mobile home & ground rods

[Smart $]

The GES is installed at the service structure.

For sure... but the debate is whether another is also required for the home itself when the service structure is adjacent... not in or on.

The EGC as given in 550.16(B)(1) is run through the feeder.

I'm not checking the reference, but yes... run with feeder conductors.

So the question is: Where is the GEC connected? Which I thought was being addressed by 550.16(A)?

Only direct reference to a GEC in 550 is 550.32(B).

 

[iwire]

I believe I have posted twice in this thread the position of the State of Nevada that mobile homes are appliances, not structures.

Not if they have adopted the NEC without amendments.

Did they amend the definition of structure?

 

[renosteinke]

Can we name any other structure that comes complete, from the factory, with a UL label?

That very UL/HUD certification also removes mobile homes from the requirements of the usual building codes, etc. Call them trailers, motor vehicles, whatever you like .... but 'structures' they're not. Not even if they're welded to the rebar of a concrete slab, and incapable of being moved without destroying them. Essentially, they're just like a real big toaster sitting next door to you.

I've mentioned some of the other quirks of the NEC and mobile homes - don't want to go off on a tangent that could easily justify its' own thread - but it's also worth noting that more places are now requiring licensing in addition to the EC license in order to work on mobile homes. Such licensing is also administered by entities completely separate from the folks who license contractors.

There's a fault with the logic that question whether it's OK to use a flexible cord on a dishwasher .... yet infer that the NEC requires you to rip apart and 'remanufacture' a listed assembly in order to comply with the code. Unlike your typical hot tub, mobile homes do not have any provision for running a GEC to the panel, nor is there a bonding lug on the frame.

So, we are left with two possible answers: Either the folks at UL/HUD have been in error for a quarter century, or the interpretation was made 'way back then' that mobile homes don't need ground rods.

 

[pfalcon]

For sure... but the debate is whether another is also required for the home itself when the service structure is adjacent... not in or on.

I'm still not seeing where the requirement for the GES is that the service is on the building. I've only seen where it says it cannot be remote. And by 550 that distance would be more than 30'.

Only direct reference to a GEC in 550 is 550.32(B).

And (B)(3) is like :huh: unless they aren't expecting to run a GEC out of a mobile home as described in 550.32(A).

250.64 specifies at not in the structure. 550 repeatedly says 30' is adjacent which to me qualifies as at the structure. I see nowhere that at each means a separate unique GEC/GES.

I hope I'm not coming across wrong. I really want to understand this; and my normal focus is industrial machines.

 

[jwelectric]

I can see you are not going to change your position based solely on textual content. So let's consider concepts. Yet to be discussed to any great depth is the size of the EGC. Under 2008/2011 the feeder EGC connects GES's at separate structures. However, no GES at mobile and manufactured homes supplied by feeder is essentially saying the feeder EGC serves the purpose of a GEC. With EGC sizing requirements as they are, there isn't a problem for 100A services and feeders. However, when we get to higher-rated services and feeders, I see the EGC as being inadequately sized to serve a dual role as GEC. Consider EGC and GEC sizing for a 200A service and feeder connection for both separate structures and m&m homes...

This concept is flawed. The EGC is not the GEC nor does in act as one. See 250.121 of the 2011 code

 

[Smart $]

I'm still not seeing where the requirement for the GES is that the service is on the building. I've only seen where it says it cannot be remote. And by 550 that distance would be more than 30'.



And (B)(3) is like :huh: unless they aren't expecting to run a GEC out of a mobile home as described in 550.32(A).

250.64 specifies at not in the structure. 550 repeatedly says 30' is adjacent which to me qualifies as at the structure. I see nowhere that at each means a separate unique GEC/GES.

I hope I'm not coming across wrong. I really want to understand this; and my normal focus is industrial machines.

