useful steps: heat the water in whatever source cylinder once a day to above 50-60°C, if particularly cautious do this heating closer to the time that the water will be used
Btw, @TheTerribleTriplet if the 40°C as heating cut-off is measured at the outlet of the vertical geyser (IIRC you have such a setup?) I would wonder about the temperature of the water temperature in the cylinder on average. With a horizontal geyser controlled by a regular thermostat set to <50°C the top half of the water volume will likely be >40°C by the time the thermostat switches off.
Don’t think the cost saving between heating to 40°C vs 50°C once a day is significant.
had a quick check. Overcast day. 11:30. Ambient temp about 22°C. Temp in roof space about 27°C. Water from cold water tap in scullery gives about 1 litre water at 26°C. Sunny day and temps in the high 20’s-30’s should comfortably push this past 30°C?
But I agree, and the research seem to support that the Legionella in the water in the pipes will likely be flushed out before Grandma will be exposed (yet if we are consistent, we should also warn Grandma when she visits over Christmas, to let both the warm water and cold water taps run a bit before starting to steam up the bathroom… ).
Timer something something - we are now back to the topic of timers
The vertical one, set to switch off at 50 at the top, means the bottom, where the element is, is probably way higher.
The element switches off on its own. So it gets really hot at the bottom.
So if I set it to cut off at the top, it sometimes cuts off at like 43deg, the temp sensor reading at the top, cause the bottom is at the elements max temp.
Geyser hot water, like SOC on a batt, is a best guesstimate.
Yes you did, I did read it and thought, mmmm, the actual documented risk vs the effort to heat, lets just leave that salient part out for the moment.
I would expect the reverse. The heat rises to the top. Unless you can heat the water fast enough that a local hot spot forms around the element faster than convection carries the lighter molecules to the top (and circles the colder ones to the bottom), the water at the bottom will always be cooler.
Let me add more context.
On the outlet outside the geyser the temp sensor sits, insulated, attached to the outside of the copper pipe.
Shelly temp sensor is there mainly to switch on the element when the outlet water pipe reaches sub 36deg.
So that temp measurement is nowhere of what is actually going on inside the geyser.
Noticed frequently, outlet temp is like 47, close as damn, Shelly says relay is on yet VRM says there is no 3kw being drawn.
Happens when no-one has used the geyser for many hours.
Nor have I seen the temp, on the outlet pipe, going above 50deg (quick observations, no study done) when used.
Hence I deduced, the top is cooler than the bottom, when the thermostat switches the element off.
Titbit:
Also facilitates waiting to heat water for a quick shower.
As there is no need to heat the entire geyser, just the part at the top needed for quick shower.
… if 36deg is too cold for one.
This Kwikot B+ rated geyser, keeps the temp pretty well being installed vertically outside the house against the wall over 24h periods.
Another reason I put the Shelly temp sensor at the top on the pipe, IF someone uses the geyser, and the temp is =>36deg, don’t switch on the element yet.
Wait for 1pm tomorrow + there is enough solar, and heat it again.
Unless it is <36deg, then override all Automation.
I think the only thing we can conclusively say, is that temperature sensors don’t tell you what is going on everywhere in the tank. You can get close, if…
In that case, the average would be literally halfway between the two.
What you can do, of course, is pull ten liters of water off a hot tank, throw away the first 5 liters (pipes still heating up) and measure the temperature of the second bucket. If that water is hotter than 50°C, then the tank is hotter than that too, and a few hours at that temp will kill your Legionella.
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