Auto Clear Air in Solar Heaters?

[beartoothweb]

I used a configuration almost identical to one I found here on this site to set up my 8 2x20' solar water heater system. Since setting it up correctly, it's been awesome, and the water temperature is now actually higher than the average ambient air temp, right around 90 degrees, which is great for our cool evenings.

I have 2 sets of 4 panels together, as shown in the image attached, everything connected together.

I put a release ball valve at the end of each set so I can release the air. It works quite effectively, but it's a manual process and sort of a pain. I tried a 75psi relief valve I found at Lowes, but that's just too much pressure required to do anything.

I ran all 1 1/2" pipe for the system, and the valves are the same. I can easily reduce to whatever I need to, but I'm looking for advice on what I can add so that when the system comes on, it will bleed the air out automatically without dumping too much water. Should I add a pressure relief valve after each ball valve, and if so, what size/psi?

BTW, the current ball valves are in a T configuration, so there is a T, which the water flows through, and UP to get to the exit for the valve. Like ____||____ (the valve is on the Up part.)

 

[Melt In The Sun]

Will the air not just purge itself out the returns?

 

[beartoothweb]

Will the air not just purge itself out the returns?

I was thinking it should, but maybe I have something else wrong. There is about an 8" grade from the input to the output, so I would think that the air would purge itself. However, it seems if I let it run for an hour or so on it's own, and then open the valves, there is still air in the system.

If you were standing at the base of the whole assembly, the part closest to you is lower than the part farther away. But, they would be "level" from right to left. I'm wondering if I actually had the grade going from left up to the right, and front to back if it would make any difference?

Here are pics of the setup.

 

[Melt In The Sun]

How much air is there in the system? Are the release valves those things sticking about 1' into the air? If so, I would expect the stickup to remain full of air, but there to be no air in the rest of it.

 

[beartoothweb]

How much air is there in the system? Are the release valves those things sticking about 1' into the air? If so, I would expect the stickup to remain full of air, but there to be no air in the rest of it.

Yep, those are the release valves.

I ended up with clear portions of the system next to the left release valve, before the valve. What can happen is if I let it run for a while, then open that valve, I can get some additional air that comes through at that point, which would indicate to me that there is at least some point in the system where air is either trapped or entering.

I suppose I could just actively ignore it for a day, take some temps before and at the end of the day to see the effectiveness, then compare when I actually go out and manually bleed it. If there's no significant difference, I can just ignore it.

Ideally, I'd have the automatic valves, but those things are pretty expensive. I'm actually considering rigging up some solenoid valves (next season) that I can use to open and close the solar side electronically.

 

[Melt In The Sun]

If air is entering somewhere, you should be able to see it in the returns. If it's just getting trapped, I wouldn't worry about it. My guess is that there's only air in the "dead end" portion of the pipes with the valves at the end.

 

[beartoothweb]

If air is entering somewhere, you should be able to see it in the returns. If it's just getting trapped, I wouldn't worry about it. My guess is that there's only air in the "dead end" portion of the pipes with the valves at the end.

You're probably right, not enough air to worry about it. I was able to keep the temp near 90, even with overnight lows 30 degrees below that, so it's definitely working well, just being anal about efficiency. Now, I need to figure out how to divert some of the water to my hot tub. ;-> Thanks for the info!

KD