Solar Water Heating Recommendations

[___]

Of course, I also have to add that 1) Everyone is entitled to my opinion and 2) I'd love to agree with y'all but there is no point in both of us being wrong. I say this thoroughly tongue in cheek because I really mean the opposite :-)

[Carl]

@plonkster, i have a 2 solar geysers (both outside) pre-feeding each other and it works very well. The second geyser feeding the house has a 2Kw backup element.

Last year winter we used the backup element for a total of 21 Hours × 2 Kw = 42 KwHours. 

Must confess that on the odd occasion we shower in 40 ⁰ C water. (I see it as an adventure like when you camp in the bush.) 

The only thing with a pre-feed system is that you double up on the tanks 24Hr standing losses which is significant.

For example lets take a 200 L solar geyser sitting at 60 ⁰ C, and has a standing loss of say 2 Kwh (well insulated geyser).

After 24 hours without any energy input the tank will be sitting at about 51⁰ C and that assumes that you have installed and insulated the geyser correctly.

I think Wetkit is onto something called stratification on his system, which is more effective in a vertical tank installation. (If i were to start all over again) 

I personally like seeing my tank and collector on the outside of my house.

[___]

33 minutes ago, Carl said:

you double up on the tanks 24Hr standing losses

Yup, I'm aware of that :-) I have the additional problem of limited North-facing roof space, which meant I couldn't fit more than a 150 liter system on the roof. I do have lots of space on the flat roof of the car port but that would make it too visible (and for all my claims that it's not THAT ugly, it is a LITTLE ugly). And so I also made a compromise. Initially I had only the 150 liters for the whole house, with a 2kw backup. It was sufficient most days... but I also shared that water with a tenant in the flat... and it was a lady tenant, so we were one bath short. With the prefeed system, I have hot water solved for everyone, and in summer the internal geyser is fed with such hot water that it barely needs to turn on to compensate for standing loss.

In the end, the system works for me, even though it is obviously not optimal :-) And that was sort of my point with the tongue in cheek comment above.

[___]

That "ugly" feeling one gets... let me derail this into a car thread again. I do not know why Toyota puts those dog-ugly plastic wheel covers on the Corolla. I mean, I understand it is the family man's car... and I will live with plastic covers... but man... I'll spend a few thousand more just to get the mag wheels and not have to look at those things :-)

[ebrsa]

I installed a 16 evacuated tube heater at 45 degrees inclination during October 2015. Connected it to my 200 liter Xtream cylinder which has exceptional insulation. My roof is a flat roof of concrete and I built a service shaft down to ground level. Easy for modifications as feeder pipes and power cables run down the shaft. Circulation pump is poweerd by 200W panel charging a battery. All hot water feeder pipes are insulated. Cobbled together a controller using Arduino as described on www.nateful.com and purchased circuit boards from him. Modified the control program so that the pump comes on at 5C difference between top of tank and collector and off at 2C difference. Installed a one way valve to prevent thermo siphoning at night. Owl meter on geyser shows 15.4 Kwh from grid so far and we have never been short of hot water. The water has never boiled and total cost is less than R8000 as I did it myself. Will be tough to justify adding a heatpump but if one has enough solar voltaic panels like JDP, it will make sense. Also its is only my wife and I in the house.

Great to have the forum and learn from others. Keep sharing information.

[Guest]

Let me rephrase my take on this. I am not saying anybody has to do what I did or should have done. But for our situation the heat pump works better. Let me tell you why. My wife takes a bath 2 times a day, sometime 3 times depending if she went to the gym. She likes being clean, don't ask , And I will also take 2, one in the evenings (I have to be clean if I want to get in bed ) and one in the morning after gym before I go to work. The 2 kinds each take a bath in the afternoons around 6pm.

