Designed for installation on water heating storage vessels to protect against over-temperature or excessive pressure. (Not for steam service) Features: CSA Compliance to ANSI Z21.22/CSA 4.4 Certified to ASME Section IV by National Board. Technical Specifications: Inlet Connection: 3/4" MNPT Outlet Connection: 3/4" FNPT Pressure Relief Setting: 30 PSI ASME Section IV: 500,000 BTU/HR.