DC Geyser Element

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Re: DC Geyser Element

Post by Hannes Meyer »

Dagse, almal.

Ek het iets oor dc/ solar elemente gevind wat moontlik kan help, kyk gerus na dit. https://www.youtube.com/watch?v=iGCMwsD ... video_user
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Re: DC Geyser Element

Post by Mud Dog »

Chris, any more feedback on this? Is your neighbour's setup working OK?

I've been putting my solar geyser project off pending a decision on which route to go. The AC / DC element would be the best option if it really works .... less disruption, existing plumbing remains as is and flat solar panels on the back roof look a lot less crappy than a geyser tank that usually mounted so high that if breaks the roof line and becomes visible from the front. I can still leave my home-made solar heater in place as it is as a pre-heating / assist feature and a geyser timer I already have.
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Re: DC Geyser Element

Post by Mud Dog »

Chris??
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Re: DC Geyser Element

Post by ChrisF »

Hi Andy :)

Sorry, been in Hermanus more than on the forum ....


YES - it works :cooldude:


BUT, and Andy I am sure you KNOW this - it needs SUN to work.


Now add the Cape Winter weather .... you DO see the temp creeping up as the sun tries to break through the clouds, but simply not enough for the heating required, thus the dual-controller can then be used to supplement the heating with 220V as per your "timer" settings.

So how does it work when there IS sun ? He currently has only 600W worth of PV panels for his system, and this is enough for Mom, Pop, and the 4 year old. However, add the cleaning lady ... and on these days the geyser gets drained ....


So what does all this mean ??
- Winter time the solar harvest DROPS.
- DONT undersize the PV panels, for these systems the max is 1kVA (I believe they are working on a 1,1 or 1,2kVA element)
- with these systems you cant over size the PV panel to compensate for winter ... :(
- PV panels DO take up 2 to 3 times the roof space when compared to the same solar hot water panel
- solar hot water systems are very limited for pipe distance !!
- I will be installing a 1 or 1,2kVA PV panels some 30m from my geyser in September.


In short - I believe this works to the point where I have already done the wiring and will be doing the installation shortly - KNOWING that there will be periods in winter where we have days of rain where I wont get any benefit from it. Looking at the bigger picture, the system will work 90%+ of the time :cooldude: :cooldude:
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Re: DC Geyser Element

Post by Mr_B »

Add a heat pump to this system and you've got a winner. I've too learnt that solar isn't effective enough in winter, escpecially in a large family environment. A heat pump does still require 220v elec to operate, but on average an air to water system has a COP of 3.8 to 4, with some being even better. Remember a heat pump will continue working when the sun goes down and is just as effective at 10deg c as it is at 30deg c ambient!

A little bit of info from Wikipedia:

Heat pumps are used to provide heating because less high-grade energy is required for their operation than appears in the released heat. Most of the energy for heating comes from the external environment, and only a fraction comes from electricity (or some other high-grade energy source required to run a compressor). In electrically powered heat pumps, the heat transferred can be three or four times larger than the electrical power consumed, giving the system a coefficient of performance (COP) of 3 or 4, as opposed to a COP of 1 for a conventional electrical resistance heater, in which all heat is produced from input electrical energy.

So typically a heat pump will use 75 - 80% less electricity compared to a normal 220v element with a COP of 1!

So add one of these to your setup, and you'll have hot water all day every day!

Typical prices:

http://www.sustainable.co.za/solar-wate ... pumps.html

B :thumbup:
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Re: DC Geyser Element

Post by dalkill »

Eish.... all this scientific calculations... my head spinning now :-)

All i know, when Swambo done in the morning in winter, there is nothing left for me, especially when she does here hair too... she likes the water piping hot !!
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Re: DC Geyser Element

Post by ChrisF »

Mr B I noted your thread yesterday, just did not have the time to reply.

YES, a heatpump has various benefits. and as you intend using it, it certainly will give you a bit of power saving.


