierdness:
How about Mfgs marketing small (15kw or less) residential grade 120/240 gens with an unbonded NG, a frame mounted 4W receptacle and CB, and a bonded NG panel mounted on the gen frame that will plug into the gen 4W recpt. The frame mounted panel is bonded, has the gfci 20A and 30A receptacles for free standing use.

Probably can't because it would cost an extra ten dollars

And yes, it is about money.

ice

 

[GoldDigger]

I like your solution better than mine, which would be to install a sophisticated circuit which injects current to detect an external bond and opens the internal bond if an external bond is detected.

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[jwelectric]

Portable generators that have receptacles are required to have the neutral bonded to the frame of the generator by 250.26 as referenced in 250.34. The informational Note in 250.34 although not enforceable the code section pointed out within is very enforceable, No FTCN does not point out the code sections but it does reference the code itself which we as installers are to conform with.

Should a lead or even the winding itself short to the frame of the generator the voltage would find the neutral through the main bonding jumper of the service equipment which is the same place that the generator is connected to earth via the supply side bonding jumper or equipment bonding jumper if the generator has overcurrent devices.

Article 225 requires that the feeders coming from the generator to land in a disconnect either outside the building or nearest the point of entrance of the feeders and that this disconnect be suitable for use as service equipment unless the requirement found in 702 applies but I don?t think that a portable generator that has devices mounted on the frame fits this criteria.

As to the listing of all the equipment that the manufactures advertised being used incorrectly I suppose the listed equipment in the attached picture would be allowed in a hazardous location, it is UL listed is it not? Maybe the instructions included in the listing is where we could find our answers if we would only take the time to stop reading advertisements and do the proper research. It will be in the UL listing that I will find that the pictured box below is not listed for a Class 1 Division 1 Zone 0 location.

No more than as an inspector can I use manufacture flyers to enforce code compliance can the electrical contractor use it to defend code compliance. As an inspector I will be looking for compliance with the NEC as adopted into the statutes of my state. This will include everything found in the NEC concerning the installation from the generator to the end use.

A careful read of the Proposal and the corresponding Comment which was made by the Technical Correlating Committee one can see that the requirements of Part II Article 225 does apply to the installation of an optional standby system.

Three wire cooking and dryers are no longer allowed as well as remote three wire buildings. There is a reason for this and I would be willing to bet that the danger involved is the reason why. It is like Knob and Tube wiring. It is allowed to remain in place but we are not allowed to install that type of installation nor are we allowed to install two wire NM cable but not required to remove it either.

 

[GoldDigger]

If the high side of one winding of the generator shorts to (for example) the neutral, it will not move the neutral voltage to that of the high end short. It will short out that winding, one end of which is already connected to the neutral.
Now if there is no bond between neutral and ground anywhere, a short at the high end of one winding could indeed raise the neutral to ground voltage to 120 volts and the opposite phase terminal to a240V above ground.
But that will not apply 240V to any 120V load. At worst, it will act like any other ungrounded system in which slash rated devices and loads should not be used. At best, there would be a neutral to ground bond in the distribution network somewhere and once again the winding will be shorted out and the load will not be affected.

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