wellinever

Can anyone give good advice on what to use to cover the glass panels during summer when no water will be used at all.
It was suggested to use the black plastic mesh, shading material. So as a trial I put some over one of the panels this morning.
After only an hour the glass on the covered panel was too hot to touch. The uncovered one was at hand temperature.
I appreciate that the mesh is black and absorbs heat, so this does not seem like a good idea, unless its not about the temeperature of the glass.
But it is only February and not August.

macliam

Shading the panels will only work if the material is not in contact with the panel - anything dark will absorb sunlight and heat up (a black bottle in the sun will heat water in no time.)

You need something reflective like that material they use for car windscreen covers - or I've seen insulation boards that are expanded polystyrence with an aluminium foil facing ..... just can't remember where! Otherwise a sheet of "esferovite" with aluminium foil bonded to it might do the trick. The problem then will be securing it against wind damage.

Either way, you will still need to ensure your system can dump excess hot water in case of failure.....

wellinever

It was the installer that told me to buy the shading mesh, but not how to fix it. Clearly no good just laying t on the glass.
Also bought a piece of carpet underfelt about 3mm thick. Thought that might do the trick, but just the same as the mesh.
Cant understand why no purpose made product as all these panels are more or less the same size.
As you say the expanded polystyrene boards should stop heat and sunlight going through but its keeping them in place if there was a gust of wind which there normally is here in the summer around noon and then around 3pm.
Yes there is a safety valve which oddly (to me at least) is in the line of the cold water in pipe. WHat they have done is to allow expansion of the hot water to remove excess pressure by connecting a hot water outlet to a T piece which is also connected to the cold fill, so what I was told is that any water that does want to escape will actually be cool and not at 90 degrees......if anyone knows if this is normal plse let me know. I can only guess that as long as the pressure can go somewhere to atmosphere it doesny matter how it gets there in th event of over pressurising.

Pulaski

I am not sure exactly what a Portuguese solar panel would look like, and how accessible it it, but based on what I imagine they look like and assuming they are accessible without climbing up a ladder or across a steep roof, I would envisage a three layer cover - thin plywood for rigidity (5mm?) polystyrene for insulation, and a foil reflective top layer, to keep the heat of the sun out as far as possible .... so pretty much what Macliam suggested. Then I would plan to hold the cover in place with either https://www.amazon.com/Stalwart-12-Bungee-Cords-Pack/dp/B01MTGFSIA or with 25mm https://www.amazon.com/Ohuhu-8-Pack-Ratchet-Logistic-Straps/dp/B07S9153C4/ref=sr_1_17?crid=1CCDRG6LCG81L&keywords=cargo+ratchet+straps&qid=1582134562&s=hi&sprefix=cargo+ratchet+str%2Ctools%2C163&sr=1-17.

macliam

The addition of the ply - or even stiff cardboard - would certanly help - as would a frame to provide stiffness and anchor points, so a foil/board/polystyrene panel with a light wood/metal frame would be your man - anyone with a minimum DIY skill should find that doable. The issue may be getting to the panels to fit them.....

I know we get some really strong gusts of wind "out of nowhere" in the Alentejo, hence my comment - and the other problem is that the strong sunlight will destroy any non-stabilised plastic in next to no time (stabilied plastic takes a bit longer - when I bought, 7 years ago, there was a Keter shed outside. Now you can push your finger through the walls!) So, I don't think plastic framing would last long and the polystyrene will need to be kepy out of direct sun.

I'm no expert on the plumbing required - but given the "advice" about shading, I think I'd get that setup checked out by someone in the know. The last thing you want is a blown collector. I've got a fairly low opinion of installers in Portugal - I'm sure there are good ones, but many seem to wing it and just whack it in (my personal bugbear is panel inclination, which is rarely suitable for the geographic location/usage anticipated). By the time your panel blows, the installer has pocketed his money and moved on....

I also didn't ask if you had pumped discrete panels or the gravity-feed cylinder/panel setup. The latter may also have issues of its own......

fergus

From what you have said I think you have a two panel system. If that is the case, I think what you may be experiencing with one panel covered and one uncovered could be caused by the hot water circulating? I am assuming the water, which is fed by gravity, goes through each panel before returning to the storage tank. If that is correct, then it would explain why you have heat in both panels, even though one is covered. Easy to test by covering both panels one night and testing again around noon next day (assuming it is sunny). If you want to cover the panels just for the summer, then you could try cardboard. This needs to be the sort that you would get a fridge delivered in, so quite thick. This has surprisingly good insulating qualities. I have done this and it works. However, it will inevitably rot. I have also thought about using a suitably sized strip of artificial grass. This is as UV resistant as you can get and it should not get hot. Fixing it on is another thing. Most cheap twine, rope, etc., will degrade in the sun very quickly. Decathlon sell some rope that may be more UV resistant, especially rope intended for climbing. Alternatively, a boat shop will sell rope that will last a good few years. It won't be cheap but you won't need to much. Rope from Chinese shops is cheap but unlikely to last. I know from experience that their tarpaulins will disintegrate or be in shreds within a few weeks. Hope this helps.

