Hi guys,

 

Does anyone have any experience with the Xtend PTC geyer elements? and how do they compare to the Geyserwise PTC?

Also what is the benefit of such an Element compared to a normal 2KW element?  I currently have a standard 3KW element and looking to change the current one to either a PTC or a standard 2KW element.

 

 

Did you ever get more info regarding the decision?

On 2022/07/18 at 9:55 PM, Megesh said:

Did you ever get more info regarding the decision?

No but I went ahead and bought the Xtend Element. Happy with it. 

I was trying to figure out why they think the PTC element is more efficient, then I came across this:

The assumption that a standard element is 50-85% efficient is the biggest nonsense I have read today. Where do they suppose the losses go? The entire element is submerged, the same amount of energy goes into the water as the PTC element, regardless of scaling. If it is severely scaled up, it will only do so at a lower rate. The only alternative scenario is that the element keeps on getting hotter until it burns out, in which case you will be replacing it (and hopefully also clearing out any scale).

 

Also note that they don't give the coefficients for these elements. In my experience, they fail to heat up the geyser sufficiently. The resistance becomes too high above 45-50°C to keep on increasing the temperature.

I have a Geyserwise PTC element hooked up to 660W PV. I experience that heating is relatively quick to 50 degrees and very slow after 60 degrees. This 900W DC element did take the 150l tank beyond 70 degrees in the summer.

I know there are a lot of debate on efficiency of these elements. Thinking out loud I wonder if surface exposure of the elements to the water may affect this efficiency ;/

Edited July 25, 20223 yr by Pieter Lourens

10 hours ago, Pieter Lourens said:

Thinking out loud I wonder if surface exposure of the elements to the water may affect this efficiency ;/

Not really, if the surface area is too low to transfer the energy to the water, the element will burn out (unless it is a PTC).

Edited July 26, 20223 yr by P1000

3 hours ago, P1000 said:

Not really, if the surface area is too low to transfer the energy to the water, the element will burn out (unless it is a PTC).

The PTC element has more surface exposed to the water than a usual element. As such it may be more efficient. Yes?

Edited July 26, 20223 yr by Pieter Lourens

58 minutes ago, Pieter Lourens said:

The PTC element has more surface exposed to the water than a usual element. As such it may be more efficient. Yes?

No, the energy/losses has to go somewhere - it will get converted to heat. If the surface area is insufficient, the element temperature will just keep on increasing until it fails.

On 2022/07/25 at 9:25 AM, Etiennet said:

No but I went ahead and bought the Xtend Element. Happy with it. 

Do you have any sort of energy monitoring on your geyser and perhaps able to shed light on their claims that it uses less electricity than a standard element?

59 minutes ago, Speedster said:

Do you have any sort of energy monitoring on your geyser and perhaps able to shed light on their claims that it uses less electricity than a standard element?

Such a test done by an independent source. Claims as we have seen that a PTC of half the watt rating of a normal element will heat the geyser in the same time is just totally out of line. Money is better spend by just reducing the normal element to a size that is more friendly for PV and using a timer to heat during the sweet spot daily. A heat pump which is PV friendly cost only 2 times a full DC plus controller system. The plus is you only use 33-50% power what any element will use.

On 2022/08/07 at 12:09 PM, Speedster said:

Do you have any sort of energy monitoring on your geyser and perhaps able to shed light on their claims that it uses less electricity than a standard element?

Hi @Speedster and @Scorp007

I replaced my 3kW element in my 150l geyser with a 2kW element to bring down my peak power usage.

Recently I replaced that with a 2kW PTC element, and it feels like the geyser reaches its designated temperature sooner. This feeling may be because I want to believe I invested well 

However, there are too many variables and without facts people can argue ongoing on this topic. I noticed that in this forum there are many debates regarding the PTC element efficiency.

As such I propose that this forum's users join me in an experiment. I suggest people that partake in this experiment:

1. Has a 150 liter stand-alone geyser
2. Has a 2kW element in their geyser
3. Has the ability to measure the duration/time of continued power applied to the geyser until the designated temperature has been reached
4. The user has the ability to accurately and timely (relatively) measure the temperature of their geyser 

Should you comply with above, please partake and share your findings?

I propose the following experiment, and this forum should please advise if we need additional constraints to ensure a better outcome.

