Dennis,
GFCI (Ground Fault Circuit Interrupters) are designed to measure the current supplied to the load via the Line and compare it against that which is returned to the source via the Neutral. An imbalance of just 0.03 ampere will instantly trip the GFCI.
Refrigerators are normally never plugged into a GFCI because of the phase shift of the current in the capacitor start motors. The phase shift is seen by the GFCI as a current imbalance.
If you are tripping the Kitchen GFCI but not the outlet in which the mill is plugged into, there is a strong possibility that the two Neutral circuits, and/or the two Ground circuits are tied together. This would cause a portion of the Neutral current to return to the source via the GFCI Neutral, thereby causing an imbalance and tripping the kitchen circuit.
It is not uncommon for contractors to skimp on wire by running a common Neutral, and I've seen many installations where the contractor just didn't understand the theory of how GFCI's worked. If possible, I would trace the Neutral of you Mill Outlet to make sure it returns directly to the Main Breaker Box. If not, run a new circuit. I have installed a sub-panel in my garage with all the outlets fed from it. If you install a sub-panel, NO NOT tie the ground bus to the Neutral Bus in this panel. The only place they should be tied together is in the Main Panel.
Hope this help, and I would be more than happy to answer any questions you might have.
Mike
Thailand
Electrical Commissioning Engineer
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