I have HWS just installed in my brand new two storey building finished two weeks ago - Solarpower SP4002. Two weeks already and water is still cold or warm 35 Celsius at the best, but weather is quite good recently on Gold Coast.
I try to investigate myself what problem could be since installer didn't turn yet to check what is going on.
The building is quite high two storey and two panel installed on the roof but cylinder on ground level 400 liters.
I have following doubt about system.
1. Sometimes circulating pump will start on at 11:50 AM but sunshine is fine since morning
2. Circulating pump has 3 settings; 40W, 60 adn 80W but circulating starts only at 80W.
I think that cylinder construction is such that water level is at ground level +1.5M and pump needs to pump water only roof to the panels 9 meters up then water return under gravity to the cylinder. In such case it is terrible waste because instead of just moving water - circulating pump needs constantly push this water to 9 meter all the time.
Am I right?
I imagine that if cylinder could be up the head pressure - 9 meters then pump needs less work - only resistance of the piping not waste energy to pump water up E=mgh
Am I right?
Are there any HWS other then Solarpower SP4002 that could do just that?
What should I do?
I was the first enthusiast of solar hot water but after two weeks of cold showers I have my doubt.
In me previous home I have cylinder and vacuum tubes on the roof and never had such problem. There wasn't any pump at all and water was boiling hot most of the time.
HWS circulating pump in two storey building problem
(18 posts) (7 voices)-
Posted Wednesday 9 Mar 2011 @ 5:52:34 am from IP #
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Greenozi, don't despair! Physics works for you.
The answers to your questions are NO and Yes-but-not-necessary.
If the system system does not leak and is fully primed, the water in the downward pipe will create the same pressure to compensate for the pressure in the upward pipe. The circulation pump has only to circulate the water, it needs not to pump the water up. There is no difference if this loop is going 9 m vertical or 9m horizontal. The only issue with a higher building is increased pressure drop from the resistance of longer pipework.
So after physics are sorted, lets sort out your problem.
1) are you sure there is no air in the system? A bit hard to tell, I suppose. Usually the lines are primed by using the mains water pressure. If there is no special tap for that purpose usually the compression fitting at the bottom of the tank after the non return valve can be opened. This will flush water through the collector circuit carrying all the air out of the system.
However as your system has just been build, you should only try this if you are sure that you will not void your warranty.
2) keep pump at 80W setting. Total electricity consumption will not increase much because running time will be shorter.
3) Can you plug pump into normal power point?
If you get hot water now , the sensor or the controller might be defective.
In that case you can help yourself for a while with a timer switch which is on during day time every second quarter hour.4) I am surprised about your patience. My customers were not that patient if they saw the performance below of what they expected.
5) You supplied the final proof that evacuated tubes are superior to flat panels ...
... just kidding.
Posted Wednesday 9 Mar 2011 @ 10:31:31 am from IP # -
S2s
Well if system is open at the bottom and sealed on top to create downward vacuum there could be next two problems:
Atmospheric pressure on panel will be enormous . at 9 m water head create almost vacuum
almost a kilo on square centimeter so solar panel would be squashed by few tones of pressure. So I believed that system must be open at the top. Also fact that pump must work at maximum RPM to get any circulation at all , any lower settings and there is none at all.Next problem with such setup could be water boiling at much lower temperature then 100 Celsius even at room temperature eventually.
You are right, if I had any option to choose I prefer evacuated tubes and cylinder on the roof, but that wasn't option with my builder.
Visiting plumber today (at another matter suggested that solar installer will probably add another pump in serial to existing to improve circulation. That mean probably that energy I save on heating water I need to spend on pumping water now. 160W on pumps wasted plus 100W on controller circuit (that data from manual)!Posted Wednesday 9 Mar 2011 @ 1:08:04 pm from IP # -
Sorry, so your circulation look is not under mains pressure?
But even so, if the loop is sealed and there is no air in the system, the water in the down pipe will compensate for the pressure needed to pump it up.
