[educk]

I am adding 4 new circuits to my house. Do I need separate neutral and separate ground for each circuit, or can they be shared?

[donf]

Depends on what you are talking about.

Foe example, if you are going to use four separate circuits, then yes, each circuit must have a netural and an equipment grounding conductor.

However, if you are going to use a multi wire circuit with a shared ground, that also is acceptable.

Several words of caution, if you choose to do a multiwire circuit then you need to use a double pole breaker that will trip and open both lines at the same time. Also, be aware, if you use a multiwire circuit and for any reason the neutral fails, you will drop 240 VAC across the circuit.

[tkrussell]

If at all possible, use separate neutrals for each circuit.

Shared neutrals in a multi-wire branch circuit can pose serious problems if the neutral is opened by a loose connection.