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03Lightningrocks wrote: ↑Tue Jun 30, 2020 7:52 pm

LTUME1978 wrote: ↑Tue Jun 30, 2020 7:13 pm An inexpensive and easy solution is to get a dehumidifier. Cost a couple of hundred bucks and should do the trick. I have used one for years. Helps to keep the humidity down without keeping the temperature too low in the house. Also helps in the humid times of the year when it is not that hot and the A/C does not have to run very much.

By coincidence, his make up air system has an option to install dehumidifiers with them. If I am understanding him correctly, his blower on his unit is running any time the make up air determines fresh air should be introduced to his home. Any time the blower in an attic is running, it is circulating air through ducts that are located in an attic that may be as hot as 125-140 degrees in the hottest part of the day. The longer the air is circulated through those ducts,the more the heat from the attic is absorbed. The ducts act as a heat exchanger and will move heat into the home which will increase humidity far beyond anything a dehumidifier will take out. The humidity in his home is not from humidity outside alone. It is being created by the luke warm air being circulated through his 76-78 degree house.

You're spot on, 03Lightningrocks. The fresh air controller opens the damper, then turns on the blower w/o manually energizing the coils to circulate air. If the AC or reverse pump heat happens to be running, then lucky me. Otherwise, not so much. Based on the ASHRAE math, the dampers open for 13.5 and 16.5 minutes per hour for each zone before I messed with the schedule.

I was just thinking of something in the shower. What if I disable the schedules and rig the units to open up the fresh air damper to 1/3rd every time the air handler blower turns on via the thermostat, then have the damper close back up when the blower turns off? That would ensure a very small mix of fresh air with recirc air every time the AC/heater turns on. Would that solve the problem? Or would getting rid of the fresh air units and going for a standalone ERV be a better solution?

Archery1 wrote: ↑Tue Jun 30, 2020 1:02 pm What system do you have? I know the Aprilaire controller will not allow operation if outside air temp is high. In a perfect world where all this stuff works as advertised, it should never allow the indoor humidity above the set amount no matter the controller settings.

They are Honeywells of some sort. They use the W8150 controllers. They'll run regardless of what the climate is like outdoors. Seriously. My upstairs hygrometer reported 65% RH about an hour ago after the unit switched on without AC...

03Lightningrocks wrote: ↑Mon Jun 29, 2020 11:57 pm

strogg wrote: ↑Mon Jun 29, 2020 10:39 pm

03Lightningrocks wrote: ↑Mon Jun 29, 2020 6:58 pm Oh... on the fresh air settings. If it were me, I would shut them down to near no fresh air in the summer months. The high heat outside is fighting your humidity removal. During the winter, crank them wide open.

What's your recommended intervals for fresh air ventilation throughout the year? I have a fresh air ventilation controller on each air handler, and I have a feeling the preset schedule is a bit too much.

I am not sure what options you have on your type controllers but I would set them up for minimal ventilation during the season it is 85 and above outside.

The unit looks like it does the ventilation math on its own based on number of bedrooms, sq ftage, and blower cfm. I decreased the number of bedrooms, so it shouldn't run as often for now. I think sometime in the next few months I'll replace both ventilation units with a standalone ERV. That should hopefully help stabilize the indoor climate. It doesn't look all that hard to install, so I'll probably end up doing it myself.

03Lightningrocks wrote: ↑Mon Jun 29, 2020 6:58 pm Oh... on the fresh air settings. If it were me, I would shut them down to near no fresh air in the summer months. The high heat outside is fighting your humidity removal. During the winter, crank them wide open.

What's your recommended intervals for fresh air ventilation throughout the year? I have a fresh air ventilation controller on each air handler, and I have a feeling the preset schedule is a bit too much.

Thanks everyone for your input so far. I've learned a lot despite my brain being over capacity as it was.

I took the temperatures of the supply and return grills with my trusty IR thermometer when the AC was operating. It was an 17-18 degree delta at its coolest (54 and 72 degrees). The filters are still clean, the outdoor units were also clean, and the coils were clean the last time they were checked a few months back. I can check in the morning when it's not so hot in the attic.

I also noticed something stupid that I can't believe I didn't piece together for the past 3.5 years I've lived here. As I was adjusting the downstairs t-stat again, I felt a breeze on my hand... The thermostat is about 6 feet diagonally from a supply duct. A little bit of cold air was blowing right at it. I'm going to move the thermostat to the other side of the wall in the morning. That side has pretty stagnant air and is also more representative of the actual temperature of the zone. The upstairs one is also 6 feet diagonally from the register, but I placed a barrier in between the two a year and a half ago, so that's no longer a real problem.

03Lightningrocks wrote: ↑Mon Jun 29, 2020 4:12 pm All of this said I am curious as to what the actual issue you are trying to solve is. Not what you think is causing it, what the actual issue is. I might be able to point you in a direction that does not involve unnecessary repairs that don't fix the problem.

Ultimately, I'd like to maintain a low humidity household. Unchecked, this place was consistently at a whopping 60-70% RH. That started leading me down this rabbit hole that makes my brain hurt. I definitely think it would help if someone came out to take a look at my current setup to give me best practices. Unfortunately, the only callbacks I've gotten so far were from the original installers. They haven't been all that helpful. The whole short cycling thing only came up when I learned that ACs running only 5-10 minutes at a time isn't exactly a good thing.

I definitely am not planning on dumping air into the attic. The only reason I closed the registers by the thermostats is to give it the illusion that it takes longer to cool down the air than it actually takes. Once a bandaid solution is in place (ie, one that doesn't require me to purchase a 2-stage), I'll open the registers back up.

Unfortunately, I'd have to route ducts through the living space to get to the garage. Otherwise, I'd be all over that. The only place to dump extra air would be the attic itself.

Yes, I know about the humidity thing. That's actually what prompted me to jump down this huge rabbit hole of a problem to begin with. Fortunately, humidity is stable at around 51-54% for now, with it hitting 54% when fresh air is introduced to the supply.

I'm well aware of the long term issues. Unfortunately, I had no control over the initial installation of the AC units. They are undersized because there are far fewer people living here than the house was designed for. I'm very leery of replacing them with smaller units right now because they're still working perfectly fine, and it would cost thousands to replace with variable speed units. I'd rather spend the money later if I can. Now isn't all that great of a time.

Anyhow, I was able to get the cycle rate to go higher by closing off the vents to the rooms with the thermostats and by lowering the temperature by a couple degrees. The average cycle time is now about 10-15 minutes. Before it was 5-10. I'd rather not do that for the long run because it's getting chilly in here.

I guess I'll rephrase my question. Does anyone have any other suggestions? Otherwise, I'll probably end up getting new thermostats as a bandage until the AC units finally give in. I am hoping with the new thermostats can increase the cycle rates while increasing the time between cycles. It'll save power and allow the temperature to be warmer during the summer months. I don't really care if there's a larger temperature swing inside. That's the least of my worries.

As the title suggests, I'm looking for a thermostat with an adjustable cycle rate. The HVAC I have right now is definitely way too large for my place and is short cycling like crazy. Does anyone have any suggestion on reliable thermostats that'll fit the bill? I would prefer thermostats that can work as designed without wifi. I'm not a fan of the whole IOT movement.