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Test of Geyserwise vs element


Scorp007

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For starters I filled a old geyser with enough water for the 2 tests. 1st test starting temp of water was 16degC.

I used a looped 3kW element which I scaled down to a lower supply of 208V to get the Watt rating closer to each other. 

Temps were recorded every 4min as well as current reading. 

Element used 2433W. Average current drawn was 11.47-11.7A and used 11.7A for calcs. 

2.2kW PTC test started later in the day and start temp was 15 degC. Power used 2193W with average current 10.2A

Both tests lasted 37 min. Temp with stirring the water through a 19mm hole in the 25L steel oil drum. Filled to the rim for about 30L for both tests. 

Power used:

PTC 1352Wh Element 1504Wh

Temp increase during 37min period

PTC 36 degC  Element 34 degC

This gives us PTC 37.56Wh per degree

Element 44.23Wh per degree. 

1 hour after the test ended with ambient temp dropping to 13 degrees the oil tank temp dropped from 51 to 48 degrees. Test done in the garage with no draft and windows and door closed. 

I expected the 2 to deliver similar results but my test shows the PTC being 17% more efficient in converting power to heat in this basic unscientific test but does give an indication. 

Lastly the 3kW looped element had perhaps 5-10% lime build up which I could not remove as the loops touched each other. Thickness of lime not more than 1mm.

Edited by Scorp007
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7 minutes ago, PowerUser said:

So, with the normal element, you started at 20deg  and increased the temp by 34deg and ended at 54deg. 
With the PTC, started at 15deg and increased by 36deg. Then ended at 51deg. 

Is the above correct?

Sorry I just had a look at my notes. The delta for both is correct but the normal element started at 16.4degC. I will go and edit it. The normal ended at 50.4degC.

Where the 20 came in was when I filled the old geyser with water at 20 prior to the test. 

Edited by Scorp007
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19 minutes ago, Scorp007 said:

That is correct yes. The difference comes in that the normal element used more power to do it. 

Well, for the power:

1504-1352=152

152/1504*100=10.1% 

So, the PTC element is about 10% more efficient (you will end up using 10% less power) over the normal element. 

I wonder how much is the test error margin. But in order to determine that, multiple tests need to be performed. 
 

Even your temperature probe could be within 10% error margin, as you probably used a consumer grade and not a laboratory grade probe. 

Edited by PowerUser
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But let’s say 10% is correct. 
 

If you are using on average 6kWh per day on the geyser, your saving will be 0.6kWh per day. That’s about 0.6kW*R2.4=R1.44 saving per day

R525 saving per year. 
 

What is the cost difference between the 2 elements and how many years, does one has to use it, in order to break even. 

Edited by PowerUser
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On 2023/06/24 at 8:14 PM, Superfly said:

That's more-or-less the conclusion I came to without all the tests. Thus I opted for a heat  pump solution  "a heat pump is an all-in-one year-round home comfort solution that can cool, heat, and provide hot water" 

Yes but that’s completely different solution and requires a lot of up front capital. 
 

We are just checking at the moment, if it’s worth replacing a normal element with a PTC one. Direct swap and no need to spend additional capital on anything else. 
 

Regarding worthiness of heat pumps, completely different tests need to be performed.

Edited by PowerUser
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The conventional element is resistive.  It will change it's resistance (slightly) as the temperature changes but this is linear.  So you can measure the current drawn every 4 minutes and then calculate the average current consumption over the total measuring period.  No problem.

The PTC is designed to change it's resistance more, but what is important is that this is non-linear.  If you take a current measurement every 4 minutes, you cannot simply work with the mathematical average.  Instead, you would need to integrate the value over time.

One day, when the Cabal/Elite will allow us to speak to the aliens and learn from their wisdom, we will make a quantum leap of science knowledge and learn the secret of traveling faster than the-speed-of-light, unlimited energy, etc.  Until then, we are still ruled by the various scientific rules as laid down by Newton, Faraday, Einstein and others.   In this case Einstein: The conservation of energy - Energy cannot be created or destroyed.
 

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Thanks guys for the comments on this basic non lab test. It was meant as an indication.

@PowerUser

I have always used the % difference using the lower figure. This means 152/1352=11.2% . Another figure that affects this is the delta which was 1 deg more for the PTC. Thus I used the Wh per degree to get to my value. 44.23/37.5=1.1775 . Is this not correct?

As indicated this is just an idea/non lab conditions so the measuring instrument error reading should not vary much as the readings measured for temp, current, volts and power should not vary much as the readings were very close for both tests. I might have it wrong. I marked a spot to ensure I take the measurement for temp at the same spot. The infra red thermometer I have found to be accurate enough even if it might not be 100% accurate. Having a resolution of 0.1 degree is good enough for me and perhaps better used than a contact instrument. Having said this I have only found the reading to be out by a bigger margin if reading from a white/shiny surface. Once again just my observation over years and I have no idea of what surfaces can introduce larger variations in the actual temp.

@Modina "The PTC is designed to change it's resistance more, but what is important is that this is non-linear.  If you take a current measurement every 4 minutes, you cannot simply work with the mathematical average.  Instead, you would need to integrate the value over time."

The method of calculating the current would not affect the power used by the power meter. What was interesting is that the current never changed more than 0.1A which is less than 1% over the temp range tested. There was thus no need to calculate the current and average it out.The reading was available all the time and I just used the 4 min time to create a table. It follow my way of keeping things simple. Even if measured every sec there would be no change as it is derived from the power used and voltage. As we have very steady voltage there was no need to measure it and the power meter would also have taken care of fluctuations. The idea was to find out if the 2kW element can heat the same quantity of water in a shorter time and less power than a normal 3kW element as is claimed by the manufacturers. I think a few of us felt that the normal element would not use 50% more power as claimed for the same increase in water temp in a geyser.