However if the system has an overflow on the top and is open to the atmosphere you may need your own power plant to pump a few 1000 litres per day 9 m up. I wonder why such a clever guy like you picked such a system?
Posted Wednesday 9 Mar 2011 @ 10:38:57 pm from IP # -
S2s I had no option to pickup anything as was provided by building company that I have contract to build complete house- so called package.
I know what crap I received now, brand is Saxon Solar
http://www.sachs.com.au/images/PDFS/Saxon_Solar.pdf
(why manufacturer is not on the sticker on the cylinder only installer contact?)and according to brochure doesn't work to higher then 6m meters level.
Looks like my all 1.5 kw solar PV now will be working only to support this circulating pump ! Why this people at Saxon so dumb in designing their cylinders and who on earth give them certification , where are Australian Standards ???
If only cylinder standing on the ground could withstand water lever to the panel hight all problem could be solved immediately and circulating pump could be 20 W even not 200W.
I guess my problem was exacerbated by high building to the point that doesn't work at all but thousands other customers buying this stupid design HWS are paying for unnecessary water pumping instead of just circulating.
If I could suggest to Australian Standard commission such design should be forbidden as the least efficient WHS on earth. Today 30 Celsius outside , sun full blown, If I had old barrel painted black I should have warmer water that my 25 coming out of solar heater now. Only advantage is minimal water consumption in my family as nobody could withstand longer the few minutes cold showers.Posted Thursday 10 Mar 2011 @ 4:10:39 am from IP # -
The system shouldn't have to be pressurised in order for the pump to gain some benefit from the down flowing water should it? As I understand it the line merely needs to be free of air and not allow new air to enter the return line from the panels for the spihon effect to take the load off the pump.
Having looked at the sachs PDF - it would seem that they limit the height differential from tank to panels and that they recommend a second pump if the height is exceeded. While it doesn't solve the electricity consumption problem you should at least be able to require your builder to install the equipment in the manner recommended by the manufacturer (ie - they should put in a second pump for you).
Posted Thursday 10 Mar 2011 @ 5:16:31 am from IP # -
Not exactly, If you want benefit of the water flowing down that will create sup-pressure in panels. I think that system is not design for that to withstand and it looks most likely like pumping water to open swimming pool/ bath upstairs - open vessel and water come back freely without any benefit to the pump which needs to straggle to pump all that water 8-9 meters up.
The prove is that at motor settings 40 W and 60W there is no flow at all ( but if system will be sealed on top is should work as well)
According to physics maximum hight that siphon may work is 10 meters -this is compensated by our atmospheric air pressure- 1 bar- any more and water head will create vacuum at the top.
Not big deal with pressure -all old electric low pressure hot water cylinder where able to withstand this sort of pressure and there was/ is overflow pipe above the roof.If you want to make simple experiment - get a long garden hose- make simple siphon by drawing water from one vessel to another 0.5m lower. Now if you keep rising hose in the middle hose will be thinner and thinner squeezed by atmospheric pressure and eventually when you rise the middle to 10 meters water will stop flowing completely.
Posted Thursday 10 Mar 2011 @ 5:30:50 am from IP # -
Sunshine
MemberGreenozi,
You should raise a fault with your builder and advise there is an issue.
Also, advise them that they have installed it contrary to the installation specification, and that will be the cause of the failure to work as it should.FYI, as a comparison, my split system (Hills) is installed with the tank on ground, with the collector with a height of around 10 metres above the tank, and it has around a 20 metre run. The single pump only uses 22 watts and it works great.
Posted Thursday 10 Mar 2011 @ 6:48:28 am from IP # -
S2s
Can you tell me more about your Hills cylinder? If also has a vent and overflow at eyes level? or on the roof?
How it is possible that you have pump 22W and I 80W that still could not push the water up?
How many collector panel do you have? I have only two but in my opinion it should be enough if water could circulate properly.