You have my head spinning :blink: :blink: :blink:

This concept is flawed. The EGC is not the GEC nor does in act as one. See 250.121 of the 2011 code

Concept is not flawed... you just have your head wrapped around text and labels. EGC, GEC ... it's a wire for Christmas' sake

Anyway, they say a picture is worth a thousand words, so here's my second thousand words of contribution to this discussion (or maybe third, but who's counting)

 

[jwelectric]

What I see in your drawing for the mobile home is a service that has a grounding electrode with a grounding electrode conductor ran to it and then an equipment grounding conductor ran to the panel in the mobile home.

What I don?t see is a separate structure that needs to establish its own electrode system. I see this conductor between the two panels being nothing more than an equipment grounding conductor.

Once we accept that 550 does not require an electrode system to be installed at the mobile home itself and accept that it is the rules in 550 that prevent the service equipment from being mounted on the mobile home then we can understand that the conductor between the two panels is nothing more than an equipment grounding conductor and plays no role in the grounding electrode system

Being that we are so quick to jump on 250.32 and the separate building or structure I am surprised that no one has yet said anything about 225.39(C) and a 50 amp supply cord that has some mobile homes connected to the service equipment.

(C) One-Family Dwelling. For a one-family dwelling, the feeder disconnecting means shall have a rating of not less than 100 amperes, 3-wire.

Are these feeders not outside and is the mobile home and is it not a one family dwelling in most cases?

With all this discussion about a mobile home and 250.32 why has no one yet included 551, 552, 553, and 555 all of which does not require a grounding electrode to be established at the separate building or structure. All these allow the connection between the power supplying that separate structure and the structure to be grounded with the equipment grounding conductor.

 

[pfalcon]

You have my head spinning :blink: :blink: :blink:

Concept is not flawed... you just have your head wrapped around text and labels. EGC, GEC ... it's a wire for Christmas' sake
Anyway, they say a picture is worth a thousand words, so here's my second thousand words of contribution to this discussion (or maybe third, but who's counting)

Hopefully not like this :rotflmao:
And I can't see photobucket stuff here, blocked by corporate filter

 

[hurk27]

Hopefully not like this :rotflmao:
And I can't see photobucket stuff here, blocked by corporate filter

Ok I attached from here can you see it now?

 

[don_resqcapt19]

Can we name any other structure that comes complete, from the factory, with a UL label?
...

I have installed a number of exterior MCCs and prefab control buildings that come complete with a UL label.

 

[renosteinke]

Thank you, Don. I assume that those structures had some provision for connecting the GEC?

 

[Smart $]

Ok I attached from here can you see it now?

Picture shows as an Attached Image thumbnail, but it don't link to full size image....???

 

[iwire]

Can we name any other structure that comes complete, from the factory, with a UL label?

A dishwasher, a refrigerator, a light fixture, a receptacle, a hot tub.

Just because something is a structure does not prohibit it from being other things as well.:thumbsup:

Structure. That which is built or constructed.

Keep in mind it is almost always used in conjunction with the word buildings.

"Buildings and structures" that tells me that structures are things that are built or constructed but are not buildings.

 

[pfalcon]

Ok I attached from here can you see it now?

Yes :hug:
A little fuzzy at that resolution but more than good enough with the browser zoom.

550 establishes that within 30' is adjacent, as in at the mobile home, both the drawings show an established Grounding Electrode System at the mobile home. So for part 1 of the question, no further GES is required.
550.16(A) establishes the connection of the grounded conductor.
550.16(B) establishes the connection of the EGC.

Okay, so now we're claiming that: The EGC is not permitted to serve as a GEC (citation?). Therefore we have to drive a ground rod and punch a hole in the mobile home to run its own GEC (250.32). Then we have to bond the service electrode to the mobile home electrode (250.50).

So now I have a (1) Service Electrode connected to (2) an EGC connected (3) a Mobile Home Electrode connected to (4) a Bonding cable connected back to (1).

I'm sorry but I'm still at :?
Cause what I see is a great antenna loop that'll detect any cars passing behind my trailer.

 

[Smart $]

What I see in your drawing for the mobile home is a service that has a grounding electrode with a grounding electrode conductor ran to it and then an equipment grounding conductor ran to the panel in the mobile home.

That is correct.

