5 ms·

>A less-sophisticated approach is to put your tank heater on a timer. Think carefully before you do this. Do not do this without understanding the lifecycle of

>A less-sophisticated approach is to put your tank heater on a timer. Think carefully before you do this. Do not do this without understanding the lifecycle of legionella pneumophila, or you will face a dramatic decrease in your quality of life. https://en.wikipedia.org/wiki/Legionnaires'_disease https://en.wikipedia.org/wiki/Legionnaires'_disease

toomuchtodo 5y ago
Yeah, timer or grid controlled water heaters are old and busted (especially with bacteria concerns due to a lack of in tank convection). New hotness are heat pump water heaters that are very efficient and can even add cool air to a conditioned spaces by their inherent operation. Electric vehicle charging orchestrated as large aggregate loads are what replaces “the humble water heater.” Tankless heaters are great if you’re burning gas, but electric versions are wildly inefficient versus a heat pump and require very large circuits and service entrances on the load center/breaker panel.
- ip26 5y ago
  Heat pump water heaters do seem promising... But many water heaters live in cold basements... Classic tanked electric is so cheap to make & operate, I have come to think they may always be with us. (Though certainly a heat pump water heater is an easy choice in the right climate)
  - otterley 5y ago
    "Cold" basements rarely fall below 50 degrees Fahrenheit/10C. There's plenty of thermal headroom below that for heat pumps to work. Heat pumps already work outdoors at below freezing. I don't think there's anything to worry about.
    - s0rce 5y ago
      More of a problem is when your water heater is within your conditioned space envelope and in the cold months when you are heating your space the hot water heater takes that heat. Its not a huge issue but you do run the heater extra for the heat that's going into your hot water. If you've got an air source heat pump outside then its just an extra step.
      - anonymousisme 5y ago
        I was thinking the same thing. You don't get something for nothing. Assuming the water heater is in the conditioned space, it will just make the central heater work harder (and consume more fuel) during the winter months. Maybe this is offset during summer months when it can help the AC cool the space. None of this applies if the water heater is not in a conditioned space, but that's not feasible in (common) environments with cold winters.
  - caf 5y ago
    There are split system heat pump hot water heaters which allows you to exchange heat with the outside environment, eg. https://reclaimenergy.com.au/products/residential/ https://reclaimenergy.com.au/products/residential/
    - ttwwmm 5y ago
      The all-in-one units can also be installed with ducting.
  - ttwwmm 5y ago
    Heat pump models usually have a resistive element for use when the heat pump can't keep up, or when the climate doesn't cooperate. Then you benefit from the efficiency whenever possible. (Here in coastal CA I have mine set to only ever use the heat pump since the climate is so mild.) The up-front cost of a heat pump is definitely an issue. IMO we should be doing instant rebates to even out the cost between the two so that it's an easy decision.
- jhgb 5y ago
  > timer or grid controlled water heaters are old and busted (especially with bacteria concerns due to a lack of in tank convection) This is literally the first time I'm hearing of this as a concern. Our local recommendations are to keep tank temperature above 70C and you should be fine.
  - toomuchtodo 5y ago
    https://patents.justia.com/patent/20180290899 https://patents.justia.com/patent/20180290899 provides background on the topic. Keeping your hot water tank at or above 50-55C constantly is a reasonable mitigation, anything hotter can cause scalding.
    - jhgb 5y ago
      You can't scald yourself with mixed water from the faucet unless you set the faucet lever wrong, so I've never had that issue. In addition to that, the recommended high temperature setting (I believe the recommended default setting on my tank is 60 C?) increases the amount of mixed water that you can use before depleting the tank, so even a smaller tank suffices for a person.
  - ttwwmm 5y ago
    My heat pump water heater is at 140F all the time, maximizing the banked energy. There's an outboard mixing valve to reduce this to a safe temperature in the house.
ip26 5y ago
Slightly smarter timers could fix this problem. Raise the tank to 140+ once a day, probably at 4am, and work that into the energy storage regime...
- cartoonworld 5y ago
  Another issue arises in that the bacteria can propagate throughout the system, repopulating the heater. Some have checkvalves, but I'm no plumber. I urge great caution, although I'd wager you'd be fine, so long as you remain healthy.
  - Scoundreller 5y ago
    Per wikipedia, it can form biofilms on pipes that will slough off. But the heater is still hitting high enough temperatures to kill it.
    - cartoonworld 5y ago
      Yeah, but only if it is flowing across the deposit. If you do the "bare minimum 140f once a day" method, you have to flush all the hot lines with this for long enough to kill it. All this also presumes correct thermostatic calibration and generally even temperature distribution in a system planned to age with minimal maintenance. The process isn't instant, you also have to ensure the hot water hits all the lines down the way at the appropriate hold temp and, well, hold it there for long enough. These outbreaks still occur today. Not a huge problem, but why design such a well controlled hazard back into your potable water?
      - Scoundreller 5y ago
        Well, energy savings. Where I am, you’re not allowed to deliver water to fixtures higher than 49C (120F), to reduce scalding risk. and this is usually accomplished through a mixing valve at the hot water tank outlet. 11m people live here, haven’t heard of any evidence of increased legionnaires: https://www.ontario.ca/laws/regulation/r04023 https://www.ontario.ca/laws/regulation/r04023
coryrc 5y ago
Man, let me tell you about my friend the Greeks. Any time they leave the house, turn off the water heater. Hotel: water heater is off until you ask. All because in the 50s (iirc) they incorrectly installed a bunch of heaters which exploded from overpressure. I'd be surprised if they have unusually high rates of Legionnaires'.
- cartoonworld 5y ago
  A quick google proves your intuition pretty spot on. Looks like there was a major increase of the disease between 2016-2018. Greek public health announcement regarding outbreaks ~2018: https://www.acg.edu/about-acg/institute-of-public-health/fact-sheets/legionnaires-disease/ https://www.acg.edu/about-acg/institute-of-public-health/fac... An anecdotal account of a man contracting Legionnaire's while on holiday in Greek apartment: https://www.irwinmitchell.com/news-and-insights/newsandmedia/2016/june/legal-action-after-man-hospitalised-by-legionnaires-disease-after-greek-holiday-jq-603550 https://www.irwinmitchell.com/news-and-insights/newsandmedia... An older account of a similar ocurrance in a hotel, just as you describe: https://www.sciencedirect.com/science/article/abs/pii/0043135494900590 https://www.sciencedirect.com/science/article/abs/pii/004313... Granted, no mention of this particular cultural artifact. Global temperature warming was cited in some reports as part of the cause of these outbreaks. It seems that the bacteria really likes to live in showerheads, so especially older shower heads can accumulate legionella especially given commonly lukewarm temperatures. This creates a perfect storm of ideal reservoirs, protected, moist, temperature conditions and aerosolized distribution. Nasty.

