The starter will have a reset button and three or more indicators, the number of indicators will depend on the number of speeds and whether the starter is a reversing type.
The push button and indicators must be of an extremely robust design and have a well proven track record. It is logical, for component commonality to use devices of the same manufacture for the local control station and emergency stop buttons as well as those in the starter or MCC.
The enclosures for the local control station when it is assembled with it’s keyswitch and push buttons and emergency stop buttons should have an ingress protection (IP) rating of IP65 (total dust ingress protection and protection against low pressure water jets from any direction).
The push buttons and keyswitch should consist of an operator with separately fitted contact block or blocks. Each contact block must have two electrically separate circuits, for maximum flexibility contact blocks with contact configurations of two normally open, two normally closed and one normally open and one normally closed should be available. The contact block rated current at 110Vac should be 10A thermal with an AC15 rating of 6A at any temperature from -15oC to +65oC and at any altitude up to 2000metres.
Each push button and keyswitch should be able to have up to six contact blocks fitted to it. The assembled operator and contact block(s) should have a mechanical and electrical life of at least one million operations at its rated current.
The indicators should be the press to test transformer type fitted with LEDs and have plastic lenses. Glass lenses should not be used as a broken glass lens in a food factory is a major hazard. The lens colour should be within the lens and not an applied coating.
Each keyswitch, pushbutton and indicator must be fitted with an engraved legend plate which is marked as shown on the wiring diagrams.