The present invention discloses ternary mixtures of fluoroethane, pentafluoroethane and difluoromethane used as environmentally friendly alternative refrigerants to HCFC-22. Rollers selectively tension and relax the web on the vertically oriented wheel, allowing them to drop away from heated lands on emergency and cycle stops. Additional time is provided for data detection circuitry to detect a first segment of data transferred over the data bus.