I worked with a company that sells vending machines, both refrigerated and non-refrigerated. The older machines had so much leakage current that GFI's wouldn't hold. Even when the chilling unit was replaced they'd still trip. (The chillers are usually a separate "skid-mounted" unit so it could be readily changed out in the field.) Most replacement units had new, modern compressors.
The problem seemed to lie more in the internal wiring of the machine breaking down than any problems with the chillers. Soda machines especially would have serious issues, that soda will eat up anything!
Some machines also had bad control transformers that would have a lot of leakage current.
Bob noted:
The NEC requires 5ma this protection in a fast growing list of locations.
IIRC, aren't ALL vending machine installations one of those locations?
