Neutral size in breaker box

Question

Hello I have a regular 3 wire 120/240 system.
Whilst looking at the service drop and breaker box I noticed the neutral wire seems very small. It is definitely smaller than the two main conductors..
I know the neutral is allowed to be smaller or at least was when the service was installed but it seems too small. Especially considering there is a 30amp outlet for an RV connected the box.
My question is can the neutral be LARGER than the conductors.. for example 1/0 if they are 2/0.
I don't know their sizes but I have some THHN wire that is 1/0
Would make quick work to have an electrician come hook it up and hard to overcharge me for 30 mins of work with me supplying the materials

Harper - Reinstate Monica · Accepted Answer

You can always make wires larger than are strictly required.
So if your hots and neutral all must be #6, you are welcome to make the neutral #4.
In fact, one sneaky reason to do this is that a #6 neutral MUST be white or gray. Whereas a #4 can be generic black, and marked with white or gray tape to designate it as neutral.  So if you wanted to avoid a run to the store, it might be a good play.
The Code requirement there is that #6 or smaller wires must be white or gray for neutral, green, yellow-green or bare for ground, and hot can be any other color.  With #4 or larger, the electrical supply houses don't want to stock 3  colors of the big stuff, so Code allows you to re-mark with tape or paint to any base color, to indicate the function.

Neutral size in breaker box

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