# solar tube temperatures



## tick tock (18 Mar 2009)

i have 40 tubes and yesterday my 300l tank was 58 C....i live in the west of ireland.i will post my temps from time to time if anybody cares just to let those who are still thinking about solar to go for it....


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## ninsaga (18 Mar 2009)

Yep - good idea - what is the orientation & who supplied/what make would also be useful info.


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## tick tock (18 Mar 2009)

well i have my panels facing south as normal and my panels are 24 metres from my tank which is a long way but i imagine how much hotter the water would get if they were closer.i got them from ecologics and a smart local plumber installed them..
last night my little girl had a bath (swim)and this morning there was 2 showers very hot showers and all that from yesterdays sun.
i have the panels since may 08 but yesterday matched one of the good days last august...


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## DavyJones (18 Mar 2009)

Interesting stuff.

So since May 08 how many cylinders of useable hot water have you got from them?


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## tick tock (18 Mar 2009)

hmmm well last 2 weeks of may first week of june were good all of july was good august maybe 2 weeks september october november december but the water was never below 15 C in those months...i remember a couple of days in december getting 34 C....i intend to track it it more this year now that i am settled into house which is highly insulated.22 c in house yesterday and kept it untill this morning .turned of boiler yesterday.


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## tick tock (18 Mar 2009)

just checked temp now...52 C in the tank. it is very sunny here all day today


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## tick tock (19 Mar 2009)

55 C at the moment in the tank and very sunny all day. the house was 23 C last night and 22 C this morning that would be passive solar energy i think.... the house is 3500 sq ft.


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## TripMeUp (20 Mar 2009)

Hey Tick Tock

this is very interesting feedback!!
What kind of heating have you (Rads or UFH) and how do you heat them (Oil, gas, geo etc??)

Thanks


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## tick tock (20 Mar 2009)

i have under floor heating every where . i use a condensing oil boiler which has being turned of since tuesday night.. actually the house has been warmer acheiving 23 C from passive solar since then. i have all stats in house set at 20 C while boiler ir running.im at work at the moment and my wife is fed up with me calling to check the tank temps...but ill call her again now....


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## tick tock (20 Mar 2009)

i also have heat recovery ventilation....so no windows open letting out my heat but fresh air all the time.


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## tick tock (20 Mar 2009)

got her... 22 C in house now..again a sunny day.the tank is 53 c...


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## TripMeUp (20 Mar 2009)

Hey Tick Tock,

thanks for the update...currently building  a similar size house myself and am installing UFH downstairs and Rads upstairs with oil condensing boiler..will have Solar tubes on south facing roof and am also installing HRV, so this all sounds positive to me....!!

Are you saying (and I know it has been exceptionally warm for last few days) that you have not had your UFH turned on since Tuesday..?? what about the evenings/night when it has been cooler?

thanks for the feedback!!


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## tick tock (21 Mar 2009)

that is correct...no heating turned on since tuesday..last night at 10pm the house was 22 C this morning it was 20.5 C. also this morning i realised 2 rooms upstairs at back of house were 18 C but the doors to those rooms were closed.
i thought when i was getting the HRV that it would move heat around the house but i dont think it does giving that those rooms at the back (north facing) are indeed cooler.
i forgot to check tank temp this morning but as normal the shower was hot.
another sunny day here in the west and another day without the boiler on.
i am thinking of replacing my 300L tank with a buffer tank 650L instead and what this does is it will run the UFH from the solar tubes.now i know it will be very efficient during the summer when you dont need it but there are lots of sunny days through out the year to make it worth while doing it.
by the way i am not into pay back times.....


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## tick tock (23 Mar 2009)

[hi
my plumber was on a daily rate of €200. but he also did my woodwork.this guy is exceptional.so i really dont know what i payed him.he also supplied at cost all the UFH stuff from the uk..oh i remember it was 2800E for all the stuff needed for UFH.very cheap.
i have all my electrics telephone tank wiring satelite all in a shed at back of house .this makes adding new things very easy.so i can do the buffer tank.


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## tick tock (4 Apr 2009)

62 C yesterday.....i had hot water courtesy of the sun for 3 days this week.. this is the hottest ever. it just shows how wet and dark last summer was..
yesterday was very sunny the other days not so but enough for 40 to 48 C....


