Exp. Tanks Flooding

Servicewiz_2

I am a seasoned HVAC mechanic who needs a little help.I have several standard (air meets water ) expansion tanks which flood monthly.The problem I believe is that the system runs between 60 to 70 or 80 PSI.(ten story bldg. boiler located in basement W/Exp. tanks).No sign of water coming from tanks after flooding (rules out leaks in tank).With this much pressure can I Expect high levels in tank or do I need to Install bladder tank and pressurize air side.Any help is greatly appreciated.Boiler is a 80 psi boiler.
Thanks SERVICEWIZ!

Mark Eatherton1

First things first...

The pressure you quoted is WAY to high. THe rule of thumb is 1/2 PSI per vertical foot PLUS 5 PSI. In the case of 10' per story, assuming piping stops at the floor of the 10th story, that would equal 50 PSI. (it's actually supposed to be set at 44 PSI based on .434 PSI/foot elevation PLUS 5 PSI)

Now, to the system and the expansion tank. If there are automatic air vents ANYWHERE on the system, they need to be eliminated, or alternately, you could leave them in place and replace the non captive expansion tank with a properly size diahragm or bladder type of tank. Auto air vents and the old non captive expansion tank will cause water logging of the tank.

Operating the system at excess pressure also chews up quite a bit of the acceptance capacity of the old style tanks.

Turn it down...

ME

ScottMP

Many commercial

Systems have gauge glass's on the expansion tanks. This is a perfect place for a leak. If you have them, close the valves and takeout the glass ( so nobody can turn it back on ). I learned that from a guy who runs a popular web site .

Besides that, follow what Mark said.

Scott

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Glen

Over the years I have come to the same conclusions as Mark - auto vents don't mix with a standard (non diaphragm) exp tank. And while I have a few ideas on this phenomena - does anyone have a really good explanation of how this happens? ??

Dougie

never heard of that...

Auto air vents causing exp tanks to waterlog? How does that work?

DanHolohan

Here you go



It pays to wander off the Wall.

DanHolohan

Here you go

Why Compression Tanks Waterlog

It pays to wander off the Wall.

Glen

Makes perfectly good sense to me - bravo Dan

MMC

put a 'blatter tank' at the highest point of the system