1) All 120 volt circuits require 1 hot wire, 1 white neutral wire and 1 equipment ground. The hot wire is typically a black wire or it can be blue. The equipment ground will be the EMT or Rigid conduit since this is a warehouse environment. The conduit will need either the 1 black or the 1 blue for the hot and 1 white for the neutral. You can leave the existing blue wire inside the conduit if you wish and just cap it off at both ends with a wire nut or you may remove the blue wire. Either way, you need 1 white wire for the neutral conductor. It may be easier to run new wires inside the conduit. Just depends on how many other existing wires, pull boxes and/or splice boxes are along the conduit path.
2) Depends what panel that the circuit originates from. If originating from a 208, 3-Phase panel, check the hot bus bar slot position using an AC volt meter. Check for 120 volts from 1 hot slot position to the neutral bus bar. If good measuring 120 volts, then use a 30 amp single pole breaker in that position. As I mentioned last night, if a 208 panel, you may not have any 120 volt slots left since the 208 3-phase breakers take up the majority of the slots in this type of panel. Depends on how the 208 panel was originally configured and if any available breaker positions. See below for originating the circuit out of a 120/240 panel.
3) You may need to originate the circuit out of a traditional 120/240 volt single phase panel such as the one located in the office area. If so, same thing as the 208 panel. Use a 30 amp single pole breaker. Land the hot black wire on the 30 amp single pole breaker and land the white neutral wire onto the panel's main neutral bus bar.
Yes in order for the hotplate to work, you need a 30 amp single pole circuit breaker that will provide the hot conductor with 120 volts.
DO NOT use a double pole breaker as this type is 240 volts and a good chance of destroying the hot plate if used.
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