Whole house dehumidifier
 

Anyone install one of these gizmos? Waking up to mid 60's humidity in the house yet temps are as set on HVAC. feels muggy and unpleasant. Looks like about $1500 for an Aprilaire unit that would be big enough but I'm running into some inconsistency in opinions about how well they work and even how they should be installed (where in the path of the air handler).

Looking for anyone with experience managing humidity in the house with an older (20yrs) HVAC system that isn't multi speed fan, etc.

You have one. It's know as your air conditioner. It's oversized if it's cooling and the humidity is still high, or you have a massive source of humidity that is seeping into the house. One of the most common complaints with an oversized system is higher humidity and lower temps. The system cools faster than the humidity is removed. Any chance your house is on a crawlspace?

When you get ready to replace your system, consider a two speed system. They don't require an upgraded ECM fan unit for the indoor unit. If the thermostat determines that high speed isn't required, it will run on the lower speed setting which would help dehumidify. My system is fully communicating, variable speed, which is nice because the indoor fan will run at a speed to meet what the outdoor unit is doing. Word of warning, this system is EXPENSIVE but impressive.

One more note: The Ecobee and other "smart" thermostats can undershoot the set temp to control humidity. I had to research it a bit but they have a setting to overcool to reduce humidity.

https://support.ecobee.com/s/articles/How-to-use-AC-Overcool-Max-to-reduce-humidity

https://support.google.com/googlenest/answer/9294957?hl=en

I'm gonna back up just a bit here. When is the last time your system was inspected and serviced? I question if you don't have a partially dry coil situation where only part of the coil is at the proper temp. I'd have someone check for blockage of the fins on the evaporator. You might just need a good cleaning. If the system charge has been adjusted over the years it will likely need checked after the coil cleaning. I'd want to make sure the indoor and outdoor coils are as clean as possible. If the coils are clean and the charge is correct, then I'd look at the thermostat. Older stats have a pretty wide temperature swing for on/off. Modern stats have a tighter swing variation and are often "learning" where they do better at keeping the indoor comfortable. Another benefit of a modern stat is the ability to use remote room sensors. If your bedroom tends to be a little warmer, you can set the stat to ignore the built in sensor and use the remote sensor in the warmer room for temperature and, if I'm not mistaken, humidity.

BTW, I'm working towards "influencer" status here.

My Ac guy is also a friend. I asked him about a whole house dehumidifier. Living in central Fl there are a couple of weeks a year that the humidity is high, but the temperature is cool.
He recommended to just run the AC cooler. Saved me a couple thousand dollars.
gary

Something else you can do is set your fan to the "on" position. This helps circulate air which gives the thermostat a better reading of the temperature. One of the things my system does is control humidity to keep it in a desired range. It will actually undershoot the set temp if humidity is too high. There are thermostats on the market that will help better control humidity but they'll do so by undershooting the set temp as you mention doing manually.

I have an older house and the water table is very high in the neighborhood; my sump pump runs more than once a minute in the rainy season and keeps going long after snow is on the ground.

After dealing with replacing those portable wood grain units every couple years, I bought an Aprilare unit many, many years ago, I bet going on 15 years now and only had to replace the on/off switch.

Since the basement is really the only humid area even when I run the AC, I just hung the thing on Unistrut from the ceiling and didn’t hook it up to the HVAC system. I did partially block the intake to simulate duct load on it. I just run the drain into a bucket because I want to know how much moisture I’m removing.

It works so well, that I can get nose bleeds in the summer if I’m not careful- turning myself into beef jerky!

Some background- a/c is serviced annually. tech's take is for how old the system is it's running well but he recently said aging outdoor unit causing 'very high head pressures'. not sure what that means. house is about 21 yrs old and has a sealed crawlspace with concrete floor and sump pump. air handler is in crawlspace. no insulation under flooring (one story house). generally feels very dry when I have to go down there but not sure humidity level. This morning here it was 99% humidity, everything outside wet, fog, the whole nine yards. Temp was 72 and a/c not having to run. My understanding is when cooler at night a/c doesn't run but humidity builds.

Sounds like a 2 speed HVAC would essentially include the dehumidifying function via the lower speed. How much delta is there in price vs one speed or variable speed?

Yeah, if the weather is cool enough that the AC rarely runs, but the ambient humidity is high, the humidity in the house will go up higher than usual (if the AC isn't running, then it's not dehumidifying). I guess the question is how often do you have the situation where the humidity is high and the temp is low enough that the AC doesn't need to run. If that happens frequently enough then I would think you would want a dehumidifier. I wonder if you could just use one of those stand alone units while running the AC fan in the on position and that would be "good enough".

On high head pressure, normally with age the two gauges start looking at each other meaning you'd have higher suction pressure and lower discharge pressure, condition is known as having an inefficient compressor. If discharge is running high, I'd look heavily at the outdoor coil for any blockage. Typically "head pressure" rises as it gets hotter out and the airflow across the outdoor coil is insufficient. I'm willing to bet a tech has adjusted the charge in the past but hasn't cleaned coils. Checking the evaporator coil requires removing a plate from the front. After 20 years, if no one has visually inspected the inside of the coil, I'll bet there's some blockage of the fins. Blockage of the fins affects operating pressures which affects operating temperatures.

Sounds like the crawl situation is good.

2 speed doesn't make the big jump in price like a true variable speed. My cost for just the variable speed heat pump, modulating gas furnace, indoor coil and copper tubing was about 10K.

The problem now is that the switch has been made to R32 and R454B, you'll have to upgrade the fan coil in the crawl as well. R410a systems are getting hard to come by. If there is an option for 2 speed communicating where the outdoor and indoor units communicate and you have a true ECM blower that will adjust to the output of the outdoor unit, I'd go that route.

When it cools in the evening and humidity is high, your only option for dehumidification is to have the feature I mentioned in the new smart stats or turn it down yourself. My variable speed just runs on the lowest output for a really long time. If you need any advice on systems, just PM me. I'd be happy to offer my .02.

Thanks cab, will let you know when we are forced to replace. asked my former HVAC guy (retired) about replacing back in 2021 but he said too much trouble getting quality equipment at the time.

Yep, that was an issue. I'd either take a look at or get someone to look at your coils and more specifically the inside of the evaporator coil that you can't see by just opening the front of the coil cabinet. Only reason I replaced my system last year was due to the changeover to R32 and R454 from 410a. I wanted a 410a system. My old system was installed in 1995 and obviously I maintained the unit. It operated fine when I took it out.

If no one has changed the fan settings, a standard fan unit has low, medium, medium high, and high, you might be able to help with dehumidification by dropping from the standard high speed setting down to medium high. You'd just want to check to see what the CFM spec is at medium versus the size of your system. You need 400cfm of air movement per ton of AC. So if you have a 2 ton unit, you want the minimum CFM from the blower to be 800cfm.