On 2/22/2019 8:57 AM, trader_4 wrote:
On Friday, February 22, 2019 at 7:47:45 AM UTC-5, Peter wrote:
On 2/21/2019 6:36 PM, trader_4 wrote:
On Thursday, February 21, 2019 at 1:14:12 PM UTC-5, Mike K wrote:
replying to Peter, Mike K wrote:
Good point unless you are using a tankless hot water system (like me 
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If you have a gas water heater set to 130F, the chances of legionaires
being a problem is extremely remote. The bacteria can't multiply at
that temperature and at slightly higher temps are dead within hours.
I've seen quite a few stories in the news of people catching legionaires
disease, but it's never been from a residential water heater. NYC had
a bunch of cases last few years, all from AC cooling towers on roofs
that sent droplets of warm water into the air. I'd be perfectly fine
living with 120F, but 130 is better for clean dishes.
130F is both an energy waster and a scalding hazard. Depending upon the
efficiency and insulation of a hot water heating and distribution
system, you might even end up spending more $ on energy costs heating
your hot water source to 130F than you save in electricity by running
the humidifier less due to greater evaporation by using a hot water
source for that humidifier. Most modern dishwashers have some sort of
pre-heat or temperature boost feature that compensates for a supply
temperature that's lower than 130F. That way, you only spend energy to
heat the dishwashing machine water, not all your other hot water which
needs to be cooled with cold water for safe hand dish washing and
bathing (to avoid scalding).
I'm sure you'll be hearing from the folks that will tell you that lower
than 130F will kill you from Legionnaires. The Legionnaire's risk is not
limited to when it's used for a humidifier. I suppose if 130F is so dangerous,
they should stop selling water heaters that can be set to not only that,
but a lot higher. Put a low limit on it like they did with hot tubs,
now people come here complaining they can't get a hot tub/spa hot like
they enjoy it. Like I said, I'm happy with 120F
myself. Pick your risk. And I never suggested anything about needing to
set the water heater to any particular temperature for use to feed a humidifier.
120, 130F are all way above 40F incoming cold water, if you need to maximize
evaporation, 120F is above the temperature that Legionnaires bacteria
can multiply. Since you're worried about Legionnaires from water heaters,
perhaps you can show us all the cases where that's actually happened,
where people contracted it, from residential water heaters? I've yet to
hear of an actual case and there are how many hundreds of millions of
water heaters out there?
That's the second time you've distorted what I've written. I never said
that you can get Legionnaire's from a water heater's water. What I said
was that a hot water supply to a humidifier increases the risk of
Legionnaires from the humidifier. The bacteria most likely enter the
humidifier from the air (carried with dust, mold spores, etc.). The
risk is from the temperature of the water on the humidifier's
evaporative medium, which is much more conducive to the growth of
bacteria when the humidifier is supplied with hot water than when it is
supplied with cold water. It is highly unlikely that the temperature
of the water on the surface of the evaporative medium is out of the
range of about 68F-113F (the growing temperature of the bacterium that
causes Legionnaire's) by the time hot water travels through the
uninsulated thin copper pipe that supplies most furnace humidifiers and
has been blown by the humidifier's fan. I never said that the bacteria
grow in typical hot water heaters. I'm on your side; I set my hot
water water heater to 120 as well.