Dehumidifier Suggestions...

[Chewwy]

You are right but for a bit more complex reason. To remove any significant heat from the house with the flow through the HVAC system, you have to cool it below the dew point. It takes a lot more heat removal to condense the water vapor than it does to cool the air, so your AC gets a lot more bang for the buck if it's cooling low humidity air. The dehumidifier cycle is optimized for condensing water instead of cooling air, so it's better overall.

People don't realize how much heat is contained in the vaporization of water. That's why "swamp coolers" that only vaporize water are so effective for AC in very dry climates.

While it may improve the cooling capabilty of the ac unit, operation of the dehumidifier adds heat to the conditioned space that then has to be removed by the ac. The dehumidifier cools the air to condense the water vapor but then returns that heat energy plus the energy consumed by operating the dehumidifier back to the conditioned space.

 

[KennyG]

While it may improve the cooling capabilty of the ac unit, operation of the dehumidifier adds heat to the conditioned space that then has to be removed by the ac. The dehumidifier cools the air to condense the water vapor but then returns that heat energy plus the energy consumed by operating the dehumidifier back to the conditioned space.

Yes, you are correct, it's about having the right equipment for the job. In my house, in the summer, I minimize the HVAC flow to the basement, since it doesn't need cooling and run a dehumidifier in the basement. For the rest of the house, once I have the humidity low, the AC runs very efficiently. Of course, I'm in an area where the temperature is seldom above 90 but the humidity is often high, so it's a different situation in other areas. I run the dehumidifier all summer but have the A/C on for only a few weeks a year.

 

[dstig1]

Air conditioning is actually pretty complex and a lot of people don't understand how proper AC is supposed to work. They talk about Latent load and Sensible load in AC. I'm not super familiar with it but think of latent as heat and sensible as humidity. If you cool down the latent load too quickly the AC shuts off and there is still a lot of moisture in the air but the temp is low. This feels clammy. You want the AC to run long enough to condense out the moisture to a decent level and cool the air temp at the same time. This is why proper sizing of AC is important. People like to oversize to make sure it will cool the place down on the hottest days, but too big means it short cycles and leaves all that moisture still in the air.

 

[JasperFrank]

We got a GE standup unit, which. as I'm just now reading, isn't that good, as said by reviewers. Yet, it has done a splendid job for us over seven years. Its plumbed to discharge into a floor drain. We get a lot of condensation in the winter here in western Oregon. This thing just worked great.

 

[quicksandfarmer]

Air conditioning is actually pretty complex and a lot of people don't understand how proper AC is supposed to work. They talk about Latent load and Sensible load in AC. I'm not super familiar with it but think of latent as heat and sensible as humidity. If you cool down the latent load too quickly the AC shuts off and there is still a lot of moisture in the air but the temp is low. This feels clammy. You want the AC to run long enough to condense out the moisture to a decent level and cool the air temp at the same time. This is why proper sizing of AC is important. People like to oversize to make sure it will cool the place down on the hottest days, but too big means it short cycles and leaves all that moisture still in the air.

It's the other way round. "Sensible" cooling is cooling you can sense -- making the air colder. Latent cooling is removing humidity from the air. The thermostat on the air conditioner only measures sensible cooling, the temperature. If you need more latent cooling than is provided you will be uncomfortable because it will be cool and clammy.

If your AC is providing adequate cooling a dehumidifier won't make it work better. The difference between an AC and a dehumidifier is the AC moves heat outdoors, while the dehumidifier removes heat from the air and then dumps it back inside. Running both an AC and a dehumidifier you're paying to cool the same air twice.

Dehumidifiers are highly efficient space heaters. When they extract moisture from the air they remove latent heat, that heat is then dumped into the room as sensible heat. They dump about three times as much heat as the electricity consumed would produce if you just used it to run a space heater.

 

[CalG]

While it may improve the cooling capabilty of the ac unit, operation of the dehumidifier adds heat to the conditioned space that then has to be removed by the ac. The dehumidifier cools the air to condense the water vapor but then returns that heat energy plus the energy consumed by operating the dehumidifier back to the conditioned space.

