jwelectric
Senior Member
- Location
- North Carolina
Anyone remember this?
Portable Generators and GFCIs 2011 NEC
- Thread starter tom baker
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jwelectric
Senior Member
- Location
- North Carolina
Help me out just a little bit here.
Should I plug a cord into the 240 volt receptacle on the generator pictured above and connect the cord to a transfer switch that does not switch the grounded neutral conductor the code mandates that the bond to the generator frame be lifted.
Do we agree so far?
Now should I decide to plug another piece of equipment into one of the 120 volt duplex receptacles on the generator above would that piece of equipment be protected as outlined in 250.34? If you answer this no then the generator can not be a portable generator as described in 250.34
Should I plug a cord into the 240 volt receptacle on the generator pictured above and connect the cord to a transfer switch that does not switch the grounded neutral conductor the code mandates that the bond to the generator frame be lifted.
Do we agree so far?
Now should I decide to plug another piece of equipment into one of the 120 volt duplex receptacles on the generator above would that piece of equipment be protected as outlined in 250.34? If you answer this no then the generator can not be a portable generator as described in 250.34
For feeding a permanent premises panelboard with temporary power when service is not energized? No permanent transfer switch necessary... but if service conductors are installed, I'd effectively isolate and lockout from the temporarily energized portion of the system.
Yes
I don't see how any issue under 250.34 would change a portable generator to a permanently installed generator. 250.34(A) simply gives the conditions under which a portable generator is not required to be connected to a grounding electrode. It does not say the frame cannot be connected to a grounding electrode.
250.34(C) says the frame must be connected to the grounded conductor when an SDS. Since I assume we are talking about a service-supplied [and normally energized] premises system, the conditions of installation you stated makes this portable generator a non-SDS alternate power source. Therefore, 250.20(D) and hence 250.30(A) do not apply. Furthermore, I see nothing in those two sections that say a protable generator falling under their purvue becomes a permanantly installed generator.
- Location
- Massachusetts
That is a 'swing and a miss'.:grin:
Nothing in what you posted supports the view that a portable generator that has been grounded becomes a 'non-portable' generator.
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ceb58
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- Raeford, NC
But the question hasn't been answered. And to cause more confusion look at 702.10 (A) & (B)
I think to keep the GFCI from triping it would have to be installed as a SDS.
If connected as a non-SDS, the grounded neutral to frame bond would be lifted. What would cause the GFCI's to trip?
ceb58
Senior Member
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- Raeford, NC
http://ecmweb.com/power_quality/electric_groundfault_current_problems/
I am going on the install of gen. in systems with GFI protection on the mains.
jwelectric
Senior Member
- Location
- North Carolina
And here-in lies the problem. First the portable generator is under the rules of 250.34. Here we are told in subsection (C) that the grounded neutral MUST bond to the frame.
If this generator has devices mounted on the frame then it must be a stand alone system therefore a separately derived ungrounded system.
Should for any reason this generator is connected to the premises wiring of a building then 250.26 mandates that the neutral conductor be connected to earth. Should this generator be connected to a premises wiring system then the bond to the frame must be lifted making everyone of the other receptacles located on this generator in violation. I couldn?t unplug the generator from the transfer switch and move it to a new location and plug in a piece of equipment without reconnecting the frame bond therefore the generator lost is ability to be portable.
I can see where you would think that it was a swing and a miss because I don?t believe you have been reading everything, have you?
I am sure that you understand that the very second that the neutral bond is lifted from the frame of that generator then every receptacle on that generator no longer has a fault path.
The informational note in 250.34 (C) refers us to 250.30 and 250.30(B)(2) sends us right back to 250.34
250.34(A) and (B) states the conditions under which a portable or vehicle-mounted generator is not required to be connected to an electrode. If the conditions are not met, it must be connected to an electrode as defined in 250.52.
250.34(C) states the grounded conductor MUST be bonded to the frame ONLY when a component of an SDS. It does not prohibit unbonding when used as a non-SDS alternate power source.
When it is not interconnected with other earth grounded systems, it is chassis grounded (a term which the NEC recognizes only by implicit wording, such as in 250.34). When connected to premises wiring, it becomes earth grounded through the EGC.
