New mains pressure HWC placement.

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neb

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#2781241 20-Sep-2021 17:05

James Bond:
This came across this on Twitter:

https://www.freethink.com/series/make-it-count/instant-hot-water

That looks a bit dubious. If you skip the original article, which tells you nothing, and go to their web site, they use "graphite electrodes and electronic controls, we increase the energy state of the water molecules, so they move faster". There's a slightly less bad explanation here, but I'd want to see it in use by others over a longer period to find out what all the failure modes are.

SomeoneSomewhere

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#2781271 20-Sep-2021 18:51

I'm going to say that's largely BS.

It seems to be a roundabout way to say that they're passing current through the water to heat it up. This seems like it has a few major issues:

Conductivity is heavily dependant on the dissolved elements in the water.
Concerns around possible electrolysis (producing hydrogen and oxygen gas) if current densities are high enough.

In addition, the actual problems with resistive heating that they're aiming to solve are pretty limited, and can be fixed by using triacs instead of relays/thermostats (which I think most are already doing), and using a bigger heat exchanger so the peak temperatures are lower.

In fact, they also say this:

> Because electric tankless water heaters (like the MODEL 3 Water Heater) all perform near the limit of efficiency of electric resistance technology, they cannot earn the ENERGY STAR.

Plus, as with any electric tankless option, NZ properties generally won't have the electrical capacity to support it.

SomeoneSomewhere

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#2781273 20-Sep-2021 18:54

Ohmic Array Technology addresses this challenge by controlling the resistance of the water circuit, and the resulting power draw: with electrode width, height and separation. By changing these parameters dynamically as the conductivity of the water changes, the power of the system as a whole can be controlled.

Wait, are they moving the electrodes around in the water path continuously? How do they expect that to be reliable?

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