1. From the meter base, I have a 3" long galvanized nipple (2" wide in diameter) leading to and external main disconnect. The nipple carries 3 2/0 copper wires (2 hots and one neutral) to the disconnect. From the disconnect, I have 2" diameter galvanized conduit running into the house to the main load distribution center, which is serving as a sub panel. The conduit carries the 2 hots, one neutral and one #4 copper ground to the sub panel. On the outside of the house, the conduit is screwed into a hub on the disconnect using a coupling (compression on one end of the coupling, threaded on the other end to screw into the hub. Not that it may be relevant, but everything will be set up for 200 amp service. I know that I will need bonding bushings for each end of the 3" nipple between the meter and the external main disconnect. Will I need a bonding bushing where the pipe connects to the sub panel? If so, do I simply run a #4 from the bushing to the ground bar?

2. I will be running #4 copper from the ground bar in the main disconnect to two ground rods. I will also be running another #4 from the ground bar in the main disconnect to the nearest accessible water pipe, which is located near the mouth of the crawl space (as an aside, the pipe entering my house from the well pump is plastic and once inside the house, the piping switches to copper). I would like to run both wires in the same pvc conduit and use a "T" fitting to branch off once the conduit reaches below grade so I can run one wire to the water pipe and the other to the ground rods. I'd also like to use another piece of pvc to enclose the length of wire that runs from one ground rod to the other. Is this plan permissible? If so, what size pvc do you recommend to accommodate 2 #4's? Lastly, I am not sure how to terminate the pvc pieces at the rods and the pvc piece that ends at the water pipe. In other words, should I simply cut off the pvc at the point where the wire attaches to the rods and to the water pipe, or is there a fitting/coupling I should know about?

The conductors to a meter and a disconnect are called Service Entrance Conductors, and raceway for these must be bonded. The conductors on the load side of a disconnect are called feeders and the raceway does not need special bonding, just to be securely connected to the metal box using locknuts. This raceway can be the equipment grounding conductor, electricians normally use a green or bare wire to compliment this equipment ground path, and not rely on just the conduit.

Only the nipple between the meter and disconnect needs one bonding bushing, at either end, and the bonding conductor can connect from the bushing lug to the neutral/ground lug in either the meter or disconnect.

The raceway between the disconnect and panel does not need a bonding bushing, only insulated bushing to protect the wires from abrasion. You may use bonding bushing if you like, but not required.

You must run the grounding electrode conductor, (wire from ground rod), to the disconnect neutral/ground bar, or the meter, and then a #4 equipment grounding conductor is needed to connect from this bar to the equipment ground bar in the panel.

The neutral bar in the panel must be insulated and isolated from any equipment grounding, including not connecting to the panel metal box. Do not install the green screw or jumper from the neutral bar to the panel box.

The bonding conductor for the water can connect to either the equipment ground bar in the panel, or the neutral/ground bar in the disconnect.

I would use 1 inch PVC for the 2 #4 grounding conductors. We do not normally use any fitting to connect PVC conduit to a water line when used for grounding conductors. We just stop the conduit short and strap it securely, letting the wire just come out and connect to the ground clamp.

Thanks tk, I appreciate your guidance. I think I got things figured out, but I want to run a couple of things by you to make sure I'm doing this right.

[QUOTE=tkrussell;1315853]The conductors to a meter and a disconnect are called Service Entrance Conductors, and raceway for these must be bonded. The conductors on the load side of a disconnect are called feeders and the raceway does not need special bonding, just to be securely connected to the metal box using locknuts. This raceway can be the equipment grounding conductor, electricians normally use a green or bare wire to compliment this equipment ground path, and not rely on just the conduit.

The raceway from the exterior disconnect to the panel inside the house is attached to the disconnect box with a hub. Between the hub and the box there is a thin black gasket (presumably to prevent water from entering the disconnect box). Is this attachment method OK? I was planning on leaving the gasket right where it is. On the other end of the raceway is the subpanel and the raceway is attached to the subpanel with a locknut. Should I substitute an insulated bushing for the locknut?