How would the receptacles be in violation? You remove the frame to neutral bond, not the frame to receptacle ground connections.
The frame bonding does not determine the portability of a generator. IMO, its portability is determined initially by its design and subsequently by its listing. If I recall correctly, the Generac portable generator I bought about two years ago came with the bonding jumper unconnected from the frame.
The EGC of the cord would carry any fault-to-frame current to the premises MBJ then back to the generator on the neutral.
You seem to be blurring the line between an SDS and non-SDS connection of the generator. The frame-to-neutral bond is only lifted for non-SDS connection.
The note refers us specifically to 250.20(D) and it refers us specifically to 250.30(A), not 250.30(B)(2).
So if connected as an SDS, 250.30(A) applies. If connected non-SDS, only lifting the frame bond is required.
Also, make sure you read and understand the two FPN's of 250.30(A).
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I've read that article in its entirety before. This time I only need look at the figures to see the article contributors do not fully understand SDS grounding. Note in Figures 1 and 2 the captions state the system is SDS... and specifically the gen-set in Fig. 1.http://ecmweb.com/power_quality/electric_groundfault_current_problems/
I am going on the install of gen. in systems with GFI protection on the mains.
If the transformer is a service transformer, this system is non-SDS because of the solidly connected neutral... and the bonding jumper at the gen-set would be in violation.
If not a service transformer, then the system must be an SDS, and the system as a whole must meet the grounding requirements of an SDS. As such, there can only be one system bonding jumper when alternate power sources are solidly connected, and the Figure's show two.
jwelectric
Senior Member
- Location
- North Carolina
And both are references to SDS
back this with code text
Okay then let me look at these sections
The Note in the 2008 book sends me to 250.20(D) which is titled ?Separately Derived Systems? which sends me to 250.30(A) which is titled ?Grounded Systems. A separately derived ac system that is grounded?..
Both are talking about a ?Separately Derived System?
In the 2011 book it sends me straight to 250.30 which is titled ?Separately Derived Systems?
Just what is the code book trying to say here? Is it saying one thing while others are saying that it is alright to do something else?
The only place that I can find it either code cycle that will allow me to connect a generator as a non-separately derived system is in 250.35(B)
Should you find somewhere that would allow me to connect a portable generator as a non-separately system elsewhere in either code cycle please post it for my benefit.
By the way neither code cycle has two notes under 250.30(A)
I also believe that you are trying to say that the cord used to connect the portable generator that I posted the picture of would require a #8 conductor to carry the fault current. (see Table 250.66)
If I understand your set-up a fault current on one of the other receptacles located on the generator would have to travel from the point of fault through a receptacle to the frame of the generator back through the fault path to the premises service panel to the neutral back through the receptacle at the building down the grounded conductor through another receptacle to the system before opening the overcurrent device on the portable generator. Yes by-golly I think this is just how UL tested this piece of equipment. Is this really what you mean to say?
- Location
- Massachusetts
Mike as is always the case you cannot focus on the question asked.
I had said nothing backs your claim that a portable generator once grounded becomes a 'non-portable' generator.
jwelectric said:
You still have not shown me anything to change that.
Forget about fault paths, forget about all the other 'stuff' and show me a code section that says that a grounded generator cannot be a portable generator.
It is a very simple request. Lets resolve this one issue before moving on to other ones.
jwelectric
Senior Member
- Location
- North Carolina
Bob to be sure that we are both on the same page here let?s be straight that the original question is based on the 2011 Edition of the NEC and is the information I am using.
What do we have on this generator that would mandate where the bonding of the electrode is to be connected? 1- We have the point of our first disconnecting means. 2- We have our overcurrent device that is protecting that disconnect.
Does this not mandate that the bonding must take place here?????
Permission is given in 250.34 to leave this system ungrounded but mandates that a connection to the Equipment grounding terminal of the disconnect be bonded to the conductor that is required to be bonded by 250.26 or the neutral if you prefer.
