system pressure

Dave_61

We have 3 hydro-air handlers. Our highest one is a good 35 feet above the boiler. One summer, about 3 years ago, we went away for a couple weeks, and I shut off the boiler. The pressure in the system dropped, and the system sucked air through the vent on the top floor air handler. So in the winter, the upper most air handler was air-locked.

I currently keep the system pressure at 24 and have had no other issues with air in system. Also, on the uppermost unit, I have a gate valve under the vent which I shut off. Occasionally, I will open the gate valve and purge a tiny bit of air out of the vent then reclose the valve.

Lately, I have noticed that the pressure of the system is around 21-22 with no obvious leaks. If I go to the uppermost unit and press the schrader valve on the vent, no air or fluid comes out. I assume that it is because the system pressure is too low to purge out of the vent.

If I leave the gate valve directly below the vent in the closed position, is there any problem with running the system at a lower pressure (20-21psi) since the system is closed? I would assume that there is nowhere for air to enter the system in the uppermost air handler.

I hate to keep adding water as it dilutes the glycol in the system.

Thanks

Dave

Charlie from wmass

water column

is 1 pound of pressure for every 26" in height. 35x12/26 = 16 pounds of pressure to reach the air handler. Depending on how accurate your gauge is 22 should be fine. The system pressure will change a bit as the water heats and cools.

Dave_61

I'm just not sure

why no air or water will come out when I press on vent. I assumed it was because the press was too low. Normally, I get a little water when I press on the needle in the valve.

Charlie from wmass

The gauge may be off a few pounds or

the vent may be clogged. If you are manually venting any ways I would remove the automatic vent and install a coin or key vent. I do not like Automatic vents in areas above finished ceilings

Dave_61

I'll look into a manual vent.

But I always turn off the gate valve underneath to prevent leaks or air entry. The vent is not clogged. So should I raise pressure at boiler until water just comes out of vent when I open it?