Automatic Air Vent

[miker]

I have a solar collector project in progress that *had* an automatic air vent installed. I found that it leaked way too much fluid when charging the system.

My 2 cents is to skip the automatic air vent and use a boiler valve if you think you'll need to purge air from the system. So far I've not had a lot of air trapped. I suspect that over the next few days, as air settles out of the fluid, that I may need to bleed air from the top once or twice.

In general, when charging the system, the pump flushes the air out pretty well. Once the return side stops bubbling, I close the drain valve and let the preasure build. When I've reached the max preasure (.2 mpa/2 bar/~30 psi), I close the charge valve side and open the center value.

Code: Select all

to solar pump --<---+--\--+---<-- from solar tank
                    |     |
     charge valve   \     \ drain valve
                    |     |
                    in   out     


The \ in the diagram are valves. The charge and drain valves are simple hose bib style valves, while the center valve is a ball valve between the charge and drain valves and inline with the cool side of the solar collector loop (bottom connection on storage tank).

[Duda]

I have also noticed that if the air vent is installed, it will spit out fluid along with the air. Some solutions to this is to install a pipe to push the air vent higher above the fluid line so there's only air and not fluid in that pipe and therefore, only air passing through the air vent.

One issue with not having an air vent installed is if your pump fails, then all of the pressure built up from a boiling fluid will go to the pipes and expansion tank. There is a chance of pipe rupturing, depending on how much fluid/pressure you have initially and how big the expansion vessel is. With the air vent, steam will generate and then blow out the valve until the collector has become emptied.

Other solutions to purging air from the system is to use a ball valve on the top, and just bleed out air every once in awhile. I am not fond of doing this but have had to before. I now use 20 psi my system, so this is not even helpful. To purge air, I circulated fluid through the system and back into a container with the fluid in it. So as it pushed the fluid through the pipes, air was purged down into the bucket and replaced with fluid going back through the inlet to the pump. I then closed the outlet valve to prime up 20 psi and connected the system back together to complete the loop. This was necessary due to the high lift in which the pump could not push through without some pressure.