Bonding ground rods

[danny pritchard]

I am a home inspector and this is my first post on this forum.I inspected a mobile home today.There was a ground rod at the rear of the home with a ground wire attached to the metal frame under the home.The main electric panel was located on a pole approximately 15' away with it's own ground rod.My question is should the two ground rods be bonded together or should the house be treated as a detached structure with its own separate ground rod.

 

[ryan_618]

Re: Bonding ground rods

Where is the first point of disconnect?

Also, is there a grounding wire from the pole to the mobile home?

 

[danny pritchard]

Re: Bonding ground rods

Ryan,

The main disconnect is at the panel on the pole.There was no grounding wire from the pole to the home .

 

[ryan_618]

Re: Bonding ground rods

Reading 550.16 I don't think this method is permitted at all. The way I see it, the feeder circuit to the mobile home MUST include an equipment grounding conductor. You might want to wait for others to chime in though, I don't have a lot of experience with mobile homes.

[ October 23, 2003, 10:12 PM: Message edited by: ryan_618 ]

 

[tom baker]

Re: Bonding ground rods

Danny: We think we know what you mean. You need to be carefull and use the correct NEC terms, ground wire could be:
Grounding electrode conductor
equipment grounding conductor
grounded conductor
Bonding jumper

 

[ryan_618]

Re: Bonding ground rods

Tom: Let me apologize for that one. I realize the necessity of proper terms, but I used the term "ground wire" first in an effort to keep it simple for our poster. My bad

 

[tonto gonzales]

Re: Bonding ground rods

On a mobile home service the meter base and disconnect are located on the customer owned pole. The ground rods are fed from the disconnect or meter base and installed near the pole. The feeder should consist of your 2 hots, neutral and ground. Ground and neutral should be isolated in the panel. A ground wire is run from the panel to the frame of the mobile home. Never heard of ground rods at the trailer itself.

 

[earlydean]

Re: Bonding ground rods

250.54 allows supplemental grounding electrodes to be connected to equipment grounding conductors, without complying with the bonding requirements of the grounding electrode system.
But, this grounding electrode is connected to the frame. I would wonder if the electrician bonded the frame to the feeder equipment grounding conductor.

 

[ryan_618]

Re: Bonding ground rods

Originally posted by earlydean:
250.54 allows supplemental grounding electrodes to be connected to equipment grounding conductors, without complying with the bonding requirements of the grounding electrode system.
But, this grounding electrode is connected to the frame. I would wonder if the electrician bonded the frame to the feeder equipment grounding conductor.

From what I can tell, the problem is that there is no equipment grounding conductor on the feeder circuit.

 

[hillbilly]

Re: Bonding ground rods

The installation at the pole should be considered a structure and comply with NEC article 230-Services. It should not be more than 30' from and in sight of the home (550-23.(a). The feeder to the home is covered under Section 550-24(a)Exception. and allows a 3 wire feeder (2 hots and a grounded conductor) between the service (pole) and the (required) mobile home disconnecting means as long as it is grounded per 250-32(b). That's the way I read and understand it. I've always run a 4 wire feeder to a mobile home and treat the mobile home as a seperate structure per 250-32.(a) and 250-32.(b)(1). This is my personal opinion and I welcome comment.
steve

 

[danny pritchard]

Re: Bonding ground rods

Let me try and explain this a little better.The feeder from the pole consists of 2 hots,neutral and ground.The neutral and ground are isolated in the panel.The grounding electrode by the trailer is connected to the frame.There is also a grounding electrode by the pole connected at the meter base.My question is shouldn't the grounding electrode by the trailer be connected to the equipment grounding conductor or the other grounding electrode or is it fine like it is?

 

[Guest]

Re: Bonding ground rods

You don't want Mother Earth in the middle of this ground loop. You only want to have one grounding loop. Is that helpful?

 

[roger]

Re: Bonding ground rods

Danny, let's clear up the only questionable part of the installation.

You are saying the ground rod at the trailer is only connected to the trailer frame and other than that is isolated (not really, but we'll get to that in a minute) from all other parts of the electrical service.

This appears as though it is only for lightning protection, this must be connected to the Grounding Electrode (GE) system per 250.106.

An article of special concern is 550.16, which will force you to treat this as a seperate structure and connect this additional rod per 250.32(B)(1)

In reality it is already done through the Equipment Grounding Conductor (EGC, what you refered to as a ground in your post of 10/24 at 4:14) and the requirements of 550.16.

I would rather see it connected with a #6 to the EGC bar as described in 550.16.


Roger

[ October 24, 2003, 06:58 PM: Message edited by: roger ]

 

[hurk27]

Re: Bonding ground rods

By Hud codes there will be a #6 insulated GEC comming from the grounding bar in the trailer panel to the trailer frame. Bonding the electrode to the same frame will be just like the bonding of a electrode to the building steel as long as there is a GEC going to the steel. as allowed by 250.64 (F)

But remember all grounding conductors have to be insulated and Not bare copper. 550.33

Also if a seprat disconect is installed to meet the 30' rule the feeders to this disconect does not have to have a GEC as long as the neutral is bonded to the grounding at that point but there after it does have to have it.

550.33
Exception: Where a feeder is installed between service equipment and a disconnecting means as covered in 550.32(A), it shall be permitted to omit the equipment grounding conductor where the grounded circuit conductor is grounded at the disconnecting means as required in 250.32(B).

 

[danny pritchard]

Re: Bonding ground rods

Thanks for all the responses.They were very helpful.