Solar Water Heating: An installers viewpoint

[kaybeach007]

Hi Guys

I'm also in the business of SWH.

Go for a good brand, Kwikot, Solarhart and have it installed properly or do it yourself properly. There is a lot of energy in 200 litre of water at 65 degrees C, so follow plumbing regulations, the regulations gave been learnt the hard way. I have seen 3 holes blown in house's roofs from botched geyser installations, not to mention rejected insurance claims because of DIY jobs, so please be careful. Replacing roofs, ceilings, cupboards, carpets etc can get pricey.

Water temps over 65 simply reduce the life span of the tank, I always laugh when installers brag about how hot their systems get.

Vacuum tubes are fine for Europe, but not suited to SA condition, they are TOO EFFICIENT. Geysers are designed to vent at certain a temp and pressure, so if the water in the system gets too hot (usually at about 14h30) the safety valve opens and vents basically half of the tank, so you get home to a tank of caold water in the evening. Currently the SESSA ombudsman is facing several hundred complaints almost all of which are vacuum tube systems, so be careful.

Flat plate collectors look like skylights, 25 year lifespan, ideal for our climate. In three years I have done several dozen installations where the client has requested NO electrical backup and 60 - 65 degree water has been no problem. Don't get confused by the whole efficiency of EVT vs Flat plate debate. EVT IS MORE EFFICIENT, but flate plate is better, we are certified to install both so I am totally unbiased. EVT is better for industrial/commercial applications, hotels and guesthouses where hot water is constantly used. Residential application always go for flat plate collectors, at least 1m2 per 100 litres, you won't be sorry.

Budget on R16 000 for 150L, R22 000 for 200L and about R26 000 for 250L. Rebate of about R2 000 for 150L, R3 900 for 200L and R4 700 for 250L.

Go to Eskom website, look under DSM for a pdf list of all accredited installers.

CSIR figures put energy spent on water heating at 43%, generally (almost 400 SWH installations experience) 30% - 40% saving residential and 55% - 60% saving B&B/guesthouse application. Payback is under 4 years, depending on usage. Yet to have a dissatisfied client! My house of 4 runs off a 200L Kwikot direct system, installed by myself when I started my business. It only uses electrical backup on rainy days (I got fancy and installed a rain sensor, from a wrecked Merc), cloudy days, winter days - no problem.

There is a lot of distrust about the solar industry, SWH prices are not going to drop much further and it is the biggest saving you can make per Rand spent. To the clever arse punting RA's, show me an investment of R22 000 that can give you GUARANTEED monthly income of R500 AND SAVE THE PLANET from day one!!!!!! I know, I have installed systems on 4 stock brokers houses, challenge me, I dare you, I double dare you.

Photovoltaics are still exorbitantly priced with enormous ROI timeframes. Wind turbines are only truly efficient on towers 15 - 20 metres high, EIA's and departures from immediate neighbours required in residential applications, so good luck (I currently have 16 clients going through the motions of wind turbine applications). Solar batteries are very expensive, standard deep cycle batteries are reasonable, but require replacement every 5 - 8 years depending on maintenance and charger/monitoring equipment quality.

All I can say is do your homework. Talk to people. Most of my time is spent educating people, I am a treehugger so I don't mind. Call me, PM me, I don't mind.

[murraybiscuit]

excellent post. you see, this is the reason i subscribe to this bb
rain sensor from a wrecked merc... all hail the ubergeek.

[McGuywer]

kaybeach007,

I guess your not in Gauteng?
Thanx for the info. Piet, you as well.

[kaybeach007]

Hi McGuywer

I own the East London and Port Elizabeth franchises (30 across the country, biggest solar installation group in the Southern hemisphere, so we know what we are doing) and I will gladly put you in touch with a franchise close to you (although I don't think we have someone servicing the infinity and beyond area). Professional, no hard selling, just the truth, fair price, fair profit, no Chinese ****.

Our head office tracks all our clients rebate applications. We do the paperwork with you. We submit it and track it. You call us if you don't have your rebate in 6-8 weeks and we track it down and sort it. Clients shouldn't have to do that, we know who to talk to and what is required.

