SylvanLMP
Hi Bob, are you asking from a code stand point?
The ASME section IV states a hot water system is considered LOW pressure @160 PSI @ 250 degrees and steam anything over 15 PSI is considered high pressure.
You can also check out the National Board Of Boiler Inspectors publications (NBBI)
Now remember you had better check the actual boiler/pressure vessel rating and know as temperature increases so does the pressure
