Score76

When the cover is on, the collector only gets mildly warm. Any of the marine fabric companies around the various marinas here will be able to make these. Happy to supply photos if that helps.

wellinever

Yes I noticed that the panel I covered in my `test` got really too hot to touch, while the uncovered one remained hand hot even at midday.
Another retailer told me yesterday that they must both be covered or one feeds the other (must admit to not really understanding what he was trying to say) but gonna cver both today and see what happens. Would appreciate any pic you can take of the panels you have and it in situ if possible. Pic worth a thousand words in this case.

wellinever

Bit of a Heath Robinson effort this morning using blue insulation and gaffer tape. Very windy at moment so havent had time to cover the lot with some garden mesh just to stop it all flying away if it comes loose. Bits of panels still exposed but cant think this will be an issue. Will see how long it takes for the water to go cold.
When I left it at 12.30 the bits of panel I can touch are very cool. If it works it will be good for me as I can store the panels under the system when not needed.

wellinever

Now all roped down (I hope). Checked the small areas of panel I can touch and really very cool, but cant feel under the insulation boards.
I took the temp of the water yesterday about this time and at the sink it was 54Deg C.
I put these panels on this morning so I doubt much sun on them today, but just checked temp at 3pm and the water at he sink is about 52, so will use more water during evening and tomorrow morning, but as there was 300 litrs in the tank in the first place I guess it will take a few days to notice what the stable covered temp is in the tank.

RichardHenshall

The mixing valve should maintain a relatively constant tap temperature until the tank is below the set temperature. Remember to switch off any electric backup or you'll get an unpleasant surprise after a summer without solar heating!

wellinever

Just a thought....the bloke I spoke with yesterday (a retailer of solar systems) said that that temp is way too high and I should turn the mixer valve down. It is currently (as installed) at 7 on the scale. The dial goes to 7 then MAX. I must admit I have no need for water at this temperature. The showers are thermostatic and set at 38. Kitchen I dont really care.
I realise that I use less hot water and therefore put less cold back in, but use more cold getting water down to hand temp in kitchen and showers.
The gas boiler is set at 48 F ( so the boiler does not fire when the water reaching it from the solar exceeds 48, which of course it does at the moment , and so shuts down.
But I am guessing that I can put the boiler at 40deg, turn down the mixer valve on the solar so it comes out at 40 ish and adjust to keep boiler from firing
Again anybody with any experience .

wellinever

hi richard
No worries on that score. I had already installed a solar sensing gas boiler for hot water before the Energy engineer told me I must install solar to get an energy certificate at all, and you cant get a habitation license without an engery certificate.
So fortunately I was thinking ahead for anyone else who bought the house in future with gas boiler, solar ready, and pre installed the solar.
But since I have this already in place I did not have an immersion heater rod put in the tank at all.

RichardHenshall

I don't think it makes any difference where/when you dilute it to lower the temperature as you will effectively use the same quantity of unmixed very hot water for your shower. However the cooler the unused water that is left in the pipes after your shower, the better from an efficiency perspective, so lowering it at the roof is best.

40C is OK for showering at but, personally, I'd prefer a little hotter at the kitchen tap, so 45C-ish for the mixing valve on the tank seems about right to me. Presumably when you expect to have solar hot water you can just switch off the boiler completely, rather than have it firing briefly or to add a few degrees.

wellinever

Yes now its been sunny for a few days I turned the boiler off completely and now just running solar water, so it will be interesting to see how long it lasts on my small daily usage.
Certainly the temp of the glycol has come down a lot during today so it must be doing something. Wont bother taking that down now, I go off next week so will trun boiler back on for the days when water is too cold.
When I get back I will look at a lower setting on the solar, unfortunately no temps just numbers so trial and error I guess.

RichardHenshall

Obviously your hot & cold temperatures will differ, so it's only a guide for the trial and error process.

wellinever

Erm interesting... Well as I said earlier, my valve is set at 7, but the highest temp of the water I have ever recorded is 54. So mine looks more like maybe 6, allowing for some loss on way from tank to tap. I will leave the position at 7 for consistency for the moment.
Continue today monitoring hot water temp at kitchen sink from now on with both panels 95% covered.
This morning after shower the temp is 46deg. So should continue to go lower from now on

wellinever

Update on this. Clearly the insulation panels are working.................after yesterdays shower the temp of the hot water at the kitchen sink was 46 C
NO usage of hot water since yesterdays shower. Full hot sun all day Saturday.
Just before shower this morning, Sunday, the best temperature of hot water at sink was 36 C, not hot enough for anything, certainly not for a shower.
So the water had dropped 10 C, after one day of no sun.