What was interesting was that the surge start current was 0.5A lower and went up over about 3 min to the stable current mentioned. As per your explanation I thought it might be higher when switched on. From this I assume it only starts reducing current drawn at much higher temps than was present. On the normal element one could see how the current went slightly up as one stirred the water.

I still feel it was worth it even if just of value for myself while the ladies were busy in the kitchen using more power that I would have liked - hehehehe

 

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2 hours ago, Scorp007 said:

The method of calculating the current would not affect the power used by the power meter. What was interesting is that the current never changed more than 0.1A which is less than 1% over the temp range tested

You only tested to about 51 degC.  I presume that the PTC is still rather linear at these low temperatures.  As a PTC is an engineered material with special, purposefully engineered characteristics.  I presume it is made with an exponential transfer function at temperatures over 55 or 60 degC, so that it can self-regulate, if the blurb is to be believed.

So congratulations, you have just prooven Einstein wrong.  You have shown that all that we ever have learned in school and varsity is a lot of fake crap and that we should not "follow" or "believe" in the so-called science.  Especially not the post-Covid science (!)

So let me get back to the 24/7 movie I have been watching - Life in the 21st Century.

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9 minutes ago, Modina said:

You only tested to about 51 degC.  I presume that the PTC is still rather linear at these low temperatures.  As a PTC is an engineered material with special, purposefully engineered characteristics.  I presume it is made with an exponential transfer function at temperatures over 55 or 60 degC, so that it can self-regulate, if the blurb is to be believed.

So congratulations, you have just prooven Einstein wrong.  You have shown that all that we ever have learned in school and varsity is a lot of fake crap and that we should not "follow" or "believe" in the so-called science.  Especially not the post-Covid science (!)

So let me get back to the 24/7 movie I have been watching - Life in the 21st Century.

Due to changes in ambient temp and a small difference the results could be skewed. Time was against me as I had to get the 2nd PTC element sorted out with only about 10mm between pocket and end of the wires to be able to connect. My previous comment with estimated 5hrs to do the test put me off to prepare earlier. Also I didn't know I had a 450mm deep container and stumbled upon a suitable one outside. I had to see what the ladies were up to and also wanted to watch the MotoGP sprint race during the test. 😀

Due to by geyser normally at 26deg after running a bath and then heating to 55deg the delta of 37deg was more than my real life delta. 

I also ran a dry test. Close to the threaded nut the temp was 55 deg and the furthest point was already at 160 deg. Temp was very inconsistent moving from threaded nut to the other end. It could be that the pocket forms a spiral inside the housing. At this point the current dropped to 5.5A. This was within 3min from powering it up. 

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@Scorp007 you doing  some good work here.

I have a nice CHINT energy meter from @Steve87, and I am already sure he wont mind you  using it for your evaluation. The counter is resolution of 10th of  kwh unit, so i am not to sure if that is enough over a relative short period of energy integration. The meter is consistent however regarding  energy billing accuracy. I am sure I can get the meter to you, even if we meet somewhere halfway between the republics of Centurion and Germiston. 😁

The problem I see is the power is  related to the square of voltage reading or the square of current reading, so that means  errors may become large, so I agree with @Modina you will have to integrate accurate power over time to get reasonable accurate energy. 

Edited by BritishRacingGreen
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Unfortunately, these tests won't really help.

You need to test in a geyser, under pressure.

PTC will definitely have an advantage in open tanks, as the lower surface temps mean less boiling at the surface. The resistive element will lose a lot of heat as vapour.

But this effect is not significant in a geyser, where the pressure reduces evaporation and it is sealed, so the heat is not lost anyway.

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1 hour ago, JustinSchoeman said:

Unfortunately, these tests won't really help.

You need to test in a geyser, under pressure.

PTC will definitely have an advantage in open tanks, as the lower surface temps mean less boiling at the surface. The resistive element will lose a lot of heat as vapour.

But this effect is not significant in a geyser, where the pressure reduces evaporation and it is sealed, so the heat is not lost anyway.

Thanks for the feedback. I would have no idea what the heat loss could be or even what the heating elements surface temp could be. It was meant just to do a kind of test even with the losses as mentioned. The drum did not have a too big opening at the top as it was only around the elements hole of 50mm and the 19mm hole to agitate the water inside. There was no indication of any vapor coming out of the drum but it does not mean there was no vapor with it's heat loss.

I agree on using a geyser which I do have but time is the limiting factor thats why I settled for a smaller volume of water.

@BritishRacingGreen Thanks for the offer to get to a better accuracy but I think for this basic test a Sonoff served it's purpose as well as the other measurements with a clamp meter and infra red thermometer.

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18 hours ago, Modina said:

In this case Einstein: The conservation of energy - Energy cannot be created or destroyed.

Not strictly correct. 

"In 1842, Julius Robert Mayer discovered the Law of Conservation of Energy. In its most compact form, it is now called the First Law of Thermodynamics: Energy is neither created nor destroyed"

Einstein spoiled the party a bit when he came up with the famous E = mc² (his theory of special relativity), which brought mass into the picture.

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On 2023/06/25 at 9:28 AM, Scorp007 said:

Thanks guys for the comments on this basic non lab test. It was meant as an indication.

Thank you for the time to perform such tests. Would be great if others would do similar tests and post their findings for comparison instead of stating theories  why your tests are seemingly flawed and should be questioned. Yes, question by all means, but then provide the own test data to substantiate it.  

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