Is it okay for a ground and a neutral wire to rest under the same lug in the main panel?

If not, why? What are the potential dangers?

Thanks in advance.

It is only allowed if the lug is rated for more than one conductor. This rating will be listed in the manufacturers instructions and specs for any equipment.

If not listed, then there is a chance the connection will not remain tight, or the connection is not correct. Loose connections can create heat that can damage equipment and cause a fire.

An additional bar can be added to any panel, as each manufacturer offers optional extra bars when more lugs are needed.

If the Main Breaker for your service is in this panel, then neutrals and grounds need to be together on the one neutral bar, but each wire should be under it's own lug. Neutral wires are considered as current carrying, and the equipment ground is a safety return.

If the Main Breaker for your service is in this panel, then neutrals and grounds need to be together on the one neutral bar, but each wire should be under it's own lug. Neutral wires are considered as current carrying, and the equipment ground is a safety return.

Thanks for the response tkrussell, that helps a lot. One more question: What can go wrong if a neutral and a ground are under the same lug? I understand that the neutral is current carrying, and the ground a safety return, but why is this unsafe?

The wires may come loose and the neutral wire can heat up.