Ask Me Help Desk - Sub panel bonding/aluminum service drop

Hi,

My post is about sub panel bonding, and the use of an aluminum service drop.

First, I'm in the process of installing a sub panel at the far end of my basement for my shop. I've researched various posts on this board, and also referenced the NEC. I know the neutral is only bonded at the main panel and isolated at the sub. The NEC refers to the use of bonding jumpers from the conduit to the box. My plan was to use an uninsulated wire bundled with the feeders in the conduit, and connect each end to a grounding bar in the respective box. I may be wrong, but from what I've gathered this is a preferred method. My question, is the bundled setup I planned on using an acceptable bonding method, should I use bonding jumpers only, or should I use both the wire and jumpers for a solid bond-or would this create a parallel ground which is not permitted ?

Second, my service entrance drop wires are aluminum while the entrance conductors from meter to box are copper. The box appears to have been replaced some time back, and I suspect the meter to box wires also replaced- local code allows copper. The aluminum wires appear to be in good condition, from what I can see. Would it be wise to have the service drop replaced with copper? Thanks

First off, why bother with conduit in the first place. NM-B cable (Romex) probably would suffice.

Ground does not have to be the same AWG as the conductors. Bonding jumpers are required when the conduit is the ground. I'm not sure if bare is permitted. If you really want to use conduit, can use use insulated? Conduit Fill is less.

Quote:

I know the neutral is only bonded at the main panel and isolated at the sub.

There are exceptions to the above rule. The corrolary is "Neutral and Ground should be bonded in only one place". On your case, replace "should" with "will".

2nd question. Nope.

Keep-Thanks for the response but you didn’t really answer my question.

Romex is not allowed, need conduit, and my question referred to bonding the raceway between the two panels, not grounding. I’ve seen various methods posted here, and various methods described in NEC Article 250, and I would just like to get some clarification on the best way and maybe exceed code. Question---Is the bonding wire bundled with the feeders and connected to eqpt. Grounds a better method of bonding the panels, bonding jumpers only code minimum, or acceptable to use both the bonding jumper and bundled wire together?

To help clarify, if I am understanding your question correctly, conduit is "bonded" when it contains service entrance conductors.

This applies to the wires that run from a meter, with no main disconnect at the meter, to a main panel, "main" panel being that which contains the Service Disconnecting Means, AKA Main Breaker.

Once you leave the Main Panel,say to feed another panel, these conductors are now called a feeder. Metal conduit, for this circumstance of a residential feeder, does not need to be "bonded". Only all locknuts and fittings must be wrench tight.

All that is needed is the equipment grounding conductor, run from the neutral/ground bar in the main panel, to the equipment ground bar in the next panel. The neutral must remain isolated in the "subpanel".

The neutral must be insulated in the wire bundle pulled between panels.

The equipment ground may be bare, but green insulation is recommended.

The aluminum service drop conductors is fine, leave it alone as long as there is no damage, even then use aluminum to replace it.

Tk-thanks much. Guess I was confusing the terms bonding and eqpt. Ground. My question was the use of the eqpt. Ground wire versus the bonding jumpers, which you answered.
One final question- for consitency should the copper SEC from meter to box be replaced with aluminum, even though code allows copper? I have contacts that do the change if you recommend. Thanks...

Quote:

Originally Posted by cabinetguy

Tk-thanks much. Guess I was confusing the terms bonding and eqpt. ground. My question was the use of the eqpt. ground wire versus the bonding jumpers, which you answered.
One final question- for consitency should the copper SEC from meter to box be replaced with aluminum, even though code allows copper? I have contacts that do the change if you recommend. Thanks....

Copper or Alum, it's up to you. Just make sure you use the correct size conductors.