Please note the following about heat pumps:
- the COP of 4 is hardly ever achieved, 3,5 to 3,8 is realistically the best. BUT, this relates to outside temperatures ... You need this to save you power in mid winter - when it is COLD outside. Now the heatpump efficiency is hardly 3 ! Okay, you WILL still save power, but not as much as the brochures want you to believe.
- a heat pump is essentially an air conditioning unit, which requires maintenance. You are close enough to the sea to have the coil treated with "BluChem".
- like any air con unit the operation of this unit goes hand in hand with a fan noise ... think carefully of the placement ...




There are now small integrated heat pump units, which may be ideal for your purposes - as a final re-heater before the water goes to the tap. Thus you will have a THREE level heating :
- solar as primary
- turn the thermostat down on the geyser to 30 degrees, thus minimal heating, but the heatpump will get pre-heated water at all times, thus a small unit should keep up with the demand of a large family.
- final step the heat pump


run this concept past your supplier .... would love to see his face when you mention keeping the element in the geyser .... certainly defeats the object of the heatpump - BUT, you will need a BIG heat pump for your family size if you dont pre-heat the water !!!!
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Re: DC Geyser Element

Post by ChrisF »

dalkill wrote:Eish.... all this scientific calculations... my head spinning now :-)

All i know, when Swambo done in the morning in winter, there is nothing left for me, especially when she does here hair too... she likes the water piping hot !!
summer time the water coming into the geyser is substantially hotter than in winter. AND in summer you dont use as much hot water as in winter.


You need a larger geyser, OR get up earlier .... :lmao: :lmao: :mocking:
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Re: DC Geyser Element

Post by Mr_B »

dalkill wrote:Eish.... all this scientific calculations... my head spinning now :-)

All i know, when Swambo done in the morning in winter, there is nothing left for me, especially when she does here hair too... she likes the water piping hot !!
Come on son... just get up earlier... and shower/bath with the wife... :thumbup: :angel:
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Re: DC Geyser Element

Post by Mr_B »

ChrisF wrote:Mr B I noted your thread yesterday, just did not have the time to reply.

YES, a heatpump has various benefits. and as you intend using it, it certainly will give you a bit of power saving.


Please note the following about heat pumps:
- the COP of 4 is hardly ever achieved, 3,5 to 3,8 is realistically the best. BUT, this relates to outside temperatures ... You need this to save you power in mid winter - when it is COLD outside. Now the heatpump efficiency is hardly 3 ! Okay, you WILL still save power, but not as much as the brochures want you to believe.
- a heat pump is essentially an air conditioning unit, which requires maintenance. You are close enough to the sea to have the coil treated with "BluChem".
- like any air con unit the operation of this unit goes hand in hand with a fan noise ... think carefully of the placement ...




There are now small integrated heat pump units, which may be ideal for your purposes - as a final re-heater before the water goes to the tap. Thus you will have a THREE level heating :
- solar as primary
- turn the thermostat down on the geyser to 30 degrees, thus minimal heating, but the heatpump will get pre-heated water at all times, thus a small unit should keep up with the demand of a large family.
- final step the heat pump


run this concept past your supplier .... would love to see his face when you mention keeping the element in the geyser .... certainly defeats the object of the heatpump - BUT, you will need a BIG heat pump for your family size if you dont pre-heat the water !!!!
Chris, as always very insightful input! Much appreciated. Even with a COP of 3 I'll be saving substantially in winter. My total bill between the 2 households has spiked R 1500/m on average. So if the heat pump costs say 20K for a 5KW unit(as spec'd by supplier/installer), it would take +- 20 winter months to save that back. This is based on the saving being R 1000/m as I'll still have to pay the R500 for the electricty it would use. Then, a big maybe... I want to investigate using the same heat pump to heat the swimming pool a bit for the other 8 months a year where it isn't really need for geyser water heating. That would be really cool(well warm actually!).

:thumbup:
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Re: DC Geyser Element

Post by ChrisF »

Mr B contact Carlo at Apollo Air - 021 905 7979


we have used many of their heat pumps over the years, also many for pool heating.

They will give you the best advise and products.