1. Similar geyser set-up
   • use of a 150 liter stand-alone electric and pressure geyser (no additional features e.g. evacuated tubes or flat plates)
   • use of a 2 kW resistive heating element (PTC or not)
   • assume geysers are in the roof
2. We will run the experiment at night
   • then the roof insulation is assumed having little effect
   • some PTC elements has a DC feed to the element as well, and this will negate such an impact
3. The geyser may not be used at least 30 minutes prior to the experiment nor during the experiment
   • E.g. no tap used on that geyser
4. We will start the experiment with a geyser temperature within a given range (e.g. between 25 and 35 degrees), as close to 30 degrees as possible
   • However, the element may not be activated/powered at least 30 minute prior to the experiment

We then measure:

1. Confirm compliance with the constraints
2. Confirm the date and time of the experiment
3. Measure the outside temperature
4. Confirm the Geyser Temperature
   • Temperature and time of starting the experiment
   • Temperature and time of reaching 10 degrees higher than the starting temperature (we note temperature because the measuring mechanism may have a delay and be a fraction out from 10 degrees)

If I can have head's up on this, I am willing to go first and other participants can use that as a template allowing us to compare our findings?

 

Yours faithfully

Pieter

Geyser                        : Kwikot 150 litre pressure/electric/in-roof (horizontally installed)
Element                       : GeyserWise PTC 2000W (AC 230V applied)
Outside Temperature : 12 degrees Celsius
Measured                    : using Sonoff TH16

Experiment Start        : 08 Aug 2022, 22h50 @ 33.9 degrees Celsius
Experiment Stopped  : 08 Aug 2022, 23h10 @ 43.8 degrees Celsius

Edited August 9, 20223 yr by Pieter Lourens

9 hours ago, Pieter Lourens said:

As such I propose that this forum's users join me in an experiment. I suggest people that partake in this experiment:

1. Has a 150 liter stand-alone geyser
2. Has a 2kW element in their geyser
3. Has the ability to measure the duration/time of continued power applied to the geyser until the designated temperature has been reached
4. The user has the ability to accurately and timely (relatively) measure the temperature of their geyser

This will only work if you can accurately measure the entire contents of the geyser (could be achieved by agitating the water). The whole point of a geyser is that the hot and cold water don't mix. Subsequently you only have to heat half the geyser from cold to when you take a shower (assuming the heating element is in the middle).

Edited August 9, 20223 yr by P1000

8 hours ago, Pieter Lourens said:

Geyser                        : 150 littre pressure/electric/in-roof (horizontally installed)
Element                       : GeyserWise PTC 2000W (AC 230V)
Outside Temperature : 12 degrees Celsius
Measured                    : using Sonoff TH16

Experiment Start        : 08 Aug 2022, 22h50 @ 33.9 degrees Celsius
Experiment Stopped  : 08 Aug 2022, 23h10 @ 43.8 degrees Celsius

Thanks for taking the time for this test. Did you perhaps measure the power used in the 20min period. @P1000 has a valid point as far as agitating the water. It would not be possible to heat the whole 150L of water with only 666W if one assumes this is about the power used. I wonder if power was measured if you looked if the power used was constant during the 20min?

@Scorp007

Yes the power used was constantly 2kW. I have a 2kW AC / 1.1kW DC PTC element with about 800W panels on this element.

The evening test negates the DC side. Furthermore, the PTC element builds resistance the higher the temperature, hence selecting the 30 degrees range so that PTC resistance has little  to no effect.

@P1000

I agree that the geyser shape and set-up will play a role. I have a Kwikot 150l geyser setup horizontally. As such the thermostat is in the middle.

I think that comparing this info (geyser type and set up) we can get closer to comparing apples with apples? Within a few minutes after shutting down the element the water settles and layers in the geyser. I can see that from the temperature measurement.

I think we can still get a relative good indication of efficiency without agitating the water: comparing temperature in the middle of the geyser and measuring temperature 3 minutes after removing power from the element.

Edited August 9, 20223 yr by Pieter Lourens

Unfortunately I don't have access to a 150l kwikot right now. I do have a heavily instrumented 200l class B (with agitation) and I can verify that the 4kW resistive heater is 100% efficient to within measurement certainty. (most of uncertainty comes from the loss model inaccuracies, mostly from the second order time constants).

Pieter it is great to have some that can try some tests around this interesting debate rather than arguing about it.

I am sure those electrical minded members would feel the heat generated is a function of the power used. It would normally not matter if it is a white hot filament bulb, a roll of wire, a resistive wire. Only doing what we talking/testing about can we measure the results and learn from it.

Thanks a lot for being part of the testing.

It would be great if a plumber can sponsor a small leaking geyser removed that can be cut open and agitated with both elements fitted to test.

I suspect losses in wiring and to the mounting on the shell are the only losses in the system. I can't see that  it would be significant or significantly different for the two elements. I propose emptying the geysers of hot water completely for your tests. 

