46 CFR § 111.87-3 - General requirements.
(a) Each electric heater must meet applicable UL 484 or UL 1042 construction standards (both incorporated by reference; see 46 CFR 110.10-1) or equivalent standards under § 110.20-1 of this chapter
(b) Each heater element must be an enclosed type. The heater element case or jacket must be of a corrosion-resistant material.
(c) Each heater must have a thermal cutout of the manually-reset type that prevents overheating and must have a thermal regulating switch.
(d) Each heater for bulkhead mounting must have its top slanted or otherwise designed to prevent hanging anything on the heater. If a heater is portable, it must have a clip or bracket to hold the heater in a fixed position.
(e) The external temperature of a heater enclosing case must not be over 125 degrees C, except that the external temperature of the enclosing case of a flush-mounted heater must not be over 100 degrees C. If a heater is mounted on or next to a deck or bulkhead, the heater must not cause the temperature of the nearest deck or bulkhead to be over 55 degrees C. For test purposes, an ambient temperature of 25 degrees C must be used.