air lock in chilled water HVAC piping??

[Steve Rhodes]

the HVAC industrial plant & office system is chilled water, 400 tons, two chillers.
the distribution system to the office raises about 20 ft to the roof across a crane bay and drops the same distance after a horizontal run of 60 ft.
i am concerned about air lock in the supply side and a little less concerned about the return side of the office piping.
i can hear what sounds like bubbles passing the control valaves in the office units. it seems that the office always gets less cooling water and is "humid" on marginal days. is this a ligitimate concern?

[cyro]

You should have a air vent bleeder somewhere
.

[Nuclrchiller]

Yep, it's reason for concern. The horizontal runs, both supply and return, need a means of bleeding air. Is there anything connected on those runs ?

[Steve Rhodes]

cyro, Nuclrchiller,
there is a separator/collector at the return point in the chiller/mechanical room that has a vent.
I looked again and there are two lines from the top of the upper piping run protruding through the outside wall. on the outside there is two devices that look like they might be air reliefs. i will have maintenance check them. do these require regular maintenance/replacement?
should the air relief on the water return line be at the end before the line turns down?

The individual office uah units piping sometimes come from the top of the distribution manuifold and sometimes from the bottom. would you expect that the air would eventually get pushed out of these smaller lines, 1" to 2", back to the large lines where the air will be vented?
what is preferred, uah lines from the top or bottom of the distribution lines?
thanks for the help.
Steve

[Shophound]

Automatic air bleed devices can sometimes become fouled and not bleed air properly. Hopefully there's a good shutoff valve located where the bleeder is so it can be removed and cleaned.

Do you have a good water chemistry treatment program for your chillers and towers?