Yes, But as they say in Arizona

"Its a DRY heat".

 

[dodge man]

I don’t see a dehumidifier adding a lot of heat inside. It’s just a small AC unit with the coils stacked together instead of the hot one outside. The fan basically is blowing the cold coils over the hot coils. Of course there isn’t going to be a 100% efficiency so some heat is going to come out.

 

[Chewwy]

I don’t see a dehumidifier adding a lot of heat inside. It’s just a small AC unit with the coils stacked together instead of the hot one outside. The fan basically is blowing the cold coils over the hot coils. Of course there isn’t going to be a 100% efficiency so some heat is going to come out.

As previously discussed, the cooling of the air to remove the water vapor involves substatial latent heat (970 BTUs/pint) removed in the change of phase. That heat is then returned to the conditioned space. In addition the energy consumed to run the dehumidifier is also released as heat into the conditioned space.

It’s not “some of the heat.” It is ALL of the heat removed plus the energy used to run the device. For a medium sized dehumidifier (30 pints/day) that’s about 8.5kW plus the energy comsumed when the device is running (~ 0.50kW)

1st law on thermodynamics in action.

 

[2manyrocks]

I've been running a 50 pint Fridgidaire dehumidifier in the basement of a property used for storage for a couple of years.

https://www.lowes.com/pd/Frigidaire-50-Pint-2-Speed-Dehumidifier-ENERGY-STAR/1000016091

Last month, I also installed a 12k Midea U shaped A/C after it had been on sale for about $360. Costco has some in limited locations for $280 I understand. https://www.amazon.com/Midea-Invert...d=1690209884&sprefix=midea+12k,aps,573&sr=8-3

I ran both to see what the electric bill would be. The bill came today for $47.47 covering 30 days in which I used 194kwh. It wasn't that much more than running the dehumidifier alone, and it's been hot.

If there is a window available to install an AC unit, it could worth considering, but useless in the winter.

Another option is to install a mini split inverter, but that will require about a 2-3" hole in the exterior wall to run the refrigerant, drain, and control lines, plus all the rest of the installation. But a mini split will also provide heat if needed in the winter.

 

[Chewwy]

I've been running a 50 pint Fridgidaire dehumidifier in the basement of a property used for storage for a couple of years.

https://www.lowes.com/pd/Frigidaire-50-Pint-2-Speed-Dehumidifier-ENERGY-STAR/1000016091

Last month, I also installed a 12k Midea U shaped A/C after it had been on sale for about $360. Costco has some in limited locations for $280 I understand. https://www.amazon.com/Midea-Inverter-Conditioner-Flexibility-Installation/dp/B0867GMW9X/ref=sr_1_3?crid=HSX4L1LKUFJ7&keywords=midea+12k+u+shaped+window+air+conditioner&qid=1690209884&sprefix=midea+12k,aps,573&sr=8-3

I ran both to see what the electric bill would be. The bill came today for $47.47 covering 30 days in which I used 194kwh. It wasn't that much more than running the dehumidifier alone, and it's been hot.

If there is a window available to install an AC unit, it could worth considering, but useless in the winter.

Another option is to install a mini split inverter, but that will require about a 2-3" hole in the exterior wall to run the refrigerant, drain, and control lines, plus all the rest of the installation. But a mini split will also provide heat if needed in the winter.

If the basement is substantially below grade, it is unlikely your ac ran very much. The dehumidifier likely ran the most. AC units are excellent for removing humidity but don’t run unless the temp in the conditioned space is below the thermostats setpoint. Conditioned spaces below grade have the benefit of the cool temp of the earth.

My basement is about 70% below grade and the ac runs very little in the summer even when the outside air is well above 90 def F. The dehumidifier runs a lot to maintain the rh close to 50%. Even with the heat released by the dehumidifier the surrounding earth still keeps the space below the thermostats setpoint (70 deg F). I could lower the setpoint and the ac would run more but the temp would uncomfortably cool and the electricity used would be much greater than running the dehumidifier. The combination of the ac and the dehumidifier in the basement is a good solution for both comfort and economy even considering the cost of the dehumidifier and its installation (> $2k).