[championc]

During Feb and March, I struggled to reach 40 deg. However, if I was only heating half the water on these occasions then I'd have a greater chance of water exceeding 45 deg after even half a days sunshine.

No heat dump necessary, my system is a Kingspan which autovents. I have the max temp set to 90 deg so it's only one or maybe two days per year that it will ever get up to this. You would need about 3 days of perfect sunshine in a row to hit this

[freddyuk]

It is important to get the correct sized collector for the size of the cylinder lots of tepid water will result.
You say your system auto vents? Please explain.
If there is an auto vent on the system you will lose all your fluid if it gets hot enough! A bypass cools the system without any drama, damage or refilling.

[championc]

Originally Posted by freddyuk

It is important to get the correct sized collector for the size of the cylinder lots of tepid water will result.

Indeed, I'm glad I never got 30 tubes with 300l store or you'd need nearly a week of sunshine I reckon to get over 60 deg - so long as to water is not heated by other means like an immersion or CH

Originally Posted by freddyuk

You say your system auto vents? Please explain.

I understand that there is something special about the manifold / tube nozzles of the Kingspan tubes. There's no loss of fluid

[freddyuk]

Rule of thumb is quoted as 7.5 litres per tube (1.8m x 58mm tubes) although some reckon 5 per tube is better as over sizing gives you a longer "season" so yours is not over sized.
The essential thing is to have a way to cool the system down in the event of over heating which will happen in Summer and a basic bypass achieves this very effectively although it relies on an electronic valve to operate. Thermomax rely on an integrated spring valve device to retain steam in the system which is great providing it lasts 20 -30 years. In the event it fails the system will evacuate into the safety container and need recharging. I am not sure there is way of servicing this device so if it is required after some years of inactivity you just hope it works and is not corroded up. I can check my valve manually to ensure it works but for most customers this would not be an option unless they are keen DIY'rs. Keep it simple!!
Let us know how the new system performs.

[Mothman]

Originally Posted by freddyuk

It is important to get the correct sized collector for the size of the cylinder lots of tepid water will result.

I don't subscribe to this thinking. Its important that supply meets the outgoings, usage plus loses. Once this happens, then generally the size of tank is not a major concern once the tank temperature is up. Though if it is poorly insulated then the losses are an issue and its harder to get through cloudy periods without backup and to keep tank temp up.

I used to have 300l tank with my 6 sq m flat plates. My tank failed and I replaced it with a 500l store. Once I dealt with the tank loses (it was badly insulated) I am really thrilled with how its performing and it seems to be performing much better than my previous arrangement. The solar coil in this store is much larger than the previous tank and I guess I'm harvesting more energy. For past 4 weeks, I haven't needed any backup. Have had panels for 14 years and have always used backup in early April. I think my new store is part of the reason, the other is the sunny weather, well above average though not as sunny as last year or 2007.

[quentingargan]

Yes - OK if the tank is stone cold and you get a half-decent day, you will end up with 500L of lukewarm water that day, but sooner or later the heat will accumulate, provided you aren't losing it through poor insulation.

By the way, there is a myriad of "solar" cylinders that have two coils, but the bottom one for solar is not a high surface area coil. I have seen 300L ones with coils that had a surface area less than 0.7M2. Ideally the coil should have a surface area of at least 0.25 sqM per sqM of solar panel.

[championc]

Originally Posted by freddyuk

Let us know how the new system performs.

There was a setting missing on the controller which I have had clarified this morning with Steca. The threshold for the upper section was set to 60 deg C but over the weekend, it kept dumping the heat into the bottom section even though the top was at 51 deg C. It needs a "Quick Charge" function to be turned ON.

So hopefully, by the weekend, I can look forward to +50 deg C hot water in the top section for a large portion of the year and the same in the bottom section full during the summer months.

[championc]

I had a call with the Steca guy in Germany today who basically said that the system balances between top loading and boosting the whole system in the cleverest way, getting the best use from the energy being harvested (at least I think that's what he was getting at)

I have reviewed my data from today and the bottom seems to be getting topped up as it goes along, staying within about 8 deg of the top temperature which is not quite what I had hoped for.

I'll reserve judgement until I have lots more data but it certainly does not seem possible, using the controller, to load the top up to a certain level and then go to the bottom.

[johnfoyvision]

could you pm the company me too please.....

[championc]

My Data is now online 24 x 7 x 365

See https://cosm.com/feeds/71436

[RTT]

Originally Posted by championc

My Data is now online 24 x 7 x 365

See https://cosm.com/feeds/71436

Impressive! Are they the temperatures you are achieving at the moment without any other source of heat other than solar?

[championc]

Originally Posted by RTT

Impressive! Are they the temperatures you are achieving at the moment without any other source of heat other than solar?

Absolutely, no other source

I have a Combi boiler if the solar comes up short during the year.

[Mad_Lad]

It costs me 30 Euro's or so to heat the water with the immersion over the 5 months a year we don't need the heat.

In winter the heating heats the water costing hardly anything extra.

That's a very very very long time to pay back a 3k + solar thermal system ?

I would have thought Solar P.V would have been a better option for people because when your solar is generating it can continually export to the grid when you don't need it making you money. Or you buy it back at half the price during the night.

[freddyuk]

Quick calculation says that is only using immersion for half an hour once a day for 150 days? (excluding standing charge and VAT)
If you use hot water for baths/showers, washing up/dishwasher, washing machine it is not a huge amount of hot water. If you have a cold fill washing machine then you not using that but if you have hot fill machines the solar goes straight in so can be a benefit.
My temp in West Cork now are 50c on the roof and 45c in the buffer. It is a nasty day for solar! 39 tubes into 200 litre buffer. It may have dumped some heat into the DHW cylinder already - but unlikely today.

[Mad_Lad]

Originally Posted by freddyuk

Quick calculation says that is only using immersion for half an hour once a day for 150 days? (excluding standing charge and VAT)
If you use hot water for baths/showers, washing up/dishwasher, washing machine it is not a huge amount of hot water. If you have a cold fill washing machine then you not using that but if you have hot fill machines the solar goes straight in so can be a benefit.
My temp in West Cork now are 50c on the roof and 45c in the buffer. It is a nasty day for solar! 39 tubes into 200 litre buffer. It may have dumped some heat into the DHW cylinder already - but unlikely today.

Including vat excluding standing charge which I and solar Thermal users have to pay anyway.

If you use loads of hot water maybe I can see a few year payback, but not for us as we conserve and we waste as little as possible.

Our yearly electric bill is around 550 per year in total. including a cold fill washing machine and to be honest you would want your washing machine close to the hot water cylinder to benefit as it would be nearly full by the time it fills up, unless you run the tap first.

We don't have a dish washer and a kettle of water does the job nicely.

I'd be more willing to install a night saver meter if I used a lot of leccy over a solar thermal.

If I could have solar thermal for my heating it might be more worth my while, but I would think that would have to be pretty large and expensive and then in winter daylight hours are short.