Purging air from closed loop system

Jan 1, 2011 01:22 pm
Purging air from closed loop system

This past September, I finally installed a SHW system on my house in Vermont. Two Sun Earth 4X10's w/ 120 gallon Superstore Ultra, Sun Earth controller and a Taco 007 pump. On a west facing roof, saw-toothed (12' apart to avoid shading) and tilted to 60 degrees.
I've had an awful time trying to get the air out. I originally charged the system with a 1/2 hp utility pump but was never able to get all the air out. I realized this when one collector would heat up while the other one wouldn't.  I put a sensor on each collector just to monitor and found that one would heat up to 130 degrees while the other would go as high as 260 degees. I repurged the system only to find that the the air would just switch from one collector to the other. I put some can vents on the top of each and tried bleeding, but that didn't work out either.
I do have a Taco air-scoop with a vent down at the manifold.
I've taken off the can vents on the collectors so I could insulate better for the winter. I re-charged the system using a 1 hp pump, cranking up the pressure hoping to blow the air out but still no luck.
Last week, I finally swithced the the collectors into a series configuration(as opposed to parallel) and recharged.
It seems to be working much better. the collectors are within a few degrees of each other and the tank is heating up.
I've installed a few flush mount systems and haven't had any problems (or call backs !).
I had taken a couple of SHW classes(Alt-e) and Bob R said to never plumb the collectors in series. Most of the Euro systems I've seen, (never installed though) seem to be in series.
Should I expect any problems because of this?
Any advice, ideas etc greatly appreciated.
Thanks, Bill Sullivan
462 Posts
Jan 2, 2011 07:31 pm
Re: Purging air from closed loop system

William, the can vent on the air scoop should be all you need. Do not install the others on the panels. Put the panels back in parallel if you can. Now, how do you fill your system? Do you have two drain valves with a check valve or ball valve in between them? If so, and you already have glycol in the system and do not want to drain completely, use your pump to pump extra water or glycol from a bucket into one of the valves filling the system. Attach a washing machine hose or short hose to the other valve at the end of the loop, and have this hose discharging into the same bucket you are pumping out of. Run the pump for several minute until all the air is purged out and the glycol flows air free. Then shut off the discharge valve and continue pumping until you reach your desired pressure, then close the inlet valve.
Jan 3, 2011 08:27 pm
Re: Purging air from closed loop system

Tom, thanks for the reply. I do have a drain and fill valve on either side of the circulator with ball valves on each. I have tried purging the air at least ten times. I've drained and flushed, blew air through, cranked the pressure up to 55 psi while filling... Each time I've run the fluid through until it appeared that all the air was out. No bubbles in the bucket, not even micro bubbles, just a nice clean green fluid swirling around the bucket. I didn't put the vents on the collectors until I had failed a few times. Then I did hoping that it would help. I tee'd off the top of the collectors with a ball valve, then the vent. I tried bleeding through the top just using the ball valves, until fluid poured out but still, no luck. I installed ball valves at the input and output of each collector for isolation, filled one at a time then opened the loop but still no luck.
I've installed a few systems, flush mounted, coupling the collectors together and never had this problem.
I swithed to the series configuration , basically to see if I could get the system to work at all. They are heating up within a few degrees of each other now as well as heating the water in the tank.
What are the reasons for not just leaving it in series as opposed to paralell?
Your input is greatly appreciated, Thanks
Bill Sullivan
462 Posts
Jan 3, 2011 10:55 pm
Re: Purging air from closed loop system

William, sounds like the problem is with the panels being at an angle. Basically as you circulate the fluid, it only goes through one side of the collector trapping air in the rest of the tubes. This may be a result of how you piped the panels.
 Usually if you have two panels laying flat, connected together in parallel, the inlet would be let's say at the bottom left and the outlet at the top right.
  Since you have them mounted at an angle ( /  / ) you may have to do a series/parallel arrangement. Pipe the inlet to the same side of each panel, on the bottom of the panel, nearest the roof ( __ /___ / ). Then connect each outlet together on the opposite side of each panel that is above the roof returning back to your tank. Cap the other 4 ends.(2 at the top of the panel nearest the roof and 2 on the bottom of the panel up in the air) This will give you the cross flow that is needed. 
It's not to a big deal if you have them in series as long as you feed the bottom of the second panel from the top of the first panel that has it's inlet on the opposite side on the bottom.   
 Let me know if you get it. I'll do a better drawing for you if you don't.
Jan 4, 2011 08:44 pm
Re: Purging air from closed loop system

Tom, I had a sneaking suspicion that the risers were not all filling up with fluid. It seems as though they should have with the outlet being the high point and the amount of pressure I was using to charge. The collectors are in a landscape set-up, the risers are basically paralell with the 10 pitch roof. I think that possibly the fluid may have been circulating through the lower risers and finding it's way to the outlet without completely filling the uppermost riser(s).
The current (series) set-up is as you described, in the lower, out the top to the lower of the second and out the top, back to the tank. 
I really appreciate your feedback on this.
Thanks, Bill
462 Posts
Jan 6, 2011 10:22 am
Re: Purging air from closed loop system

William, another suggestion is, when you fill the system, add the water real slow in order to make sure each panel completely fills and purges....

Disclaimer and Disclosure

The Alternative Energy Store, Inc reserves the right, within its sole discretion, to refuse or delete any posting or portion thereof, or terminate or block the access to this forum.

The opinions and statements posted on this forum are the opinions and statements of the person posting same, and do not constitute the opinion or act of the Alternative Energy Store, Inc (AltE). The Alternative Energy Store, Inc does not endorse or subscribe to any particular posting. No posting shall be construed as the act or opinion of the Alternative Energy Store, Inc.

Click here for BBB Business Review

McAfee SECURE sites help keep you safe from identity theft, credit card fraud, spyware, spam, viruses and online scams
Desktop Website | Mobile Website


Click on an icon to share! If you don't see the method you want, hover over the orange "+".


What can we do to help you?

Please enter a summary
Sorry, the copyright must be in the template.
Please notify this forum's administrator that this site is using an ILLEGAL copy of SMF!
Copyright removed!!