In fact they are NOW busy commissioning a 400 kW heat pump for us, for an olympic size pool. .....
IMG_7793 (Small).jpg
NOT your standard home heatpump :lmao: :lmao:
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Re: DC Geyser Element

Post by Mr_B »

Ok then... I'll have one of those pretty please! Hehe!
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Re: DC Geyser Element

Post by ChrisF »

only 16 week delivery period ....


and you dont want to know what THAT baby costs !
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Re: DC Geyser Element

Post by ChrisF »

Time to revive an old thread.

12 months later, and actively researching this topic, and SEEING how it does AND does not work for my neighbour I can now provide the following feedback.

I need to start with some maths .... sorry :crazy: :mocking:


TWO people, no kids, no cleaning staff - thus minimal wastage. Our geyser usage has now been measuerd, in August, as follows:
Using a geyser timer - daily average over a week - 7,59 kW.h per day.
Timer on over ride - daily average over a week - 8,76 kW.h per day.

This with a timer set to be on three times a day, thus not maximizing energy savings. Still, at out electrical rate, is just over R 1 000 savings per year.

The other item that was noted during these experiments - about 0,9kW.h energy lost each night due to heat losses from the geyser. With higher day time temperatures in the roof void the losses will be significantly less during the day. This for a geyser with no geyser-blanket and no insulation on the pipes - this will be addressed shortly.


Now look at the various PV retrofit solutions out there. They all started with 750W DC elements, most of the current selection have 1kW DC elements. Effective maximum sun hours are typically 6 hours in summer and 4 hours in winter.

Thus a current PV retrofit can only provide 4 to 6kW.h per day .... this while a family of two USE more than 7kW.h per day.

That said, we will be going this route, for the following reasons:

- no overheating of the system
- no component failure due to excessive system temperatures
- much easier installation/retrofit (NO work required on the pipes)
- No pipes passing through the roof, thus less risk of water leaks
- in our case there is only one small spot on the roof near the geyser where solar panel could fit, right in the shade of two palm trees .... 30 m away I have ample roof space for PV panels, and this distance is no issue for the electrical wires.


COST - Solar hot water systems are still cheaper to install than PV retrofits, with the solar hot water systems providing a LOT more energy harvesting than the PV systems.



Future development - todays "problems" are tomorrows progress. Today the systems have the follow scope for improvement:

PV :
- small homes could get by with a 1kW element, 4 person homes homes would need a 1,5kW element.
- the next step would be MPPT units that regulate the OUTPUT power, thus one could add 1,2kW PV panels to a 1kW element and actually get 1kW to the element for longer periods ....

Solar hot water :
- over heating of these system are certainly the one aspect that can do with some research .....
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Re: DC Geyser Element

Post by pietpetoors »

Thank you Chris, is always lekker to read your reports.
Thus a current PV retrofit can only provide 4 to 6kW.h per day .... this while a family of two USE more than 7kW.h per day.
The water in a geyser is always too hot to use as it is, so if the geyser can supply 6Kw out of the 7 Kw you need I am sure you will still have usable hot water, especially for only 2x people.

My mother has one of then vacuum tube systems with a fancy controller, I saw there that even on 48 degrees the water is too hot to shower in.

Let me know when you going to buy your hardware.
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Re: DC Geyser Element

Post by ChrisF »

Pieter Riaan bought some components in bulk, so he already has everything except the PV panels. I was just waiting to wrap up my testing and measurements to confirm what route I want to take.


YES, 40 odd degrees is more than one need, EXCEPT, every so often the water should exceed 60 degrees to kill all the "goggas" .....



I was also torn between the cheaper route of solid state switching vs an MPPT system ..... with these system so borderline in terms of capacity I will go the MPPT route to extract as much energy as possible.



Oooops, forgot to mention the potential savings in the previous post. The potential savings depends a lot on your electrical tariff scale. With most people now heading towards R 2 per kW.h consider the following:
300 sun days per year
5 kW.h harvested for each of these days
That is a saving of R3000 per year !!
Thus a payback period of about 5 years.

