Inside the Elon 100
Outside of the Elon 100 control unit.
The temperature controller box is installed remotely from the Elon control unit.
The temperature controller box is installed remotely from the Elon control unit.
Thanks.
A Pandora’s box is an apt description. (Question: What do you get when you open the box?)
The polycarbonate enclosure is locally made so make so there’s a clue.
This got me into my roof measuring the current from the MPPT to the PTC element.
On a sunny day I measured with and without the MPPT to check if does improve the power and it does until about 10am. Thereafter there’s no benefit.
But what I couldn’t figure out was why the power didn’t exceed 1kW even at noon.
Eventually I deduced that a PTC element limits the power even if its below the
cutoff temperature. Clearly they must be designed like that. (A regular element cannot limit power since its resistance is fairly constant)
The heat transfer of the ceramic resistor to the sides of the housing that then heats the water is limited.
PS: PTC elements are great at limiting the temperature of your geyser preventing it from boiling.
It does, but the curve is not linear. When it hits the designed temperature, the resistance shoots up quick. Here is a random image I googled, but they all look like that (NTC is more linear):
Maybe your water was already nice and hot by noon?
This is an explanation I often hear from salespeople (selling those PTC elements), telling me that the traditional element gets all clogged up in deposits and then it becomes inefficient. Which is an argument I’ve never bought. There is only one place for the heat to go: Into the much colder water. There is only one speed at which the heat goes into the water: The joules per second (aka watts) rating of the element. If the insulation gets so bad that you cannot get the heat into the water, the element will overheat and burn out.
The PTC element of course will not burn out, but will go high resistance. Still, with the amount of energy water can absorb, I simply don’t buy it. If there is heat to be absorbed, it will be absorbed. The interface between the water and the element is unlikely to be the limiting factor here (unless it is extremely poorly designed).
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This video demonstrates this issue of matching the impedance of the panels to the element but not too much detail.
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On request of our client, we moved old panels that was suspected of having insulation issues unto this controller thinking we would get away with it. Did not think that this unit would be able to sense PV insulation breakdowns. Seems like we were wrong, received this screenshot from the client today.