By the way, most rebates have doubled since the 11th January 2010, so make sure your installer is giving your sound advice and costing based on the new rebates. I did a B&B last week, 4 x 250 litre systems, R105 000,00 capex, R31 700 rebate, 14 month ROI, residential ROI is down to 36 months in most cases. Rebates will decrease each year though, so get it done NOW!

[TooHotTooHandle]

Hi Kaybeach007
Seems like you know your figures, but lets check how well your tree hugging abilities are for punting the brands mentioned:
-Should your systems not be made completely in SA to prevent the long distances of transport and also to support local production and the resulting value chain to the whole economy (Unlike Solarhart)
-How long do you think a K... cylinder will last compared to other brands (for argument sake that are made in copper that could be repaired or even turned in for scrap) If the "good" brand fails 3 times within the life cycle opposed to another brand, would a lot of return on investment not be wasted through the additional costs? P.S. - cheaper mass produced and insurance driven 'brands" are not necessarily good... Have replaced countless K's with other brands, especially when a solar collector is added to the system that raises the corrosion factor(higher temp=more potential for corrosion)

P.S. for a rebate to qualify with ESKOM one may not install yourself, but in fact should have a plumbing qualified and solar certified installer sighing off the work and also a electrician to certify and sign of his part.Not only being qualified in two distinct trades, but also being registered at SESSA and ESKOM.
An installer must have R5M contractors liability insurance to qualify with ESKOM to install for rebates and only a particular SABS approved/compliant system(as tested only)
If solar was easy and cheap to install, then the ESKOM process would have been much simpler (for the rebate process)
Solar systems vary tremendously according to a clients needs and requirements, and people advising home DIY systems are playing it for a quick sale and then disappearing when things turn sour.
Sure there are many people that can do these installations, but in order to provide a durable and efficient system, not many can do that. Only time will tell in this case.
From my experience, solar companies/franchises can be formed at the drop of a dime, but what are their track records and experience that they offer...

Hats off to your efforts though, but clarify your "branding" before calling yourself a "tree hugger"

[killkom]

Hi I just have a quick question about solar water Geysers

I have recently made it my own min project to cut down my electricity consumption to do this I find that information is power

If you don't know how much elextricty stuff is using you can't see what the saving is

I installed a Geyser timer so I can have some control when this thing switches on and off

I also installed one of those E2 Efergy monitors to see how much I use and monitor what effects changes have on my consumption

I ran my geyser for 2 hours in the morning and 2 hours in the evening and surprisingly it still accounted for 40% to 50% of my daily usage

So a Solar geyser makes sense to me

The question I have is the following

The way I unserstand it is the Solar geyser sits on your roof and it warms the water up with the sun and stores it in the tank it then feeds into you normal electrical geyser so the input water is at a higher temp

What happens during the night or during the day when no one is home you are not using hot water so the solar Geyser is not flowing into the electrical geyser so the electrical geyser will cool down and turn on won't it.
Or is it setup that the Solar geyser water is always circulating through your electrical geyser?
What temperature does the water get to in the solar geyser?

[TooHotTooHandle]

@Killkom to answer your question

Generally a solar cylinder should be 25 % better insulated than a conventional electrical geyser to carry a SABS mark. Therefore it should keep its stored heat better even when placed outside on the roof.
As a rule of thumb(may be slightly off) a cylinder should not drop with more than 4 degree C over a 24 hour period.
A electrical element is 99.8 % efficient in converting electricity into heat in the water stored in a cylinder. Therefore if one can perfectly contain the heat (through insulation) inside the casing of a geyser given that all geysers usually have at least 30-60 mm of insulating barrier (around the inner cylinder that holds the water) then no energy should escape. All cylinders have a degree of heat loss (mostly through its insulation but also through conduction through it's connected pipework.
With the above in mind, putting a geyser blanket onto a cylinder and lagging exposed pipework would minimize losses. Without losses it would therefore not help to control the electrical element when it comes on , as all the energy is kept contained.
The true reason for geyser timer control is due to many cylinder brands not insulating their cylinders properly, and ESKOM trying to keep electrical elements form drawing power within peak power demand time.
What must be kept in mind also is that when water is used, cold water enters the cylinder that must be electrically heated (or preferably by solar) or else it will (over 2-4 hours) mix with the hot water in the cylinder, and thereby reduce the initial hot water temperature in relation to the amount of cold water added. The energy in the water would therefore appear to be lost (lower temperature at taps) but would actually be distributed in the whole volume of the cylinder(the hot water got colder, but the cold water in took some heat from the hot water)
An element is controlled with a thermostat (in conventional geysers) and that temperature point can usually be set to between 35-85 degree C. Any measurement of the thermostat below your set point would enable power to the element until the set point is reached where it will switch off.
Some things to know about the principles of cylinders are that:
hot water rises, therefore one removes the hottest water from the top of a cylinder(at the hottest point) and feed cold water at the lowest point(where the coldest water is)
Cold water has a higher density to that of hot water, and therefore lies at the bottom of the cylinder.

