The proper way is to have both of them the same. Normally the lower one is going to control the tank's temperature until the lower element burns out and then the upper one will be in charge until you repair the heater.
Insulation will minimize it at 120 F as well, and 140F will still be higher heat loss in that comparison and at the same ratio as both without. Nozzles, projections and thermosiphon appear to be as large a factor as the wall in storage tank losses. Most of these losses are at the top of the tank that you suggest running at 140 F.Yes there will be higher heatloss at 60c to the ambient air but proper insulation will minimise that.
It is if you don't have that; and I've yet to live in a house that had it. It is very relevant in the five homes in the last three states I've lived in.The risk of scalding is not relevant if thermostatic mixing of the water takes place at the shower or via thermostatic mixer to the hot tap.
Stratification of the tank is what the principle of solar heated cylinders work on I don't see why it is a problem within a cylinder heated electrically. If the upper element is used only the upper part only will be heated. But if the lower coil is used then hot water will rise to the upper level. The water will be heated to higher than 50c at the lower coil when it is on but it will only switch off when 50c (probably 51.5 -53c given the tolerance on the thermostat) so it will heat a greater part of the store to an acceptable temperature for hot water use than the upper alone.
Perhaps it would be better to have both elements set to 60c and have a timer operate both to heat the store. The bottom element can switch off before the upper element if the upper part of the store only is suitable to meet demand and on longer when the whole store is required.
It is if you don't have that; and I've yet to live in a house that had it. It is very relevant in the five homes in the last three states I've lived in.
I said you could with a provisoYou suggested 45 C before for the lower, which would be counterproductive if you are concerned about legionella.
Of course and I haven't suggested otherwise. Heating with both elements raises the temperature in the upper tank quicker. But if you only draw off the upper amount then why heat the whole store.A gas water heater has actual heating of the base of the vessel so that the coldest portions of the tank get the hottest firebox temps. This is a far superior mixing distribution profile to an insertion element. It is more logical than trying to do top down heating of water because it works with natural convection rather than against it.
which is what I said, 60 and 50. if you want to heat the store to 50 there is no problem but again it will be a demand on hot water driven setting that suits the end user best. but if you only want to heat the upper part of the store then you can with the upper element alone. There is no reason not to use timers, the tank doesn't need to be constantly heated if you know when your demand is then heat the water prior to that. It's wasteful of energy to run it 24hrs.Why not just run them both at a more moderate temperature and skip the complication of the timer? Timers only make sense if your electric billing has higher rates for peak hours.
That's like saying I'll wear a condom when I meet someone with chlamydiae. You know if they're not dead from legionellae their hardly going to wear a t shirt advertising that they had it.I'll be more concerned about legionellae when I meet someone who has actually contracted it.
Do the math, figure the loss rate. Then explain how many kwh/ccf that timer might save. I've done it before and it is very little, actually surprisingly so. You can add insulation to the tank and all of the hot water piping for less than the timer and save an order of magnitude more energy doing so.There is no reason not to use timers, the tank doesn't need to be constantly heated if you know when your demand is then heat the water prior to that. It's wasteful of energy to run it 24hrs.
That's like saying I'll wear a condom when I meet someone with chlamydiae. You know if they're not dead from legionellae their hardly going to wear a t shirt advertising that they had it.
Well from practical experience on a tank weused to have heated by electric our energy bills were higher having the tank up to temperature than only prior to demand. A 13amp timer will cost what $5 -10??Do the math, figure the loss rate. Then explain how many kwh/ccf that timer might save. I've done it before and it is very little, actually surprisingly so. You can add insulation to the tank and all of the hot water piping for less than the timer and save an order of magnitude more energy doing so.
but they'll be cooling after the hot water is drawn off?Timers make sense for getting off peak rates. They would probably make sense if your tank was cooling rapidly/completely uninsulated. Problem is, the tanks don't cool rapidly, particularly electric which has a higher EF. The change in differential temperature that would drive your econ is much smaller than the unnecessary 120 to 140 F recommendation.
Typical of the legionella hysteria and why I don't take it seriously. The number of legionella deaths is small compared to the number of infections, which is itself pretty small. And then only a portion is coming from water heaters. And since I have a gas water heater, I'm not at risk for it. By your criteria, I'm already "wearing a condom."
On the other hand the suggestion of running the bottom of the tank colder is equivalent to cutting off the end of your condom and thinking you've done something really clever.
So which way are you really going with this, because from what I can see your energy saving ideas don't hold water and seem to increase the risk you are concerned about rather than reduce it.
I'm not saying that it wouldn't be prudent for electric water heater users to take some precautions, but I am saying that what you suggest is both wasteful and ineffective.
The presence of sediment, sludge, scale, rust, algae and organic material in
water systems can act as a source of nutrients .......
From what I've read, a pre-1998 electric water heater (US anyway) is about the only time this will amount to much (other than for those who have off-peak rate charges.) With current standby losses on electric heaters being so low, I doubt you would get 10 kwh/month reduction out of a timer even doing as you suggest. My shower draws are short enough and tank large enough that there wouldn't be much theoretical advantage to it and certainly not enough that I could identify it in a monthly electric bill, even though I'm down in the 400+ kwh/month range in non-summer weather.Well from practical experience on a tank weused to have heated by electric our energy bills were higher having the tank up to temperature than only prior to demand. A 13amp timer will cost what $5 -10??
but they'll be cooling after the hot water is drawn off?
You credit me far more than I deserve I'm just a regular plumber sorryOur pleasure to have a master from across the pond sharing the discussion. Obviously, some things are different, hence the testy discussion!
Lawyers ... Well yes it is an issue here but the option here is thermostatic blending valves at point of use to prevent such.First I would say that algae and organic material in the water supply are not an issue for most of our population. I am not a chemist, but would question whether mineral sediment and sludge are supporters of virus. Anyway, perhaps the other thing which weighs heavliy on our procedures is the well know law firm of Dewey, Cheatham, and Howe. ALL water heater manufacturers, and many of our plumbing codes, SPECIFY that water heaters should NOT be set higher than 120ºF ( about 50ºC) for the reason that if someone gets scalded, the plumber and the manufacturer will get sued.
Sorry I quickly googled to find two places that referred to it, no bias was intended.By the way, "masterplumbersdotcom" is a commercial site selling products and services. They are entitled to their opinion, but it is not a site that I frequent for technical advice.
While I often do use WIKI, I also take everything with a grain of salt.
broadly that's true here re grandfathering.Personally, except for outbreaks involving the ventilation system in a public building, I have never heard of a case of legionaires from water. But certainly it is possible. There is some movement to update codes to require higher temp settings in conjunction with tempering valves. But such changes occur slowly, and often will only apply to new construction and ALL existing buildings are grandfathered.
This is awkward, but...
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