My main sub panel is rated at 200 amps I will be installing a new 200amp sub panel in my garage wich is located behind my main panel outside... I have a few questions It looks like there is only a 100 amp breaker feeding my sub panel as it is now and its rated at 125 amps... What size breaker should I use to feed the new sub panel... Also there is no neutral wire only 2 hots and a ground coming from the main panel... Should I run a neutral wire off my main to my sub panel.. how would I do that where do I hook it up if I need to... Its a g.e main... also inside my sub panel it looks like the grounds and the white wires are all on the same bus... Iv read this is wrong.. and that they need to be seprated... but I've also read places that it might need to be bonded... enlighten me

Before we get into which panel needs a separate neutral and equipment ground bar or conductor, I need to get a handle on your panel(s).

Where one bar can accept both neutrals and grounds depends on where the Main Circuit Breaker is located.

Can you be clearer about what panel you now have, and where is the Main Breaker, and amp ratings of each?

Photos help greatly.