7 hours ago, chrisc said:

A 2.2kW PTC element is equivalent to a 3kW conventional element

Where is this claim coming from? Do you have a link to an actual study or this is just a marketing claim from the companies selling PTC elements? If this is true, this results instantly in almost 27% energy saving.

Do you have any reliable reference to support your claim? 

Edited June 20, 20233 yr by PowerUser

3 hours ago, Scorp007 said:

PowerUser has given the answer how to get power to a load that is normally on non essential to connect to essential. The same one can do with say the pool pump.

I've thought about this. In my case it would be just one circuit on the main DB. That's to the sub DB in the outbuildings.

My trouble would be remembering to switch it back to the other side. So I need to look for some solution that will reset at a certain time each day. 

Oh no! Then I have to remember to turn it on!

1 hour ago, PowerUser said:

Where is this claim coming from? Do you have a link to an actual study or this is just a marketing claim from the companies selling PTC elements? If this is true, this results instantly in almost 27% energy saving.

Do you have any reliable reference to support your claim? 

What is very interesting is that Extend elements claim that Kwikot tested their element and found that the 2kwDC is as quick or faster than a normal 3kw. Yet Kwikot staff indicate that their company have done the tests and found no advantage of the DC element as far as power used goes. 

48 minutes ago, Scorp007 said:

What is very interesting is that Extend elements claim that Kwikot tested their element and found that the 2kwDC is as quick or faster than a normal 3kw. Yet Kwikot staff indicate that their company have done the tests and found no advantage of the DC element as far as power used goes. 

Interesting . I like the way @Modina puts it , the good old element converts about 100% of its electrical energy to heat (unlike the incandescent bulb , which is meant to convert to light , but generates unwanted heat). So I cannot see that when I produce 2kW electrical energy that I will be losing much thermal energy during the conversion. There is a last stage as well , that's transferring that amount of  energy to the  water volume , which is the efficiency factor. But what difference does the dc element make to the ac element in this regard.?

48 minutes ago, BritishRacingGreen said:

Interesting . I like the way @Modina puts it , the good old element converts about 100% of its electrical energy to heat (unlike the incandescent bulb , which is meant to convert to light , but generates unwanted heat). So I cannot see that when I produce 2kW electrical energy that I will be losing much thermal energy during the conversion. There is a last stage as well , that's transferring that amount of  energy to the  water volume , which is the efficiency factor. But what difference does the dc element make to the ac element in this regard.?

The other day I bought a burst geyser hoping it was only leaking under pressure. Well that side turned out very well as it does not leak when filled but perhaps only under pressure.

What a luck when I got home to see that it had a 2000W AC/900W DC PTC element in that was only manufactured in Aug 2022. You cannot have everything. The plumber cut the wires off right at the cover. I have since managed to join wires to 4 of the 6. So I can test the DC element as well as the 1 AC element which is 1000W. To shorten the test time I need to join wires to the 2nd AC element.

What I can share at this stage is that even if one connects 220V AC on the DC element made for only 72V that it does not burn out after a 10min test while immersed in water. The surge power was 5kW and while agitating it dropped to a steady 1.3-1.5kW. 1.5kW when left for about 20sec with no agitation.

This is thus on my to do list one of these weekends then one can share to results. I also have a screw in element to compare. My idea would be to fill it with water and measure the start temp of the water. Then use my pressure pump to circulate the water all the time between the cold inlet and back to the hot water outlet. Record the temp as heating takes place with each element and record the power used with my Sonoff Powr2.

I just have to find the 5 hrs for the test. The ideal would be to have a container 450mm high to reduce the test time. This would have higher losses due to the open container.

@Bobster. You can always set the relay in the main DB to switch the moment there is grid and transfer the loads that were on the essential side back to the non essential. When the the grid is off the relay will be off as well  to switch these non essential loads to the essential side. I just mentioned the Sonoff as the driver to be able to monitor the weather to only use the PV power on the essential side for this non essential load. This is close to the way @BritishRacingGreen assisted to do the E to N bond over the weekend.

Edited June 20, 20233 yr by Scorp007

9 minutes ago, Scorp007 said:

This is thus on my to do list one of these weekends then one can share to results

Looking forward to your findings , and sharing with us 

 

9 minutes ago, Scorp007 said:

I just have to find the 5 hrs for the test

Ai , that's always the big challenge , even now that I am retired ,  time is just flying , maybe I am getting slower at things , cause last time I have checked , a minute is still 60 000 000 micro seconds !

72VDC . Wonder how the dc element will perform if I wire 2 x  550W 45V panels directly to it . Just a thought . I know there are people that's doing it with some AC elements, but seeing that power is 'I squared R' , the loss of power is logarithmic  as the current  decreases .

 

 

4 hours ago, PowerUser said:

Where is this claim coming from? Do you have a link to an actual study or this is just a marketing claim from the companies selling PTC elements? If this is true, this results instantly in almost 27% energy saving.