What I don?t see is a separate structure that needs to establish its own electrode system. I see this conductor between the two panels being nothing more than an equipment grounding conductor.

What does it take for you to call something a separate building or structure? Typically, anything supplied by an outside feeder not part of the originating structure is a separate structure. We know this can include an Article 550 installation because of Table 225.2.

Once we accept that 550 does not require an electrode system to be installed at the mobile home itself and accept that it is the rules in 550 that prevent the service equipment from being mounted on the mobile home then we can understand that the conductor between the two panels is nothing more than an equipment grounding conductor and plays no role in the grounding electrode system

Let's be more specific. We are discussing the requirement of a GES at a manufactured home... not a mobile home. Additionally, one which is supplied by hard-wired feeder, not cord-and-plug connected.

Furthermore, I am not contesting that the grounding conductor run with the feeder is called an EGC. What I am saying is, without a GES at the mfd home, any current which must flow to earth on the electrical system must be carried entirely by that EGC to earth. With a GES at the home, a more direct and lower resistance path is established, thereby reducing the current on said EGC.

[Being that we are so quick to jump on 250.32 and the separate building or structure I am surprised that no one has yet said anything about 225.39(C) and a 50 amp supply cord that has some mobile homes connected to the service equipment. Are these feeders not outside and is the mobile home and is it not a one family dwelling in most cases?

As I said above, I don't consider mobile homes or cord-and-plug connected manufactured homes as part of the discussion. Opon being supplied by hard-wired feeder, a manufactured home is no longer as easily movable as one cord-and-plug connected.

With all this discussion about a mobile home and 250.32 why has no one yet included 551, 552, 553, and 555 all of which does not require a grounding electrode to be established at the separate building or structure. All these allow the connection between the power supplying that separate structure and the structure to be grounded with the equipment grounding conductor.

Of the Articles mentioned, only 555 is listed in Table 225.2. I have not reviewed it as I do not consider other Chapter 5 Articles as having any bearing on the discussion. As the title of Chapter 5 indicates, these Articles cover special occupancies, so each will have its own nuances.

 

[Smart $]

550 establishes that within 30' is adjacent, ...

Being adjacent has no bearing IMO. The supply conductors between service and home are outside feeder conductors.

So now I have a (1) Service Electrode connected to (2) an EGC connected (3) a Mobile Home Electrode connected to (4) a Bonding cable connected back to (1).

It is not required to bond electrodes at service with electrodes at manufactured home. The feeder EGC connects them and all that is necessary.

 

[pfalcon]

Let's be more specific. We are discussing the requirement of a GES at a manufactured home... not a mobile home. Additionally, one which is supplied by hard-wired feeder, not cord-and-plug connected.

I haven't abandoned mobile homes. Though I'll grant you that we're discussing feeder connected homes, not cord and plug.

Furthermore, I am not contesting that the grounding conductor run with the feeder is called an EGC. What I am saying is, without a GES at the mfd home, any current which must flow to earth on the electrical system must be carried entirely by that EGC to earth. With a GES at the home, a more direct and lower resistance path is established, thereby reducing the current on said EGC.

Article 550 repeatedly defines within 30' to be at the mobile home. Therefore the service GES is at both structures.

As I said above, I don't consider mobile homes or cord-and-plug connected manufactured homes as part of the discussion. Opon being supplied by hard-wired feeder, a manufactured home is no longer as easily movable as one cord-and-plug connected.

Welcome to the world of Mobile Home / Manufactured Housing parks. To prevent liability on cord trips, and the expectation of longer residence compared to RVs, many mobile homes are hard-wire feeders. So no, cord vs. feeder is not a good separation between the two.

Of the Articles mentioned, only 555 is listed in Table 225.2. I have not reviewed it as I do not consider other Chapter 5 Articles as having any bearing on the discussion. As the title of Chapter 5 indicates, these Articles cover special occupancies, so each will have its own nuances.

