Posted by Harold Kestenholz - Hydronic Network on January 16, 2000 at 18:08:57:
In Reply to: Adding Hot Water Baseboard to a steam plant. posted by Bill on January 16, 2000 at 12:35:15:
Water boils at 212F degrees at atmospheric pressure. Water weighs .43 pounds per square inch for every foot it is raised above the pump that lifts it. Now suppose you have 212F water pumped upstairs; what happens to the hot water when it falls back down to the basement? The water turns to steam because there is no pressure to keep it water, it flashes to steam and causes noise and banging.
You can take water from the bottom of a boiler and heat with it. The idea is as old as circulators. Thousands of church basements were heated that way a half-century ago. But church basements are where the boiler was - the hot water was taken off to run through pipes or baseboard below the water level.
If you want to heat using the water in the bottom of the boiler, run the boiler water through a heat exchanger. Use the other side of the heat exchanger to heat the hot water that will run through the heaters upstairs. There will be no problem.