So we run out of hot water in the mornings as there is no sun to heat the water during the night (and when I say run out it is still fine for me but not my better half, +- 40 degrees). So if I want to stay married then I need to make sure there is hot water for the wife in the morning. Thus my ultimate solar power and solar water solution will be as it is now. Grid tied inverter that feeds back to the grid the extra power, then we can run the heat pump any-time of day. I don't have any elements inside the tanks, the tubes will heat the water to a point during the day and the heat pump will the top it up or heat it all together.

But if I had to do it again, I would just use the heat pump as it did the job for 3 years already.

 

PS when I say ugly my wife told me I am not allowed to install a "Hoender Hok" on the roof LOL. It still needs to look good, so that is why I went for the retrofit system.

[Guest]

After having had 3 geysers over years burst as per the normal 5 years plus minus a day, now THAT is ugly Plonkster, the geysers are now outside.

Having gone double storey about 3 years ago I had the opportunity to extend the back roof quite a bit outwards to not only mount the panels there, but also to provide shade below for the geysers and their electronics below.

Using a short ladder all is now easily reachable when there is a problem and IF the geyser bursts, and watch now it will not happen, it is all outside.

Nothing is seen from the street for them tubes with the cylinder on top ... just does not do it for my eye.

Ps. I took one bath out and replaced it with a shower. SWAMBO was rather upset, so I told her, WOMAN!!! If YOU want to stay married to ME, you will say YES SIR, my master, please remove the bath as you wish.

Came out of the hospital 2 weeks later ... but the bath is out, shower is in, she is still around here somewhere. 

 

[Arandoza]

Greetings all,

Just on the EV tubes and shadenet to stop them overheating item.

One of the suggestions that had been made to me was to simply remove some of the copper heat pipes during summer months if overheating was a problem, and replace the glass tubes without heat pipes, til winter and then put them back.

We have 2 X 150liter external geysers, each geyser has 18 heat pipes.

The first geyser feeds into the second geyser and this second geyser can get up to just over 90 deg c if we are not home, the tp valve opens and drains off the 2nd geyser till the temp drops. The hot water feeds into a rain harvesting tank, so at least it's not a total loss. The first geyser seldom reaches much over 74 in summer, and have never seen its tp valve open.

Also we have the first geyser connected to a geyser wise max, which has a 2kw element, and the second temp probe we connected to the 2nd geyser. So we monitor both geyser temps, but only heat the first one.

Both geysers are at 30 deg inclination facing mostly north. The advice I collected suggested to keep the inclination similar to your latitude (PTA 26 deg) but I did not want to lean the geysers backwards so made the 30 deg inclination decision.

We only had to electrically assist July 2015, via Geyserwise programmed to heat from 3-6am, as I hate cold showers. The only other time has been when heavily overcast for 3 days, just left the power on, and felt the Eskom sting.

Also an important tip - make sure you have a non-return valve on the cold inlet to the geysers to ensure no hot water can flow back down the cold inlet.

And also insulate the cold

Inlet water pipe, ours froze one Saturday morning in winter last year, so no hot water would come thru till the blockage melted by about 8:10am, but the water was toasty. My wife was quietly sweating at me and my solar geysers...... until the ice in the pipes melted, along with her Icy demeanor under the hot shower.

Ps: we mostly shower these days, (family of 4 + domestic), it saves water and power, usually using the bath on the weekends at out leisure. If we used the baths more often I think we would

also have to consider a heat pump, or just live with electrical heating when needed.

[Guest]

Today is the perfect day to show what I mean by our situation.  Again this is only my view based on our situation  

 

 

[KLEVA]

18 hours ago, The Terrible Triplett said:

Ps. I took one bath out and replaced it with a shower. SWAMBO was rather upset, so I told her, WOMAN!!! If YOU want to stay married to ME, you will say YES SIR, my master, please remove the bath as you wish.

Came out of the hospital 2 weeks later ... but the bath is out, shower is in, she is still around here somewhere. 

 

[Guest]

17 hours ago, Arandoza said:

Greetings all,

Just on the EV tubes and shadenet to stop them overheating item.

