Two weeks between purges

salisboss

I posted on here recently about air in my system. In the spring I plan to replace my air scoop with a spirovent and get estimates to reconfigure my three zone hydronic heating system to pump away (the book was fascinating). This year for some reason a purge only lasts a few weeks before the air is back. Can air scoops 'go bad'? My AAV on top of the scoop is doing nothing and I have replaced it recently. Also one of the zones hardly ever gets used. Could water be evaporating in it creating air pockets that get circulated around?

salisboss

To add to the dilemma I can't find any leaks.
Some other aspects I was thinking about:

Can you clean out an air scoop?

Although I think it's fine based on sound and heat to touch, would a improperly pressurized expansion tank lead to air issues?

Before I purge should the system cool down for a bit or can I immediately start purging?

MikeL_2

Salisboss,
There are several types of air in closed loop hydronic heating systems. Entrained & dissolved O2 can be most troublesome, especially if your system is not set up to " pump away ". Certain circulator locations can create a pressure differential that causes the auto feed valve to overfeed, and Aav's to draw in air creating flow restricting pockets of air.......

salisboss

> @MikeL_2 said:
> Salisboss,
> There are several types of air in closed loop hydronic heating systems. Entrained & dissolved O2 can be most troublesome, especially if your system is not set up to " pump away ". Certain circulator locations can create a pressure differential that causes the auto feed valve to overfeed, and Aav's to draw in air creating flow restricting pockets of air.......
>

After I purge again should I just close the AAV cap down tight to try and avoid the drawing in of air?

Intplm.

To answer your above question........^^^^^^YES^^^^^^....👍🏼Close it and🤞

EBEBRATT-Ed

@salisboss

What type of expansion tank do you have and what is the system pressure??

Can you post some pictures?

salisboss

> @EBEBRATT-Ed said:
> @salisboss
>
> What type of expansion tank do you have and what is the system pressure??
>
> Can you post some pictures?

I will check the tank pressure tomorrow when I purge the zones.

dopey27177

Do you have water vent valves on your heating elements?

The way the circulating works is part of the problem.
The pump sucks the water out of the system, it cant make a sufficient pressure differential to pull the air rut the system.

When you purge or bleed the system you need to open the heating element vents to bleed the air out of the system.

You can only do this when the pump is operating.

Have to do this one zone at a time. to do this you need to have the boiler pressure (cold water ) 2 psig above the static head of the system, Each heating element has to be done one at a time. This is a tedious task as it can days to remove all the air from the zones.

When pumping away is installed it puts a higher pressure on the discharge side of the system that forces the air though the piping system and sets up a higher differential pressure between the suppl\y and return.

The air goes thru the boiler an is vented out of the vent on the diverting fitting. This results in constant air removal. Each heating cycle has air released until there no more air in the system.

When you set the new Xtrol tank in place (usually charged at 15 PSIG you need to lower the pressure in the tank to the pressure in the piping system. Assume the system pressure is 10 psi you need bleed off from the Xtrol. This will keep the bladder in Xtrol from flexing a lot. The xtrol will live a lot longer,

Jake

salisboss

> @dopey27177 said:
> Do you have water vent valves on your heating elements?
>
> The way the circulating works is part of the problem.
> The pump sucks the water out of the system, it cant make a sufficient pressure differential to pull the air rut the system.
>
> When you purge or bleed the system you need to open the heating element vents to bleed the air out of the system.
>
> You can only do this when the pump is operating.
>
> Have to do this one zone at a time. to do this you need to have the boiler pressure (cold water ) 2 psig above the static head of the system, Each heating element has to be done one at a time. This is a tedious task as it can days to remove all the air from the zones.
>
> When pumping away is installed it puts a higher pressure on the discharge side of the system that forces the air though the piping system and sets up a higher differential pressure between the suppl\y and return.
>
> The air goes thru the boiler an is vented out of the vent on the diverting fitting. This results in constant air removal. Each heating cycle has air released until there no more air in the system.
>
> When you set the new Xtrol tank in place (usually charged at 15 PSIG you need to lower the pressure in the tank to the pressure in the piping system. Assume the system pressure is 10 psi you need bleed off from the Xtrol. This will keep the bladder in Xtrol from flexing a lot. The xtrol will live a lot longer,
>
> Jake

The radiators do not have individual air vents. The only vent in the system is above the air scoop.

salisboss

I also am going to try one of the watts auto vents with auto and manual purge instead of the maid o mists I have been using that just immediately fill with water.