Being that this generator comes with everything needed for the entire system such as disconnecting device, overcurrent, branch circuit devices, as well as the fault current bond it is a stand alone system or a Separately Derived System.
Should we want to connect this generator to a fixed wiring system such as a home, store, shop or whatever the Information Note gives us information on how to accomplish this. Notice that a change took place here and it now refers the reader to 250.30 which although has many revisions is still for Separately Derived Systems. One of these revisions was the addition of subpart (C) which covers such things as transformers and generators that are outdoor sources. See Page 90 of the Analysis of Changes 2011.
I don?t see anywhere in 250 that would allow me to connect a portable generator as outlined in 250.34 as a non-separately derived system. I do see where installing a generator as a non-separately derived system to a fixed wiring system is covered but I am afraid it is not a portable generator.
Can you show me where a portable generator as Tom and I are talking about can be installed as a non-separately derived system?
No? Well I can show you where a generator that is connected as a non-separately derived system is not a portable but instead a permanently installed generator even if it is only connected for 10 minutes. It can even have wheels or be built on a trailer. It can be three phase or single phase.
What it can?t have is overcurrent as outlined in 250.35(B) as part of the generator as the one Tom and I are talking about and be installed as a non-separately derived system.
Any generator that does not have overcurrent devices weather or not it has wheels or on a trailer does not fit the description outlined in 250.34 as a portable generator.
Where does the Code say you have to have permission to connect to any system? The Code does not even say you have permission to connect as an SDS to a fixed wiring system... it only implies that you can.
Ooops! My mistake. The two notes referred to are under 250.20(D) in 2008, and I believe (I only have the 2011 ROP Draft as a referemce) they were moved to 250.30 under the opening paragraph [not under subarticle (A)].
250.34(A) says it don't have to be connected to an electrode... which means there is no GEC.
The only earth grounding requirement is 250.34(C) which requires the frame to be bonded to the [earth] grounded conductor... but ONLY when a component of an SDS. This requirement can be overridden by 250.6(A) when applicable, and falls under the alteration means and conditions of 250.6(B). Thus the PG can be a component of an SDS and required not to bond the frame to the grounded conductor!!!
An example of the above is where an SDS system is powered by a non-service, isolated-primary-secondary-type transformer and the PG, through a transfer switch where the grounded conductor is not switched, and the SBJ is located somewhere other than the PG.
Additionally, since this is a portable generator, it will never be considered part of the building or structure it may serve. With the disconencting means integral to the PG, the connecting cord is considered a feeder... and only an appropriately sized EGC is required to the building or structure's disconnecting means. It is the building or structure which is required to have a GES... and that gets bonded to the feeder EGC.
So again, a GEC is not [absolutely] required to be directly connected to the PG.
I think you put a little extra distance on your path... but otherwise, yes, the fault current has to travel on EGC's to wherever the system MBJ/SBJ is located, the back through the neutral feeder's EGC... but it is a path and sufficiently sized to carry the fault if the connection to the fixed wiring system is made through the grounded 3-wire receptacle. I would never consider connecting to a fixed system though one of the 120V receptacles. How about you?
jwelectric
Senior Member
- Location
- North Carolina
Boy you had my head reeling and rocking there for a second. What is a PG???
Where does 250.34(C) require any connection to earth???????
On a self-contained generator where would there be objectionable current? Where does all this come from???
I sure wish I knew what this PG creature was. If this transformer is a non-utility transformer then it will fall under the requirements of the NEC and will require that the bonding take place either at the source or at the first disconnect. If this is from the outside then the first disconnect will be mandated by Article 225
I don?t think that the fact that it is a ?portable? generator makes the conductors supplying the load feeders. I think that because the receptacle on that generator is protected by overcurrent mandates that any and all bonding MUST take place on the generator. Overcurrent on the feeders would allow us to size the equipment grounding conductor by Table 250.122. If there is no overcurrent device on the feeders then the supply side bonding jumping is required to be sized by 250.66
Well now being that I have no idea what a ?PG? is I can?t argue this point one way or the other.
There is no such thing as an equipment grounding conductor on the supply side of the main bonding jumper.