Do you have any reliable reference to support your claim? 

Well, I investigated the technology in PTC geyser elements before I bought one and fitted it.  After doing electricity consumption measurements for 8 months in conjunction with a Geyserwise controller, I decided to change to a Geyserwise ECO controller and 2 x 550 watt PV panels

A Daikin heat pump was fitted in the roof in 1989 and lasted until 2016.  It worked really well.  This was despite several plumbers telling me a heat pump would never work in a roof.  This one did.  It used 1100 watts of power and in the 26 years it was in service I never had to switch on the geyser element

After 2016 I sought quotes from 4 plumbers to remove the Daikin unit and replace it with the system that ITS Solar supply.  There were 4 widely different opinions and prices ranging from R28k to R65k, plus the hardware 

A conventional 3kW geyser element used an average of 153 units of electricity a month.  This is to heat the water to 55 deg
A 2,2kW PTC element used an average of 112 units to do the same amount of work

The Geyserwise ECO controller manages both the 72 volt and 230 volt heaters.  The 72 volts is supplied by the 2 PV panels.  It  requires 5 hours of sunshine to heat the water to 74 deg, which is the cut-off temperature.  Should the water in the geyser be below 55 deg by 19h00, then the Geyserwise switches on the 230 volt heater

During the last 10 days, there has hardly been any sun in Cape Town and most days, the water is still below 55 deg by 19h00.  Today it was sunny from 10h00 to 15h30 and the water got to 56 deg by 19h00

So to summarise and answer your question, I read the spec of the ceramic PTC heater and did my own measurements before investing in one

The Geyserwise ECO, PTC heater and 2 panels cost R 9000 and cost me very little to fit, simce 2 of my staff mounted the panels on the roof and I did the wiring up inside

I operated an electronic security business and a locksmith from 1980 to 2016

 

19 hours ago, BritishRacingGreen said:

 

72VDC . Wonder how the dc element will perform if I wire 2 x  550W 45V panels directly to it . Just a thought . I know there are people that's doing it with some AC elements, but seeing that power is 'I squared R' , the loss of power is logarithmic  as the current  decreases .

 

 

I see no problem at all using 90V directly with no controller. You might just have to look at a thermostat that can break this DC voltage. Half of me says with about a 10uF 400V cap over the AC thermostat contact might prevent the contacts welding. 

Edited June 21, 20233 yr by Scorp007

45 minutes ago, chrisc said:

A conventional 3kW geyser element used an average of 153 units of electricity a month.  This is to heat the water to 55 deg
A 2,2kW PTC element used an average of 112 units to do the same amount of work

Do you use DC as well on the same 2.2kW PTC element? If yes, are those 112 units only used on the AC on top of the DC power?

The PTC heater has 4 wires.  Red and black for 72VDC.  2 x blue for 230VAC

Blackout here from 18h00 to 20h00.  Low clouds all day, so water at 20h00 was 26 deg.  Now it's 20h45 and water is 38 deg.  So it will reach 52 deg in about 70 mins 

 

(If I misquoted the colours, I apologise. I did not go into the roof to look and relied on 2-year old recollection)

Edited June 22, 20233 yr by chrisc

22 hours ago, Scorp007 said:

I see no problem at all using 90V directly with no controller. You might just have to look at a thermostat that can break this DC voltage. Half of me says with about a 10uF 400V cap over the AC thermostat contact might prevent the contacts welding. 

The solid-state heater in a PTC heater does not behave like a hot wire.  The resistance curve is quite different.

At peak temperatures the resistance increases sharply

1 hour ago, chrisc said:

The PTC heater has 4 wires.  Red and black for 72VDC.  2 x blue for 230VAC

Blackout here from 18h00 to 20h00.  Low clouds all day, so water at 20h00 was 26 deg.  Now it's 20h45 and water is 38 deg.  So it will reach 52 deg in about 70 mins 

May be the 1500/900W element but not the 2000/900W element. As you can see there are 3 elements and thus you cannot just have 4 wires. 

 

Do you imply that the Geyserwise manual is also wrong. It clearly shows the white & blue is for DC. 

Edited June 21, 20233 yr by Scorp007

What is all the fuss about?  I know exactly what I purchased and what it took to install.  There is no ambiguity 

The invoice shows:  Dual voltage PTC solid state heater.  2200 watts and 900 watts.  I mentioned the voltage specified by the ECO controller

To my mind it represents a substantial improvement in domestic water heating.  The conventional system was developed over 100 years ago.  Improvements in metal technology have enhanced the reliability and longevity of the element but the heating efficiency has hardly improved

As informed consumers, with unreliable electricity supplies, we should be doing all,we can to reduce the amount of electricity we use

I tell all my customers of the obvious advantages of a PTC heater and all are saving money 

12 hours ago, chrisc said:

but the heating efficiency has hardly improved

Only because it is hard to improve on 100%...