I called today manufacturer Saxon Solar and been advised to run booster ! ( at this moment electrician also mixed up and booster doesn't work so I am on solar only).
If your cylinder is indeed pressurized I should replace my crap with other that works.
Anyway don't you think that pumping design without siphon should be by default forbidden in Australia like incandescent lights! Why to use 100-200W pumps in the HWS when 20 should be enough.
I guess there are thousands customers like me that overpaying for pumping water across Australia when simple forced circulation should be enough.I think we at ATA should officially ask HWS certifier body in Australia to eliminate from the market inefficient design when market is full of good quality and efficient products. Actually I am trying to find the path to contact this body and ask for their criteria. Eventually government also give away generous donation to the schema but part is completely wasted on inefficient system like mine.
For most customers without without understanding of physic and dynamics magic word " solar water heater" is ultimate warranty that they have a right stuff.
ie my wife is happy to run electric booster 24/24 to have hot water at any price in this solar installation, for me it is matter of Principia and I feel cheated.Posted Thursday 10 Mar 2011 @ 1:50:38 pm from IP # -
Sunshine
MemberGreenozi,
I have a 315 lire Everlast stainless steel tank with the Hills system. I have a 30 tube evacuated collector on the roof. It has a vent in the manifold on the roof, as well as on the tank.
Have a look at the Hills website, they should have a detailed diagram of the Everlast tanks.
I know all water pumps have a head height rating. If your system/pump, has a head height rating of 6 metres, then they are only suitable for low set homes and shouldn't be installed on high set homes.
If the Saxon Solar spec sheet states that the pump has a head height of only 6 metres, then it's a issue with your builder/plumber who installed a system which is not suitable for the application.Posted Friday 11 Mar 2011 @ 2:04:37 am from IP # -
Think Andy, we are talking about pressure exacerbated by going downward pipe.
Upside down "U" that sucks water from cylinder when returning from the collector at another end. Do you think it will work on the moon? Even if gravity is only 1/6 of that on Earth?
Since cylinder on the ground is open and vented there is not traditional "U" siphon.
Anyway good news. I received call from installer that I should received bigger pump next week.
I hope that heat generated by 200W pump will help a bit with warming a water.
If company that invented this particular HWS will install 2KW pump than even solar collector could be removed from system and big motor could heat the water like a electric booster !
What a saving? ! I could foresee next generation of SAXON / Solarpower HWS come without redundant now solar collectors and electric heating element but with big electric motors in circulating pumps! The best will be using diesel or petrol motors since they produce a lot of waste heat.Posted Friday 11 Mar 2011 @ 8:10:29 am from IP # -
Johnnojack
MemberQuote: No drinking water is circulating in coil under mains pressure inside cylinder, but water level and overflow is just 1.5 above ground and 7-8 meters below roof panels.
Does this mean the circulating pump pumps from an open reservoir near ground level and water from the panels runs back into the reservoir? If so that is the main problem. That reservoir needs to be above the solar panels. Then the lift from the pump will be matched by the draw down back to the panels. The ideal situation for a vented or open system would be to have the pump up at the panels just under the reservoir. Have not seen one like that yet but most have the pump as part of the pressurised system (mains pressure) and therefore no air is in the system and the up column of water balances the down column. Rambling on but trying to make it clear.
Posted Monday 14 Mar 2011 @ 7:10:21 am from IP # -
My Solar Water system is vented in two places : at the ground, bottom where cylinder is and at the top where panel are and escaping steam is whistling every sunny day, but water remains cold in the reservoir.
It should be some official audit of installed solar systems and all REC, and grants taken off the installers that does not meet efficiency standards.Posted Wednesday 16 Mar 2011 @ 12:33:23 am from IP # -
Greg
MemberDoes anyone have the specs for the solar controller on the Hills Solar system ? Specifically interested in the circulation motor, power consumption, voltage, draw etc?
Hills site does not list anything apart from they closed business in January.Posted Wednesday 19 Jun 2013 @ 2:05:47 am from IP #
