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Similarly, I've heard of HVAC systems that just use city water for cooling. It comes in cold, dump heat into it and let it run down the drain. Running like tha

Similarly, I've heard of HVAC systems that just use city water for cooling. It comes in cold, dump heat into it and let it run down the drain. Running like that all the time seems unconscionable, but it makes a lot of sense as a backup while the primary is down for repair, as a very cheap-to-install but wasteful-to-run system that would be appropriate for short durations only.

anewdirection 6y ago
Airconditioning is still a luxury to the world. Not sure running clean, treated drinking water down the drain for comfort is ever worth it.
- amluto 6y ago
  There are plenty of hot places with enough fresh water supplies that trying to conserve water is of dubious value. The problem with fresh water isn’t the overall supply of fresh water. It’s getting it to communities that need it, when they need it, and distributing it without contaminating it.
- bcoates 6y ago
  I think the biggest costs of sewage treatment is removing solids and hazardous contaminants. Diluting wastewater with moderate volumes of potable water may not mean much to the whole-cycle. It's not nearly as bad as watering a lawn, where water goes out clean and comes back as contaminated runoff that has to be captured and treated or dumped.
CrazyStat 6y ago
> Similarly, I've heard of HVAC systems that just use city water for cooling. It comes in cold, dump heat into it and let it run down the drain. My grandparents had a system that worked basically on that principle. Since they lived in a farming town it used irrigation water which was much cheaper than tap water.
gruez 6y ago
Are you sure you're not confusing what you're describing with evaporative cooling? I don't think that the thermal delta between tap water and a warm room is enough to justify the cost of filtered municipal tap water. For comparison, if the HVAC system simply fed the water into the radiators and dumped it, the max amount of heat you can capture is around 63J per gram of water (opportunistic assumptions of the water coming in at 5C and leaving at 20C). By comparison, if you evaporate the water, the latent heat of evaporation of water alone is 2257J per gram.
- myself248 6y ago
  I don't know for certain, but I didn't see any evaporators at the facility. Some places with high atmospheric humidity might have a hard time with evaporative cooling anyway. I think they might've been running a Freon loop with the condenser in tap water, to achieve higher thermal delta and just skip the enormous radiators and fans.
  - gruez 6y ago
    >I don't know for certain, but I didn't see any evaporators at the facility. They're generally on top of the building, and they kinda look like generic air conditioning units. https://www.munters.com/en/munters/products/coolers--humidifiers/oasis-indirect-evaporative-coolers-iec/ https://www.munters.com/en/munters/products/coolers--humidif...
catalogia 6y ago
> Similarly, I've heard of HVAC systems that just use city water for cooling. It comes in cold, dump heat into it and let it run down the drain. Whether or not that's wasteful really depends on where exactly it's happening. If the city water is being pumped out of a fossil aquifer, that's obviously a problem. If the water is coming out of a reservoir with abundant supply, the water being "used" is merely taking a slight detour from what it would otherwise do ("river→reservoir→hvac→river→ocean" rather than "river→ocean".) There could be some energy losses in the pumping and processing of the water, depending on where it's happening, but that's not the water itself being wasted.

anewdirection 6y ago

Airconditioning is still a luxury to the world. Not sure running clean, treated drinking water down the drain for comfort is ever worth it.

amluto 6y ago
There are plenty of hot places with enough fresh water supplies that trying to conserve water is of dubious value. The problem with fresh water isn’t the overall supply of fresh water. It’s getting it to communities that need it, when they need it, and distributing it without contaminating it.
bcoates 6y ago
I think the biggest costs of sewage treatment is removing solids and hazardous contaminants. Diluting wastewater with moderate volumes of potable water may not mean much to the whole-cycle. It's not nearly as bad as watering a lawn, where water goes out clean and comes back as contaminated runoff that has to be captured and treated or dumped.

CrazyStat 6y ago

> Similarly, I've heard of HVAC systems that just use city water for cooling. It comes in cold, dump heat into it and let it run down the drain. My grandparents had a system that worked basically on that principle. Since they lived in a farming town it used irrigation water which was much cheaper than tap water.

gruez 6y ago

Are you sure you're not confusing what you're describing with evaporative cooling? I don't think that the thermal delta between tap water and a warm room is enough to justify the cost of filtered municipal tap water. For comparison, if the HVAC system simply fed the water into the radiators and dumped it, the max amount of heat you can capture is around 63J per gram of water (opportunistic assumptions of the water coming in at 5C and leaving at 20C). By comparison, if you evaporate the water, the latent heat of evaporation of water alone is 2257J per gram.

myself248 6y ago
I don't know for certain, but I didn't see any evaporators at the facility. Some places with high atmospheric humidity might have a hard time with evaporative cooling anyway. I think they might've been running a Freon loop with the condenser in tap water, to achieve higher thermal delta and just skip the enormous radiators and fans.
- gruez 6y ago
  >I don't know for certain, but I didn't see any evaporators at the facility. They're generally on top of the building, and they kinda look like generic air conditioning units. https://www.munters.com/en/munters/products/coolers--humidifiers/oasis-indirect-evaporative-coolers-iec/ https://www.munters.com/en/munters/products/coolers--humidif...

catalogia 6y ago

> Similarly, I've heard of HVAC systems that just use city water for cooling. It comes in cold, dump heat into it and let it run down the drain. Whether or not that's wasteful really depends on where exactly it's happening. If the city water is being pumped out of a fossil aquifer, that's obviously a problem. If the water is coming out of a reservoir with abundant supply, the water being "used" is merely taking a slight detour from what it would otherwise do ("river→reservoir→hvac→river→ocean" rather than "river→ocean".) There could be some energy losses in the pumping and processing of the water, depending on where it's happening, but that's not the water itself being wasted.