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## jashar99 (10 Apr 2009)

Hi, i am in mayo, wonder if you could PM me the contact/address for your plumber, i'm thinking of installing the Connaught Gold SOlar water heating system
Regards
jashar99


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## tick tock (14 Apr 2009)

63 C in tank yesterday...turned of boiler yesterday untill weather changes again.


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## MLM1 (19 Apr 2009)

*Solar temperatures*

Great to hear peoples experiences with solar panels, I have a great interest in all things to do with green energy, I imported two complete solar panel systems from China[ most of the solar panels around are made in the far east] 1 with 300 litre twin coil cylinder for my own use and 1 with a 500 litre twin coil cylinder for a larger house with underfloor heating, both came with pump stations and system controllers, after reading the temperatures from tick tock I went and checked mine at just before 8 pm this evening the temp at solar panel was still at 46 degrees and 42 in the middle of the cylinder, I would just like to say a word of warning its very important to make sure the cylinder is correctly sized for the amount panels and of good quality, it might also be good practise to have a heat dump to releave excess heat to in the event we get a prolonged hot summer, I have a radiator on mine,I am also at the moment working on simple heat exchanger system that can be inserted into an existing cylinder in the place of the emersion heater it will also be run completly from the solar energy using a PV panel, 12 volt controller and a 12 volt pump, I have all the parts sourced apart from the PV panel I will be testing soon and will post again with some results if anyone is interested.
PS i also have wind turbine if anyone wants to chat.
info@powerm2.com
MLM1


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## tick tock (24 Apr 2009)

for the last week i have set my boiler to come on at 7:30am to 8am and i have only one zone in the hallway calling for heat at 20 C ..
the solar panels are keeping the water hot during the day...saving loads of oil.
temps in tank varying between 32 C to 51 C for the past week.


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## cunninghams (6 May 2009)

Hi Tick Tock. Unfortunately, I have had a horror story compared with you. 2 years ago my plumber installed 30 evacuated tubes on my south facing garage (brand of tubes are the German make "Viesmann" Actual name of tubes are "Vitisol 200"). The plumber installed a 300 litre highly insulated Stainless steel cylinder which has a large surface area solar coil. Like yourself the distance between the cylinder and the panels is about 20 metres but I have not been getting anything like the temps you have got for example the best panel reading I got last Saturday on the controller (Vitisolic 100 is the name of controller) when it was bright and sunny all day was 42 degrees which corresponded to a max of 32-34 degrees in the cylinder. Have you opr anyone else any thoughts? There is no issue with air being in the system and there is definitely enough glycol. Maybe you could PM me your plumbers name??


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## cunninghams (6 May 2009)

MLM1, perhaps you may be able to offer me some help??


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## tick tock (6 May 2009)

i think for a 300L tank the minimum amount of tubes is 40..... i want to get an extra 10 tubes to make mine 50..
sounds to me thats all you need .those are not bad temps you are getting and the 10 tubes would make a difference...


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## cunninghams (6 May 2009)

thanks tick tock. But the thing is thats as good as its been getting all year 32-35 in the cylinder. So do you think I would get 65 degrees with another 10-20 tubes?? My system must have been sized incorrectly so


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## bamboozle (7 May 2009)

we've 60 tubes facing west/north-west and we're getting average temperatures of around 55-65 degrees by sunset.
Heating has not been on in weeks!


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## tick tock (8 May 2009)

yes i think you should get 20 more...and yes you were undersized...but im no expert. i believe it is easy to add on extra tubes..go for it


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## gary71 (10 May 2009)

cunninghams said:


> thanks tick tock. But the thing is thats as good as its been getting all year 32-35 in the cylinder. So do you think I would get 65 degrees with another 10-20 tubes?? My system must have been sized incorrectly so


 
From my understanding of solar(from a solar course i did last year and talking to manufactures), a panel has a maximum output which can be achieved when the sun is at it's hottest, the cylinder coil rating shouldn't be smaller than the combined panels output, so you can have as many panels as the cylinder coil can take, you want the cylinder to absorb the heat and the solar pump to keep running, the solar panel should not to get so hot that it shuts down, i would contact the suppliers http://www.precisionheating.ie/ who supply all things Viessman and ask them to confirm panels are the correct size for your cylinder and if so see if they have a engineer to advise you on the best setup, setting for your system and if it's fitted properly, Gary
(No connection with Viessman)


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## purrfect (12 May 2009)

some excellent stuff here. I've been planning on switching to a thermal store and tubes for a while. Is nice to get some real world stats.

I'm thinking of about 40-50 tubes (to start with) south westerly facing east coast location, with a 270 litre thermal store, with less than 4 meters between tank and tubes. I'm thinking thermal store rather than twin coil hot water tank, as I can harness the solar better, plus other sources too, eg wood burning stove, PV  panels, and standard boilers. I can also run rads and underfloor as well as mains pressure (potable too) hot water, quite something these thermal stores!  www.heatweb.com has some fantastic tools and design tips. 