A Geywerwise PTC element is advertised as 2000 watts AC and 1100 watts DC (48/72 VDC) and costs R2490,00

Yet the picture (on Livesustainable) only shows 2 wires

Anyone used one of these attached solely to PV panels?

Fitted the Geyserwise PTC element

There are 4 wires - red/black (AC) and blue/white (DC)

It works well

The next step are 2 x 450 watt PV panels and the Geyserwise ECO controller

Three questions please:  (Geyserwise said I must speak to an installer, but 3 I spoke either do not know, or said they can only supply info if I order the job through them)

1 - I see the ECO controller connects to AC and DC (from the panels).  Does this mean it only operates with AC present?

2 - At what stage does the controller use AC and DC to heat the water?  (I am wondering about cloudy winter days in Cape Town)

3 - I have a older Geyserwise controller.   The geyser and connections are in the roof and the display unit downstairs, some 30m away.  This works fine using a 4-core cable.   Does the ECO use the same system?

Thank you

Regards

On 2022/07/25 at 10:00 AM, P1000 said:

The assumption that a standard element is 50-85% efficient is the biggest nonsense I have read today. Where do they suppose the losses go? The entire element is submerged, the same amount of energy goes into the water as the PTC element, regardless of scaling. If it is severely scaled up, it will only do so at a lower rate. The only alternative scenario is that the element keeps on getting hotter until it burns out, in which case you will be replacing it (and hopefully also clearing out any scale).

I vaguely remember studies that scaling actually increased the efficiency of a heating element due to the larger surface area. 
Up to a point and not applicable to boilers etc.

Edited September 4, 20223 yr by Pietpower

On 2022/09/04 at 11:25 AM, chrisc said:

Fitted the Geyserwise PTC element

There are 4 wires - red/black (AC) and blue/white (DC)

It works well

The next step are 2 x 450 watt PV panels and the Geyserwise ECO controller

Three questions please:  (Geyserwise said I must speak to an installer, but 3 I spoke either do not know, or said they can only supply info if I order the job through them)

1 - I see the ECO controller connects to AC and DC (from the panels).  Does this mean it only operates with AC present?

2 - At what stage does the controller use AC and DC to heat the water?  (I am wondering about cloudy winter days in Cape Town)

3 - I have a older Geyserwise controller.   The geyser and connections are in the roof and the display unit downstairs, some 30m away.  This works fine using a 4-core cable.   Does the ECO use the same system?

Thank you

Regards

Hi @chrisc,

I did not use the eco controller, however, the AC and DC side of the PTC element can work independently. I have my AC disconnected and can see the DC power heating the Geyser using an IoT temperature monitor. What I do not know is how the Geyserwise controller manages the AC vs DC source.

Hi,

Good to know the Geyserwise controller is not dependent on AC pwr. The MPPT solar controller connects directly to the PTC element. This means that your MPPT must deliver output Voltage (Amps, P=IV) to match the demands of the PTC. The controller takes a 12V, 2-4Ah batt. for backup power for the controller and display unit. I assume the controller and display unit would otherwise be powered by AC 220V, the internal transformer converts to AC to necessary DC. 

According to the programming, the controller will either use DC from the MPPT solar array or AC when there is no MPPT power. Now, MPPT load is taken from the batteries, not sure if this is only when there is no solar. My MPPT has settings to run the load 24 hrs, cut the load at low PV voltage, etc. Ideally, I want my MPPT to feed PV current direct to the PTC during daytime hours only. The MPPT jsut keeps a small battery array charged which I can use for some after hours or emergency power, independent of the MPPT load contacts. 

I have no experience of the Geyserwise MPPT unit, tho'.

Hope I have a correct understanding of the Geyserwise setup for PTC elements.

Their claims make no sense:
Body of water = the same (150l)
Draw different : 2kw vs 3kw

and yet you claim that 2kw of energy outperforms 3kw??

It is like saying a 100kw Gti will go 0-100 the same or faster than a 200kw model? Makes ZERO sense and the "tests" they did would have to be verified by independent 3rd party.

I mailed them to say if my Sonoff shows that their 2kw does not equal or better the "cold start" heating time and energy then they have to refund me.... DEATHLY silence.
I will not be going this route, smoke and mirrors while paying a substantially higher price for a doubtfull benefit.

Edited May 7, 20251 yr by L_D

13 minutes ago, L_D said:

I mailed them to say if my Sonoff shows that their 2kw does not equal or better the "cold start" heating time and energy then they have to refund me....

You won't notice the efficiency gains of a PTC over a conventional element. The benefit will be in using solar power.