Gravity hot water system

Chris V

Ran across a 1 year old gas boiler that was installed in a old house that had a open type gravity system. It was converted to a closed system wiyh a High velocity Taco Circulator. No Flow valves. Seperate Water heater. Properly down sized supplies out of boiler. House over heats like crazy.Should there be flow valves? How come new boiler could not be used for gravity heat? Thermostat anticipator was set for longest run cycle because large radiators near thermostat...were causing heat to shut off to quickly...Upstairs bedrooms were cold. (Large House)

Al Letellier

gravity hot water

I think the key (based on your info) is the high velocity circulator. Water will take the path of least resistance and it sounds like those big pipe mains are taking all the flow. You should have some means of balancing the flow on the returns, and to slow down the water. That's how the dead men designed those old system...slow flow!!
The new boiler may not be suited for gravity installation. Things like thermal shock can destroly a boiler if not poperly installed on gravity. You need a boiler design for such applications like Buderus 215 and Viessmann Vitola, to name a few.

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