are met:
(1) The electrode boiler is marked with a minimum con- ductor size.
(2) The conductors are not smaller than the marked mini- mum size.
(3) A temperature- or pressure-actuated device controls the cyclic operation of the equipment.
424.83 Overtemperature Limit Control. Each boiler, de- signed so that in normal operation there is no change in state of the heat transfer medium, shall be equipped with a temperature-sensitive limiting means. It shall be installed to limit maximum liquid temperature and shall directly or in- directly interrupt all current flow through the electrodes. Such means shall be in addition to the temperature- regulating system and other devices protecting the tank against excessive pressure.
424.84 Overpressure Limit Control. Each boiler, designed so that in normal operation there is a change in state of the heat transfer medium from liquid to vapor, shall be equipped with a pressure-sensitive limiting means. It shall be installed to limit maximum pressure and shall directly or indirectly interrupt all current flow through the electrodes. Such means shall be in addition to a pressure-regulating system and other devices protecting the tank against excessive pressure.
424.85 Grounding. For those boilers designed such that fault currents do not pass through the pressure vessel, and the pressure vessel is electrically isolated from the elec trodes, all exposed non-current-carrying metal parts, in cluding the pressure vessel, supply, and return connecting piping, shall be grounded.
For all other designs, the pressure vessel containing the electrodes shall be isolated and electrically insulated from ground.
424.86 Markings. All electrode-type boilers shall be marked to show the following:
(1) The manufacturer's name
(2) The normal rating in volts, amperes, and kilowatts
(3) The electrical supply required specifying frequency, number of phases, and number of wires
(4) The marking "Electrode-Type Boiler"
(5) A warning marking, "All Power Supplies Shall Be Dis- connected Before Servicing, Including Servicing the Pressure Vessel"
The nameplate shall be located so as to be visible after installation.
IX. Electric Radiant Heating Panels and Heating Panel
Sets
424.90 Scope. The provisions of Part IX of this article shall apply to radiant heating panels and heating panel sets.
424.91 Definitions.
Heating Panel. A complete assembly provided with a junction box or a length of flexible conduit for connection to a branch circuit.
Heating Panel Set. A rigid or nonrigid assembly provided with nonheating leads or a terminal junction assembly identified as being suitable for connection to a wiring system.
424.92 Markings.
(A) Location. Markings shall be permanent and in a location that is visible prior to application of panel finish.
(B) Identified as Suitable. Each unit shall be identified as suitable for the installation.
(C) Required Markings. Each unit shall be marked with the identifying name or identification symbol, catalog number, and rating in volts and watts or in volts and amperes.