Posted by: @morgan

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I assumed it to be obligatory.

Thank God we haven't reached that state of coercive healthism yet, though it has to be said that that blasted pandemic and worse, the authorities response to it, moved us closer to such a terrible state of affairs. For the ordinary housegolder, choice over such things, at least for now, is 100% yours, just as you can choose whether to accept a doctor's treatment or not, you can choose whether to run a Legionella cycle or not. I should mention the situation is different in rental and commercial properties, primarily because of duty of care obligations, but also because commercial properties are inherently more at risk. 

It is not for me to make individual recommendations, but I can certainly point out that the case for domestic hot water Legionella cycles if far from cut and dried. Google it, or start here with the Heat Geek:

HEATGEEK.COM "https://www.heatgeek.com/hot-water-temperature-scalding-and-legionella/"

Legionella and Water Temperature: What You Need To Know

Stay informed about Legionella water temperature management! Learn about the risks in water systems and how water temperature can prevent Legionnaires' disease

Posted by: @sunandair

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It’s fascinating how how even Heatgeek hovers on saying the risks are very low but,

As you posted that, I was writing a post with a link to his post on Legionella. It is a good post, well researched, considers most eventualities, includes scalds and burns risks, and best of all totally avoids coercive healthism ie he concludes it is a matter of individual choice.

It is extremely dangerous to allow the state to make individual health decisions.   

@cathoderay great points and perfect timing. 👍

@cathoderay I'm not going to go into a discussion as to the governments, around the world, reaction to Covid. Nor do I intend a lengthy and rather pointless discussion as to the extreme danger of others looking out for ones health.  My thoughts are based upon my assumption that the Legionella cycle is obligatory as part of the MCS certification and RHI payments being tied into that certification.  I was not addressing the possibilities of government conspiracy to control the masses.  It was a very simple throw away comment/question.

Another way I thought of checking efficiency was how long the DHW reheat took. Since there are less chances of cycling etc.

So I set up a forced DHW reheat at 9.12am today here is the hourly graph reading

Set temp/target was 48c starting at 38c. Coincidentally it appears to have taken 38minutes to reach the target temperature (9.50am). The HP was working on room heating before the test and reverted back to room heating at the end.

HP Ecodan 8.5kw, tank capacity 250L, bespoke construction, deltaT 6, flow rate 13LPM. I guess if I had a MID meter I would also know energy consumption. 

Addendum : I also have a thermistor at the top 300mm of the tank so even though the mid sensor which controls the heat pump read 48c the temperature at the top was 56c. This extra sensor is part of our solar temp difference controller, not part of the Ecodan.

Posted by: @sunandair

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This extra sensor is part of our solar temp difference controller, not part of the Ecodan.

Interesting, do you have more than one temperature sensor input into the solar thermal controller?

My temperature sensor is in the bottom 1/4 of the tank measuring the temperature of the water around the solar coil, and triggering when the dT is 10 or greater.

@william1066 yes there’s are three sensors in total but only 2 are needed to activate the pump for the solar circuit.

one is mounted in the roof top manifold (LWT) and the other is mounted at the cylinder heat exchanger at the bottom of the tank. When there is a 5c temp difference the controller activates the pump. But the third one is mounted for information purposes at the top of the tank and displays the temperature on the display.

This spare thermostat has been handy to compare Ecodan readings by placing it alongside primary flow and return etc.

(edit: pump activated when 10c difference shows and runs until below 5c or less)