We are on dual tariff system where our savings would be on a scale of R2,88. Add a bit of saving on the installation costs and our potential savings of R 4 000 per year means a payback of about 3 years.
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Re: DC Geyser Element

Post by Mud Dog »

Thanks Chris, interesting. I've been procrastinating on a solar assisted geyser pending a decision on which route to take, all the while paying eskom's rates. Will have to reach a decision soon.
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Re: DC Geyser Element

Post by pietpetoors »

Chris what do you need for the whole system?
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Re: DC Geyser Element

Post by ChrisF »

Starting from outside -

PV panels - we are going for 6 off 170W 112Voc panels (high voltage, low amps)
Mounting brackets
Wires to inside - due to my longer distances we used thicker wires, these were installed a few months back as part of the lights project
Geyserwise Dual Controller - controls both the Eskom element and the PV element, allowing different timer and temperature settings .... thus you give the PV max opportunity to do its thing, then set the 220V element as backup to ensure you have the correct temperatures at given times, ie 50degrees in the morning, and maybe only 40 degrees at a different time for the dishes.
MPPT controller, OR a solid state relay - more than R2k difference in price, but I do believe it is best to go for the MPPT to ensure you get all the energy if you are more than one person in the house.
Dual element - 2kW AC, 1kW DC.


Rough figures -
R3k for the element and controller
R3k for the MPPT, less than 1k for the solid state relay
R8,5 for the PV panels, without the mounting brackets ...
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Re: DC Geyser Element

Post by pietpetoors »

Geyserwise Dual Controller - controls both the Eskom element and the PV element, allowing different timer and temperature settings
The sun don't shine at night, isn't it as simple as when the sun shines the PV gives its best, when not, Eskom does its job.

Won't a simple timer, which I already have, work?
My timer only switches geyser on when it is dark, ie late at night or very early in the morning, so AC element is switched off anyway during sunshine hours when DC element will be working.
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Re: DC Geyser Element

Post by ChrisF »

Pieter some of the other brands do it like that - thermal probe that controls the PV on/off according to the water temp, and a timer on the 220V element.


It all depends on your needs - when do you need hot water ?

The Geyserwise unit is very nice, if not over complicated .... you now have multiple time zones for the 220V element and can set different temperatures for each zone, thus the water is just hot enough when you need it, but if the sun shines the PV will take it higher .....
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Re: DC Geyser Element

Post by ChrisF »

little teazer .... :laugh2:

7 days - monitor the geyser with a traditional ON/OFF timer : 7,59kW.h average per day, that is just for the geyser !

7 days - monitor the geyser with the timer on override, ie no timer : 8,76kW.h average per day ... which actually ties in well with the 1kW.h re-heat in the morning. I did not add a geyser blanket to test the potential saving of this ....

We then started the install of the PV system and Geyserwise dual element system. The geyser retrofit was done before we finished the PV install. This afforded me a good opportunity for one more test .... :thumbup:

3 days - monitor the geyser power draw with the Geyserwise dual controller. This allows for times the geyser will be on, but also provides to opportunity to set different temperatures - remember the lower the temperature the less energy losses. For these three days the average power was about 6,8kW.h per day.


And Friday afternoon we "quickly" got onto the roof to wrap up the install .... is mos gou om n paar panele vas te sit en die drade klaar te maak ..... :siffler: :surrender:

Have you ever heard of a job that FIGHTS you ?????

What should have taken less than an hour ended up in a 6 hour nightmare .... The track system that came with the panels are NOT nice !! Then we had to make 4 small solder joints on the roof - in a mild wind .... Eventually went and bought a 200W soldering iron for this. All just sapping the time.

Saturday and Sunday were proper rainy days in the Cape, yet the geyser used less than 2kW.h from eskom, with the PV providing the bulk of the power. :cooldude: The last two days less than 0,5kW.h of eskom power was used per day for the geyser :thumbup: :yahoo: By Monday afternoon the water was up to 69 degrees !! :thumbup:


I am logging the data every morning and every afternoon and will give feedback at a later stage as to our experience with this system.
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Re: DC Geyser Element

Post by Mud Dog »

This is the way that I would prefer to go, but what has had me procrastinating is the number of reports that I've heard that the saving is not significant enough to warrant the cost. From what you are saying, this seems not to be the case.

