I checked my Grant tank and the 200 litre is 1.88kWh/24h and 300l is
2.21kWh/24h, so that's roughly comparable. That's at 60C - one advantage of running at a lower tank temp is reduced thermal losses.Also worth checking your pipe insulation, as losses from the pipes connected to the tank can also contribute.
Theo
I don't know where the EU Regulations ended up but one methodology for the Standing Loss from water tanks assumed 45C. If that is the basis of WB's figure then your standing loss could be much less if e.g. you keep the water at less than 65C and the room stays above 20C.
Why so low ?
Yes.
That's very arguable.
It actually started to be a problem when lots of places were airconditioned and the cooling towers exposed lots of people to legionella in the mist from those.
sorry, should have read "assumed 45C delta-T"
Is the temp sensor a thermistor or a conventional make/break stat?
If it is a thermistor, then you could use your timer and relay to insert an extra resister in series with the NTC so that the boiler reads the cylinder temp lower that it actually is, and thus heats it a bit further one day a week.
If it is a make/break type, then insert a run on timer so the boiler sees an extended call for heat - say adding an extra 15 mins after stat is satisfied. Again set enabled by a timer so that it happens just once a week.
Yup, my unistore is room temperature to the touch.
That is a "loss" into the envelope of the building usually though - so only equates to heat the CH does not need to provide.
I checked for my 210L Unistor and the closest model I could see now was the 200L "standard" one. That claims 1.22 kWh/24 hours.
I deliberately did not insulate some of those since I wanted some heat in the airing cupboard.
Another interesting idea. In this case the sensor is connected to a box which sends the info over an 868MHz ISM link to a controller, but I've no idea what the spec for the sensor is. Many years ago the state spent money on me for 3 years to become an electronic engineer, but my interest in designing and dabbling has waned significantly and, these days, I just want things to work :-)
That's a good question. Looking on PubMed I can find quite a bit, eg:
60-70% of domestic showers in Adelaide had Legionella in them:The cases in commercial settings have been identified because there's a cluster. Like the original legionnaires conference, dozens of people get sick and it's traced back that they all stayed in the same hotel. So somebody visits and takes samples to work out the common cause.
I'm not sure we'd have a good way to identify domestic cases, because there's no screening that would pick them up. Hospitals don't routinely sequence bacterial infections so we don't attribute respiratory infections to legionella, they just treat it as pneumonia.
This paper from China:
So it seems like it's not uncommon to have it lurking in hot water systems, and then it's down to how susceptible the occupants are to infection.
Theo
Or simply that hotels, offices and other premises started installing air-conditioning, with wet cooling towers and people started switching from baths to showers. Both produce aerosols that can be inhaled. Legionella is only a problem when inhaled - you can drink contaminated water with no effect.
Use a strap-on. Just scrape a patch of insulation off where it sits. Ensure it can't fall off, danger can result if it ever does.
Could Legionella become more of a problem when the population installs more air sourced heat pumps in locations? At certain times of year the conditions must be right for aerosols to be output in locations close to the house/back yard.
Nope, they don't have water cooling towers.
Nope, no water based cooling tower or aerosoled water either.
Even what the yanks call swamp coolers arent a problem because they do get hot enough to kill the bacteria.
Looking at one set of Vaillant diagnostics they give NTC values for DHW sensing of:
Resistance at 25 degrees C = 10K OHMS.
Resistance at 60 degrees C = 2.5K OHMS.
NTCs are a bit non linear without some compensation, but I expect that is done in software rather than in the sensor. So the raw reading from the NTC at 70 deg C I would guestimate at around 2K ohms.
So adding in 500 ohms would allow the actual cylinder temp to reach 70 before the boiler thinks it has reached 60.
(I would use a 1k linear preset pot, so one can tune the temperature)
No, it is/was only the large commercial units that caused a problem. They might have an air conditioner in each room, fed by chilled water from central chiller unit. Much of the excess heat was removed from the water by trickling it dowm surfaces in an open cooling tower, which meant that droplets could be blown from the tower and infect people nearby. Home heat pumps/aircon units have their heat transfer fluid in a self contained loop (and don't use water anyway), so they cannot cause this problem.
My control system for my gas boiler, includes a once per week Legionella program, to do exactly that. I don't both with it, because I set it to
60C every day.
Once per week is considered enough, and so long at it gets to 60C that is all that is required.
No, providing they are regularly used, the water in them will be free of Legionella. If the water is left to stand in the pipes, maybe during a holiday, best to flush first before use.
I had searched on Startpage and DDG using the search terms "domestic water legionella OR legionnaires" (without quote marks). There were no PubMed refs in the first 100 Startpage hits, and the first PubMed ref was 84th in the DDG list (although not one of your refs). I tried PubMed with "legionella domestic home", again without quotes, and it returned a couple of pages of hits (including your refs, but not the UK showers one! Wrong keyword, I guess!).
A rather throwaway comment in the summary seems to negate much of their findings: "However, examination of risk factors associated with L. pneumophila found that there were no statistically significant associations (p >
0.05) with L. pneumophila concentrations and temperature, type of hot water system, age of system, age of house or frequency of use."And as 60 - 70% of showers have Legionella spp, why isn't the incidence of Legionnaires Disease much higher?
Unfortunately the full article is not available FoC. Although not mentioned in their summary, the full Adelaide paper is free and in the text refers to the UK study, noting "Interestingly, the UK study did not find a statistically significant association between the presence of Legionella spp. and water temperature."
I doubt it. Legionnaires' Disease is notifiable in England and Wales, so if suspected I think the hospital would be somewhat negligent if they didn't try to establish if it was LD or not.
I agree that it certainly looks like a confirmed case from domestic infection.
Meanwhile this study in Quebec:
It may be that those more susceptible are, such as at
In an effort to save energy, we are being told to "stop using the bath and shower instead". If Legionella is to be found in domestic hot water system, I would have expected showers to have a higher risk factor than baths!
Presumably because running the hot water at less than 60C is a relatively recent thing.
But not unless the boiler is run at less than 60C
Rod Speed snipped-for-privacy@gmail.com posted
That's because building regulations require it. Doesn't mean it actually does any good.
The pertinent question is not whether Legionella is present in DHW systems - as somebody pointed out, it's everywhere - but whether it is a significant cause of symptomatic infections.
[snip]
That's China. I wouldn't even drink the tap water there.
So two out of three of these legionella patients *didn't* catch it from their DHW systems. Seems to me quite likely that the other one out of three didn't either. And of course the researchers did not investigate the DHW tanks of people who *didn't* get Legionella. Quite likely those tanks contained Legionella too, as it's ubiquitous.
Their results are perfectly consistent with the hypothesis that *all* these Legionella patients caught it from some other source, and the presence of Legionella in their DHW was purely coincidental.
Seems unlikely that they would require it if it isnt necessary.
Although you lot have some very silly rules about what can be done in a bathroom power wise that none of the rest of the world requires, even when their standard voltage is 220V etc
It is trivial to prove that it does good.
Brian's line is that it isn't actually necessary due to built up natural immunity. Hard to se why people get killed by commercial cooling towers if that is the case.
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