Also, my disconnect is a 200 amp Murray external disconnect. Regrettably, I don't have the model number with me, but I'll do my best to explain the layout as it is fairly simple. On the lower left side of the box there are 2 grounding lugs sized to accommodate #4 wire. Those lugs are attached directly to the back of the box. (I used those lugs for the #4 wire that I ran to my ground rods and another #4 that I ran to the water pipe.) In the middle, there is the breaker switch, with hot lugs at the top of the switch for the feeders to the subpanel and 2 hot lugs the bottom of the switch to receive the wires from the meter. On the right side of the box, there are 2 neutral lugs, one on top of the other. Immediately to the left of the neutral lugs, there is what I believe to be another ground lug. It appears to be connected to the neutral lugs. I was planning on running a #4 ground from that lug to the ground bar in the subpanel. Is this setup OK?

The neutral lugs and ground lug on the right side of the box appear to be attached to a plate and the plate is screwed to the box; however, the plate appears to be isolated from the box because it is sitting on top of a black piece of "cardboard" (for lack of a better way to put it). The cardboard also runs along the side of the neutral lugs in between those lugs and the side of the box. The cardboard is clearly preventing the neutral lugs/ground lug from touching the metal of the box. Is this something I should pay attention to? Also, what do I do to make sure that the neutral/ground is bonded in this box? There is a small hole directly under the ground lug, but I don't know if it is for a large green screw. Besides, no screws came with the disconnect.

Lastly, what size conductor do I need to use with a bonding bushing that is attached to the conduit between the meter and disconnect? I was planning on running that wire to a ground lug in the meter because I don't have anymore ground lugs left in the disconnect. Is that permissible, or do I need to purchase another ground lug and mount it to back of the disconnect box.

The hub fitting is OK. They are intended to prevent water entry.

Do not remove the locknut, it is the fitting that must be there to electrically connect a raceway to an enclosure. Simply add a bushing to the exposed threads.

Fine on the grounding and neutral lugs. Be sure the neutral lug is connected directly to the meter metal box. Use the green screw provided to insert into a hole in the neutral lug to attach (bond) the neutral lug to the metal box.

If you have enough slack in either one io the #4 grounding wires, you can lay this conductor into the bushings lug. Or you can use a separate #6 wire.

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Originally Posted by tkrussell

The hub fitting is OK. They are intended to prevent water entry.

Do not remove the locknut, it is the fitting that must be there to electrically connect a raceway to an enclosure. Simply add a bushing to the exposed threads.

Fine on the grounding and neutral lugs. Be sure the neutral lug is connected directly to the meter metal box. Use the green screw provided to insert into a hole in the neutral lug to attach (bond) the neutral lug to the metal box.

If you have enough slack in either one io the #4 grounding wires, you can lay this conductor into the bushings lug. Or you can use a separate #6 wire.

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Thanks TK. On the right side of my disconnect box there is a piece of cardboard between the back of the box and the plate that the 2 neutral lugs and 1 ground lug sit on. Should I just leave the piece of cardboard alone or do I need to remove it? Can I run my #4 from that ground lug to the ground bar in my subpanel? The 2 ground lugs on the other (left) side of the disconnect box are being used by the #4's that run to my water pipe and the ground rods I put in over the weekend.

Yes leave the cardboard, just insert and tighten the green screw into the hole.

Yes you can use the lug mentioned. Once you bond the neutral lug to the metal box, all the grounds and neutrals are connected as intended.

Is bonding bushing required on 480 volt raceway?

Raceway containing conductors over 250 volts to ground all need to be bonded, depends on the type of raceway, it may or may not need a bonding bushing.

Methods of bonding shall be, as per the 2008 edition of the NEC:

(2) Connections utilizing threaded couplings or threaded bosses on enclosures where made up wrenchtight
(3) Threadless couplings and connectors where made up tight for metal raceways and metal-clad cables
(4) Other listed devices, such as bonding-type locknuts, bushings, or bushings with bonding jumpers