Look closer then:
553 Floating buildings
500 Hazardous (classified) locations
510 Hazardous (classified) locations - specific
555 Marinas and boatyards
550 Mobile homes, manufactured homes, and mobile home parks

Being adjacent has no bearing IMO. The supply conductors between service and home are outside feeder conductors.

Outside feeders is not contested. But adjacency means at and the service is at the mobile home therefore the service GES is at the mobile home.

It is not required to bond electrodes at service with electrodes at manufactured home. The feeder EGC connects them and all that is necessary.

250.50 says otherwise

All grounding electrodes as described in 250.52(A)(1) through (A)(7) that are present at each building or structure served shall be bonded together to form the grounding electrode system. ...

Therefore if you drive a separate rod for the mobile home then you have a second electrode present at both structures. The code is clear in 250.50 that they must be bonded together.

 

[Smart $]

Article 550 repeatedly defines within 30' to be at the mobile home. Therefore the service GES is at both structures.

No, it does not use the at. It uses the word to. That is, adjacent to.

Also note you are recognizing the service and the home as two structures.

The word adjacent means "next to", but the distance is relative and not defined by the NEC. Where the NEC requires the distance to be minimal, it uses the combined term: immediately adjacent. As an example of how differing the distance can be, look at 250.184(C) where the adjacent distance is up to 1300ft.

Welcome to the world of Mobile Home / Manufactured Housing parks. To prevent liability on cord trips, and the expectation of longer residence compared to RVs, many mobile homes are hard-wire feeders. So no, cord vs. feeder is not a good separation between the two.

That's a fair point, but you confirmed the likely more permanant residency... which was my point.

Look closer then:
553 Floating buildings
500 Hazardous (classified) locations
510 Hazardous (classified) locations - specific
555 Marinas and boatyards
550 Mobile homes, manufactured homes, and mobile home parks

Missed 553. As for 500, 510, and 550, they were not in the list mentioned by Mike.

Outside feeders is not contested. But adjacency means at and the service is at the mobile home therefore the service GES is at the mobile home.

Discussed above.

250.50 says otherwise

But you are considering the service and home as one building or structure. I am not.

Therefore if you drive a separate rod for the mobile home then you have a second electrode present at both structures. The code is clear in 250.50 that they must be bonded together.

Again, this is a consequence of you considering the two structures as one. But even as separate structures, there is nothing which prevents you from bonding the electrodes together AFAIK.

 

[don_resqcapt19]

Thank you, Don. I assume that those structures had some provision for connecting the GEC?

Most of the time they had a disconnect that was suitable for use as service equipment.

 

[jwelectric]

What does it take for you to call something a separate building or structure? Typically, anything supplied by an outside feeder not part of the originating structure is a separate structure. We know this can include an Article 550 installation because of Table 225.2.

Let me say this one more time, I agree that by Article 100 the service pole and the home are two different things call it structure if you like, I don?t object.

Let's be more specific. We are discussing the requirement of a GES at a manufactured home... not a mobile home. Additionally, one which is supplied by hard-wired feeder, not cord-and-plug connected.

by definition both are the same see definitions in 550. Both can be hard wired.

Furthermore, I am not contesting that the grounding conductor run with the feeder is called an EGC. What I am saying is, without a GES at the mfd home, any current which must flow to earth on the electrical system must be carried entirely by that EGC to earth. With a GES at the home, a more direct and lower resistance path is established, thereby reducing the current on said EGC.

WOW! I didn?t know that any current flowed into earth. I have always though that the earth connection was for lightning, power surges, unintentional contact with higher voltage line and all them other things outlined in 250.4(A)(1)

As I said above, I don't consider mobile homes or cord-and-plug connected manufactured homes as part of the discussion. Opon being supplied by hard-wired feeder, a manufactured home is no longer as easily movable as one cord-and-plug connected.

Neither is a hard wired mobile home

Of the Articles mentioned, only 555 is listed in Table 225.2. I have not reviewed it as I do not consider other Chapter 5 Articles as having any bearing on the discussion. As the title of Chapter 5 indicates, these Articles cover special occupancies, so each will have its own nuances.

Look at Table 250.3