Solar Thermal


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Tel:     01905 821691
Mob:   07834 619080

Update April 2010: Eco-nomical has now joined forces with JWSS in becoming MDS accredited.  Eco-nomical/JWS PV installations are now eligible for the current Feed in Tariff regime, and Solar Thermal installations will be for the proposed Renewable Heat Incentive when it comes into force.

Justin has compiled his production and consumption figures into the following charts.  The previous information which we have published has been left further down the page for reference.




These charts are derived from the data tabulated below.

PV         Thermal         Usage         Usage against generation
2008 2009 2010     2008 2009 2010     2008 2009 2010     2008 2009 2010
Jan   42.99 72.08   Jan   65 49   Jan   150 147   Jan   107.01 74.92
Feb   64.29 98.00   Feb 168 83 71   Feb   116 116   Feb   51.71 18.00
Mar   178.02 229.9   Mar 240 249 215   Mar   104 102   Mar   -74.02 -127.90
Apr   219.51 314.18   Apr 300 267 330   Apr   85 70   Apr   -134.51 -244.18
May 37 330.93 452.84   May 245 247 340   May   76 61   May   -254.93 -391.84
Jun 66.9 321.54     Jun 204 240     Jun   75     Jun   -246.54  
Jul 92.6 300.64     Jul 239 222     Jul   79     Jul   -221.64  
Aug 98.4 269.04     Aug 171 201     Aug 188 65     Aug 89.6 -204.04  
Sep 84.3 233.33     Sep 181 171     Sep 134 84     Sep 49.7 -149.33  
Oct 69.1 139.71     Oct 181 91     Oct 179 103     Oct 109.9 -36.71  
Nov 27.6 86.06     Nov 52 41     Nov 167 113     Nov 139.4 26.94  
Dec 30.49 67.63     Dec 61 44     Dec 159 134     Dec 128.51 66.37  
506.39 2253.69 1167     1334 1921.00 1005     827 1184.00 496     517.11 -1069.7 -671



Justin is a solar installer local to Eco-nomical.  He and his family are  committed to a sustainable way of life, as evidenced by his remarkable 80 tube solar hot water and heating installation (is there a roof under there somewhere Justin?) and his LPG vehicle.  In addition to solar hot water  installations, he also is happy to install solar pool heating, fits woodburning and multifuel stoves, does general plumbing work and will even carry out tiling and similar if you ask him nicely enough!  He has various relevant City and Guilds qualifications as well as being qualified to install and inspect unvented hot water cylinders.   If you are looking for an installer within around 100 miles of Worcestershire either let us know and we will put you in touch, or call Justin directly on 01905 821691 or 07834 619080.  He would be happy to install an entire system, work with a householder on their own installation, commission a system, attend a breakdown, or just offer consultancy.  Also, he will deliver systems by arrangement and offer advice while on site, useful if you are worried about elements of the install!  He is a friendly chap, is proud of his competitive prices, and judging by his work he certainly knows his stuff.

Justin's installation started off with 2 Eco 58-1800-20's, a Resol RF pumping station and a BS4 controller.  Note that it is a work in progress, scroll down the page to see the latest improvements.

An interesting feature of Justin's system is that he has upgraded the installation with a very accurate monitoring system utilising a flowmeter and a Resol ES controller to allow him to determine the power output of his system.   Scoll down the page for more information about this upgrade. .


Justin writes:

"Hope you are well and business on the Solar front is going well.  Sorry for the delay as I managed to finish my Solar installation at the end of January. System has been running very well throughout February, I have pump running readings for this month at 79 hours and total KWH of 124 (able to generate this info using the 4th sensor I purchased from you guys). This is very impressive considering the weather over the month, I even manage 65 degrees for 250 Litres of water in one day!!! Total output for the month figure would have been higher but I only just installed the shower so not really using much of the hot water generated this month"  (remember that a solar collector works more efficiently the cooler the solar fluid.  If the temperature of the water in the cylinder is already high, the power output of the collector will reduce.  See here for more figures about this).

