Circulation Heaters Type Ex. Designed for forced flow or natural flow applications. Standard designs ranging from 0.6 to 672kW… higher kWratings are also available.Optional features include built in high limits and thermostats, stainless steel wetted parts. moisture resistant or explosion-proof housings. CRN registered vessels for Canada. Authorized to bear the U and N stamps, depending on ASME code classification (Section VIII or III)