toomuchtodo 5y ago

Yeah, timer or grid controlled water heaters are old and busted (especially with bacteria concerns due to a lack of in tank convection). New hotness are heat pump water heaters that are very efficient and can even add cool air to a conditioned spaces by their inherent operation. Electric vehicle charging orchestrated as large aggregate loads are what replaces “the humble water heater.” Tankless heaters are great if you’re burning gas, but electric versions are wildly inefficient versus a heat pump and require very large circuits and service entrances on the load center/breaker panel.

ip26 5y ago
Heat pump water heaters do seem promising... But many water heaters live in cold basements... Classic tanked electric is so cheap to make & operate, I have come to think they may always be with us. (Though certainly a heat pump water heater is an easy choice in the right climate)
- otterley 5y ago
  "Cold" basements rarely fall below 50 degrees Fahrenheit/10C. There's plenty of thermal headroom below that for heat pumps to work. Heat pumps already work outdoors at below freezing. I don't think there's anything to worry about.
  - s0rce 5y ago
    More of a problem is when your water heater is within your conditioned space envelope and in the cold months when you are heating your space the hot water heater takes that heat. Its not a huge issue but you do run the heater extra for the heat that's going into your hot water. If you've got an air source heat pump outside then its just an extra step.
    - anonymousisme 5y ago
      I was thinking the same thing. You don't get something for nothing. Assuming the water heater is in the conditioned space, it will just make the central heater work harder (and consume more fuel) during the winter months. Maybe this is offset during summer months when it can help the AC cool the space. None of this applies if the water heater is not in a conditioned space, but that's not feasible in (common) environments with cold winters.
- caf 5y ago
  There are split system heat pump hot water heaters which allows you to exchange heat with the outside environment, eg. https://reclaimenergy.com.au/products/residential/ https://reclaimenergy.com.au/products/residential/
  - ttwwmm 5y ago
    The all-in-one units can also be installed with ducting.
- ttwwmm 5y ago
  Heat pump models usually have a resistive element for use when the heat pump can't keep up, or when the climate doesn't cooperate. Then you benefit from the efficiency whenever possible. (Here in coastal CA I have mine set to only ever use the heat pump since the climate is so mild.) The up-front cost of a heat pump is definitely an issue. IMO we should be doing instant rebates to even out the cost between the two so that it's an easy decision.
jhgb 5y ago
> timer or grid controlled water heaters are old and busted (especially with bacteria concerns due to a lack of in tank convection) This is literally the first time I'm hearing of this as a concern. Our local recommendations are to keep tank temperature above 70C and you should be fine.
- toomuchtodo 5y ago
  https://patents.justia.com/patent/20180290899 https://patents.justia.com/patent/20180290899 provides background on the topic. Keeping your hot water tank at or above 50-55C constantly is a reasonable mitigation, anything hotter can cause scalding.
  - jhgb 5y ago
    You can't scald yourself with mixed water from the faucet unless you set the faucet lever wrong, so I've never had that issue. In addition to that, the recommended high temperature setting (I believe the recommended default setting on my tank is 60 C?) increases the amount of mixed water that you can use before depleting the tank, so even a smaller tank suffices for a person.
- ttwwmm 5y ago
  My heat pump water heater is at 140F all the time, maximizing the banked energy. There's an outboard mixing valve to reduce this to a safe temperature in the house.

