Bonding straps & Screw

Please explain to me what the green screw does for the main service panel ? Please explain to me what the bonding strap does? When is the bonding screw required and when is the bonding strap required ?
Are both bonding strap and bonding screw required in a GE main service panel ? As you can see the service wiring is two hot, a neutral and ground rod. Just wanted to make sure I understand.
Thank You In Advance

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Yes, either a bonding strap or a bonding crew would be required in a service panelboard. The strap or screw, called the main bonding jumper, connects the equipment grounding conductor to the service neutral conductor to provide a low impedance path to open an OCPD during a ground fault.

Since the bonding jumper is connected, what does the bonding screw do ?

Where is the bonding jumper? The bond screw bonds the neutral to the can. If this was a subpanel the ground bar would be bonded to the can.

Also, to the OP: I notice 4 wires, is this a subpanel by chance?

Where is the bonding jumper in the photo’s? I see a place for the main bonding jumper (a screw) which is the empty hole in the neutral bar.

No screw was there, only the bonding jumper strap at the top.

Ah that strap at the top is nothing more than a connection between the neutral bar on the right to the neutral bar on the left. There is no visible main bonding jumper in the photo’s.

http://www.nachi.org/forum/attachments/f19/80751d1420851324-bonding-straps-and-screw-indiantrail-106.jpg

A “real” bonding strap will bond the neutral buss bar to the enclosure, something like you see in this picture:

Due to the nature of the evidence…

  1. 4 Conductors supplying this panel enclosure and panelboard itself
  2. No Main Bonding Jumper
  3. lack of knowledge to mark the grounded conductor (at all)…lol…just had to add that.

I would indeed say this is more than likely a Remote Distribution Panel (RDP), if this is the case they need to remove that bar you are asking about…and then re-configure their grounded and grounding conductors accordingly and connect the grounding bus to the enclosure…or without getting into a list, Defer for a licensed electrical contractors evaluation ( hopefully not the one that originally installed it…lol )

But we all know I hate commenting on images with unknown variables…so that is my assumption at this stage…that their is a service disconnection means upstream somewhere.

He did that this was a service, that fourth conductor could somehow be from the ground rod.

lol…well I did not read it quite that well…if that is the GEC in that raceway then he has some other things they need to do as well…

I do not like posting on WHAT IF images…without the facts so I will stop giving my comments on them…lol…I think outside the box too much and based on the question I dont want to assume they actually know what a main panel is.

So I will refrain…lol

In any case this panel would be a defect. A missing bonding jumper is an issue, or if a subpanel; ground an neutral are on the same buss.

Electrical always seems to be the hardest to grasp.
Thanks to all you guys and your patience for all you do to help.