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What is a PTC element for geysers?


KLEVA

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Hi All

I am a but distrusting of the PTC element tech that seems to be only offered by Geyserwise in South Africa (haven't really been able to find other sources).

Geyserwise have a decent solar controller product (ugly as all sin), but I find it really clunky and needs much more quality development - So I am very skeptical when they are the only ones that have come up with this PTC technology with some quite impressive claims. It seems fairly pricey compared to a standard resistive element, so I would like to hear others thought and possibly experiences.

Regards

KLEVA

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PTC stands for positive temperature coefficient. The element itself is usually a ceramic material instead of the usual nichrome wire used for resistive heating. The ceramic material's resistance increases as the temperature rises, thus lowering the power used. The downside of that is that it heats less as it gets warmer and at some point the losses and the power used will equalize and the temperature will stop increasing - the elements on the market don't advertise this set-point, and it is sometimes too low to be considered safe. The upside of that is that you don't need a thermostat, which is a common failure point for geysers.

The claims with regards to energy efficiency is nonsense, as both PTC elements and normal nichrome elements are resistive heating devices and both have the same ~100% efficiency numbers.

One possible advantage in PV solar installations is that instead of switching a 2-4kW element on and off, the power draw lowers until it matches the geyser losses when it comes up to temperature, which could help with managing your loads.

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4 hours ago, KLEVA said:

Hi All

I am a but distrusting of the PTC element tech that seems to be only offered by Geyserwise in South Africa (haven't really been able to find other sources).

Geyserwise have a decent solar controller product (ugly as all sin), but I find it really clunky and needs much more quality development - So I am very skeptical when they are the only ones that have come up with this PTC technology with some quite impressive claims. It seems fairly pricey compared to a standard resistive element, so I would like to hear others thought and possibly experiences.

Regards

KLEVA

If you Google PTC heater you will find some heaters using it. A number of years ago I bought such a heater. We actually like the heater as it does not produce the intense heat an element heater would. This is a safety feature. No or few things will catch fire. The Goldair heater is a common brand in the shops.

It is not strange to see the PTC units only producing and using 50% of their rated power once they heat up. With this in mind they can never produce double the heat compared to an element using the same power.

Edited by Scorp007
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Just now, Scorp007 said:

If you Google PTC heater you will find some heaters using it. A number of years ago I bought such a heater. We actually like the heater as it does not produce the intense heat an element heater would. This is a safety feature. No or few things will catch fire. The Goldair heater is a common brand in the shops.

Some info on Wikipedia.

In the 1980s, some manufacturers were making advertising claims that critics such as New York Times writer Matthew L. Wald found dubious. In particular, manufacturers claimed ceramic heaters produced more heat than conventional ones, even when both were rated with the same heat output.[6]

Consumers Union has not found significant differences between ceramic and conventional heaters. However, in its 1989 review, the testing organization did treat ceramic heaters as a separate category, as a response to manufacturer claims. The only significant difference it found was ceramic heaters were substantially more expensive. As a category, the conventional heaters it tested that year slightly outperformed ceramic heaters in the areas of evenly heating all parts of a room and at holding the room at a steady temperature. Consumers Union did find ceramic heaters' characteristic of sharply reducing heat output when airflow was blocked to be a useful safety feature. However, it found that the tip-over switches and overheat-protection sensors included in many conventional heaters also provided good safety.[4]

 

 
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A friend of mine had the element on his geyser fail. The plumber convinced him that a PTC element will last longer. A year later the geyser started leaking and had to be replaced. If I didn't remind him, the PTC would have been gone with the old geyser. I like the Geyserwise control but would stick to common and cheap geyser parts.

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Thank you all - I think I now understand the pros vs cons - In my personal installation it doesn't seem to make a difference - but hopefully it will help others. Also you gave me an idea into new tech out there that I wasn't aware of, thank you.

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1 hour ago, Pieter Lourens said:

Hi @KLEVA

I use the PTC element because it can use both AC and DC power.

The DC powered by 2x solar panels ensures that in the day I do not have to top-up because of heat losses. My AC power applied to the geyser is purely to supply for consumption. Furthermore, the element seems much more durable.

Your application is surely working for yyou Great to have the option of using the AC or DC element.  I always thought that 2-3 panels should be good to top up during the day and keep the temp at a certain level. One has the whole day to do it provided not a lot of hot water is used during the day. The problem of using a AC thermostat is then solved via the geyser wise controller?

We read a lot about normal elements burning out. I have only replaced 1 element in over 45 years so it seems my water has always been of low lime content. Yes I have my share of steel geyser tanks rusting and normally they last about 6 years. Keeping me busy between the 2 I have in use. The one burnt out only tripped on the DB once and burnt open circuit. I was quite shocked when going to investigate to find the whole isolator also burnt quite badly which could have been a fire hazard. I was sure the connections were good but the result did not look good.

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2 hours ago, Scorp007 said:

Your application is surely working for yyou Great to have the option of using the AC or DC element.  I always thought that 2-3 panels should be good to top up during the day and keep the temp at a certain level. One has the whole day to do it provided not a lot of hot water is used during the day. The problem of using a AC thermostat is then solved via the geyser wise controller?

Hi @Scorp007

Yes, it works very well for me. However, I implemented a solution differently than the default GeyserWise package.

Firstly, my expense was less than 10G per geyser. With home automation I can top-up the geysers from the inverter if the geysers are not sufficiently warm at a given time. With home automation I can also spread my load so that the two geysers does not consume electricity concurrently.

Secondly, having the two geysers on their own systems allows them not to be impacted by load shedding. The AC top-up capability is on my inverter's non-essential load.

I need to officially measure my DC values. However with 2x panels on a geyser I get more than a 5 degrees Celcius increased heat in an hour. The DC power does more than just maintaining the temperature.

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  • 9 months later...

Why is it not possible to simply connect 50v solar panels directly to the geyser if you install a 50v 1 Kw element into the geyser. You can leave the thermostat as the means to avoid overheating. If you have a 300l geyser once the water is hot you easily have sufficient hot water for all purposes overnight and the geyser will re heat the water from sunrise to sunset?

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