13 NCAC 13 .0406             HIGH PRESSURE OR TEMPERATURE LIMIT CONTROL

(a)  Each automatically fired steam boiler or system of commonly connected steam boilers shall have at least one steam pressure control that shuts off the fuel supply to each boiler or system of commonly connected boilers when the pressure reaches a preset maximum operating pressure. In addition to the required operating pressure control, each individual automatically fired steam boiler shall have a high steam pressure limit control that shuts off the fuel supply to the boiler to prevent pressure in excess of the maximum allowable working pressure. The high limit control shall be equipped with a manual reset that shall prevent the boiler from being fired after the maximum pressure has been reached until the operator resets the switch manually. Steam boilers shall be provided with a syphons or equivalent that will provide a water seal and protect the pressure controls from being damaged by the steam.

(b)  Each automatically fired hot water heating boiler, hot water supply boiler, water heater or each system of commonly connected hot water heating or supply boilers shall have at least one temperature-actuated control to shut off the fuel supply when the system water reaches a preset operating temperature. In addition to the required temperature control, each individual automatically fired hot water heating boiler, hot water supply boiler, and water heater shall have a high temperature limit control that prevents the water temperature from exceeding the maximum allowable temperature for the respective equipment. The high limit control for the hot water heating boilers and hot water supply boilers that are either stamped with the ASME "H" designator or are not constructed in accordance with the ASME Codes shall be equipped with a manual reset that shall prevent the boiler from being fired after the maximum temperature has been reached until the operator resets the switch manually. A manual reset is not required for boilers that bear the AMSE "HLW" designator or for unfired pressure vessels.

(c)  Automatic resets or remote resets by electronic means are prohibited. The manual reset may be incorporated in the high limit control. Where the reset device is separate from the high limit control, a means shall be provided to indicate actuation of the high limit control. Each high limit and operating control shall have its own sensing element and operating switch.

History Note:        Authority G.S. 95-69.11; 95-69.14;

Eff. May 29, 1981;

Recodified from 13 NCAC 13 .0407 Eff. January 1, 1995;

Amended Eff. July 1, 2011; July 1, 2006; January 1, 1995;

Pursuant to G.S. 150B-21.3A, rule is necessary without substantive public interest Eff. July 22, 2018;

Amended Eff. April 1, 2022.