Auto air vent + Circuit Setter/balance valve

Mx2

Hydronic heating system. End of heating loop hangs a Trane power fan coil in shop. Commercial complex, 1” supply and return to unit entering shop via wall penetration. Several fan-coil heaters upstream (larger lines) feeding offices.

As the horizontal lines enter shop area they are graded up +4” to above the hanging power fan unit and then both lines drop down to the units respective connections about 30”. There appears to have been an auto vent on the return line (1” tee, 1/2” valve on top and auto-vent combination) where the vertical 1” return line turns horizontal. It appears the auto-vent above has been removed and 1/2” insolation valve closed & plugged.

Customer is complaining that it never seems to heat “it just blows Luke air.” As both supply and return lines are at a high point where the horizontal turn vertically above unit (potential air trap), on the supply side I will cut out the 90deg elbow and install a new 1” Tee with 1/2” valve (for service of auto vent) and new auto-vent at apex. This should eliminate the potential air trap issues on the supply side.

Concern: On the horizontal return line (via the Tee, vent assembly) about 2ft downstream there is a “Circuit setter”, or some call them a “balancing valve”. The glycol/water mix Travels through the Circuit Setter where it then appears the horizontal return line fluctuates in elevation a couple inches + & - till supply & return lines travel back through the wall penetration 60 feet away as it returns to the boiler room 200 feet away.

Q: Does trapped air travers a Circuit Setter/Balancing valve or is air trapped either side?

With the new auto-vent installed “return” high point Tee, is there a need for another auto air vent on the downstream side of the circuit setter? (trapped by the Circut Setter) or will air push back to the boiler? In this described scenario , would there be an expected auto-vent on the down stream side of Circuit-Setter?
sorry so wordy. Hey, it’s me. Thank you for your thoughts/experience.
The Wall is all powerful.

mattmia2

the glycol will hold on to bubbles more than water. a microbubble air separator at the boiler will help with that. the auto air vent with glycol probably isn't a great idea. they tend to leak and they tend to leak more with glycol. it would be better just to get the air out with a manual bleeder.

Mx2

Air separator in boiler room functioning.
At the unit, that’s how they fixed the last auto-vent. Removed it.
I was surprised not to see vents on supply side. Manual or otherwise. I’m cutting one in.

Agree, anything mechanical and deals with glycol will leak, someday. They put a desk with office type in chair under piping. Thus, removed, plugged and fixed.

Unit is pain to get to for manual bleed. What about tubing from vent port, to wall, down to catch bottle?

Your response appreciated.

Thoughts?

mattmia2

you could run the manual valve down to somewhere that you can reach it with soft copper. auto valves will leak, it is just a question of when.