Any experience of Grundfos recirculating pumps with "autoadapt"?

Grundfos claim that their "autoadapt" DHW circulation pumps "learn" hot water usage over a few weeks and switch on/off accordingly. I don't think that our usage follows any particular pattern so I'm wondering how it will respond. Has anyone here installed and used one?
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On Friday, 21 September 2018 21:56:42 UTC+1, snipped-for-privacy@aolbin.com wrote:

from my experience of computers so far I expect the answer is whatever way is most annoying.
NT
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Ah the old artificial intelligence again. What was it Monty python said? If there is such a thing as artificial intelligence it has to be a good thing as there is bugger all of it on the Earth. Trouble is, its us humans wot make these so called artificial intelligences in the first place. One of the most annoying is those which try to predict what you are typing all the time.
What is your query? Did you mean pubic transport? Bah humbug. Brian
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wrote:

That’s completely silly with siri and alexa etc alone.
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Um, that’s a CH circulator. The OP is asking about a hot water circulator.
Tim
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On 22/09/2018 07:48, Tim+ wrote:

Why does DHW need to be circulated? Doesn't it rely on either mains or gravity pressure?
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It's the circulation of hot water from the boiler to the storage tank.
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No it’s not. It’s circulation of hot water from the tank around the whole hot water system and back to the tank (in order to provide near “instant” hot water from any hot tap). Common in hotels, rare in domestic situations.
Tim
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On 22/09/2018 12:45, Tim+ wrote:

Not that rare in larger houses. I installed a loop in my previous house when I put the tank and boiler in the garage. This house has long pipe runs to the furthest tap.
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Great idea - most builders can't even be arsed to insulate the DHW pipes. Having a loop would require good insulation. I would like to implement it
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To keep the pipe filled with hot water would only require a very slow circulation rate. Therefore the return pipe from the furthermost tap could be very small bore, say 10mm. Less heat loss from a small pipe too.
Phil A
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Good point. But the full bore would need insulating.
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Well yes, the lower the heat loss in the recirculation circuit, the the smaller the recirculation flow-rate needed. Thinking further, perhaps sufficient flow rate could be achieved by thermal circulation, e.g. by wrapping heater tape around the lower part of the return pipe. Might only need a metre or so warmed up to a few degrees above the delivery temperature.
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On Sunday, 23 September 2018 19:19:52 UTC+1, Phil Addison wrote:
e:

t
maller the

rate could be

lower part of the

ve the delivery

The return leg needs to stay at at least 60 for legionella risk. What you d escribe has nowhere near the temp rise or bore of old gravity backboiler HW systems, so I'd expect close to zero circulation. Even slow gravity circul ation would significantly raise the temp at which the HW would need to be d elivered to the pipe run.
NT
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On Sun, 23 Sep 2018 12:30:02 -0700 (PDT), snipped-for-privacy@gmail.com wrote:

In the system I describe the return water is heated just after the final tap and since the whole point of recirculation is to maintain full delivery temperature to the tap/s, it follows that the water in the return pipe is hotter than the DHW delivery, which should have been designed to kill legionella.

Err, I did say "a few degrees" and "10mm". We are not trying to heat the whole DHW tank; that's already been done.

We are talking of only the few litres (maybe 10-15 max) in the leg to the furthest tap, plus a fraction of that in the small-bore recirculation pipe. Heat loss from (X) metres of lagged 15mm pipe (or whatever size it is) equals the required wattage of heater tape round the 10mm pipe. The heat loss also enables to you to calculate the temperature drop, tank to tap. Knowing the water density at these two temperatures you will know the circulation head available. Now you just need to work out the pipe friction to see if the head exceeds the friction. If it does you get circulation; if not you can increase the bore of the recirculation pipe and/or put more heat into the tape. The excess will be absorbed in the tank which will be compensated by the boiler shutting off a little sooner.
I think there is a good chance this would work. Someone just needs to do the sums to say yay or nay.
Phil A
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On Sunday, 23 September 2018 21:59:03 UTC+1, Phil Addison wrote:

I think you're very optimistic about the power of gravity circulation.
NT
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wrote:

It might -- however: the circulation does increase the heat losses, lagging or no. The circulation pump can be shut off, more difficult to do with a gravity system...
These systems are fairly common in Treznal, where the mandated legionella testing for larger sharer DHW systems. Usually, it's lagged pipe out, 10mm lagged back, because it's less loss per meter, easier to route and easier to lag. Gravity tends to need serious diameters, and it's harder to get the entire pipe system hot using gravity. This can be a concern because testing is relatively expensive, and any savings by using a gravity system will me lost many times over if legionella are found, and a retest is necessary. (The system is cleaned by running it at 65°C or so, while circulating, and flushing all legs to get the pipes to the water temperature.) The pump is usually on a simple timer to shut off the circulation when not needed, to reduce heat losses when it has no use. Fancier heaters include the timer, and fire up the circulation once weekly in the early a.m. as part of a routine "heat everything" disinfecting...
There are a lot of more-or-less homebrew control systems for the pump: one assumes you open the hot tap for a moment, and takes that as a signal to fire up the pump, detection by two temperature sensor along the hot water "out" pipe. Or a radio-linked button one presses to call for hot water. Or microprocessor control of the hot water return temp, via pump speed. Or track usage with varying ingenuity, i.e. accounting for weekdays, holidays, etc.
Thomas Prufer
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snipped-for-privacy@gmail.com formulated the question :

Well, the risk of L has to be less than with a conventional system, where the HW can be static for weeks cold in a pipe.
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formulated the question :

There is no Legionella risk with weeks cost in a pipe. The problem is with it sitting at a warm enough temp that is below the temp that kills it.
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There is virtually no Legionella risk in a domestic HW system anyway. It only happens in large commercial or industrial premises and in practice hardly ever there either.
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Jack

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