Justin continues:

"Setup as follows;
Albion 250 Litre Eco-Cylinder
2 x 20 tube 58mm Panels
Resol Pump station
Resol BS4 Controller
Total antifreeze contents of system is 5 Litres
Bar setting 2.4 (I will be monitoring this in the more productive months)
I did explain to you previously that I had restricted the flowrate to 3 litres per minute. After further investigation, I realised that the BS4 controller came in trumps with its variable pump speed. Set pump speed at 50% (3 Litres per min at 50%, 6 Litres per min at 100%) saving unnecessary wear on the pump and also using half of the electricity. The BS4 increases speed by 10% every 2 degrees above a set level (on setup program) as panel temp increases. Considering it only cost about £20.00 more, I will some recoup this money and not go through so many pumps. Maybe worth mentioning to your customers? Also just a note on the AAV (automatic air vent), I found the most effective way to remove air from the system was to leave the system to it's own devices for about 5 days (the heat generated seems to move air much better than a cold solution)".

I assume that this is because water varies a surprising amount in viscosity depending on temperature.

"For these 5 days I left the isolation valve open and then closed at the end of the 5th day sealing the system, this worked very well. I have also added extra insulation to the cylinder to reduce heat loss. (Loft insulation space blanket 200mm) This has slowed down heat loss and allows water to go a little further when weather is poor. I found the traditional hot water jackets very poor and the loft space blanket was very easy to install!

I would just like to say many thanks for your help with this project and have already recommended a few people to your services. I found that you guys were very helpful but also allowed myself to decide exactly what I wanted to buy. Many thanks for your patience and helping me to achieve a great result. As promised I have a number of photos I will post for you tomorrow, if you could just let me know when they arrive? If you wish to use any of this info or photos to promote your product then feel free to do so.
Finally I anticipate that this system will give me free hot water for approx 9 months of the year and still contribute in the remaining 3 months depending on weather conditions. With the removal of the 10.5KW electrical shower I anticipate that I will save approx £250.00 per year off my electric bill with a payback in the region of 5 to 6 years to break even.
Many thanks again for all your help and I wish you all the success in this growing market"

and a few days later..

"Will keep you up to date on the all the info I generate, will e-mail my monthly results. Great results for the first 2 day this month. Generated a total of 24KWH and ended up with 250 Litres of water at 65 Degrees, a new record for the system!!!
Just had my electric bill and prior to installation was using 13 day and 13 night units. Amazingly my day units have now gone down to 5 day units. This does sound like a lot but is saving approx £0.80 a day in electric. Work that over the year and that's a real saving! (Those 10.5KW electric shower cane your electric) This has without a doubt accelerated the payback period and who wants to use those kind of KW's for a cold shower in the summer? Just for your info have installed a Mira Exel (Gravity System, as my pictures show the 50 gallon cold water tank but of course you could get away with a smaller one if required".

Justin has installed a very accurate monitoring system using a flowmeter and Resol ES controller.  The figures shown below are from the installation of this monitoring.  Note that he uses his full array in the winter months and covers some collectors in the summer, to reduce the collection of unwanted heat (we think he should sell hot water to his neighbours instead!).  Justin records these figures monthly, the per day figure is average for the month.  The bypass column shows the number of hours the heat dump circuit is in operation.  The per solar hour column shows the average output of the array for each hour in the month that the solar circuit pump is in operation.

Year 2008 Tubes in Use Pump Hours Pump Hours Bypass KW Hours Average KWH Average KWH
    Per Month Per Day Hours Month Per Day Per Solar Hour
February 80 115 3.97 5 168 5.79 1.46
March 80 160 5.16 20 240 7.74 1.50
April 80 206 6.87 42 300 10 1.46
May 40 243 7.84 14 245 7.9 1.01
June 40 235 7.83 6 204 6.8 0.87
July 40 267 8.61 1 239 7.71 0.90
August 60 198 6.39 0 171 5.52 0.86
September 80 143 4.77 13 181 6.03 1.27
October 80 143 4.61 2 181 5.84 1.27
November 80 64 2.13 0 52 1.73 0.81
December 80 71 2.29 0 61 1.97 0.86
Total/Average   1845 5.5 103 2042 6.09 1.11


Year 2009 Tubes in use Pump Hours Pump Hours Bypass KWH Average KWH Average KWH Average KWH
    Per Month Per Day Hours (Dump) Month Per Day Per Solar Hour Per Tube Hour
Jan 80 83 2.68 0 65 2.10 0.78 0.0098
Feb 80 86 3.07 0 83 2.96 0.97 0.0121
Mar 80 191 6.16 5 249 8.03 1.30 0.0163
Apr 60 194 6.47 0 267 8.90 1.38 0.0229
May 40 219 7.06 0 247 7.97 1.13 0.0282
June 40 201 6.70 0 240 8.00 1.19 0.0299
July 40 212 6.84 0 222 7.16 1.05 0.0262
Aug 40 173 5.58 0 201 6.48 1.16 0.0290
Sept 40 166 5.53 0 171 5.70 1.03 0.0258
Oct 40 107 3.45 0 91 2.94 0.85 0.0213
Nov 40 61 2.03 0 41 1.37 0.67 0.0168
Dec 50 46 1.48 0 44 1.42 0.96 0.0191
Total   1739 4.755 5 1921 5.252 1.039 0.0214


