Dennis,I would wire the fan frame to Household ground and be sure to keep it far enough away from the HV stuff with non-conducting ductwork so as to eliminate HV jumping to the frame.
Your current arrangement could impose a high voltage potential between the frame and the fan windings, likely a situation for which the amount of insulation in the fan was not designed to handle, hence the release of the "magic smoke".
Dave
When wiring in the fan, I had only the hot & neutral wires going back to the mains, not the 3d prong ground. I had the chassis of the fan grounded to the NST case which is connected to the RF ground and a pipe driven into the ground outside of the garage. This is the second fan that I smoked and both were wired in the same fashion. I'm wondering whether I got it wrong relative to grounding the fan to the RF ground. - I thought this was a best practice, but maybe not. I'd welcome any suggestions. Thanks, Dennis Hopkinton MA
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