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Geysers with two elements in South Africa?


mmacleod
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It seems to be quite common place in various other countries for "water  heaters" to contain two elements (each with own thermostat) instead of a single element. (It also seems more common for them to be vertical which may be related...)

e.g. as pictured here:
image.png.ce7c365e713b658b99bac5b2d88a1754.png


I have been trying to find similar in a za context, and either I'm searching for the wrong keywords, or they just don't exist here.
I was wondering if anyone knows.

1) Are there products that can be bought locally that can take two elements?
2) If so which? Or what do we call it here so that I can search for it?
3) Why is it not common here  if its common in other countries?


The best I could find so far was this forum thread, but as far as I can tell these are custom modifications and not actually supported by the product?
 

 

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1 hour ago, mmacleod said:

3) Why is it not common here  if its common in other countries?

Cost.  SA we are content with less features and lower cost.

Yes the vertical configuration and dual element is related. It only use one element at a time. When cold the top element will heat the top half of the water heater and you quickly have some hot water to use. Then it will switch over to the bottom element to heat the bottom half.  If you don't use a lot of hot water then only the bottom element is active.  Think these have only one electrical connection thus not suitable for eskom and solar dual supply without modification.

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5 hours ago, Pietpower said:

Think these have only one electrical connection thus not suitable for eskom and solar dual supply without modification.

hrm, not sure about that, I've run into a lot of material over the years on various solar forums etc., suggesting that they seem to take separate wiring for each element "out of the box" (seems especially common in Australia/USA) - I've never read of any difficulties wiring the two elements to take separate power sources.

e.g. This site as an example http://techluck.com/
 

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28 minutes ago, mmacleod said:

hrm, not sure about that, I've run into a lot of material over the years on various solar forums etc., suggesting that they seem to take separate wiring for each element "out of the box" (seems especially common in Australia/USA) - I've never read of any difficulties wiring the two elements to take separate power sources.

e.g. This site as an example http://techluck.com/
 

From that site:
"Only minor modifications are needed for most standard water heaters, simple wiring modifications. NO HEATING ELEMENT CHANGES NEEDED. The wiring modifications are easily reversible."

Units I came across in Europe only had a single power supply to the water heater.  Explanations, most likely based on USA heaters, explained that the elements are interconnected.  But then again the European market also had a vast range of different water heater types.  Pipe in tank systems, tank in tank systems, some connecting to the central heating system, some using gas or combined with electricity.

From the quote above I presume it is easy to rewire a system to work with solar.

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4 minutes ago, Pietpower said:

From that site:
"Only minor modifications are needed for most standard water heaters, simple wiring modifications. NO HEATING ELEMENT CHANGES NEEDED. The wiring modifications are easily reversible."

Units I came across in Europe only had a single power supply to the water heater.  Explanations, most likely based on USA heaters, explained that the elements are interconnected.  But then again the European market also had a vast range of different water heater types.  Pipe in tank systems, tank in tank systems, some connecting to the central heating system, some using gas or combined with electricity.

From the quote above I presume it is easy to rewire a system to work with solar.

hrm, okay, either way it doesn't really matter much if nobody sells them here.

They're clearly superior (ease of modification for off grid purposes aside) so its crazy to think that price alone is enough to keep them completely out of the local market. An extra element/thermostat barely even costs that much...

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I believe Voltex sells a dual-element replacement. So you buy the normal one, and then retrofit the dual element thinga-ma-bob later.

I believe some people have also bought the cover plate from a failed unit and took it to an engineering shop to add a spot for a second element, making their own.

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5 minutes ago, plonkster said:

I believe Voltex sells a dual-element replacement. So you buy the normal one, and then retrofit the dual element thinga-ma-bob later.

I believe some people have also bought the cover plate from a failed unit and took it to an engineering shop to add a spot for a second element, making their own.

Yeah, I've seen both of these, neither of them is really as good as an actual unit thats just designed for two elements though.
Also from both a safety and efficiency perspective I'd (personally) like some decent space between the two elements (wiring further apart and so on)

I guess the other option and probably closest I can get to a proper two element geyser,  is to go for two geysers that just connect to one another.

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1 hour ago, mmacleod said:

They're clearly superior (ease of modification for off grid purposes aside) so its crazy to think that price alone is enough to keep them completely out of the local market. An extra element/thermostat barely even costs that much...

