Steam w Vacuum Return

Bernie Riddle_2

F/T traps dump air into the consenate return line. Also at start up the boiler sends steam to the main header then to the radiators, ... this action pushes more air into the consenate return line. Anything & everything & everything else pushes compressed air into the condensate return line. I have pulled fittings & trap lids here & there to see what the Hell is going on. The main condensate return line is loaded with a lot of compressed air. How does the air get out? I have a lift fitting at the end of my condensate return line just before the vacuum pump, ... same as the one shown on page 193 of "The Lost Art of Steam Heating". This lift design (14" vertical) may allow the water to be lifted up but not the air. The air appears to be trapped in that line forever. Is my system missing a blow off valve, or a swing check valve, or a air release valve or what ? I am not talking about the air vent mounted on top of the vauum pump collection chamber. I am asking about the air trapped in the main condensate return line before the hard piped verical inverted "U" lift. How is it vented ???

Brad White_9

In a vacuum system

the air is vented via the vacuum receiver normally. When the steam enters the mains, normally traps will vent the air to the return all to be extracted via the vacuum pumps.

You said that the return line is under positive pressure? All I can suspect is that the steam is forcing that and the vacuum pump cannot keep up.

Maybe I am missing something from your description and I only skimmed your original post, so sorry if I am missing some background and details.

Unknown

I'm with Brad

That lift fitting should pull right through (consuming a part of the vacuum) and show a vacuum in the return before start-up, all of the way to the boiler. As the boiler steams and makes gobs of condensate from cold piping, that pump has to keep up with the steaming rate, through the lift fitting.

Like Brad said the pump is too small for the boiler, or the boiler is to big for the pump. The question is....

Which one is the correct size for the system?

Noel

A.J.

Is your system holding a vacuum

when it is on the off cycle ?

BAB

The Answer

Thanks everyone for your imput, ... made us look at the system differently. Made us look in detail & found an open swing check valve in the main header. This valve was left from last week's investigation of the steam/condensate return equalizer line. During heatup or steaming the valve was closed, as it should be. After the heating cycle, as the steam cooled, the main header developed a vacuum and the swing valve opened. This open valve pulled in all that air I was complaining about. During heatup the system tried to burp all that air & then on the next heating cycle we picked up more air. The equalizer line is reattached correctly & things appear to have settled down. Thanks again.

Bromley