I have read on many threads and I believe it is code in some areas that the total connected load should not be more than 80% of the rating of the overcurrent protection devices.
Is this correct? Should it be less of a concern since the steam generator is the only load on this circuit?
I have always said to take anything you read on these forums with a grain of salt as most of what you read is the opinion of the poster and carries no merit.
210.19 Conductors — Minimum Ampacity and Size.
(A) Branch Circuits Not More Than 600 Volts.
(1) General. Branch-circuit conductors shall have an ampacity not less than the maximum load to be served. Where a branch circuit supplies continuous loads or any combination of continuous and noncontinuous loads, the minimum branch-circuit conductor size, before the application of any adjustment or correction factors, shall have an allowable ampacity not less than the noncontinuous load plus 125 percent of the continuous load.
If I was doing the calculation of lights in a store then I would do the 125%/80% factor simply due to the fact that the lights in the store would be on for more than three hours.
If I was calculating the number of lights I would add the lights and do 125% of the total.
Example 8 lights with an ampacity of 2 amps each would equal 16 amps. 16 amps times 125% would equal a 20 amp overcurrent device (breaker).
If I had a 20 amp breaker and wanted to know how many continuous amps it would carry I would
multiply the 20 by 80% and come up with 16 amps.
When I am installing a piece of equipment that has the amperage on the nameplate then I match the conductor and overcurrent device to the nameplate.
With the nameplate on a motor it is just a little different, see Article 430 for more details.