National Electrical Code Articles and Information

1. It applies to boilers using resistance-type heating elements, as opposed to other types such as electrode-type [424.70].

2. This is a trick question. In all cases, the boiler must be suitable for the installation [424.71].

3. Yes, it matters. One set of requirements applies to an ASME-Rated and Stamped vessel [424.72(A)]; another set applies if the elemen is rated more than 48A and the vessel isn't ASME-Rated and Stamped [424.72(B)].

4. They must be sized at least 125% of the load served [424.72(E)].
   
5. Overtemperature control, if in normal operation there is no change in the state of the heat transfer medium [424.73]; Overpressure control, if in normal operation there is a change in the state of the heat transfer medium [424.74].