Solar systems rely quite heavily on the layering between hot and cold water for it's circulation and working principles.
At night the system will retain it's heat by the mere fact that hot water rises and will stay at the highest point of the system( in this case the solar cylinder)
In the daytime, as soon the collector turns radiation into heat, an imbalance is created and the collectors heat will start to rise from the highest point of the collector towards the middle point of the storage cylinder and in turn pull cold water from the lowest point in the cylinder and enter the lowest point of the collector. This is called thermo-siphoning and requires a collectors' highest point to be lower than the lowest point of the solar cylinder.
If a collector cannot be placed lower than the cylinder, then a hot water circulation pump and a 'differential' controller is used to circulate the hot water back and forth to the solar cylinder. With this type of installation, a lot of expertise is required to prevent heat rising towards the collector at night and achieving a circulation path that is free from air(which will stop or hamper the circulation)

The amount of heat gathered from a solar system would be determined by the following:
-the size of solar collector used in relation to the water volume (large area small volume= higher heat , small area on large volume= low heat)
-the system's efficiency due to type of system chosen and the degree of installation expertise
-the location (where it is installed)
-the type of solar system chosen (pool panel, flat plate collector, vacuum tube collector, vacuum drawn flat plate collector,parabolic trough collector, parabolic concentrator collector, concentrating tower collector and many types in between...)

[killkom]

Thanks for the reply Toohottoohandle

I airolited my house a few years ago at the same time I put a Geyser Blanket on and got them to insulate all the pipe work in my house so i have done that.

On a normal day if I leave the geyser without the timer I used to get about 25 to 28 units of electricity usage per day when the maid is there that figure jumped up to 40 to 45 units this supports what you said above

I then installed a timer and started to experiment. Now on a normal day I will use 16 to 20 units of Electricity and when the maid is there I use 25 to 28 units of electricity this is a nice saving so the timer works
The geyser does loose energy slowly but I find my thermostat to be very sensitive if the geyser is allowed to switch on and its at temperature as soon as I switch a hot water tap on a few seconds later the element comes on.

I would like a solar system that is stand alone and does not have an electrical backup this will bring my daily usage down to 7 to 11 Units on a a normal day and when the maid is there so the monthly saving is huge but I am just worried that I do that and the system runs out of hot water do some solar geyser systems come with there own electrical element as backup so i can get rid of my current geyser?

[TooHotTooHandle]

@ Killkom
The system that you refer to would be a "Pre-feeding solar system" that is classed as a "push thru" type.
This system feeds solar heated water in at the point where your "mains/inlet" to the electrical geyser usually fed in. This feeding process would only happen when a hot water tap is opened, and water from the solar cylinder is "pushed" from the solar outlet(solar tank highest point) to the geyser inlet(lowest points on the electrical geyser)
This type of installation would then not necessarily have a electrical connection to the solar cylinder(it could for extra back-up volume though) but would allow you to disconnect the electrical geyser in future (if it breaks one can bypass it) and run it's power line(wire) to the solar cylinders electrical element and thermostat.
Alternatively you can look at a solar system called a "Integral type" which will contain no heating element but which will only be suitable if you use most of hot water before 8 in the evening (this system type is cheaper than a full conventional solar system, but has drawbacks due to the nature of it's design= loses the heat back though it's glass at night)
Please Google for "Integral solar system" and "Pre-feed solar system"

[Tweak]

Thanks for you're efforts pietb. Such a great topic I printed it!