One of the suggestions that had been made to me was to simply remove some of the copper heat pipes during summer months if overheating was a problem, and replace the glass tubes without heat pipes, til winter and then put them back.

We have 2 X 150liter external geysers, each geyser has 18 heat pipes.

The first geyser feeds into the second geyser and this second geyser can get up to just over 90 deg c if we are not home, the tp valve opens and drains off the 2nd geyser till the temp drops. The hot water feeds into a rain harvesting tank, so at least it's not a total loss. The first geyser seldom reaches much over 74 in summer, and have never seen its tp valve open.

Also we have the first geyser connected to a geyser wise max, which has a 2kw element, and the second temp probe we connected to the 2nd geyser. So we monitor both geyser temps, but only heat the first one.

Both geysers are at 30 deg inclination facing mostly north. The advice I collected suggested to keep the inclination similar to your latitude (PTA 26 deg) but I did not want to lean the geysers backwards so made the 30 deg inclination decision.

We only had to electrically assist July 2015, via Geyserwise programmed to heat from 3-6am, as I hate cold showers. The only other time has been when heavily overcast for 3 days, just left the power on, and felt the Eskom sting.

Also an important tip - make sure you have a non-return valve on the cold inlet to the geysers to ensure no hot water can flow back down the cold inlet.

And also insulate the cold

Inlet water pipe, ours froze one Saturday morning in winter last year, so no hot water would come thru till the blockage melted by about 8:10am, but the water was toasty. My wife was quietly sweating at me and my solar geysers...... until the ice in the pipes melted, along with her Icy demeanor under the hot shower.

Ps: we mostly shower these days, (family of 4 + domestic), it saves water and power, usually using the bath on the weekends at out leisure. If we used the baths more often I think we would

also have to consider a heat pump, or just live with electrical heating when needed.

Mmmm seems I am not the only one that have these issues after all. 

I was told that you may not install a non return valve on the other side of your main pressure release according to law. I wanted to do the same to make sure that the system does not run dry when there is no water pressure. 

I am working on a device that will cover my tubes with shade as and when needed. I dont want to get on the roof all the time. That is why my gutters look the way they do as a result of the ladder. Will paint then when I have installed the device. 

[Chris Hobson]

32 minutes ago, jdp said:

I was told that you may not install a non return valve on the other side of your main pressure release according to law. I wanted to do the dame to make sure that the system does not run dry when these is not water pressure. 

To prevent water draining from a system a 300mm riser  with a vacuum breaker.

[Guest]

Chris do you have a sample image of that. 

[ebrsa]

How about installing a non-return valve on the cold water feed to the geyser. Glad you guys are discussing it as I never thought about that problem. Then at least the geyser will be full when we are not at home and the main supply is shut off. I have a stop valve in the main supply in the garage which I close when we go away. Don't relish the idea of coming back to a flooded house if something goes wrong. Fortunately I installed the stairway for the double story house to go all the way to the roof which is flat so it is just a matter of walking up the stairs, opening a door and I am on the roof. Necessary as the years advance.

[Carl]

I think this picture shows what Chris was referring to.

If you install a NRV valve on the cold supply side then it must be installed before the PRV (pressure control valve in pic below) and not after.

On the geyser heating cycle the water expands and builds up pressure. The PRV controls this pressure by releasing some water (usually drips) through it's relief valve. 

So if you install the NRV after the PRV you will inhibit the valve from regulating the pressure in your geyser and associated pipework. 

[Guest]

OK my system does have that. Yep Carl that is what ITS said, you may not have the NRV after the main release valve. But my question is does the TP Safety valve not count as a pressure release as well.?

[Carl]

Yip, but the TP valve is designed for emergencies and does not always seal properly after operation. 

[Kloon]

Wow, blown away by all the feedback, thanks! Hopefully I did not ruffle too many feathers with this topic

I will be going through each reply in more detail and making notes for the installer.

