expansion tank pressure
expansion tank pressure
(OP)
Our expansion tank (glycol system for comfort cooling) runs at a positive pressure when the system is off and goes into a vaccuum when running, sometimes as much as 20 Hg. Is this normal.Seems like a pretty high vaccuum.
System: Three 540 ton chillers, two 260 ton chillers. supplying 6 main cooling fans and multiple small chilled water units in the ceiling.
System: Three 540 ton chillers, two 260 ton chillers. supplying 6 main cooling fans and multiple small chilled water units in the ceiling.





RE: expansion tank pressure
I have seen the suction side of a pump drop into a "deep" vacuum on a closed loop, but it was when the pump was pumping against the compression tank, "the point of no pressure change". This was on a primary/secondary system and the primary pump was discharging into the secondary loop near the compression tank.
Is this a new system or an existing problem? Could you be pumping against a large air trap?
Lots of possibilties.
I'm not a real engineer, but I play one on T.V.
A.J. Gest, York Int./JCI
RE: expansion tank pressure
---KenRad
RE: expansion tank pressure
RE: expansion tank pressure
RE: expansion tank pressure
Is this 180 psig hydrostaic head, with the pumps off? If it is, it looks like you may not have the system up to full fill pressure. A rough calculation at 180 psig accounting for the placement of your pumps on the third floor gives you a rough calculated elevation of 415 Ft. divide that by 32 floors puts you about 13 Ft. per floor average does that sound right? This would mean you might be at 0 psig with out the pumps running, and when you turn them on that could be what's putting you into a vacuum on the return side, depending on the connection point of the compression tank. I would prefer to see at least 5 - 10 psig at the top of the system minimum, when the system is running.
I'm not a real engineer, but I play one on T.V.
A.J. Gest, York Int./JCI
RE: expansion tank pressure
RE: expansion tank pressure
I'm not a real engineer, but I play one on T.V.
A.J. Gest, York Int./JCI
RE: expansion tank pressure
Thanx.
RE: expansion tank pressure
Are you saying that when you fill the system up to a normal 10 psig of pressure while it's cold, if the system is shut down and warms up, the pressure rises above the safety relief valve setting and opens? Where is the relief valve located and what is it's setting?
That sounds like it might be a symptom of the bladder in your compression tank has failed and filled with water, or you may not have a large enough compression tank for the system volume. Assuming a chilled water temp of 40-45 degrees, and when the system goes down an ambeint temp. of 85-95 max. I would think that the compression tank should be able to handle the volumetric expansion of 40-50 degrees for water without risk of over pressurizing the system.
I'm not a real engineer, but I play one on T.V.
A.J. Gest, York Int./JCI
http://home.comcast.net/~offsetaj
RE: expansion tank pressure