Thermal buffer: avoid surface evaporation of hot water with oil or other blocking product?

[dede2002]

It was just in case there was really no air entering the circuit of the panels. This would not be normal operation for a self-draining system.

I think you have an air inlet in the circuit, ideally air from the buffer.

[sicetaitsimple]

I think you have an air inlet in the circuit, ideally air from the buffer.

That's kind of what I was thinking too. I imagine (perhaps wrongly) that there are several return pipes to the buffer, if only to be sure to ensure good drainage from the upper collector during nighttime frost. It would be enough for only one of these pipes to emerge not below the water level of the buffer but above to no longer have this (possible) problem of vacuuming, and risk of incomplete emptying of the panels.
But obviously the initial design of the installation was different, the air intake being made in the upper part by two vacuum breakers, which Christophe condemned. In short, not obvious. Unless an air inlet is created "spontaneously" in the upper part of the installation.

[Christophe]

It was just in case there was really no air entering the circuit of the panels. This would not be normal operation for a self-draining system.

I think you have an air inlet in the circuit, ideally air from the buffer.

Not normal maybe but as long as it works where is the problem? It's the not normal systems that work that get things done, not the copied / pasted systems...

There for the moment, I have no idea where the possible other air intake could be (originally it was via the 2 vent valves of the ridge...)

[Christophe]

I think you have an air inlet in the circuit, ideally air from the buffer.

That's kind of what I was thinking too. I imagine (perhaps wrongly) that there are several return pipes to the buffer, if only to be sure to ensure good drainage from the upper collector during nighttime frost. It would be enough for only one of these pipes to emerge not below the water level of the buffer but above to no longer have this (possible) problem of vacuuming, and risk of incomplete emptying of the panels.
But obviously the initial design of the installation was different, the air intake being made in the upper part by two vacuum breakers, which Christophe condemned. In short, not obvious. Unless an air inlet is created "spontaneously" in the upper part of the installation.

Yes the double return is a good idea...but in this case I should hear the water coming to the surface, like a waterfall sound all the time...

But I only hear the sound of the air expelled (= sound of bubbles) when the solar water begins to return...it lasts about 2 to 3 seconds...and after more than the noise the noise pump and a little return flow...if there are bubbles coming back into the buffer, they are not noticeable...

As I said above I would have to look in the buffer on a pumping cycle... something I've never done...

And at the moment there is not too much sun... so we'll have to wait a bit...

[Christophe]

Here is the solar pump:

Suction at the end, radial discharge at the top...

If ever the emptying was no longer done, I could always add a "trick" at this level...

For example a solenoid valve on the loop on the left which returns directly to the buffer and which is always closed by a valve.

I never really understood the usefulness of this loop except perhaps to reduce the flow in the solar part or to mix the hot water in the buffer?

I have never used it (loop valve always closed)..if you have any idea of ​​its usefulness???

[sicetaitsimple]

I never really understood the usefulness of this loop except perhaps to reduce the flow in the solar part or to mix the hot water in the buffer?
I have never used it (loop valve always closed)..if you have any idea of ​​its usefulness???

I'm thinking more of the second hypothesis (mixing the water in the tampon). During the winter periods when you have no or very little circulation in the solar loop, you will inevitably (wax or not ) create a "cold bubble" around each of your immersed heat exchangers. A little forced circulation (you would have to see where this pipe is backing up) should help break it.

[Christophe]

It is quite possible except that in winter the solar pump starts very little... suddenly... an independent mixing pump would have been better for the mixture, in summer it is winter the water must be the coldest (bottom) arrives in the panels ... so no point in mixing.

Otherwise I just thought a little (exni TG!) and I wonder if the air drain was not there...before my eyes:

a) this small dead volume contains air, ok?

b) when the pump is running this air is compressed to about 1.2 bars, ok?

c) when the pump stops, this small bubble of compressed air is physically supposed to rise and therefore... defuse the circuit... and allow emptying, ok or ko?

[sicetaitsimple]

It is quite possible except that in winter the solar pump starts very little ... suddenly ... an independent mixing pump would have better for the mixture

I am not responsible for the design of your installation! But a single pump that serves (possibly) two different uses depending on the season is not necessarily stupid...
For the rest, sorry I did not understand your cogitations.....

[Christophe]

For the rest, sorry I did not understand your cogitations.....

With the annotations this should help?

[sicetaitsimple]

How much is your "dead" volume? 2 liters, 4 to 5 Normal liters at 1,2 bar? And given the geometry it will inevitably fill with water and evacuate the air after starting the pump. No, it's bullshit....