Anyone using a thermal store with tubes and boiler to heat a house (3 bed smallish house)? whats it like? do you have to rely on boiler much? how long does your tank stay hot? how many degrees an hour drop? ie. If its sunny, will there be enough energy the next morning to have a bath/warm the house? any figures on temp drop over time (with no output load) would be appreicated if anyone has them (think heatwebs stores have about 50mm insulation), as the mornings are usually the main time for hot water consumption and heating for my house.


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## RVR (12 May 2009)

> see if they have a engineer to advise you on the best setup


Have to agree with what gary said above.  It's hard to give proper advice based on "number of tubes".  

E.g.:

Some collectors have a reflector which means they need less tubes
Some collectors have larger diameter tubes
Some have smaller  
Optical efficiency and zero loss coefficients also determine the output of the collector (e.g. some collectors are good at collecting and retaining energy, others are poor)
Thermal store size also affects system efficiency

The only way to get you system sized properly is to talk to your supplier and make sure they know what they are doing - If you can talk to their engineer and ask them why they sized your system the way they did.

Advice based on "Number of tubes" is not always a good sign!!!

Cheers

Des

(PS - if you are interested have a look at http://www.estif.org/solarkeymark/collector-theory.php - it gives a good overview of the solar efficiency equation!)


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## Slim (12 May 2009)

This is a fascinating thread which only serves to pique my interest and underline the depth of my ignorance. Can anyone point me towards a basic book/website to commence my education on this subject?

Slim


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## tick tock (12 May 2009)

if i was to do it all again i would have 60 X 70mm tubes and a buffer tank....my tubes now are 40mm.
i didnt know any different last year but i believe 70mm are the way to go.


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## villa 1 (12 May 2009)

The SEI website is usefull for information on solar water heating and has many relative links.
Coming from a background in lecturing in the plumbing/heating/solar industry and being a time served plumber I would recommend
 1. Insulating your home to it's limits
 2. Install solar panels/tubes to heat domestic hot water alone (tubes are slightly more efficient, panels look better)
 3. Install gas/oil fired condensing boiler to heat radiators
If you ask most plumbing contrators they will recommend solar for hot water and condensing boilers for space heating... end of story!!

Solar heated buffer tanks are suitable for larger installations or one off builds. These cylinders/tanks are huge when fitted into a three bed semi and are very heavy 1 litre = 1 kilo
Radiators used on solar/buffer need to have larger surface areas and can be quite expensive. I would not recommend using standard off the shelf convetor radiators on a solar/buffer system.


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## tick tock (13 May 2009)

so a buffer tank /eco tank is good with UFH???????????


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## villa 1 (13 May 2009)

in my opinion yes. much better to run ufh from a buffer than to run radiators from same. provided each individual underfloor heated area/room has it's own independant control.


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## tick tock (13 May 2009)

under floor heating (UFH) runs at i think 45c and that temperature is achievable even in december with the solar tubes so if you are going to do solar do it with a buffer tank and good big tubes!!!!!


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## Abbica (19 May 2009)

Hi, can I ask, before I ring our heating engineer, when I go home in the evening, this is for the last few weeks, (_we have the usual evacuated tube, south facing panels_), when I turn on the tap, it is cold but not really cold but you couldn't use it for anything, we always have to turn on our condensing boiler to heat it up, we have never been able to use it as is, I find the whole thing useless or is there a problem? Do you think I should ring the engineer? My husband says it has been very cloudy but it isn't just sun, it is light??


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## RVR (19 May 2009)

Abbica said:


> Hi, can I ask, before I ring our heating engineer, when I go home in the evening, this is for the last few weeks, (_we have the usual evacuated tube, south facing panels_), when I turn on the tap, it is cold but not really cold but you couldn't use it for anything, we always have to turn on our condensing boiler to heat it up, we have never been able to use it as is, I find the whole thing useless or is there a problem? Do you think I should ring the engineer? My husband says it has been very cloudy but it isn't just sun, it is light??



Ring your engineer - sounds like there's something seriously wrong!

The solar should be able to bring your tank should be up at near or above 60 degrees every day for the rest of the summer.  The panels don't need direct sunlight as they still collect the diffuse radiation that comes through the clouds.


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## Abbica (19 May 2009)

Thanks for that, I will ring him today. Clarity at last.


