The maximum allowable working pressure on a standard boiler may not exceed the pressure stamped or cast by the manufacturer on: The boiler; or A plate secured to the boiler. The maximum allowable working pressure on: The shell of a nonstandard riveted heating boiler shall be determined in accordance with Regulation .22 of this chapter, except that the maximum allowable working pressure on a: Steam heating boiler may not exceed 15 PSIG; and Hot water boiler may not exceed: 160 PSIG, or 250°F. A nonstandard steel or wrought iron heating boiler of welded construction: May not exceed 15 PSIG for steam; and For service other than steam, shall be calculated in accordance with the ASME Code, Section IV. A nonstandard boiler composed principally of cast iron, or having a cast iron shell or heads and steel or wrought iron tubes, may not exceed: 15 PSIG for steam service; and 30 PSIG for hot water service.