Volute Centrifugal Pumps PN 16 / PN 25 for Heat Transfer Media Hot. The series NTWH NBWH and NIWH (PN 16) can be used with hot water at temper atures up to 360 °F (183 °C). The series CTWH CBWH and CIWH (PN 25) at temperatures up to 400 °F (204 °C). The application limits are specified in the table "Application Limits"and in the diagram ...