That's a bit taken out of context.  This is an outdated technology that has reached the end of its design life.  A more efficient alternative is to hand

For a 25% reduction in power input, the same heating effect is realised

I have repeatedly measured the efficiency of my good old 3kW resistive element at being 100% (within measurement error).  You can't get 25% more efficient than 100% unless you are a magician (or a marketing consultant).

The only time resistive elements are significantly less that 100% efficient are when they are so badly scaled that they are pretty much dead - but I haven't seen an element scale like that in 20 years now.

7 hours ago, JustinSchoeman said:

I have repeatedly measured the efficiency of my good old 3kW resistive element at being 100% (within measurement error).  You can't get 25% more efficient than 100% unless you are a magician (or a marketing consultant).

The only time resistive elements are significantly less that 100% efficient are when they are so badly scaled that they are pretty much dead - but I haven't seen an element scale like that in 20 years now.

A resistive element should be 100% efficient when measured on its own. Have you checked the system efficiency when measured from the DB? I expect some volt drop over the supplying wires.

12 hours ago, chrisc said:

That's a bit taken out of context.  This is an outdated technology that has reached the end of its design life.  A more efficient alternative is to hand

For a 25% reduction in power input, the same heating effect is realised

In order to prove your claims I would like to see the following test:

1. Put a normal 3kW element in a geyser with a temperature probe inside and and test how long it will take to heat the water from let’s say 25deg to 65deg. 
2. Replace the element with a PTC 2.2kW and test the same again.

If it takes the same amount of time, then you are right about the efficiency. 
 

However, I’m still to see anyone perform the above 2 tests and publish the results. All I’ve seen so far is marketing claims. 

On 2023/06/19 at 8:43 PM, chrisc said:

If you use a PTC geyser element instead of a conventional one, it would be more efficient

A normal geyser element is almost 100% efficient at converting electrical energy to heat energy, any claims on a PTC element being 40% more efficient are defying the laws of physics and a defy anyone to show me how it can make heat energy out of nothing. 

 The heating efficiency of a PTC heater is identical to the efficiency of a normal element, the difference with PTC heaters is that they self-limit their temperature so they can be used without thermostats and safety limit devices in the correct applications and they're often use to heat temperature sensitive materials that would be damaged by the unregulated surface temperatures of a standard element.

On 2023/06/22 at 9:32 PM, chrisc said:

What is all the fuss about?  I know exactly what I purchased and what it took to install.  There is no ambiguity 

The invoice shows:  Dual voltage PTC solid state heater.  2200 watts and 900 watts.  I mentioned the voltage specified by the ECO controller

To my mind it represents a substantial improvement in domestic water heating.  The conventional system was developed over 100 years ago.  Improvements in metal technology have enhanced the reliability and longevity of the element but the heating efficiency has hardly improved

As informed consumers, with unreliable electricity supplies, we should be doing all,we can to reduce the amount of electricity we use

I tell all my customers of the obvious advantages of a PTC heater and all are saving money 

PTC elements have other advantages, but saving money on electrical costs are not one of them.

They can't defy the laws of physics  https://www.schoolphysics.co.uk/age14-16/Heat energy/Heat energy/text/Electrical_energy_to_heat_energy/index.html 

The only way to be more heat energy efficient is to extracts heat energy form the atmosphere and heats the water up using it i.e. a heat pump.  

 

3 hours ago, PowerUser said:

In order to prove your claims I would like to see the following test:

1. Put a normal 3kW element in a geyser with a temperature probe inside and and test how long it will take to heat the water from let’s say 25deg to 65deg. 
2. Replace the element with a PTC 2.2kW and test the same again.

If it takes the same amount of time, then you are right about the efficiency. 
 

However, I’m still to see anyone perform the above 2 tests and publish the results. All I’ve seen so far is marketing claims. 

The PTC element will take 1.36 times as long to heat the water up as the 3kw element. 

The only time you will loose efficiency on the normal element is if it is very thickly coated in scale and even then not by much.

 

3 hours ago, Sc00bs said:

The PTC element will take 1.36 times as long to heat the water up as the 3kw element. 

Did you test that yourself? Where is that coming from?

5 hours ago, Sc00bs said:

The PTC element will take 1.36 times as long to heat the water up as the 3kw element. 

The only time you will loose efficiency on the normal element is if it is very thickly coated in scale and even then not by much.

 

What I surprise when testing both. Refer to my new topic with the basic results done today. 

The PTC does come out on tops but not at the rate that marketing is trying to tell us. 

I'd suggest it's not the efficiency of elements that is in question.

It's the principle that a PTC element uses less power to achieve the same heating effect.  A solid state element gets to the same temperature as a conventional element using less power (watts)

39 minutes ago, chrisc said:

I'd suggest it's not the efficiency of elements that is in question.

It's the principle that a PTC element uses less power to achieve the same heating effect.  A solid state element gets to the same temperature as a conventional element using less power (watts)

Check this thread and the test @Scorp007 performed. That’s a real result. Do you have any real results to back up your 26% efficiency claim?