Justin has recently provided updated information about his electricity usage before and after his solar installation (he previously used electric showers and an electric immersion heater for hot water, in the absence of gas).  This shows even better savings.  Comparison of the two winter periods shows expenditure of £1.93/day before the solar installation and £1.03/day after.  He has actually cut his electricity consumption by 50%, in the winter, but the difference in day and night unit costs accounts for the actual savings of 46%.  Justin has reduced his carbon footprint, by about 5.5kg/day in the winter!  The summer figures are obviously much more positive because there is far more sun (bearing in mind this is for hot water, not heating)..


Electricity Bills        
Date Days Day Units Used Night Units Used Total Charge
09/02/2007 59 795 764 £114.48
11/02/2007 Solar installed and running 2 off 58mm/ 20 Tube Panels
01/05/2007 81 421 476 £68.28
28/07/2007 88 476 215 £64.03
16/10/2007 80 429 206 £58.93
01/11/2007 System increased from 2 to 4 off 58mm/ 20 Tubes Panels
06/01/2008 82 604 462 £85.16


Justin made improvements to his system at the beginning of 2008 as follows:

 Resol BS4 Controller has now been changed for a Resol ES controller. This allows up to 10 different temperature probes and lots more pumps used on 36 different programmed setups ranging from single stores to incorporating solid fuel boilers etc. I need to make this change due to the installations of a secondary hot water cylinder. Also allows connection of CS10 & V40 measuring instruments (see below).

Installed a second hot water cylinder with 2 coils sized at 180 Litres. This now means I have 430 litres of hot water, allowing me to make full use of the 4 collectors now mounted on the roof. Incorporated into this setup is an Eco-nomical 3 port valve. The ES controller monitors both separate water stores and heats the primary store to 65°C. The controller switches the 3 port valve once this temperature is reached and starts to heat the secondary store. This now means that rather than having cold water entering my cylinder at around 10 degrees it is preheated and also due to the low water feed temperatures allows my system run more efficiently. (Feb 6th there was 60 degrees in the Primary store and 40 Degrees in the Secondary store, a good result for the beginning of Feb) A great function of the ES controller is a function called ‘TRUN’. This monitors the collector temp against both stores. After a set time (currently 15 minutes) it will automatically start loading Secondary store if the Primary cannot be loaded. This makes use of heat in the collector that would be otherwise wasted and transferred into the Secondary store. The run times can be changed but I have required my system to check every 15 minutes and run for 5 minutes in temperatures allow.

A Resol CS10 sensor has now been added to allow measurement of sun intensity in W/m2.  This is mounted next to my collectors on the roof.

A Resol V40-0.6 Flowmeter has also been installed along with temperature probes on flow and return solar pipe work.  This is a water meter style flow meter which allows the output measurements of my system to be recorded with greater accuracy.  I will make sure all is operating correctly in February and start recording system figures from March. If all goes well I will introduce a Resol Datalogger to record all figures automatically.

Due to the size of my array I now have released the second coil in the primary cylinder for the ‘Heat Dump’ and have moved this to the coil on the Secondary store. This will allow me to keep the Primary store up to a good temperature and bypass from the Secondary store that is feeding the Primary store. Total output of this heat dump is 3.5 KW at water temperature of 70 Degrees and is completely independent to the solar system. Control for this section will be made through a Resol BS4 controller that I also intend to also use for controlling my solid fuel burner Backboiler.

These heat dump radiators are positioned in the Conservatory 1KW, Bathroom 500W and a 2KW radiator in the loft area. The loft radiator is not used in cooler weather when heating is required.  I would expect that these radiators will start operating from Mid Feb, depending on the weather.