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## galwaytt (19 May 2009)

9th May, 16:57 hours, 3 south facing flat panels, (7.5m2 total), 1000l buffer tank. Water temp off the panels : 78.7deg C, water temp in the tank: too hot to touch !


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## tick tock (19 May 2009)

wow.....do you have UFH????is your buffer tank connected to it????


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## Macs (19 May 2009)

Reading through the threads most people appear to opt for solar tubes rather than flat panels.  

Does anybody know how more efficient tubes are over panels.  I assume this is why the choice of tubes as they are more obtrusive and expensive that the panels.

Another query how realistic is it to use solar panels for UFH say for a 3500ft house


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## villa 1 (20 May 2009)

tubes are approx. 10% more efficient than flat panels. In-roof Flat panels are far better looking than tubes. In regard to heating your house solely with panels, rain is not solar.
We have to be realistic here in this country. We get a lot of rain and even though our sunlight, when it happens, will heat hot water quite successsfully, I would definitely recommend that you put in a supplementary heating boiler to look after your heating needs. You can only fit so many panels(SEI website-regulations) on a roof.
If you fit a large buffer tank with your panels you will have to plan for fiiting it in a plant room/garage which may be too far away from your roof panels. Large buffer tanks fitted in doors should be apropriately supported
1 litre water weighs 1kg eg, 1000litre buffer tank weighs at least 1000kg


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## tick tock (20 May 2009)

yesterday at 6pm..65 at tubes and 61 in tank
today at 2pm...61 at tubes and 49 in tank.


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## tick tock (21 May 2009)

today @2pm 61C at tubes and 51C in tank


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## galwaytt (21 May 2009)

tick tock said:


> wow.....do you have UFH????is your buffer tank connected to it????


 
You bet.  



Macs said:


> Reading through the threads most people appear to opt for solar tubes rather than flat panels.
> 
> Does anybody know how more efficient tubes are over panels. I assume this is why the choice of tubes as they are more obtrusive and expensive that the panels.
> 
> Another query how realistic is it to use solar panels for UFH say for a 3500ft house


 
My house UFH on 3 floors + garage, 316m2 iirc.   Solar only contributes to the buffer, mine's backed up by a Vaillant gas boiler.


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## tick tock (21 May 2009)

does your buffer feed into the UFH??????


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## galwaytt (22 May 2009)

tick tock said:


> does your buffer feed into the UFH??????


 
yep, it's the only source of hw for the UFH.  Buffer is topped up by boiler if required.


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## tick tock (22 May 2009)

thats great then.......


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## Charlie 07 (11 Oct 2009)

tick tock how're the solar stats these days with the ufh?? 
Thinking of installing panels to garage roof and hooking up to ufh to help with heating costs.


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## allthedoyles (11 Oct 2009)

Can I ask , what is the extra electricity costs associated with UFL and solar panels .


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## tick tock (12 Oct 2009)

i gave up tracking the temps...we havent had our heating on since may.i suppose we will turn on heat by the end of this month. July and August were bad for keeping tank hot..


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## tick tock (12 Oct 2009)

there is a misunderstanding....my panels heat my water tank only..but someday i will get more tubes and bigger tank to do UFH..


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## Charlie 07 (12 Oct 2009)

thanks tick tock.perhaps you could post temps the odd day when you do turn on the heating...


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## tick tock (13 Oct 2009)

i can do that...


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## quentingargan (23 Oct 2009)

Macs said:


> Reading through the threads most people appear to opt for solar tubes rather than flat panels.
> 
> Does anybody know how more efficient tubes are over panels.  I assume this is why the choice of tubes as they are more obtrusive and expensive that the panels.
> 
> Another query how realistic is it to use solar panels for UFH say for a 3500ft house



Tubes and flatplates are roughly the same output over a whole year. The difference tends to be that tubes work slightly better in overcast or cold conditions, whereas the flatplates work better on sunny hot days. Overall, tubes extend the season quitre a bit by working better in Spring and Autumn. Both systems give more than you could possibly use during good summer days anyhow. 

But tubes will lose their vacuum after about 20 years. If you use the flask type, replacement flasks are only about €5 each, but if you use the tube type (which is a single layer of glass with a small flatplate in the middle of the tube) then replacement tubes are a lot more expensive. 

I agree with the previous poster about space heating. Forget it. Doesn't work in Ireland. It was developed in countries like Austria which have more than double our light intensity in December and January. Large arrays of panels would have to have their surplus heat dumped in summer time. 

If you have a 1,500L buffer tank already for something like a log gassifying stove, then you will get some benefit from having a few extra panels, but I wouldn't lash out on the tank just to use solar for space heating.


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