What is the total wattage and amperage of the PV array?
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Re: DC Geyser Element

Post by ChrisF »

Andy a quick Google of the options will show how the PV element has gone from 750W to 900W to 1000W and now to 1100W over a period of about 2 years.

Frankly the sooner it gets to 1,5kW the better !!

I now have six off 170W panels with a peak voltage of 87V. Thus about 12A at 100% duty of just over 1kW.

This is still just 6kW.h in summer and 4kW in winter. While our geyser use an average of 7,5kW.h per day.


The better timer of the Geyserwise unit also brings about a small saving - you can now set lower temperatures for certain time zones, ie only 40 degrees during midday for the dishes, while ensuring a higher temp for the morning shower or the missis bath in the evening.

I am now seeing about 0,5kW.h energy loss during the night .... time to fit that geyser blanket !!


PV panel -
DSCN2712 (Small).JPG
1,6kW on the roof, and wter heating for the pool -
DSCN2715 (Small).JPG

Andy the payback remains an issue ..... 4 years back a standard solar hot water system was 12 to 16k, but with the electrical unit tariff at the time it made little sense ..... Now electricity costs so much more, but those same solar hot water systems are now R25k to R30k.

By comparison this PV retrofit should now cost about R25k. It is very tempting to get carried away by the good figures I see now .... but being more realistic, working on an average of 5kW.h saved per day, for only 330 days per year, at our current electricity rate of R 1,76, this amounts to a saving of about R 3000 per year. Thus the payback just does not make sense ..... unless you get the parts yourself, shopping around for the best prices .... then a payback of 5 to 6 years (at the current electricity rates) are possible. Allow for eskom increases and it becomes tempting.


Why go for which option, or not ?
Solar hot water :
- more plumbers know this
- MUCH smaller footprint required on your roof !! 1,5m2 vs 7,5m2 !!!
- you get more savings from the solar hot water system
- BUT, these systems overheat too easily .... leading to water wastage and system damage .... THIS is certainly the biggest downside of solar hot water systems.

PV retrofit :
- you dont need a plumber, ie no changes to the water piping
- panels can be FAR away from the geyser, in my case 25m distance between the panels and the geyser. Cant do this with solar hot water. In my case I need this due to the shade of trees and a less than optimal house roof layout, for others with a double storey house this may well be the pratical solution ....



to conclude on a positive note - the last 5 days our average geyser power draw is 0,725 kW.h :thumbup: :cooldude:

between the 12V lights and the PV geyser our electrical usage has reduced by almost 50% :thumbup: :thumbup: :thumbup: Okay, the year round average cant be that good ....
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Re: DC Geyser Element

Post by ChrisF »

feedback time -

End September we rapped up the installation, getting all the settings the way we want.

Thus we have now concluded four months of using the installation.

The energy meter is still connected, and I still keep track of the energy use.

Time = 4 months
Eskom usage = 3 kW.h

yes the total usage over the 4 summer months was a princely total of 3kW.h.

Thus already more than R 1 600-00 saving. Depending on the winter savings it is possible we could save close to R4000 for the year. Thus a payback period of 6 years, ignoring the absurd eksdom increases ....


I will continue to monitor and record the usage, throughout the winter, and keep you posted.
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Re: DC Geyser Element

Post by Mud Dog »

Thanks Chris, valuable info! I have still not reached a decision on my own installation, but it looks more and more like I will go the PV route and save the extra plumbing work. :winkx:
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Re: DC Geyser Element

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Thanks for feed back :thumbup:
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Re: DC Geyser Element

Post by ChrisF »

Can see winter is approaching ....

PV system is still providing 99,9% of our hot water.

But a few weeks back it would reach the max of 70 degrees with some sunlight to spare ....

Now it only goes to mid 60's when the sun sets ....


So for 6 months of the year this setup safes us 99,9% of our water heating bill.


Now to see how much it saves us in winter .....