 System overview as of Feb 08;

 4 x 20 Tube 58mm Evacuated Tube Collectors

Flowcon RF pump station

Resol ES controller currently using ‘Array 5’ setup

250 litre vented primary store cylinder

180 litre vented secondary store cylinder

Eco-nomical 3 port valve

Resol CS10 irradiation sensor

Resol V40-0.6 flowmeter





The automatic air vent.  This is the correct place to fit it, at the highest point in the system.  Note the attention to detail shown in the insulation on this and the following picture.  Think of insulation like a bucket.  It is easy to leave difficult areas with the idea that it is only a small part, but that is just like a bucket with only a small hole.  The heat will leak away like water.




This is Justin's super-insulated hot water cylinder.  Even a new hot water cylinder with insulation that meets the building standards will lose a surprisingly large amount of heat.  A simple, cheap measure which as Justin says, is easy to install.


This is the BS4 controller.  Justin opted for the Resol RF pumping station which does not have a built in controller, because he wanted the pumping station in the loft but the controller easily accessible in the house.


The loft plumbing, showing cold water tank, pump station and expansion vessel.


The following pictures are of Justin's newly expanded 80 tube collector array.




Here are some pictures which also show the installation of Justin's neighbour, Salvi Reilly, which is separately documented here.




After installing his solar thermal equipment, Justin decided to install a photovoltaic system, again in several stages.

Justin writes:

Well this project has been quite a journey. I have learnt a huge amount about Solar PV on the practical front and unlike a lot of people within the industry have lived with it day in, day out throughout the last 14 months. I have tried different facing arrays and now optimised that information using the space I have to give me the best possible system. I really enjoyed the challenge and seeing the huge improvements from April 09. I would not have got to this point if I had not taken the time and effect to experiment. There seems to be huge amounts of theory on this subject but not a lot of practical help.

The project first started in April 2008 where in purchased panels totalling 480 watt PV panels along with a Mastervolt Soladin 600 inverter. This Inverter was small, easy to install basically being able to plug straight into a power socket. It is of course G83 UK compliant. These panels were placed on my garage facing South (160 degrees). Construction for the mounting frame was made from timber as this was very temporary and they would soon be changed.

At this time I changed my electricity supplier to Southern Electricity and applied for an Export Meter. This took about 3 months in total and was pretty straight forward. All G83 installation paper work was completed and a qualified electrician looked over the work and signed off the system. We decided to call the array ‘JWSolar’ with OFGEM. Paperwork was received from E.ON, Central Networks on May 13th, 2008 giving approval for our Photovoltaic Generator to operate in parallel with Central Networks distribution system. Export meter was fitted at the end of June and we would be paid 18 pence for every KWH Exported from our system.

Having mastered the concept of Solar PV I decided to purchase the same amount of equipment again as above bringing the set up to 960W with 2 Inverters. The system would then be set up in an East/ West configuration with one Inverter running each array. The above array was dismantled and panels were placed on each side of the garage. The roof angle was around 12 Degrees and output would be lower in the winter but would improve as the summer progressed.  Each side was now 480w and ran throughout the summer without any problems with additional capacity being added to the arrays, bringing each side up to 560watts.  Due to the positioning of these arrays design software was quoting 720KWH per 1KW installed on the West facing roof (250 Degress) and 680KWH per 1KW installed on the East roof (70 Degrees)

The next challenge was to have a look at a Tracker system. I purchased a Lorentz ETA-400 Tracker with 4 x panels totalling 520watts, and another Mastervolt Inverter. A 97mm mounting pool was placed through the Garage roof and inserted into a concrete base. The tracker frame was mounted and PV panels added to the tracker and all connected to the inverter. This tracker is single axis but dual axis ones can be purchased. The tracker follows the sun from the East first thing in the morning and slowly moves throughout the day finally arriving at the West by last afternoon. It returns itself to the central position at the end of the day facing South in direction. The tracker uses a small PV panel to keep the Voltage as high as possible throughout the day maximising output. The best output I have had from this array is 4.0KWH in any one day as I write this. I have found this very impressive when the best quotes normally promise 4 to 5 times output of your array in the summer.

Now extremely busy with Solar Thermal Installs I did not have any time until the end of November. At this point I installed another 700watts of capacity along with a SMA Sunny Boy 700 Inverter to run this array. Panels were placed on my porch area which was pretty easy due to the low height. Everything connected and away we go.  I found the SMA Inverter extremely well made, easy to set up and using a heat sink mounted on the top of the unit rather than a fan to cool the internal parts so no internal moving parts. Voltage can also be selected using a jumper system internally so different operating voltages can be used.