You get similar stuff in the local market.  But your eyes are going to water when I give you a price.

Last one I did was a fair bit larger but without any elements (for heat pump) and it came in at R27,000. Smaller unit I would guess about R10k-R15k

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8 minutes ago, mmacleod said:

I guess the other option and probably closest I can get to a proper two element geyser,  is to go for two geysers that just connect to one another.

Yes. Two geysers in series with the first one on solar and the second just doing top up temperature is what I am also looking to do.

Two 150 liter geysers is below R6k excluding electrical supply and installation.

Edited by Pietpower
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12 minutes ago, Pietpower said:

Yes. Two geysers in series with the first one on solar and the second just doing top up temperature is what I am also looking to do.

Two 150 liter geysers is below R6k excluding electrical supply and installation.

This is what I have done, only I have a 2KW electric geyser running from PV on sunny days feeding into my gas geyser that only ignites when the incoming water temperature is lower than required.

I chose the gas to diversify my energy sources.

More expensive to install than a second electric geyser but vastly superior in my opinion.

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34 minutes ago, Pietpower said:

Yes. Two geysers in series with the first one on solar and the second just doing top up temperature is what I am also looking to do.

Two 150 liter geysers is below R6k excluding electrical supply and installation.

Does seem like the way to go, looks like two smaller geysers barely costs much more than a single large one, and its kind of neat in a way  having the two mostly separated from each other.

I'm convinced 😀 Now I just need to decide which of the dozens of potential options for feeding PV into the PV one is going to be the most sane.

Edited by mmacleod
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  • 2 weeks later...
8 minutes ago, DaveSA said:

Why would you want 2 elements - for Solar ?

I have dual elements available on a single 1 1/4" boss. One for 220V AC 1000 Watt and the other for 525 Watt (+25% rated) 36VDC (Solar).  

Other than generally being considered more efficient for various other reasons (and thus more common overseas)

In the case of solar two elements makes it easier and cleaner to have one element powered by solar and one by mains, with different temperature settings while still being appropriately sized. This is how most people who dump excess solar as heat seem to do it overseas.

 

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5 minutes ago, Richard Mackay said:

If I may I think the term '2 elements' and 'dual elements' that is causing some confusion here is the same thing.  

Not at all, 2 seperate elements (quite common overseas; seemingly incredibly rare here):

image.png.0ee889cc62d861be9b502a59001e7100.png


'Dual' elements on a single 'boss' (some small market availability here in various shapes/forms):
image.thumb.png.fd896073db249a39f8de5676a56085ed.png

Edited by mmacleod
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  • 1 month later...

In my view I would also like to separate the elements into distinct separate elements one mains and the other solar. The reason being that you do not want to be stuck with a 1000w for solar and say a mains one of 2/3 kW. Also you could use a 110v 2kW element with a DC solar supply directly off the panels and the normal mains element for overcast days or nigth time usage with independant thermostats and supply wiring! Alternately the smaller/larger dual geyser system is probably best for winter when the water supply temperature is first fed into a preheating geyser before being fed into the larger geyser that is feeding the taps/showers. Lots of energy is wasted when the ice cold supply water is fed directly into the larger geyser during usage. It seems that these dual separate element geyser options are not readily available in South Africa unfortunately!

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  • 4 months later...

Just as a follow up to this, now that I actually pulled the trigger on something.

I did finally track down an option, Tecron will actually "custom" make a geyser with two element positions (one at bottom of tank, one at middle of tank) if you ask them.
It ends up at R9500 for a 200L geyser with two elements, this is a bit pricey but I guess there are (depending on your opinion) some added benefits to copper, not having to keep changing the anode etc.
Another nice things is the tecrons take a standard "1 1/4 inch screw" type element, which many low voltage DC elements are available for on ebay/amazon etc. - so if you want to go with a 48v heating system this opens up a bunch of options.

They were unable to do this for me before October though, due to material shortages (covid) so I ended up just getting 2x 150L geysers, which cost me R3000 per geyser, plus R1200 for the four vacuum breakers and the pressure valve, and R550 for 2x drip trays. R7735 in total...

So in the end you have ~R10000 for a 200L copper geyser with 2x elements/thermostats, that conveniently can fit a wide range of imported elements.

