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strogg wrote: ↑Tue Jun 30, 2020 12:11 pm

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.

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.

03Lightningrocks wrote: ↑Mon Jun 29, 2020 4:12 pm How long the system stays off once the stat is satisfied is a function of heat gain within the home. How long it takes to cool the home off once the system stat calls for cooling is a function of unit size. Thermostats are simply switches that automatically turn the system on and off depending on the temperature it senses.

You do bring up an interesting point to consider concerning heat gain and time elapsed. Yes, they do make thermostats with 3-degree variance, or adjustable to 3-degrees, but from what you point out, it isn't about that anyway. Plus, you then have to feel the temp swings more.

Heat gain being the function of the home design, it's going to gain the same amount no matter the change up on time a/c running. So it runs longer per period? Might be better on unit with longer cycling. But, for RH, seems total run time over 24 hours is a matter of heat gain v. heat removal (unit size and function) so total day's run time will be almost unchanged. Trying to learn a new zoned system myself with Aprilaire fresh air settings and RH settings. Still can't figure out why fan runs almost constantly some days and not so others no matter RH setting?

strogg wrote: ↑Mon Jun 29, 2020 11:14 am 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.

You could try a thermostat with a greater variance, but that's a big "if" you can tolerate the swings. Some can go up to 3-degree, which doesn't seem a lot, but it can leave times you are uncomfortable waiting till it kicks back on. It's might not be the same as constant temp where you never notice the 1-degree variance.

Closing off too many registers, much of the house, is basically like manual zoning, but without a bypass or dump they use to maintain efficient airflow across the evaporator, it puts a strain on your system, and slow air is not good for the system. Think about whether you would run with a dirty air filter to do basically the same thing, slow down airflow to make system run longer. It's not running longer now because it has less air to cool an area, it's because it's efficiency through the coil is being greatly altered, which is bad on the compressor as well.

If a thermostat with variance is your first option, try that with all registers open like system was designed to run. If that won't give you at least 20-30 minutes run time in Texas heat and humidity with a comfort level you can tolerate, I would call an HVAC and see what other options you have.

Don't dump cold air into the attic. Cold air and hot air make condensation, and you do not need that, water, in the attic.

strogg wrote: ↑Mon Jun 29, 2020 8:53 am 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.

One option is have an HVAC service see where some air could be "dumped", say an unused utility room or room of some size or anything that's not mixing with the house even if the air is lost to cooling the house and can be controlled via flow/temp controlled dampeners. Zoned systems sometimes need to do this. Equipment wear aside, you run a risk of developing mold issues with the lack of humidity removal due to short cycling. Shutting down register vents is not good, as that messes with the airflow rate across your coil(s) and compounds the issue of cycling damage.