NOTE TO SELF : Must install a geyser blanket !!!!!!!!!!!! seems to loose about 4 degrees during the night ....
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Re: DC Geyser Element

Post by Knuppel »

Losing only 4 deg is very good!!, would love to see if your blanket would make a difference!
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Post by ChrisF »

Marius maybe I should leave the blanket OFF until mid winter, so really test the effect of no blanket vs using a blanket.
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Re: DC Geyser Element

Post by Knuppel »

Chris, in mid winter I lose about 10 deg. My geyser is on the roof though and quite exposed to the elements. So yes it would be a good test to do it then.
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Re: DC Geyser Element

Post by Mud Dog »

Geyser blankets work - the difference won't be big, but it will be there.

What's more important is the lagging / insulation of the pipes. The cold feed should be insulated for the last 1 - 1½ metres at the geyser (only if it's an in-line type geyser and not the old combination type with header tank and ball-valve), and the hot supply should be insulated in it's entirety.

Note that the 'modern' foam type insulation does not stand up well to external weather conditions and should be replaced after about six years or so. This can be dramatically extended if you cover the foam with sisilation - easy enough to do by cutting strips wide enough to wrap around the foam and securing with cable-ties. Be sure to cover past the ends of the foam and close them off so as to prevent water / moisture ingress since this will significantly reduce the life and effectiveness of the foam. (The old asbestos rope lagging was still the best, so keep it if you still have, just paint it to prevent moisture ingress and fraying.)

:winkx:

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Re: DC Geyser Element

Post by ChrisF »

bring on the winter .... testing time ... :mocking: :subscribed:
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Re: DC Geyser Element

Post by Knuppel »

I am awaiting your test results!
Have been running my setup since 2007!
Have replace the foam insulation once already

How will the blanket stand up to the elements?

I Am 95% completely off grid regarding my heating and electrical needs. So every improvement gets me closer to the 100%
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Re: DC Geyser Element

Post by ChrisF »

my geyser is inside the roof space.

Thus the insulation should last.

PLEASE NOTE - on many solar hot water systems the water gets close to boiling point on long sunny days. TOO hot for most insulation materials !!

Since I have the PV system the temperature is controlled by a thermostat and the water dont get hot enough to damage the insulation.
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Re: DC Geyser Element

Post by ChrisF »

Marius I am actually looking forward to this winter. Really want to see how the pv system does in the Cape winter - overcast for days on end ....


Hoping to get a year round saving, on the water heating, in excess of 75%. That is a very optimistic value !! Even the SANS codes indicate an average saving of 50% as a good value .. at least I KNOW I am already past 50% :yahoo: :celebrate:
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Re: DC Geyser Element

Post by Family_Dog »

I have a 200-litre in-roof geyser heated by means of two external panels with Glycol as the heat carrier. During Summer, I never use electricity but I do prefer using electricity as well as the SP during Winter, even though one can shower with just the SP providing heat but it is a warm, rather than hot, shower. One still saves electricity however because the element only has to heat the water up from around 38-40°C and not from near freezing conditions overnight.


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Re: DC Geyser Element

Post by ChrisF »

Eric the glycol systems are certainly the best in the solar hot water game.


Combining this something like a Geyserwise controller for the electrical element really tweaks the efficiency to the max. Now you can set different temperatures for different time zones.

Thus you know you will have hot water for the morning shower, irrespective of the weather.

Midday even 40 degrees is enough for the dishes.

By afternoon you can again ensure enough hot water the shower.
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Re: DC Geyser Element

Post by Family_Dog »

Must say that this system paid for itself in no time at all.

Must be a good system, Chris, it came from Cape Town... ;)


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Re: DC Geyser Element

Post by ChrisF »

summer she is a memory ....

sun she is not hanging around long ....


the day time is shorter by a good few hours, and the pv system SHOWS this !!


December the system would reach 70 degrees, the electric cut off for this system, early in the afternoon.

By late February it would get close to 70 ...

As March marched on the end of day temperature was lower day by day ...

By
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Re: DC Geyser Element

Post by ChrisF »

summer she is a memory ....

sun she is not hanging around long ....


the day time is shorter by a good few hours, and the pv system SHOWS this !!