Or R7735 for 300L (150Lx2) regular steel geysers with 2x elements, but that can't take imported elements - it does look like conversion plates to take imported elements can be had for around R400 though, so throw one of those in and its R8000.
Plus I guess some additional labour for someone to install two geysers instead of one, not sure how much extra that is though, my builder isn't passing any costs onto me there...

Or around R6500 for a single 200l geyser with a single element, which is what was specced for my house on the plans.

The two are close enough that both are decent options I think, there might be reasons to consider the tecron, I do like the idea of copper, and not maintaining anodes, and theoretically longer life...
However the extra 100L of storage is nice I think if the PV is going to be doing most of the heating, larger capacity means more heat can be stored for later, so probably in the end 2x 150L seems to be the way to go - not sure if its a volume/popularity thing or what but the pricing on 150L geysers vs other sizes is just very hard to beat.

Edited by mmacleod
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There's nothing wrong with a thread that spans a period. It shows you aren't changing your mind too often. (However when you find yourself commenting on a thread that's a few years adrift I do get a little uncomfortable!)

As an engineer my head tells me that we should produce hot water as we need it. This isn't as easy as one might imagine, given the massive hot water geyser industry that exists. But no harm in trying..

I was encouraged by seeing the significant improvements in the energy required to heat water by using a heat pump. My first reaction was to use a heat pump big enough to heat water on demand. To hell with the geyser and having to keep it at an elevate temperature! Sadly this isn't that easy but I still don't know why.. 

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22 hours ago, Richard Mackay said:

As an engineer my head tells me that we should produce hot water as we need it. This isn't as easy as one might imagine, given the massive hot water geyser industry that exists. But no harm in trying..

I was encouraged by seeing the significant improvements in the energy required to heat water by using a heat pump. My first reaction was to use a heat pump big enough to heat water on demand. To hell with the geyser and having to keep it at an elevate temperature! Sadly this isn't that easy but I still don't know why.. 

It boils down to the heating capacity.  Say you need 2kW to heat 50l of water in 30 minutes.  If you shower you need to heat the water in 5 minutes and thus need 12kW of heating. As you said, not easy, but a heat pump that can do this can be attained. Cost will be much higher.

Hot water as we need it would be good. What do you save?  From my setup and tests it looks like between 1-3kWh per day. 2kWhx30daysxR2 = R120 per month.

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23 hours ago, mmacleod said:

The two are close enough that both are decent options I think, there might be reasons to consider the tecron, I do like the idea of copper, and not maintaining anodes, and theoretically longer life...
However the extra 100L of storage is nice I think if the PV is going to be doing most of the heating, larger capacity means more heat can be stored for later, so probably in the end 2x 150L seems to be the way to go - not sure if its a volume/popularity thing or what but the pricing on 150L geysers vs other sizes is just very hard to beat.

You would think that two 150L geysers would use double the energy than a single 150L but no.  The energy usage is dependent on the volume of hot water used.  The second geyser increase the energy usage due to standing losses. Thus it increase with say 10-30%.

Mine have just one electrical element to heat the second geyser and a pump to circulate water to the first geyser to heat both with one element.  Losses are a bit more this way.

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1 hour ago, Pietpower said:

It boils down to the heating capacity.  Say you need 2kW to heat 50l of water in 30 minutes.  If you shower you need to heat the water in 5 minutes and thus need 12kW of heating. As you said, not easy, but a heat pump that can do this can be attained. Cost will be much higher.

Hot water as we need it would be good. What do you save?  From my setup and tests it looks like between 1-3kWh per day. 2kWhx30daysxR2 = R120 per month.

In order to save on wasted power (heat loss) I manually control my geyser element. So in 20 min I know a shower is scheduled and needs hot water so on goes the element. This then heats the water to 'just hot enough' for a comfortable shower..

The idea is to dispense with my input here and for the system to produce the hot water on demand!

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13 hours ago, Pietpower said:

You would think that two 150L geysers would use double the energy than a single 150L but no.  The energy usage is dependent on the volume of hot water used.  The second geyser increase the energy usage due to standing losses. Thus it increase with say 10-30%.

Yeah thats what I'm getting at with the extra heat storage capacity being useful, if you store 300L at high temperature (generated during the day with solar) than drawing e.g. 1 or 2 showers from that after sunset will still leave you with lots of hot water at decent temperature and no need to start heating from the grid before the next morning.

While with only 200L you might not have enough and might need to start heating from the grid after usage.

