Bonding/Grounding Generator

[National Electric]

I have two situations that don't fall in the norm. First, I have a large generator (Semi size) and need to supply a MDP that exists at the site. There is no utility power. With this said no transfer switch is needed. Can I just ground the Generator to an electrode; run a 4 wire to the MDP that is already bonded? Would the Gen feed be the same as power Co. (4 wire)
Question two: Same situation (no utility power up here) this time I need two Gens. (Only run one at a time) I have a 4 pole transfer switch. The MDP is existing and bonded. Should I only ground the gens, run 4 wire to transfer switch and out of transfer switch to MDP? Again isn't the feed like the utility?

 

[iwire]

First, I have a large generator (Semi size) and need to supply a MDP that exists at the site. There is no utility power. With this said no transfer switch is needed. Can I just ground the Generator to an electrode; run a 4 wire to the MDP that is already bonded? Would the Gen feed be the same as power Co. (4 wire)

It could be four wire under some conditions.

See 250.30 for information.

Question two: Same situation (no utility power up here) this time I need two Gens. (Only run one at a time) I have a 4 pole transfer switch. The MDP is existing and bonded. Should I only ground the gens, run 4 wire to transfer switch and out of transfer switch to MDP? Again isn't the feed like the utility?

250.30 again, :smile:

 

[RUWired]

Again isn't the feed like the utility?

Like the utility, but seperate articles. Utility power Seperately derived systems (transformers) don't have an OCPD at the transformer and allow an additional bond to be made at the transformer. With generator power SDS's, the system bonding jumper must be made at the SDS or at the first OCPD. This would be at the generator if equiped with an OCPD.

Both utility and SDS's both do not allow the grounded conductor to be reconnected past the first OCPD. In both of your conditions, the generators are SDS's, and require the system bonding jumper to be made at the generator. A seperate ground and neutral conductor will be required from the generator on out. The main bonding jumper in the MDP should be removed in both cases.

Rick

 

[Cold Fusion]

I have two situations that don't fall in the norm. First, I have a large generator (Semi size) and need to supply a MDP that exists at the site.

What is your generating voltage? I ask becuse with a "Semi size" it could be meduim voltage - although with a four-pole transfer switch, it likely is 480V.

The design practices and applicable code sections are different.

cf