Need help with gravity hot hater

Kevin_32

I recently purchased a 1920's era two-story house with the original gavity hot water system. The boiler was converted from oil fired to gas and runs well, delivering water at 180 degrees. The expansion tank is located in a second story closet at the high point in the system with an overflow pipe to a utility sink in the basement and a vent pipe into the attic space. Because the fill valve is in the basement and the glass is on the tank, we have to use phones to signal when water enters the glass.

After putting water into the expansion tank, I checked to see that all the radiator valves were open, bled the air from all radiators and turned on the system. The first floor heated up quickly to 4 degress over the set temperture and shut down before the heat had made it up to the second floor, leaving it cold.

We let the system run for 48 hours, refilled the expansion tank and bled the radiators again, but still the first floor is overheated and the second floor is cold.

Any suggestions?

Mike T., Swampeast MO

Gravity systems should have an altitude gauge on the boiler. Frequently it's a "tridicator" for temperature, altitude and pressure. The altitude portion will have an adjustable needle (it's usually red). It should be set right under the needle that moves with pressure when the attic tank is properly full. Afterwards, you only add water to bring the needles in conjunction. No need to return to the attic! Look carefully at/near your boiler. The gauge should be there and already set.

The circulation problem is likely age related. As pipes age, they get more rough. More roughness means more restriction to flow. The 2nd floor radiators usually have much longer runouts (thus more pipe to get rough) and were originally and intentionally sized for roughly twice the restriction of the ground floor rads. Put all that together, and you get a system that quickly heats the ground floor with very little flow to the upper. (When new the difficulty was keeping nearly all the flow from going to the upper radiators!)

You might be able to help things by significantly closing all of the downstairs rad hand valves. This is a delicate balancing act...

If all fails, it's time to convert to forced flow. If at all possible, install thermostatic radiator valves (TRVs) when you do the conversion. You'll get completely independent temperature adjustment in every room with extremely tight temperature control. While your existing boiler (quite possibly the original) may still last for a long time, it is poorly efficient. Give highest consideration to a condensing/modulating boiler. Old gravity systems LOVE them--especially when you have TRVs!