On Fri, 08 Dec 2006 16:14:22 GMT, Al Tsiemers
wrote:

I want to put in 2) 20A curcuits in my shop area. I would like to have them
both go to a string of twin duplex boxes, with the left-hand duplex
recepticle in all boxes on one curcuit, and the right-hand on the other
circuit.
My calculations show a 32 c.i. box is required for 12ga. wire.
Questions:
1) I assume the grounds for both circuits can/should be tied together,
correct? They are uninsulated, so I can't see how that could be avoided.

YES on the grounds.

2) If the first box in line gets two GFCI outlets (one for each circuit),
does that change the calculation for box size? Does the yoke count of 2 for
each device change because of the depth of a GFCI receptacle?

I never get this technical. If the device fits in the box, plus the
wires (without overcrowding or pinching a wire), it will work. GFIs
take up quite a bit of space compared to a common outlet. Either get
a large box, or just use 2 boxes. Dont evn think of trying to put a
GFI in a standard handy box. It wont easily fit. I tried it once,
that was a major headache. I just use a 4 inch quare box now for each
GFI, and get the special cover plates for the larger box,