Below are the kWh figures that I compiled at the end of December 2008 from each array;

                                                East                        West                     Tracker                 South                   

May 08                                  37.0                        -                              -                              -

June 08                                 54.0                        12.90                     -                              -

July 08                                  46.80                     45.80                     -                              -

August 08                            35.90                     36.60                     25.90                     -

September 08                   25.10                     25.00                     34.20                     -

October 08                          15.50                     18.30                     35.30                     -

November 08                    5.90                        5.90                        11.20                     4.60

December 08                     3.57                        4.23                        6.20                        16.49

Total Output 506.39KWH for 2008

Basically with all the changes the above is for reference but is useful to compare outputs from very similar systems. Our electricity bill from April 21st until the end of December 08 was £117.49 for everything including standing charge. We received a credit of £43.80 on our account for exported electricity.

In March 2009 Southern Electric announced that from April 1st, 2009 the Export rate would be increased to £0.28 per KWH Exported which was a big increase. With this in mind it was time to optimise all equipment and some changed would be required. The very impressive 80 tube solar thermal collectors were repositioned with 2 of them removed to allow room for the PV array. A frame was then constructed on the South Facing roof to house the panels mounted on the Garage. Due to the size of the arrays the Mastervolt Inverters were replaced with SMA Inverters. 2 rows of collectors were installed on the roof, each row connected to a SMA Sunny Boy 700 set at 250 Volts. The frame in future could still house an additional 4 panels in Landscape at the top and another 3 along the Solar Thermal Panels. The roof now was sized at 1440watts and can be increased to 2080watts if required without any major work. Good ventilation was ensured using fixings that left good space between PV Panels and roof. At this point radio sender units were also added to each of the 3 inverters and a Sunny Beam remote display was added. This device is wireless and communicates with the Inverters every 15 seconds telling the user outputs on each of the arrays and also keeps output records every day for the previous month. This information is downloaded daily and is stored on the SMA Website. It can be viewed by following this link; http://www.sunnyportal.de/Templates/PublicPageOverview.aspx?plant=509158bf-cb83-4dc7-b1fe-d0ef10d9553a&splang=en-GB

It shows all daily outputs from the arrays and daily peaks. All days are available from April 09 to view. At this moment in time the info will not show the outputs from the tracker mounted array, hopefully I will get to sort this out at some point.

The above changes have completely changed the efficiency of the system and the results have been excellent. The system in total is 2.66KW and uses 4 Inverters. It is important to separate arrays if they face different directions as the voltage is normally determined from the panel which is outputting the lowest amount. Also shading is very important to avoid. A shaded area the size of an A4 sheet on 1 panel can reduce your output by 90% and by using a number of Inverters this problem can be considerably reduced. DC Cabling should also be kept to a minimum to reduce loses. The figures so far is that we have produced 1223.23KWH, exporting 940KWH for a 6 month period up to June 30th, 2009. Export payment so far would be £246.72 and basically our electric bill so far this year is -£162.46. With everything in place and a good export rate we anticipate an electric bill a £0.00 and a credit of approx £400.00 per year. So far with Solar Thermal and PV we have produced a total of 2374 kWH YTD.

In May 09 I attended a course with SMA to learn how to install all of their communication equipment for their Inverters."


In the course of fitting his PV array, Justin removed two Eco-58-1800-20 collectors, which had been on his roof for a while.  He writes:

"We recently carried out a strip down of 2 Eco-nomical solar collectors to see what shape and condition they were in after 28 Months of continuous use on a roof. Here is what we found;

When dismantling, all 40 tubes came free from the manifold without any
issues. All heat transfer paste was easily removed from the heat pipes removed
from the manifolds.
All fixings, rubber parts and clips were intact and in good condition.
There was no rust on any part of the manifold, frame or reflector.
Reflectors were in excellent condition with no deterioration on the
mirror side.
Insulation within the Manifold intact and showing no signs of

I'm very happy with the panels after this period of time and they show no
sign of ageing. JW Solar Solutions are very keen to demonstrate to our
customers that these collectors are of a quality build and will serve them
well for years to come producing lots of free hot water .

After this exercise the collectors will be put back into use within the next
month and again will be heating lots more hot water for free!"

Below are some photos of the dismantled panels.

Thanks for the information and pictures, Justin.


Send mail to SW@eco-nomical.co.uk with questions or comments about this web site.
Last modified: 17-03-10