Mobile Homes, Ground Rods and Disconnects

[jar546]

We have a mobile home park built on the side of a hill, actually base of a mountain that has clusters of services from the POCO with about 8-12 meter bases mounted on posts framed out, depending on the area they serve. Because they are located behind the lots and there are different length mobile homes, some of the runs from the meter base disconnects are 60-80' away and certainly not within site. FEMA has renovated this area for post flood victims and now have to install disconnects between the units to feed the sub panels in the mobile homes. They too have a rule for a disconnect to be within site and so many feet of the mobile home.

So, this is what we have.

The service group of meters and disconnects is already installed and has a GE system.

The new posts with plywood that supports (structure) the disconnects between the units also have a grounding electrode system. They are fed by PVC pipe. Then the feeder goes from that disconnect to the mobile home which is another structure and they have their own grounding electrode system.

We have had some debate back and forth but the inspector that works for me that is in charge of the project and working with FEMA says that FEMA believes the ground rods are required because there are 3 separate structures and he concurs. We initially had some resistance to this by the contractor who has since backed off due to FEMA saying this is what they want and my guy confirming it.

I have had some discussion with other inspectors that are trying to say that the mobile home is not a structure, therefore does not need rods and the pole and frame that holds the mid point disconnect is not a structure so the only rods should be at the service disconnect,

What say thee?

 

[Dennis]

I concur that each is a separate structure but I see no reason for rods at the middle pole. Basically a rod is to deal with surges & lighting protecting equipment down line. The fact is the only equipment you are protecting is down line so the trailer already has the rods. Now does it help to have the extra rods-- certainly but IMO they should not be required at the middle disconnect.

It really comes down to your areas definition of a structure. If it is a structure then grounding electrodes are required.

 

[Dennis]

I should add if the run were continuous from the service to the house the extra rods would not be there so why when adding just a disconnect would it be required... That is my logic. If there was other equipment at the pole by the trailer I would feel strongly for the rods.

 

[jar546]

In one of the situations where I had to do an inspection in one of the areas I told the electrician to use the rods in the middle as GE's for the middle disconnect and the mobile home since they were so close but to please protect the GEC which he did by burying it in the same trench as the feeder conduit. After a that one they started putting the rod just on the edge of the mobile home nearest the middle disconnect and using them so they were not in the middle of the yard between the homes and the landscaping would hide them. Then they got smart and ran the GEC continuous between the mobile home and middle disconnect so they only needed 1 acorn per rod.

 

[jar546]

I should add if the run were continuous from the service to the house the extra rods would not be there so why when adding just a disconnect would it be required... That is my logic. If there was other equipment at the pole by the trailer I would feel strongly for the rods.

There was a wooden structure between the homes to house the disconnects back to back and feed each mobile home sub.

 

[Gregg Harris]

FEMA's

Definition/Description

A structure, transportable in one or more sections, which is built on a permanent chassis and is designed for use with or without a permanent foundation when attached to the required utilities. The term manufactured home does not include a recreational vehicle. Generally, manufactured homes must meet the same requirements as stick built or conventional housing. Because they are usually residential buildings, they must be elevated so that the lowest floor is above the Base Flood Elevation (BFE).

 

[Dennis]

Then they got smart and ran the GEC continuous between the mobile home and middle disconnect so they only needed 1 acorn per rod.

Then they wouldnt need two sets of rods. Use the rods at the house to cover the disconnect by running the grounding electrode conductor in the trench between the structures.

 

[Dennis]

There was a wooden structure between the homes to house the disconnects back to back and feed each mobile home sub.

Yes I know that-- I was saying if there were no pole in the middle you would only have the rods at the house and at the service so what safety does adding rods at the disconnect 30' or so away from the house add?

 

[jwilly3879]

SO there is a meter with a disconnect and 2 rods, then an intermediate disconnect with 2 rods and then on to the mobile home with 2 more rods?

Couldn't the two rods just be at the 1st disconnect and then 4 wire run to the intermediate disconnect and on to the MH if the intermediate and MH bonding screws were removed, isolating the grounds?

 

[raider1]

SO there is a meter with a disconnect and 2 rods, then an intermediate disconnect with 2 rods and then on to the mobile home with 2 more rods?Couldn't the two rods just be at the 1st disconnect and then 4 wire run to the intermediate disconnect and on to the MH if the intermediate and MH bonding screws were removed, isolating the grounds?

Check out 250.32(A).

Chris

 

[raider1]

550.16 would allow you to not drive 2 ground rods at the mobile home provided that the service equipment is located within 30' of the wall of the mobile home in accordance with 550.32(A).

Here is what 550.16 says;

550.16 Grounding. Grounding of both electrical and nonelectricalmetal parts in a mobile home shall be through

connection to a grounding bus in the mobile home distribution

panelboard and shall be connected through the

green-colored insulated conductor in the supply cord or the

feeder wiring to the grounding bus in the service-entrance

equipment located adjacent to the mobile home location.

Neither the frame of the mobile home nor the frame of any

appliance shall be connected to the grounded circuit conductor

in the mobile home. Where the distribution panelboard

is the service equipment as permitted by 550.32(B),

the neutral conductors and the equipment grounding bus

shall be connected.

Remember Chapter 5 requirements modify the general requirements located in Chapters 1-4.

Chris

 

[globe trekker]

Doesn't sound like the middle disco's are within the 30' range of the outside wall of the

mobile structures.

.

 

[Dennis]

Doesn't sound like the middle disco's are within the 30' range of the outside wall of themobile structures.

.

We don't know that. I understood that the meters and service discos are 60-80 feet away so another disconnect had to be added because FEMA has it's own requirements. We were not told what that was-- I'll assume closer than 30' but IDK for sure.

 

[jar546]

FEMA specified disconnects within sight and 30' of mobile home. Most of the meter banks w/discos were outside that requirement except where they were directly behind the mobile home.

 

[Uncle Bob]

Move the electric service poles (with meter and disconnect) within 30 feet of each HUD manufactured home. Good grief your driving ground rods into the ground (pun intended)