3 ms·

I wonder if cooling without dehumidifying is possible. A lot of times I want it cooler in the house but it starts getting uncomfortably dry.

dymk 4y ago
You could run a humidifier at the same time
verall 4y ago
Use a swamp cooler
- More-nitors 4y ago
  ditto this efficient dehumidifier+AC will do wonders on wet+hot regions (south-east asia)
influxmoment 4y ago
You are noticing a change in relative humidity even tho the cooling did not change the absolute humidity
- lukevp 4y ago
  Relative humidity rises for the same volume of water/air as temperature decreases. The dryness of an A/C is because of the condensation accumulating from the air passed across the evaporator, it is dehumidifying at the same time it’s cooling.
- b112 4y ago
  If that was the case, it would be more humid, not less.
  - SoftTalker 4y ago
    The air tempertature at the evaporator is cold -- maybe 40 degrees or so? The relative humidity is about 100% (as evidenced by liquid water condensing on it). But the house itself never gets that cold, heat moves in from outside by radiation, the air temperature is higher, maybe 70-80 degrees, which results in a lower relative humidity.
    - b112 4y ago
      Not sure why you're replying to me, read upthread in more detail.
- deleted 4y ago
  [deleted]
jonnycomputer 4y ago
Use an evaporative cooler instead, then, if you live in a place that is arid enough. https://en.wikipedia.org/wiki/Evaporative_cooler https://en.wikipedia.org/wiki/Evaporative_cooler Or use a humidifier, I guess.
amluto 4y ago
Yes, easily: just operate the evaporator (or other heat exchanger) above the dew point. Sadly, most air conditioners are not capable of doing this. As far as I can tell, this is a weakness in the software or control system and is not a hardware limitation, although it might cause some systems to have to operate off their most efficient point or to require more airflow than the design supports well to get enough cooling. This is a notable exception: https://www.chiltrix.com/chiller-controller/ https://www.chiltrix.com/chiller-controller/ In principle, any hydronic cooling system could be adapted to do that trick, by adding a mixing valve, an air temperature and humidity sensor, and a little computer. AFAICT the Chiltrix device works by adjusting the air-to-water heat pump’s supplied water temperature directly.
- lazide 4y ago
  They operate below the dew point because; 1 - drier air feels cooler, and has other advantages (reduced condensation on surfaces, etc). 2 - it’s more efficient for them to do so, considering heat exchanger surface area, the phase change temperature of the refrigerant, etc. For the most part, those are the priorities people have. Subtle things like ‘not drying out the air too much’ are less noticeable and not generally a competitive advantage.
  - amluto 4y ago
    > 1 - drier air feels cooler, and has other advantages (reduced condensation on surfaces, etc). This is the cargo cult problem. When it’s too humid, dry air feels better. So HVAC engineers pick a nominal coil temperature based on some design climate and use it everywhere. Dryer does not feel better in hot, dry places. > 2 - it’s more efficient for them to do so, considering heat exchanger surface area, the phase change temperature of the refrigerant, etc. I have not gone through all the math, but I’m willing to bet that this follows from #1. Engineers picked a coil temperature and designed from there. There are multiple refrigerants on the market, the operating pressure of a system can be controlled at least a little bit, and it’s even possible to operate the coil warmer than the refrigerant with no fundamental change in COP. (Hydronic systems do the latter regularly by recirculating some of their working fluid.) As far as I can tell, there is no market for an air conditioner with better humidity control because no one has created a market — everyone expects that air conditioned air is unpleasant, and no one has marketed their superior system well. (Lots of people in very humid climates think that comfortable air conditioned air is too cold — they have to set thermostats to 70 or even lower to be comfortable. This is because of inadequate dehumidification. Lots of people in hot, dry climates think that air conditioned air is too dry. These people aren’t wrong.)
washadjeffmad 4y ago
Ideally, add more mass to your home. We're most sensitive not to absolute temperatures but to the characteristics of radiant heating and cooling in our environments. In-floor heating or cooling would do a lot more to stabilize your comfort than blowing around conditioned air.
hgomersall 4y ago
That's easy, just aerosolise a load of water in your house.