December the system would reach 70 degrees, the electric cut off for this system, early in the afternoon.

By late February it would get close to 70 ...

As March marched on the end of day temperature was lower day by day ...

By April the system only reaches mid 50's on good days. Add extra cloud cover and we start using bits of power from eskom to ensure sufficient hot water for our use.


The total eskom use for the first two weeks of April (4,48kW.h) is still only about half of one day pre solar ! :thumbup: :celebrate: :cooldude:


would be most interesting to see what this system does when the real cold rainy winter days sets in .....
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Re: DC Geyser Element

Post by Mud Dog »

Thanks Chris, what's the biggest DC element available now with this system?
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Post by ChrisF »

Andy I will ask them.

The element size has gradually increased over the last few years.


The system my neighbour installs mostly - 900W (3x300W panels), think this has a 1kW element. Best "bang-for-the-buck" system. Smallest roof space required. Much easier to install three panels, as compared to my 6x170W panels.

He actually has the 900W system in his own house. Works for the three of them ... but not on the day the cleaning lady is there .... SCARY to see the figures the day the cleaning lady is there ... one would swear she never closes the tap ..
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Re: DC Geyser Element

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Thanks. Just want to know where I'm going with this - 90% committed to the PV system.
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Re: DC Geyser Element

Post by ChrisF »

still logging the units used.

But this post gives a slightly different feedback - water temperature.

During summer months a geyser temperature of 50 degrees Celcius was more than enough.

Over the last 2 weeks the very same 50 degrees just did not feel hot enough. To rephrase it - when using only the hot water it is fine, but obviously that drains the geyser very quickly !! Add to that the fact that the incoming water is now so much colder .... Becoming an issue to actually shower and shave and still have hot water at then end.


just turned the temperature up to 55 degrees for the morning and the afternoon, with a mid day temperature of 45 degrees, for the dishes etc.


With the PV already stretched to deliver 50 degrees with the shorter sun hours this obviously means more Eskom power over the mid 4 months of winter. So be it.


The idea is NOT to save power by taking a cold shower ! :lmao: :tease:



I know it is absolutely impossible to not adjust behaviour patterns when doing research such as this. But the idea IS to TRY and stay with standard usage patterns, while still having hot water as needed.


On the topic of "behaviour" .... previously I often opened the taps and took a moment to take "leak", now you ARE so much aware of the hot water being wasted, and these obvious losses are avoided.
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Re: DC Geyser Element

Post by Knuppel »

I have the evacuated glass tubes. I think heating water with PV is crazy! Every time you covert enery you loose!
At the moment I get to 70 deg no problem.
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Post by ChrisF »

Marius crazy may be a strong word ... :)

PV to DC electricity, this goes straight into a DC element in the geyser. No funny conversions of power ....


Add to that, in my layout the only place I could put a solar hotwater panel it would be in the shade each afternoon.

I could move the PV panels to a more practical position

downside of PV - panels are about three times the roof area for the same amount of heating as with evacuated tubes.

downside of evacuated tubes - serious system over heating .... and early component failure .....
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Re: DC Geyser Element

Post by Knuppel »

Very true Chris. In my mind its crazy but in your mind its very practical. I have total understanding for your situation.

Regarding evacuated glass tubes. I have now had my system running for 10 years and the only component that has failed is the float in the top up system.
Yes it does overheat, about 2 to 3 times per year it gets to boiling point. Safety valve opens, it dumps a load of hot water and no further drama. What I dont understand is what else would fail due to the overheating?

I slightly disagree with your conversion theory. For your geyser you are converting radiant energy to Electrical and then again from electrical to thermal energy whereas the geyser I have is straight from radiant to thermal. But again that argument is nullified taking your practical situation into account.

I am not arguing or nitpicking to stir, I learn in the debating process. ;-)
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Post by ChrisF »

All just sharing our experiences, saving the next guy some school fees. :)

Taking a step back :

- heat pumps - we do install many of these, for larger and commercial use. I am not convinced it is the optimal solution at a house .....

- Solar hot water - certainly has many benefits. Dumping of boiling water, and premature component failure being its primary drawback. Of 200 units we installed we had about a 10% early failure rate ....