I cant help thinking there is something wrong with this installation. Covering the panels is the same as would happen after cloudy days, ie no sun.
Despite all of the sun over the last week (every day start to finish of each day) with only one shower a day of hot water being used for 5 mins max during all that time and there really is no hot water after only 2 days.
This just about summed up my opinion of this when it was first installed, for me at least, useless.
It shows that at best this equipment can work, but only if there is full sun, dawn to dusk.
Unless of course my system is crap, and the whole 300 litrs is not being heated up to max .
I have no immersion in the tank and so the normal auto backup is not there.

fergus

Hi again. I appreciate how frustrating this can be, especially if you suspect the fitting was not done well. I am no expert and I am sure there are other posters that know more than me. But here are a couple of things to think about before I also go back to your original concern. The solar panels, if uncovered will still heat the water on cloudy days, but it not as much as you would get on cloudless days. It is a bit like being able to get sun burnt on cloudy days. And here in the Algarve, for about 9 months of the year you get enough sunny days anyway. In any case, you have your gas boiler as back up for when you need it.
With regard to the water dropping to 36c after a couple of days there may be a couple of other things. When it was really hot you were happy to have the cold mix set to number 7 and if you have not changed it, then the same amount of cold is being mixed with less hot water, before you are measuring the temperature. Also, as you use draw off the hot water in the tank, it is being filled with cold water. So both of these would combine to deliver a quick drop in temperature as measured at a tap in the house.
Turning back to your original comments and concern about the pressure relief valve spilling scolding water onto your flat roof; you have solved the problem by not heating it when you are not there. However, this does not rule out the possibility of this happening in the summer when you are there. So you might want to rethink and see if you can't get a hose pipe to fit the relief valve. I have a solarhart and the relief valve is threaded and will therefore receive a hose pipe, with the correct fitting.
Finally, you may also need to think about legionella? Not really sure about this. But a hot water tank should have a minimum temperature set to prevent legionella. You may have already achieved this if you heat the water via the gas boiler.
Good luck.

wellinever

Hi Fergus
Yes of course I know that for every litre of water taken from the tank (and that includes the 40 seconds worth before any hot water comes through at the taps. But even then with the average shower using 8 litr /minute then with a 4 minutes shower and 40 seconds worth of start up water that would make a usage of around 40 litrs of hot water. And so yes water at (currently 18 deg of cold water replaces it in the tank) and in 2 days that would amount to 80 litrs.in a tank of 300litrs.
Remember this is only one person using any hot water at all.
So the way I see it if 2 people were having the same time in a shower that would not quite double but close, rendering the hot water too cold for shwering within a day.
I used this system over the winter, and found that when I turned off the backup boiler, the hot water also lasted 2 days, during times of no sun.
There is 4.18 m/2 of panel and I would have thought this would be sufficient, it was certainly sufficient (on paper at least) to be approved by the energy certification, but I cant help thing something is not right, or this would be hopeless for a family of 4.
Indeed I do think about legionella, but as you can see my water never goes above 54 (well at least over the last week of full sun) and yes I appreciate that this is not the height of summer, but that is irrelevantm in that the system is being used all of the time.
There are calculations regarding reduction in temp of water as cold water is added.

IMO instant electric showers as used in the UK are the answer to all of this. Yes they need 8kwH while they are on, but no hot water storage. But they are not on sale in Portugal and I cannot understand why not. Only cold fill, cheap (£45 in UK) easy to install, immediate hot water , and most important is that with the State providing more renewable electricity this is best for the planet as well. Individuals being forced to install renewable is a waste of time, especialy when 80% at least of all property has not and will never install solar water heating. But very good for IVA collection......
I will leave it all alone until I get back and then investigate why after such small use I have water at 36 deg after only 2 showers
But thanks for your input, only through exchange of ideas/thougths/knowledge can we learn.

BillBullock

An interesting discussion for us to follow and it seems to come to the sensible conclusion that I came to a long time ago when I was trying to decide the way forward on the production of hot water and electricity here in the Algarve. My house was built in 1996 and had no solar panels for hot water production. In 2003 when I bought the place, I got quotations for solar panels and decided that I would continue with instantaneous gas-fired water heaters for the 2 parts of the house (main wing where my wife and I live, and guest wing which is not in full-time use). Then the price of bottled gas shot up so I installed a hot water storage tank in the main wing which only uses the cheap-rate electricity, the cost of solar panels still being too high. We are still on this system even though electricity prices have gone up over the years. It works very well for us although an instantaneous electric water heater under the kitchen sink would be perfection.

As discussed in this thread, solar panel hot water systems have many problems and my son has experienced some of them. He has a very long run from the storage tank to the kitchen sink so gallons of cold water are wasted before the hot water arrives at the sink. This is borehole water so it's not apparently such a waste of money (it ends up back in the ground after overflowing from the septic tank) but is is very inconvenient and the tank then fills up with cold water, cooling the tank as a result. Goodness knows how much electricity is used by the borehole pump to get the water to the cisterna and then to the roof of his house. Likewise goodness knows how much electricity is used by the immersion heater in the hot water tank as that can come on at any time. My son has quite a high monthly electricity bill. Then there is the problem of scale in the hot water tank. He has replaced it once and the old tank had to be cut into smaller sections to get it down from the roof, such was the weight of the empty tank as a result of years of scale building up inside, despite an expensive water softener in the system.

My conclusion has not changed despite the cost of solar panels coming down over the years. I am sticking with the mains electricity supply on dual tariff and believe that the electricity companies are in the best position to produce electricity from solar power (as well as wind power, etc). I fully agree that the Portuguese building regulations should not be forcing people into installing solar hot water systems. As for individuals producing electricity for home consumption in this country, without a feed-back tariff like in the UK, I have also discounted this scheme as uneconomical for the present. I am not persuaded by the EDP scheme into parting with my money, nor any other argument just yet. I am ever hopeful that the price of electricity will come down once the electricity companies have finished investing in sustainable production of electricity but it may not be in my lifetime.