Drainback solar panel clogged with brown powder?

[Willaupuis]

Hello,

I have two Marvin solar panels, and this winter no luck one of the two leaks due to frost,

It is a drainback system, so it empties on its own when there is no sun,
I use rain water and central heating antifreeze

I start to dismantle it and realize that the bottom inlet pipe is almost filled with the butcher on its length of very dark brown / red powder, in my personal opinion not being a chemist it looks like oxide or copper phosphate

anyone know how and why this powder is formed in clogging the panel ??? in order to correct the problem and no longer have these worries

for information in summer when the boiler temperature is reached the system stops empty the panels but in theory according to the technical information they resist 207 degrees if I remember correctly

thank you for your answers

alex region of tournai belgium

[dedeleco]

The UV antifreeze, may have been chemically transformed and deposited, like any organic product under UV, which is stuffed with free radicals, and turns into solid junk ????
Copper with air and oxygen and these radicals is attacked strongly.
The salts in the water can also deposit, especially if you constantly add water.

UV is very chemically reactive.

[Christophe]

Copper oxide is green ...
Brown is more like iron oxide ...

Why do you use anti-freeze in a drainback?
Which pump do you use?

A photo and diagram would help us a lot to help you!

[Willaupuis]

antifreeze is always for safety I told myself, you never know if despite the angle that I have planned a small area of ​​water remains stagnant ...

- the water reserve is made of stainless steel,
- all system piping is copper
- the engine comes from a central heating system
- the boiler is a recovery boiler on ebay which comes from
also a central heating exchanger with original coil inside but I do not know what materials it is made of?

if it is iron oxide there was a fairly large amount I find after three years of use

[Christophe]

Well it can be something else but there are various sources of iron corrosion in your installation ...

Could you make us a photo of the "powder" and a diagram of the installation?

[manet42]

Different metals in the system ...
If iron in the recovery boiler and copper pipes in the installation, not good at all

See chemistry course: redox, iron and copper do not have the same potential (as in batteries) where corrosion therefore these deposits.

JC

[Christophe]

See chemistry course: redox, iron and copper do not have the same potential (as in batteries) where corrosion therefore these deposits.

JC

Yes but no (I think it's far ...) ... for the battery effect to occur significantly, there must be direct contact or use an electrolytic liquid ... which is not the case with "soft" water!

Iron and copper are also redox and there are plenty of copper and iron installations ... starting with circulators (copper does not exist)!

I think that an oxygen source is much more harmful (by the way, how is your emptying done?)

[manet42]

Yes, there are iron / copper installations, in my home for example, but I would point out to you that in the installation instructions for electric cumulus, it is indicated that you must put an intermediate sleeve between the copper pipes and the iron pipes of the water heater to avoid direct contact with copper iron and therefore corrosion ...

In addition, I am not sure that the rainwater is neutral, see the problems of acid rain (H20 + C02).
I have a friend who had this corrosion problem with galvanized iron pipes. and copper, with drinking water (bad electrolyte, however).

My emptying of the sensors is done when the inlet temperature is no longer at 3 ° (adjustable) above the return temperature, if the temperature above. at 90 ° (adjustable), if T ° tank = 85 ° (adjustable), there is also a protection system against ice formation with a higher and adjustable start-up T ° (normally it is T ° sensor exceeds that of the return by 13 °).

JC

[Willaupuis]

ultra gross scheme but good if it can help.

A: stainless steel water reserve, higher than the engine and the boiler
B: boiler
C: engine lower than the water reserve and halfway up the boiler
D: two solar panels
E: opening allowing air to pass through the reserve

for purging it is simple the engine stops, the air entering by "E" in the reserve the panels is emptied (the engine is always under water like the boiler obviously stopped and in operation)

there is a valve to fill and bleed the system at the lowest point between the boiler and the engine not shown.

the boiler, engine was connected together in the past with a copper installation but for central heating ,,, so I did not see too much the problem at the time of the transfer of use

[loop]

Bonjour,

Dedeleco wrote

UV antifreeze, may have chemically transformed and deposited

There is no direct exposure of the heat transfer liquid to UV in a solar circuit.
On the other hand, stagnation of the sensors with very high temperature rise can cause degradation of the additives.

Christophe wrote

I think that an oxygen source is much more harmful (by the way, how is your emptying done?)

Agree with this explanation.
Venting the reserve allows the air, and therefore the ambient oxygen, to "enter" into the circuit.
In addition, there is mixing in a self-draining system.

As a solution I offer what is found in some auto-installer on the Apper site:

"closed loop self-draining system"

A+