ip26 5y ago

Slightly smarter timers could fix this problem. Raise the tank to 140+ once a day, probably at 4am, and work that into the energy storage regime...

cartoonworld 5y ago
Another issue arises in that the bacteria can propagate throughout the system, repopulating the heater. Some have checkvalves, but I'm no plumber. I urge great caution, although I'd wager you'd be fine, so long as you remain healthy.
- Scoundreller 5y ago
  Per wikipedia, it can form biofilms on pipes that will slough off. But the heater is still hitting high enough temperatures to kill it.
  - cartoonworld 5y ago
    Yeah, but only if it is flowing across the deposit. If you do the "bare minimum 140f once a day" method, you have to flush all the hot lines with this for long enough to kill it. All this also presumes correct thermostatic calibration and generally even temperature distribution in a system planned to age with minimal maintenance. The process isn't instant, you also have to ensure the hot water hits all the lines down the way at the appropriate hold temp and, well, hold it there for long enough. These outbreaks still occur today. Not a huge problem, but why design such a well controlled hazard back into your potable water?
    - Scoundreller 5y ago
      Well, energy savings. Where I am, you’re not allowed to deliver water to fixtures higher than 49C (120F), to reduce scalding risk. and this is usually accomplished through a mixing valve at the hot water tank outlet. 11m people live here, haven’t heard of any evidence of increased legionnaires: https://www.ontario.ca/laws/regulation/r04023 https://www.ontario.ca/laws/regulation/r04023

coryrc 5y ago

Man, let me tell you about my friend the Greeks. Any time they leave the house, turn off the water heater. Hotel: water heater is off until you ask. All because in the 50s (iirc) they incorrectly installed a bunch of heaters which exploded from overpressure. I'd be surprised if they have unusually high rates of Legionnaires'.

cartoonworld 5y ago
A quick google proves your intuition pretty spot on. Looks like there was a major increase of the disease between 2016-2018. Greek public health announcement regarding outbreaks ~2018: https://www.acg.edu/about-acg/institute-of-public-health/fact-sheets/legionnaires-disease/ https://www.acg.edu/about-acg/institute-of-public-health/fac... An anecdotal account of a man contracting Legionnaire's while on holiday in Greek apartment: https://www.irwinmitchell.com/news-and-insights/newsandmedia/2016/june/legal-action-after-man-hospitalised-by-legionnaires-disease-after-greek-holiday-jq-603550 https://www.irwinmitchell.com/news-and-insights/newsandmedia... An older account of a similar ocurrance in a hotel, just as you describe: https://www.sciencedirect.com/science/article/abs/pii/0043135494900590 https://www.sciencedirect.com/science/article/abs/pii/004313... Granted, no mention of this particular cultural artifact. Global temperature warming was cited in some reports as part of the cause of these outbreaks. It seems that the bacteria really likes to live in showerheads, so especially older shower heads can accumulate legionella especially given commonly lukewarm temperatures. This creates a perfect storm of ideal reservoirs, protected, moist, temperature conditions and aerosolized distribution. Nasty.