dymk 4y ago

You could run a humidifier at the same time

verall 4y ago

Use a swamp cooler

More-nitors 4y ago
ditto this efficient dehumidifier+AC will do wonders on wet+hot regions (south-east asia)

influxmoment 4y ago

You are noticing a change in relative humidity even tho the cooling did not change the absolute humidity

lukevp 4y ago
Relative humidity rises for the same volume of water/air as temperature decreases. The dryness of an A/C is because of the condensation accumulating from the air passed across the evaporator, it is dehumidifying at the same time it’s cooling.
b112 4y ago
If that was the case, it would be more humid, not less.
- SoftTalker 4y ago
  The air tempertature at the evaporator is cold -- maybe 40 degrees or so? The relative humidity is about 100% (as evidenced by liquid water condensing on it). But the house itself never gets that cold, heat moves in from outside by radiation, the air temperature is higher, maybe 70-80 degrees, which results in a lower relative humidity.
  - b112 4y ago
    Not sure why you're replying to me, read upthread in more detail.
deleted 4y ago
[deleted]

jonnycomputer 4y ago

Use an evaporative cooler instead, then, if you live in a place that is arid enough. https://en.wikipedia.org/wiki/Evaporative_cooler https://en.wikipedia.org/wiki/Evaporative_cooler Or use a humidifier, I guess.

amluto 4y ago

Yes, easily: just operate the evaporator (or other heat exchanger) above the dew point. Sadly, most air conditioners are not capable of doing this. As far as I can tell, this is a weakness in the software or control system and is not a hardware limitation, although it might cause some systems to have to operate off their most efficient point or to require more airflow than the design supports well to get enough cooling. This is a notable exception: https://www.chiltrix.com/chiller-controller/ https://www.chiltrix.com/chiller-controller/ In principle, any hydronic cooling system could be adapted to do that trick, by adding a mixing valve, an air temperature and humidity sensor, and a little computer. AFAICT the Chiltrix device works by adjusting the air-to-water heat pump’s supplied water temperature directly.

lazide 4y ago
They operate below the dew point because; 1 - drier air feels cooler, and has other advantages (reduced condensation on surfaces, etc). 2 - it’s more efficient for them to do so, considering heat exchanger surface area, the phase change temperature of the refrigerant, etc. For the most part, those are the priorities people have. Subtle things like ‘not drying out the air too much’ are less noticeable and not generally a competitive advantage.
- amluto 4y ago
  > 1 - drier air feels cooler, and has other advantages (reduced condensation on surfaces, etc). This is the cargo cult problem. When it’s too humid, dry air feels better. So HVAC engineers pick a nominal coil temperature based on some design climate and use it everywhere. Dryer does not feel better in hot, dry places. > 2 - it’s more efficient for them to do so, considering heat exchanger surface area, the phase change temperature of the refrigerant, etc. I have not gone through all the math, but I’m willing to bet that this follows from #1. Engineers picked a coil temperature and designed from there. There are multiple refrigerants on the market, the operating pressure of a system can be controlled at least a little bit, and it’s even possible to operate the coil warmer than the refrigerant with no fundamental change in COP. (Hydronic systems do the latter regularly by recirculating some of their working fluid.) As far as I can tell, there is no market for an air conditioner with better humidity control because no one has created a market — everyone expects that air conditioned air is unpleasant, and no one has marketed their superior system well. (Lots of people in very humid climates think that comfortable air conditioned air is too cold — they have to set thermostats to 70 or even lower to be comfortable. This is because of inadequate dehumidification. Lots of people in hot, dry climates think that air conditioned air is too dry. These people aren’t wrong.)

washadjeffmad 4y ago

Ideally, add more mass to your home. We're most sensitive not to absolute temperatures but to the characteristics of radiant heating and cooling in our environments. In-floor heating or cooling would do a lot more to stabilize your comfort than blowing around conditioned air.

hgomersall 4y ago

That's easy, just aerosolise a load of water in your house.