Setting up myself for comfortable sleeping this summer. Does this basic rule seen right to keep my bedroom comfortable in the summer. I do not care about the temp as it is typically colder than needed outside but the humidity creeps up.
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Potentially, there's an issue with this rule:
- How long does it take the relative humidity to drop from 49% to 45% when you run your A/C? Is it long enough that the compressor will not short-cycle?
There is possibly a second issue. Relative humidity is temperature dependent. So at least initially when it starts cooling, your relative humidity will increase, but then decrease as water condenses on the evaporator grill. So you might need to put some check in place to ensure that a second iteration of your rule is kicked off within a few minutes of the first.
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Could the opposite also be true, could the humidity also stay high, so the cooling stays on 65 for longer than you may like and drop the temp lower than you may like? Maybe it's just me, we probably have more humid conditions, so 50% can be a distant dream some Summer nights.
I'd also wonder whether the settings should be reversed. I thought dropping the temp slower may be the more effective. So set it to 72 to begin with, let the temp drop a little, then step it down, giving the compressor a change to do it's thing. I have a DRY mode on my ducted system, which typically comes on periodically, I think even leaving the fan off in between or at least on low. If not switching the settings in the current rule, perhaps introducing a temperature element into the mix may help...?
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Dang this is a good idea. I am going to have to make something like this as well. I keep waking up feeling hot due to the humidity in my room.
Let us s know what you come up with as a rule. After reading above comments I'm not sure mine is very smart. I feel like from experience it only takes a few minutes to refresh my bedroom air since it's a small room. Maybe just a flat 5 minutes would serve me better.
Anyways I'm interested in hearing others ideas on this subject as this was the driving force to get me started in home automation. HVAC companies told me it wasn't possible without spending thousands of dollars, and here we are with a $20 sensor, $30 thermostat, $120 hub, and thousands of dollars in buying every useless smart home device to play with, LOL
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One good thing to start with is measuring your air conditioner's discharge air temp. With your AC running, check the air temperature a few feet from the coil. Let it run until the temperatures stabilize. You should be looking for roughly 55 degrees. If its too high, your system likely isn't removing enough moisture no matter what you do. Slowing down your blower is the easiest way to lower your discharge air temp. If your primary concern is humidity control, you could push this number as low as 50 or even 45 degrees. But there are tradeoffs and risks of going too cold. And the climates in Phoenix/Orlando/Minneapolis/etc. all have their own "rules of thumb" to help optimize system performance.
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Air Conditioners both cool and remove water from the air. Typically the focus is on cooling and the associated reduction in humidity is a welcome benefit. This is why we use temperature to cycle the air conditioner. In your case you appear to want to have a reduction in humidity be the main operating goal, with an associated reduction in temperature as something that takes place due to the nature of running an air conditioner.
If your primary goal is the reduction of humidity then you want your evaporative coil to be as cold as possible without freezing. The temperature of this coil is a function of both the amount of air travelling through the evaporative coil (controlled by the furnace fan speed) and the wet-bulb temperature of the air being feed into the evaporative coil (supply air wet-bulb temperature). These two items are not entirely independent of one another and change as the system is running.
For example, when the air conditioner first starts the wet-bulb temperature of the supply air is at it's highest, at this point you can slow down your fan speed without freezing your coil. But as you continue to run your air conditioner, the wet-bulb temperature of your supply air will decrease, requiring an increase in fan speed to prevent a freezing of the coil. Typically air conditioners are never set-up to run this close to freezing.
You mention that you sometimes want to accomplish a reduction in humidity when it is "colder" outside. Typically AC systems are not well set-up for this task as they are designed to cool a home down to 68 degress (at the coldest) along with the associated reduction in humidity being whatever it happens to be based on the current environmental factors. Most homes could freeze up their evaporative coil if you tried (typically not on every day of the year, but definitely on some), the home would be uncomfortably cold, but the humidity would continue to drop, right up to the time the coil freezes.
HVAC companies understand this reality and as such were most likely considering a system that has dehumidification as its main goal as opposed to temperature reduction. These systems are obviously not as common as air conditioners and are more expensive. But I applaud your efforts, if you find a way to have a rule monitor: humidity, and supply air wet-bulb temperature; and then have the rule control: compressor on/off and furnace fan speed. You could probably get a long way to having a standard ac system be more focused on humidty as opposed to cooling the air.
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Didn't anyone mention the Community fee? 
Now if we could get some heat I could test this out. Where the heck is that global warming we've been promised.
You can take some of my heat. I am sure everyone here would appreciate it.
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