When it comes to brands for tanks and tubes, are there any specifics I should try and avoid? For example is Suntank geysers okay to use? I could not find anything on tube brands but would appreciate any advice there as well!

[Guest]

10 minutes ago, Kloon said:

Hopefully I did not ruffle too many feathers with this topi

Not at all. We have lively debates sometime when we do not agree completely with some answers. 

Duratherm geyser. Tubes I have installed are not sold anymore due to them being "too expensive". Apparently at the time a price war started and pipes got very cheap, making mine obsolete ito being too expensive at the time. They are quite thick compared to most I have seen.

I can allegedly have them imported if one breaks.

So the bottom line: If you have the same problems as i.e. JDP and some others, then your system is installed incorrectly. Never should it overheat and cause damage.

And if you can, have the GeyserWise equipment and pump on solar with a battery that they can run for days in bad weather, or in good weather with no Eskom.

[Chris Hobson]

1 hour ago, Kloon said:

When it comes to brands for tanks and tubes, are there any specifics I should try and avoid? For example is Suntank geysers okay to use? I could not find anything on tube brands but would appreciate any advice there as well!

HI Kloon

Chat to Carl (on this thread), he had very competitively priced gear.

 

[Guest]

If you are installing retrofit and want to add a tank I was told to stay away from Kwikot tanks as they tend to burst in 2 years time.

I can not comment on any other brand than ITS as that is what I have. The system look a lot like what Carl showed here on the forum. Same controller and tubes.

[ebrsa]

Carl thank you for your clear explanation and graphic. Of course itshould obvious that a NRV on the geyser side of the PRV will only serve the purpose of ensuring a burst geyser. I have an Xsteam geyser and it is manufactured of synthetic  materials including the vessel which nullifies any galvanic action. Also the insulation is so effective that the outside is cold so little if any heat escapes. What would be interesting is an analysis of evacuated tubes plus grid electricity vs evacuated tubes plus heat pump electricity consumption and capital financing and replacement costs. I am sure geo-thermal heat pumps would be more effective in the colder areas of the country but would cost more to install. I have not come across any advertisements for them locally. A South African architect in Toronto, Canada, to whom I used to chat on Skype told me that he gets $6 of heat for $1 of electricity with his geothermal heat pump with some 2000 feet of plastic pipe about 2 meters under the surface. I believe the ambient temperature was about -27C with wind chill on the day we spoke. An air heat pump would surely have had a hard time producing acceptable heat.

[Carl]

On 5/3/2016 at 7:56 AM, Kloon said:

is Suntank geysers okay to use

Hi Kloon, i have a suntank solar system that was installed as part of the Eskom Pilot project, before the rebate scheme was introduced, and can make the following comments:

1) The suntank system (right hand side of pic) has given me 8 years service so far at a system pressure of 400 kPa.

2)  As the tank inner is made out of stainless steel, it has a sacrificial anode that has to be periodically replaced depending on your water quality in your area. (I replace mine every 3 years.) This entails isolating and partially draining the geyser. A new anode costs about R180.

3)  The insulation on the tank is good. 

4) The collector panels are quite flimsy and starting to show signs of corrosion on some of the copper pipework.

If i was starting over i would probably go for a maintenance free geyser such as Tecron (full copper geyser), Solartherm (PEX lining) or maybe Xstream. (a friend of mines Xstream lasted just over 5 years so not convinced about there longevity) 

On the collector side i would look at the locally made Solarmax. (Have heard some good reports)

Anyway these are just me opinions and would like to hear what other members suggest.

 

 

 

 

[Guest]

The rust on the roof sheets under the frames ... 

[Carl]

Hey TTT  you were meant to look at the sunset and not those sheets. 

Am dreading replacement day.

Have tried some rust converter products and also a special metal paint but no luck. 

Green Bum suggested NS4 so that's my next attempt.

Any suggestions?