But I just wonder why this other nab has decided to hijack it Oo

[TooHotTooHandle]

@Tweak
Please be more specific who you are calling a nab...

[Paulr]

I'm enjoying the discussions in this thread between people who seem to know what they are talking about. Keep it up.

[kaybeach007]

Hi TooHotTooHandle

Excellent points you've raised. Let me try and and respond to them.

K brand tanks are locally manufactured in Benoni and mated to an imported collector panel. There are currently no VIABLE collector manufacturers in SA, we are about 18 months from having a locally manufactured collector panel of sufficient quality standards. So there is a carbon footprint, but far smaller than a fully imported system.

Copper requires about 4 times the energy to mine, about 6 times the energy to refine and a host of relatively toxic chemical to refine. So steel is a far lesser evil than copper from an environmental perspective (it's the metallurgical engineer in me speaking). Steel tanks use sacrificial anodes to combat corrosion. We faithfully service and change anodes in geysers manufactured and installed in the 80's and are still going strong, every 3 years we ring up our clients to remind them. Most South Africans don't know that they should change anodes every 2 - 3 years resulting in average geyser lifespans of about 7 years (read that stat somewhere, can't remember where) mainly due to negligence. Bronze and galvanised fittings, copper piping, thermostats and elements all make one big galvanic battery, but if the correct materials are used and installed in the correct sequence (ask old school plumbers about that one) and change the anodes every three years, tanks will last and last. As far as mass production is concerned, the little factory in Benoni does churn out a fraction of the tanks the boys in China do. I don't like glass fibre tanks, the F brand basically destroyed my faith in them, I'll watch their performance over next few years. I don't believe that they can handle the thermal cycling for long.

All solar geysers are 400kPa systems. The lower pressures will mean less stress on the tanks, besides very few municipalities in SA can supply 6 bar pressure. It's usually your houses in valleys that sit with high pressures like that, majority of towns sit between 3 - 4 bars. It costs money to pump at that pressure.

I don't condone DIY geyser installation, but DIY weekend warriors do it and you cannot stop them, but I like to spell out the consequences to them, so that they aren't dissapointed when the insurance company gives them the finger or they scald the baby to death in its cot.

The industry is in its infancy and there are many flybynights out there, which is why we have to try and keep the public as informed as possible. The number of systems coming out of the East and flying through SABS testing is horrifying. Hence the reason to stick with brands you know. The K brand is no silver bullet, but it is a good solid product with a good solid track record (you don't have a 100 year old company that holds a 60 odd percent market share but selling rubbish), made on our shores. Local is lekker.

I have to just mention that this config does not make Eskom happy

This type of installation would then not necessarily have a electrical connection to the solar cylinder(it could for extra back-up volume though)

and they will refuse to pay the rebate to you. In any configuration with an existing geyser, only one may have an electrical element, either the conventional or solar, not both. Eskom do random inspections, so beware, they'll withold the rebate and pull the installers accreditation. I am not a big fan of prefeed systems, they tend to not be as efficient as a stand alone solar system, because the conventional tanks just don't have the thermal insulation that the solar geysers have. Geyser blankets work, but they have their limits.

I agree, this is an good discussion. Education is power.

[I am Penguin]

In PE you can buy geyser like the one in the flyer next to the road for R7000.

Is it not the same system builders are selling too?

[I am Penguin]

Hi all, Pietb, thanks for a candid thread.
I am currently looking at quotes from 3 installers.
One of them has suggested that he can link the 200l swh to my existing geysers (not sure of the sizes, but lets say 250 and 150).
The guy recons that the thermo siphon will be enough to heat both geysers.
How ever one of the other installers said something about energy loss.

My question is, 'does linking the SWH to existing geysers make sense?'

Ishisheean

Yes it will work and could work very well depending on your hot water usage. The solar geyser will act as a pre-heater for your existing geysers.

Please ask the installer to insulate ALL hot water pipes.

Can the solar geyser handle the high pressure? Not all can as far as I know. But can the vacuum tubes??