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Mobile Homes and ground rods

jar546

jar546

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Are mobile homes considered a "structure"?

Are mobile homes required to have ground rods since they are a sub-panel/feeder from a pole mounted service?

We are debating this right now due to the amount of FEMA trailers going in our area.
 
Do not have the code reference at hand but yes; the Grounding Electrode System is installed at the main disconnect.

BEWARE; Many of these FEMA trailers are being sold that do not meet local thermal zone requirements. Check with your state regulations or AHJ if necessary on how they can be retrofit and recertified.

Francis
 
Let me clarify a few points.

The service already has a disconnect and grounding electrode system. The trailers are underground subfeeds with PVC conduit, away from the service.

The trailers are not sold. They are owned by the US Govt (FEMA) and placed for 18 months. We issue a temporary CO, only good for 18 months.
 
I've looked at more than a few state codes dealing with manufactured homes and many manufacturers installation installations, none have ever required a separate ground rod at the home unless the main disconnect was mounted on the home.Attached is the graphic form the Nevada code.

View attachment 509

View attachment 509

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jar546 said:
Are mobile homes considered a "structure"?Are mobile homes required to have ground rods since they are a sub-panel/feeder from a pole mounted service?

We are debating this right now due to the amount of FEMA trailers going in our area.
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a. Yes, they are structures manufactured under HUD standards (as defined in NEC, IRC or your state code).

b. No; (2205)NEC 250.32 via 550.32

Thanks for clarifying.

Francis
 
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jar546 said:
Are mobile homes considered a "structure"?
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550.2Manufactured Home. A structure, transportable in one or more sections, that, in the traveling mode, is 2.4 m (8 body-ft) or more in width or 12.2 m (40 body-ft) or more in length, or, when erected on site, is 29.7 m2 (320 ft2) or more and that is built on a permanent chassis and designed to be used as a dwelling, with or without a permanent foundation, when connected therein. The term manufactured home includes any structure that meets all the provisions of this paragraph except the size requirements and with respect to which the manufacturer voluntarily files a certification required by the regulatory agency, and except that such term does not include any self-propelled recreational vehicle. Calculations used to determine the number of square meters (square feet) in a structure are based on the structure's exterior dimensions, measured at the largest horizontal projections when erected on site. These dimensions include all expandable rooms, cabinets, and other projections containing interior space but do not include bay windows.

For the purpose of this Code and unless otherwise indicated, the term mobile home includes manufactured homes.

FPN No. 1: See the applicable building code for definition of the term permanent foundation.

FPN No. 2: See Part 3280, Manufactured Home Construction and Safety Standards, of the Federal Department of Housing and Urban Development, for additional information on the definition.

Mobile Home. A factory-assembled structure or structures transportable in one or more sections that are built on a permanent chassis and designed to be used as a dwelling without a permanent foundation where connected to the required utilities and that include the plumbing, heating, air-conditioning, and electrical systems contained therein.

For the purpose of this Code and unless otherwise indicated, the term mobile home includes manufactured homes.
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...........
 
Francis Vineyard said:
b. No; (2205)NEC 250.32 via 550.32
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??? I don't have the 2205 yet and won't live that long but I would say GE is required as per 2008 NEC.

250.32 Buildings or Structures Supplied by a Feeder(s) or Branch Circuit(s).(A) Grounding Electrode. Building(s) or structure(s) supplied by feeder(s) or branch circuit(s) shall have a grounding electrode or grounding electrode system installed in accordance with Part III of Article 250. The grounding electrode conductor(s) shall be connected in accordance with 250.32(B) or ©. Where there is no existing grounding electrode, the grounding electrode(s) required in 250.50 shall be installed.
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Francis Vineyard said:
Funny!Is there an exception in the '08 to 250.32?
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Indeed there is but it won't apply to Jeff's situation.

Here is the whole thing with the 08 changes highlighted in grey.

250.32 Buildings or Structures Supplied by a Feeder(s) or Branch Circuit(s).(A) Grounding Electrode. Building(s) or structure(s) supplied by feeder(s) or branch circuit(s) shall have a grounding electrode or grounding electrode system installed in accordance with Part III of Article 250. The grounding electrode conductor(s) shall be connected in accordance with 250.32(B) or ©. Where there is no existing grounding electrode, the grounding electrode(s) required in 250.50 shall be installed.

Exception: A grounding electrode shall not be required where only a single branch circuit, including a multiwire branch circuit, supplies the building or structure and the branch circuit includes an equipment grounding conductor for grounding the normally non–current-carrying metal parts of equipment.

