Solar Thermal - getting rid of air in the system

[goldenflakes]

Hello hello,

Hope all our well. I have a solar thermal system that an engineer friend of mine installed at my house. It has provided me with hot water between Mar and October for about 7 years. He has now left the area so I am left doing the maintenance myself as solar plumbers are hard to find here. One of the fixings came loose and the system took in a big chunk of air which effects my pellet stove because the pressure has great movements.

I have looked for a way to bleed air out of the system but can not find anything. In the end I put circulated fluid into the system with a manual pump. Unfortunately this does not work as well as if you have the electrical system charger. Are there any other tips for getting air out of the system?

Also what is the function of the gold items in picture 1 (left side) on the and 2?

Than you for your help.

Paul

[J.P.M.]

What type of solar thermal system is this, an open or direct flat plate system (potable water circulates through the collectors directly from - to the house water supply) an indirect or closed system (a non freezing fluid like propylene glycol/H2O mixture circulates through the collector loop and transfers the gained heat via a heat exchanger to the potable water loop for the house), or a passive type system without a pump, or something else ?

In the U.S. most plumbing codes for solar thermal and other residential hydraulic systems, including solar thermal systems, to have an air bleed valve at the highest point in the system (at or slightly above the highest point in the system near the top of the highest collector. Sometimes, or if not maintained, such air bleed valves won't operate by virtue of mineral deposits or other schmutz collecting in/on such valves and so not release trapped air in the system. Also, if the piping design has "local" high spots, air can get trapped at those points and reduce or stop flow.

It looks like the picture on the left functions as an air bleed but it also looks like it's not at the system high point. the picture on the right may be something called a "check" valve whose function is to prevent reverse flow, but those valves usually have an indicator arrow to show which way to install the valve.

There are lots of other causes of flow blockage but without a lot more info, it's hard to diagnose hydraulic system problems.
Before I went further, I'd give Spirotech a buzz and pick their brain.

[goldenflakes]

Hello JPM, Thank you for your response. I have a non freezing fluid that is pumped through a heat exchange with flat panels. I expected some kind of a bleed at the top but could see nothing on the roof. Thanks for your response.

[J.P.M.]

Hello JPM, Thank you for your response. I have a non freezing fluid that is pumped through a heat exchange with flat panels. I expected some kind of a bleed at the top but could see nothing on the roof. Thanks for your response.

You're most welcome.

I change out the air bleed valve on my system every 2 yrs. as part of routine system maint. as it gets crudded up by the minerals in my water supply and usually needs replacement after 2-3 years if not changed out.
That air bleed valve on my system is a Maid O' Mist Can I connect solar panels of differ...s in parallel? and is fit for purpose for potable water systems.
I have an open system (potable H2O through the collectors) so my system is somewhat simpler than yours.
I believe that air bleed valve is most likely suitable for glycol/water or other working fluids as well as potable water but I'd call the Co. and enquire.

This isn't a plug but that valve is fit for my purposes.
See the net (Google "Maid O' Mist") for prod. descriptions, spec. sheets and contact info.
A decent plumber should be able to install it. My guess is a solar specialist is probably not necessary.
Unfortunately, my guess is the installation will be somewhat costly due to the location (probably on a roof), possible system mods that may be required, and any glycol disposal and handling costs due to the possible danger of poisoning to stray neighborhood animals and perhaps humans.

Check what's called the "MSDS" sheet for the working fluid, whatever it is, for toxicity and other information.

While you're at it you might want to check what the working fluid actually is. If the working fluid is glycol/water, that fluid deteriorates with time and working conditions and if so may cause system corrosion problems.
Also, and more importantly, and not knocking the system designer, but if ethylene glycol was used instead of propylene glycol, you have a problem with most plumbing codes as ethylene glycol can be toxic to humans and other species and so is disallowed for use in residential solar water heating systems, at least in N. America and most of the rest of the developed world. Hopefully, your installer knew that, but maybe not.

Good Luck.