A larger capacity (within reason) is therefore quite desirable and compliments any kind of solar water heating (IMO at least).


Geyser 1 (inlet) will be set to a very high thermostat setting and will be powered only by PV, geyser 2 (outlet) will be set to a much lower temperature and will be powered only by the grid (but should barely ever operate) - this element serves only to ensure that the outlet water never drops below an acceptable temperature while the element in geyser 1 should do the bulk of the work.

The only thing that remains for me to decide is what system to put on geyser 1.
I'm currently still having an internal argument myself over whether to go with an elon 100, a solarhotty a geyser robot or a 48v dc element.

 

Edited by mmacleod
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On 2020/03/12 at 11:59 PM, mmacleod said:

It seems to be quite common place in various other countries for "water  heaters" to contain two elements (each with own thermostat) instead of a single element. (It also seems more common for them to be vertical which may be related...)

e.g. as pictured here:
image.png.ce7c365e713b658b99bac5b2d88a1754.png


I have been trying to find similar in a za context, and either I'm searching for the wrong keywords, or they just don't exist here.
I was wondering if anyone knows.

1) Are there products that can be bought locally that can take two elements?
2) If so which? Or what do we call it here so that I can search for it?
3) Why is it not common here  if its common in other countries?


The best I could find so far was this forum thread, but as far as I can tell these are custom modifications and not actually supported by the product?
 

 

The reason for the two element geysers, in the UK at least is that you have the option to get "Economy 7" supply when the electricity is cheaper from midnight to 06:00 or 07:00 in the morning, during the day the top geyser element will switch on according to the thermostat setting, heating only a little amount of water, due to stratification, during the cheaper tariff the bottom element will be switched on, and heat a larger volume of water,  and that is also why they are vertical. This option is mostly when you have an electricity only energy supply.

https://en.wikipedia.org/wiki/Economy_7

The geyser @Vasan has shown is used when you also have a gas supply and uses a gas boiler for water / room heating, the electrical element is mostly for backup as the price for gas in the UK per kWh equivalent is far less that electricity per kWh and probably now also less than we pay per kWh for electricity in SA, last time I checked it was around 5 pence per kWh equivalent i.e. ~ R1.10. also depending on supplier as you can actually choose from a number of suppliers.

https://powerforum.co.za/topic/5431-geysers-with-two-elements-in-south-africa/?do=findComment&comment=83693

So much then for Eskom argument of our Electricity being relatively cheap, when you can get cheaper energy using gas in Europe.

 

Edited by WeNotGood
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4 hours ago, mmacleod said:

While with only 200L you might not have enough and might need to start heating from the grid after usage.

200L and four people we sometimes run out of hot water if we only heat during the day.  Thus added another 150L geyser.

 

4 hours ago, mmacleod said:

Geyser 1 (inlet) will be set to a very high thermostat setting and will be powered only by PV, geyser 2 (outlet) will be set to a much lower temperature and will be powered only by the grid (but should barely ever operate) - this element serves only to ensure that the outlet water never drops below an acceptable temperature while the element in geyser 1 should do the bulk of the work.

The only thing that remains for me to decide is what system to put on geyser 1.
I'm currently still having an internal argument myself over whether to go with an elon 100, a solarhotty a geyser robot or a 48v dc element.

Don't know those systems, but with a hybrid inverter we already send excess pv power to the geyser.

Geyser 2 is on PV power and soon geyser 1 will be on flat plate solar power.  The idea is that geyser 1 is whatever temperature the flat plate can reach and then feed geyser 2 with pre heated water to save on pv energy used on geyser 2. Geyser 2 will be at a constant temperature for the best user experience.  Can set the temperature higher on geyser 2 to effectively store more hot water (you use less at higher temp). Should be enough to last overnight and only use eskom as a last resort.

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On 2020/09/16 at 9:58 PM, Richard Mackay said:

As an engineer my head tells me that we should produce hot water as we need it. This isn't as easy as one might imagine, given the massive hot water geyser industry that exists. But no harm in trying..

You could perhaps order one of these "electric showers" from the UK 🙂 They heat as you use the water. Not sure if they are available in SA.

https://www.screwfix.com/c/bathrooms-kitchens/showers/cat820272

But then again if you can heat the geyser with excess produced renewable electricity (if you produce excess energy) then it acts as as a "store" of energy and the hot water is pretty much free.

 

Edited by WeNotGood
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