(B) Grounded Systems. For a grounded system at the separate building or structure, an equipment grounding conductor as described in 250.118 shall be run with the supply conductors and be connected to the building or structure disconnecting means and to the grounding electrode(s). The equipment grounding conductor shall be used for grounding or bonding of equipment, structures, or frames required to be grounded or bonded. The equipment grounding conductor shall be sized in accordance with 250.122. Any installed grounded conductor shall not be connected to the equipment grounding conductor or to the grounding electrode(s).

Exception: For existing premises wiring systems only, the grounded conductor run with the supply to the building or structure shall be permitted to be connected to the building or structure disconnecting means and to the grounding electrode(s) and shall be used for grounding or bonding of equipment, structures, or frames required to be grounded or bonded where all the requirements of (1), (2), and (3) are met:

(1) An equipment grounding conductor is not run with the supply to the building or structure.

(2) There are no continuous metallic paths bonded to the grounding system in each building or structure involved.

(3) Ground-fault protection of equipment has not been installed on the supply side of the feeder(s).

Where the grounded conductor is used for grounding in accordance with the provision of this exception, the size of the grounded conductor shall not be smaller than the larger of either of the following:

(1) That required by 220.61

(2) That required by 250.122

© Ungrounded Systems. The grounding electrode(s) shall be connected to the building or structure disconnecting means.

(D) Disconnecting Means Located in Separate Building or Structure on the Same Premises. Where one or more disconnecting means supply one or more additional buildings or structures under single management, and where these disconnecting means are located remote from those buildings or structures in accordance with the provisions of 225.32, Exception No. 1 and No. 2, 700.12(B)(6), 701.11(B)(5), or 702.11, all of the following conditions shall be met:

(1) The connection of the grounded conductor to the grounding electrode, to normally non–current-carrying metal parts of equipment, or to the equipment grounding conductor at a separate building or structure shall not be made.

(2) An equipment grounding conductor for grounding and bonding any normally non–current-carrying metal parts of equipment, interior metal piping systems, and building or structural metal frames is run with the circuit conductors to a separate building or structure and connected to existing grounding electrode(s) required in Part III of this article, or, where there are no existing electrodes, the grounding electrode(s) required in Part III of this article shall be installed where a separate building or structure is supplied by more than one branch circuit.

(3) The connection between the equipment grounding conductor and the grounding electrode at a separate building or structure shall be made in a junction box, panelboard, or similar enclosure located immediately inside or outside the separate building or structure.

(E) Grounding Electrode Conductor. The size of the grounding electrode conductor to the grounding electrode(s) shall not be smaller than given in 250.66, based on the largest ungrounded supply conductor. The installation shall comply with Part III of this article.
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Hello All,

Rather than my opinion would you like the opinion from one of the staff electrical engineers and contributors to the NEC Handbooks position? Here you go.

"the two arrangements for service equipment installation and their associated grounding requirements are specified in 550.32(A) and (B). Section 550.32 (B) covers service equipment mounted on or in the mobile/manufactured home. Section 550.32(A) requires grounding at the service disconnecting means in accordance with 250.32. This arrangement where greater than 30 ft from the mobile home facilitates the installation of feeders to the required mobile home disconnect. The establishment of a grounding electrode system at the mobile home is required in order to comply with 250.32(A) and the grounding and bonding requirements of the feeder is required to comply with 250.32(B). Section 250.32(B)(1) requires the equipment-grounding conductor to be connected to the building or structure disconnecting means (see Article 225) and grounding electrode in the equipment supplied by the feeder or branch circuit. Additionally, 250.54 does not prohibit the installation of auxiliary grounding electrodes in the area of electrically operated equipment."

Quoted by :

Mark Cloutier

NFPA Senior Electrical Engineer
 
Chris...how about just Paul Abernathy....I am no GURU...just someone who likes to teach the code and chat about codes without being RIPPED by those with motives. So I am just plain ole' Paul.. ;)

The reason I posted the quote above was to be able to post the image below....now that was the stance (Above) of one of the NFPA Senior Engineers and below is a Quote from a book providing instructions on inspections by Mr. Jeff Seargent of the NFPA.

View attachment 1159
attachment.php


We all have opinions....I should probably give mine but I want you all to see that even the NFPA gets confused on the requirements.
 
deleted . . . Paul answered faster!

To clarify my ealier post meant to say mobile home disconnects are usually sub panels.
 
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PaulAbernathy said:
just someone who likes to teach the code and chat about codes without being RIPPED by those with motives. So I am just plain ole' Paul.. ;)
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Understood, looking forward to your contributions.
 
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