QUESTION: What is the method for determining the loading of attachment plugs?
1. Determine the ampere load. This should be the machine operating in the way it is intended to operate with a typical mechanical or electrical load. This would be the most severe use that the machine would be put to. This would not be a deliberate overload. This is now the nameplate ampere rating.
2. Determine if the load is continuous of non continuous? Rule 8-104 defines what is continuous and what is non-continuous. If the load is on less than 1 hour in a 2 hour period then it is non-continuous.
3. If the load is determined to be continuous, then follow Table 3 in SPE-1000 for maximum continuous loading limitations of the attachment plug.
For example, the "Maximum Continuous Loading" for a 15P is 12 amperes (1440 watts at 120 volts).
The machine should be labeled "Rated 12 Amperes Continuous"
4. If the load is not continuous from rule 8-104 and maximum current does not exceed 15 amperes (1800 watts at 120 volts) and the supply cord ampacity is not exceeded, then the machine can have a 15P attachment plug. The machine should be labeled , "Rated 15 Amperes Non-continuous".
5. If the equipment follows rule Electrical Heating and Cooking Appliances as per rule 26-742 and the attachment plug is 15 amperes, then the wattage can not exceed 1500 watts at 115 volts (13 amperes).
This follows SPE-1000 as well as a number of equipment specs such as Electric Air Heaters C22.2 No. 46, Motor Operated Appliances (Household and Commercial) C22.2 No. 68 and Vacuum Cleaners and Floor Polishers C22.2 No.67.