Posted by Harold Kestenholz - Hydronic Network on October 29, 2001 at 13:36:45:
In Reply to: Re: Oversized Boiler, Is It Costing Me Money, How Much? posted by Joe Howell on October 29, 2001 at 12:12:15:
Converting the existing system to hot water by replacing the steam boiler with a hot water boiler will save significant energy. Provided the existing pipes are not rotten and can hold to 25 psig, very little in the existing 2-pipe system requires change. You can place zone valves or non-electric valves on the radiators to give individual room control.
Savings will occur because you will not have to heat the entire system to boiling temperature on every or any thermostat demand. Major losses occur from the large pipe surfaces in the system. When the water must reach but 100F in mild weather to heat the home, the pipe and boiler losses are greatly reduced. The average water temperature in the system over a season will be 130F instead of 212F. As the weather becomes colder, the boiler water becomes hotter simply by thermostat demand. You can run a very weak circulator constantly so there is never a cold cycle all winter and yet, save money. The boiler can then be IBR water rated to the radiation without concern for oversizing.
If the pipe must be replaced, the existing pipe can be cut to serve as a chase for running tubing inside to existing or new radiation as the water system does not require as large diameter as steam vapor requires.