Well if the fixed system was 120 volts I would fly right into plugging it into one of the other devices located on that portable generator.
But what I wouldn?t do would be have the system bonding take place at any place other than where the first overcurrent device was located.
Even with your correction should something be plugged into one of the 120 volt receptacles on the generator and the path you purpose become lost (someone unplugged the cord to the main bonding jumper) then the 120 volt receptacle would be unprotected from fault current. This is a life safety issue.
hurk27
Senior Member
- Location
- Portage, Indiana NEC: 2008
PG = Portable Generator?
PG = portable generator
Assumed you could figure that out being we are discussing them.
It requires the frame to grounded conductor bonding when part of an SDS. Connected as an SDS, the neutral is required to be earth grounded, which also means the grounding conductor is earth grounded. :roll:
When it is a component of an SDS having two sources of energy. See the article ceb58 provided a link for in his most recent post.
Man you sure do jump around on issues :roll:
Everything we've discussed falls under the NEC. And I thought we were talking about grounding of a portable generator. How did we get on outside branch circuits and feeders? Oh... on second thought, don't answer that question.
The fact that there is a disconnecting means integral to the generator and another disconnecting means at the other end of the cord, which is not the final ocpd for loads, makes the cord a feeder.
On a service supplied system, yes... to the service-supply side of the MBJ. But when a PG is connected to the same service-supplied system as a non-SDS source, the grounding conductor to (or should I say from?) the PG is an EGC.
When PG is connected as a single-source SDS to a fixed wiring system, the grounding conductor is part of the feeder, so it is also an EGC. This is where you have to consider providing a GES at the generator.
And just how many 120V systems do you see nowadays?
So that would be at the generator if you are connected to a fixed wiring system via cord-and-plug... and the PG is not part of any building or structure and is outside the building or structure being supplied, right? So drive a couple ground rod and GEC them to the PG.
...and that is likely the reason for requiring GFCI receptacles, as noted in the the OP...
jwelectric
Senior Member
- Location
- North Carolina
Well now you sure have found something in you code book that I can?t find in mine. Which year are you using? Just where does it require to be connected to earth in 250.34??
In the 2008 code cycle there was a change in the language in 250.34 for clarification on the frame of portable generators and their relationship to earth. Frames of portable generators are not an electrode and the portable generator is not required to be connected to a grounding electrode. The portable generator is an ungrounded standalone electrical system just as the slide I posted states.
Unless this portable generator is in the basement I would say that it is outside. If it is outside then any and all wiring to and from would fall under 225. I thought you knew that we were talking about outside PGs.
Any conductor that is on the supply of the bonding jumper IS NOT an equipment grounding conductor!!
Equipment grounding conductors are sized on Table 250.122 and are sized based on the size of the overcurrent device protecting the ungrounded conductors.
The Supply Side Bonding Jumper is the conductor between the generator and the first disconnect at the building being served when the generator is being installed as a non-separately derived system and is sized using Table 250.66 The name changed in the 2011 cycle but the method of sizing is still the same. Before 2011 it was called the equipment bonding conductor.
Under the new provisions outlined in the 2011 code cycle where there was many changes concerning such things as this generator.
First as outlined in 250.34 a portable generator is an ungrounded system and there is no requirement that it is to be connected to earth in order to use this piece of equipment. Fault current path is established through the frame of the generator.
In the informational note we are referred to 250.30 should we want to install this generator to ground this portable generator.
New to 250.30 is a section just for SDS installed outside, 250.30(C).
The conductors coning from the generator to the building are feeders by definition and are located outside therefore they must comply to the provisions as supplying a separate building. 250.32 once again has some changes one being the new 250.32(C) which guides us through the provisions of connecting this unground system to the building supplied by feeders.
Now you can say that the generator as posted in the original post and pictured in the post I made can be installed as a non-SDS but I will continue to argue that you are in violation of the listing and labeling of the unit as the other devices are now not protected by the bonding to the source as outlined in 250.34(C).
I will also give three cheers to the Code Making Panel for the new requirement that all receptacles be GFCI protected in order to stop these type generators from being connected to the premises wiring systems.
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