electricalwiring
I bought a Murray load center for use as a subpanel. Why do the large terminals in the grounding bar have three different kinds of screws?
Which of them should I be using for the feeder (4-gauge aluminum)
The instructions have no guidance on the different screws in the large terminals:
If this panel serves as the main disconnect, and the grounding and neutral bus bars are bonded. Then yes, you can terminate both grounded (neutral) and grounding conductors at the same bus bar.
Notice that the bus bars are bonded using a bonding strap.
If the bus bar is able to accept multiple conductors under some or all of the terminal screws, it should be labeled as such either on the bar itself or in the panel documentation. Terminating multiple conductors under a screw that is not rated for it, can cause bad connections, excess heating, damage to the conductors, etc.
Some panels are configured to allow additional bus bars to be installed. If your panel is one of them, you could install an additional bus bar and terminate extra conductors there. Other panels may accommodate extended (longer/larger) bus bars, that can be installed in place of the existing bus bars.
Best Answer
If you notice, it has 15 small openings and 3 large. The others are for securing tbe buss to the panel.
Also, you'll need a lug adapter to secure the #4 grounding conductor as per the panels specifications only up to #6 will fit in the three larger openings.Edit to (2): I believe anything over #4 will need a lug adapter.