"Bill" wrote in message
...
Check with a plumbing company which does steam heating. If it is a closed
system and the water gets above boiling, steam will be created and there
could be an explosion! Need a high temperature / high pressure relief
valve.


Why would it get above boiling? Home heating systems reach 180 and a high
limit switch turns off the burner. Same thing with an indirect fired water
heater and glycol. You set the desired temperature on an aquastat.

Expansion, yes; explosion, no.