I have gas-fired Crown Boiler (c 1991), used in a closed heating system. Steam flows to my radiators, however no cold water returns to the boiler from the radiators. As a result, I have to fill the boiler twice a day, or more.
If you can't find any leak in the line then I would say that the problem is in the air vents. They are not shutting off and letting too much steam into the atmosphere. The steam dondenses and returns to the boiler. The vents should only open for a few seconds to let the air out and shut off. It is not good to add water to the system that much as the boiler will fill up with sediment and sludge and have to be blown out. Air vents run about $8.00 and $20.00 for adjustable ones
Something's leaking somewhere. Is this one-pipe or two-pipe steam? If one-pipe, the air vents (usually made by Hoffman) may be letting the steam out. If two-pipe, the there may be a leak in the condensate return piping. Either way, you should get it fixed. When you add water to a boiler, you're introducing more minerals. It's best if it just uses the same water over over.
