6 Degrees of Inner Turbulance

hvacfreak

Saw a job the other day that still has me wondering. This brand new boiler room with 2 -1,000,000 + btu hot water boilers , all new piping and components , and an older expansion tank. The top of the "centrifugal" air separator is piped in common with expansion tank line and make up water. With out an air vent , what is the point of the air separator ? I guess it could ask the make up water very nicely to move to one side of the pipe so it can go to the expansion tank ?
One complaint of this system is eratic pressure increase and expansion tank water -logging. This tank has to be 5000 gal and looks to be in good condition. It could be too small , but I doubt it. I think that lack of air removal is the problem. Fill pressure is about 20 psi , roughly 25 ft rise. I was there just to repair a flow switch , but this thing has some people shaking. Thoughts ?---JACK

Steamhead

That piping setup

is supposed to send the air up into the tank to maintain the air cushion. But from what you say, it isn't. Is there anything such as improper pitch, use of globe rather than ball valve etc. that would keep the air from going into the tank? Is that model of air separator even supposed to be used with a non-diaphragm tank?

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hvacfreak

Make- up water is tee'd between tank and air sep. Even if it were not , would air go to the tank? Been awhile since I've read Pumping away , I need to buy that today. I say that air separator is no better than a piece of pipe with out having an air vent.I could be wrong.

Steamhead

Make-up water

shouldn't be entering the system fast enough to impede the air. If it is, you probably have a leak!

Where is the circulator located in relation to the separator? It should be on the supply line after the separator, pumping away from the separator and out toward the system.

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Tom M.

Automatic vents

With this piping arrangement it is important that there are no automatic vents anywhere else on the system. Air absorbed in the expansion tank could be released through them over time.

Jerry Boulanger

Conventional tanks waterlog...

for two main reasons. Gravity flow between the system and the tank, and leaking gauge glass gaskets. If the tank is hot, you have the former - this can be solved by installing an airtrol tank fitting. If there is a gauge glass, valve it off to prevent air leakage from the top gasket on the glass, which is normally dry.

Almost any type of air removal device can be used with a conventional tank as long as the pipe is properly sized and pitches up to the tank so that the air can get into the tank where it belongs.