wellinever

Yes fergus you are correct. Its a 2 panel (2m x 1m each) and is a normal thermosiphon type so no pump. And yes I think the water goes from one panel to the next.
(in fact even there is condensation in one of the panels every morning, but not the other. The installer says this is normal during the winter months.)
I must admit that my concern is this is a bungalow and the solar is on a flat roof, so easily accessible. The roof is felt covered and painted, all brand new but nevertheless I am sure would not appreciate boilng hot water spewed over it. For that reason I wanted to put a tube from the safety valve to one of the rain water pipes coming off the roof, and that is when the installer said that any water being pressurised would mix with the cold feed and so not be so hot and would not be a problem, and that is whey when asked about turning all water off to the property during my absence, he said that I must not do that. The mains must be left on at all times. (pic attached of the safety valve in line, no place to attach a tube to)
But like you I am very cautious about what I am being told by the building profession in Portugal, as you say it ain`t their problem if it all goes wrong, although in fairness the installer is a Leroy recommended installer and was very efficient installing the system. But on he other side it was him that said I need to use the shading mesh, which clearly is a recipe for disaster, and clearly any mishap would not be the installers or Leroy fault.
The most annoying factor is that I would never have considered installing Solar water as I knew this issue would crop up, and with only needing one shower a day the esquenatdor that I had installed would supply that all year on one gas bottle and give immediate hot water. But the new building regs and Energy Certificate state that a certain proportion of a new house must come from renewables and that does not include PV panels, so can either be pellet fire or solar, and if solar for a 3 bed house must be 300litre 2 panel jobby..If not installed then you cannot get an energy certificate at all, and therefore no Habitation License. I am not surprised there is a water shortage, as this system takes 40 seconds of full running water to get it hot at the showers, all down the drain With the esquentador it was 10 seconds and hot. Something fundamentaly wrong here. But I suspect IVA collection is the reason. Also OK now but during Dec and January after 3 days without sun water was only warm so esquenatdor was being used !!!
But back to the panel covering. I must admit to looking for a annual cheap, easy solution and I have no where to store large fixed panels when not needed other than tethering them on the roof, which is not ideal.
Oddly I have some 2m square thick packing cardboard from some furniture that I have not got rid of yet so will get that on the roof (if I can lift it up the ladder) and see how that goes on for a day. Probably be cloudy now for days !!!!
Will let you know how it goes. If it works OK, I will also get some plastic sheeting as the cardboard will disintegrate if it rains.

RichardHenshall

I'm not entirely sure what that device you're concentrating on actually is but I am assuming it's some sort of expansion control valve:

However I do not see evidence of a conventional pressure/temperature relief valve in the system, though maybe it is fitted to the primary syphonic circuit at the other end (which is otherwise a closed loop).

If your device is designed to release water regularly, it would seem to me that, as a minimum, it should discharge beside or below the pipe run to avoid wetting the pipes and insulation. I'm also surprised it seems to have exposed moving parts and no apparent means for connecting to a drain.

dingg

It's a psv fitted on the inlet, not ideal but will work, if the tank gets too hot and overpressure occurs it'll relieve the water from the vent on the side, you can just see the spring through the hole.
Your installer is correct it will relieve water from the cold side.

It may have an adjustment screw on the top, and you might be able to have it lift earlier.

wellinever

Thanks for both replies. Yes there is a spring but it's not adjustable from the top or anywhere else I can see.
the original diagrams do show a pressure relief valve at the top of the tank at the other end, I am guessing that would release hot water as it's direct from the hot tank.
Another retailer told me today that to cover just one panel even as a test would not work as they must both be covered.. So now back to drawing board with some 30mm Blue insulation boards, see what happens with it all covered .with them, if the sun is out

fergus

If it is like a solarhart there will be a relief valve on the tank and it will blow hot water out. This should be threaded so that you can fix a hose. That might be simpler.

wellinever

Hi all
Yes at the other end of the tank is a valve I have attached a pic of it in situ.
This is what the diagram shows as a Localizacao de seguranca (1,5bar for 300 litros) and is clearly marked in English as a closed circuit safety valve
Although I must admit that the installation manual diagram does not look the same as the tank fitted.
Will attach the blue insulation boards tomorrow as too late to mess about any more and in need of a beer.

Score76

I use a piece of sturdy, white canvas for this. Sew a hem round all sides so it's just the right size then fit marine steel eyelets in each corner. I then use small bungey cords in each corner to secure against the wind.

My system is slightly different, I have 2 x 200L systems with one feeding the other. I cover the first in summer as it makes too much hot water when there's only the two of us here and otherwise vents 90°C water.

fergus

Wow. I always knew a proper canvas cover, like a boat cover would be just right. Could you make one for me? Sounds silly but I wouldn't know where to start but I do know this is the ultimate solution.

Pulaski

That may not actually be a barrier to direct sunlight - I'd insert a piece of thin board of some sort, with foil pasted on one side, or foil-faced insulation foam board (something light weight), inside the canvas over the solar panel.