On Wed, 9 Nov 2011 19:10:58 -0800, DaveC wrote:

Hint: Don't use the chassis ground symbol as a "Vref" symbol. It's
confusing
and someone along the line might get hurt. Grounds should be.

Yeah, I wasn't sure about that. How should I have indicated 2 separate
grounds?

It's not ground. It's Vcc/2. I generally call it Vref, or some such thing.