boiler overfilling

smc

We have recently had problems with a couple boilers overfilling. One of them is a 175,000btu 3apt house. Owner says been ok till we repiped little bit of return and hartford. Plumber says put back same thing. we have skimmed couple times seems to be dry steam. Radiators in hallway are two pipe with no traps, didn't get into apts. Owner did comment that was overfilled and no water would come out of drain valves bottom of return. We changed main vent directly above it thought had it but owner says still overfilling. Could try lower psi now running little over 1to 2.5 cuts out. Feeder has three position switch m/m, safegard, ect not set to safegaurd but been like that not sure if that affects it. Any ideas vacuum somehow holding return water or psi? thanks scott

Jamie Hall

Can you describe the "radiators ... two pipe with no traps" a little more? Inlet high or low, valve or no valve? Outlet low? Simple elbow or... ? (A picture might help). Where does the outlet go?

I ask because this may have been a vapour system, in which case the pressures are much too high ((hey are too high anyway, but not as much)(assuming that the control is a pressuretrol, try it on 0.8 psi cutin and 1.0 psi differential for starters -- if it was vapor at one time, you will need to use a vapourstat and about 10 ounces per square inch cutout).

2.5 psi will raise the water about 6 feet. If there are returns which are adequately vented (that is, they would be at or near atmospheric pressure) they could easily be being flooded at that pressure. The auto feeder would feed, and then when the boiler shut down you'd be overfilled when the water held up in the returns was able to come back.