-PV - works for me, and I am hardly objective :) The main downsides - PV panels take up way to much rood space !! Would LOVE to see this with a 1,5kW system ..
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Re: DC Geyser Element

Post by Mud Dog »

ChrisF wrote:Andy I will ask them.

The element size has gradually increased over the last few years.


The system my neighbour installs mostly - 900W (3x300W panels), think this has a 1kW element. Best "bang-for-the-buck" system. ....... the cleaning lady is there ... one would swear she never closes the tap ..
Any news on the bigger elements / systems, Chris?
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Re: DC Geyser Element

Post by ChrisF »

Andy nothing yet. But I did ask Riaan to let us know as soon as something is released ....
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Re: DC Geyser Element

Post by Mud Dog »

So the biggest is a 1KW DC ?
How many KW AC ?
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Re: DC Geyser Element

Post by ChrisF »

My een is 1kW DC, en my meter wys 2,5kW op Eskom.


http://www.geyserwise.com/" onclick="window.open(this.href);return false;

http://www.geyserwise.com/products/pv-w ... 00l-system" onclick="window.open(this.href);return false;
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Re: DC Geyser Element

Post by ChrisF »

Record so far, total monthly eskom power usage for the geyser :
October (half month only) - 1,46 kW.k
November - 1,13 kW.h
December - 0,4 kW.h
January - 0,04 kW.h
February - 1,46 kW.h
March - 3,17 kW.h
April - 21,64 kW.h

Thus the first 6 months, granted these were the prime summer months, already netted nearly R 3 000 saving.


now let's see what savings the winter months deliver ...
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Re: DC Geyser Element

Post by Knuppel »

Watching with interest.
Will also like to see those temp loss figures in mid winter.
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Post by ChrisF »

Knuppel wrote:Watching with interest.
Will also like to see those temp loss figures in mid winter.
I must remember to check that when the cold sets in ...

Must actually get the materials to wrap the geyser and pipes as soon as the readings have been taken .....
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Re: DC Geyser Element

Post by Mud Dog »

Chris, is your geyser still the old combo type (i.e. with header tank and ball-valve)? The advantage of these is that they are typically placed in the roof space, thus being a little more protected from the elements. Not to say that the in-line geysers are typically fitted externally, but they sometimes are, especially in houses that were built from the 80's where flat roofs were more common.

The combo's are mostly vertical, so fitting a blanket is a lot easier than on a unit that lies horizontally in a tray. One disadvantage (aside from lower pressure at the faucet), is that there is internal heat loss through the internal filler pipe between the header and geyser tanks. There is only a 30 to 40mm insulated gap between the thanks, and given that heat rises, the hottest water in the geyser is right up against this gap with significant conductive heat loss through that small section of filler pipe - not much you can do about this except cover the header with the blanket as well. This way some of the loss to the header will act as pre-heating.
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Re: DC Geyser Element

Post by ChrisF »

Nope, Reasonably new geyser, maybe 10 years old. The house is probably only about 20 years old. .... wou sê is n nuwe huis, toe onthou ek ons woon al 9 jaar hier !

It is a high quality product, and I do expect the losses to be minimal - from the geyser. Classic horizontal mount. Will drape Isotherm over it, and tuck in as best possible.

That said, there is absolutely no insulation on the pipes from the geyser .... insulating the first 2 to 3 meters may well reduce the "standing" heat losses. Also not practical to reach the rest of the pipes ....
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Re: DC Geyser Element

Post by Mud Dog »

Lag the first 1½ to 2 metres of the feed - all others should be lagged in their entirety especially the hot supply right up to where they enter the walls at the faucets .... big losses there if you have long runs.
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ChrisF
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Re: DC Geyser Element

Post by ChrisF »

JIP, that certainly is the ideal. And on our projects I wont sign off on any payments if this is not done, ie full lagging of all hot water pipes.

But when you buy a house ..... aai toggie .... and it simply is not possible to retro-fit everything that should have been built right in the first place ..... will insulate what I can reach.
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