Quote:
Originally Posted by jeff5may
Ok so the dirt cheap twisty knob window units are all over the place because they don't work too well. Nearly all of them have the lowest efficiency ratings ever. For your goals they don't have enough surface area to dehumidify well either.
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I disagree.
First, the particular unit I have makes 5,000BTU at about 350-400 watts depending on temperatures. This gives a COP of roughly 3.75. No, not as good as a mini split, but not bad...better than my heat pump. (which is only 6 years old) How long would I have to run a more expensive unit to save several hundred dollars in electricity? Also do not want to run an expensive air conditioner 24/7 and burn it out in a couple years. That would negate any energy savings.
Secondly, I've used this exact air conditioner as a dehumidifier. (Not mounted in a window) I don't have access to my data at the moment, but it was equal to or more efficient than most dedicated dehumidifiers on the market based on the amount of water removed and amount of electricity used. It really removes a massive amount of water when it does not cycle on and off.
The goals here are:
1. Reduce the number of cycles on the main heat pump. It will definitely do this. Excessive cycling causes higher electricity use and higher humidity. Also go from hot/cold/hot/cold all day on my body, I hate this.
2. Remove more humidity than the main heat pump. The fact that it would be running continuously is the biggest factor for this. That is what gets a lot out of the air. When you have a heat pump with a short cycle time, like I do, it doesn't have time to dehumidify before it finishes it's cycle and turns off. Last summer it hovered around 60-70% humidity inside.
The big question is would this use more or less electricity than just leaving the heat pump as is? And will it make the house more comfortable with fewer temp swings and less humidity? That is something that is going to be hard to determine without testing.
I don't know what you mean about the control board "suiting my needs better". The only thing I "need" is an on/off switch. It doesn't even need a thermostat. If it never cycles off then there is no big current rush when it starts. From a humidity perspective I don't think a unit this size will ever get below about 40% when it is 90%+ outside, simply from the outside leakage into the house.
Another thing I wasn't thinking about, my heat pump is rated at a particular efficiency, but my duct work and air handler are all in a very hot/humid crawl space. Even the cheapest window unit is probably more efficient if you account for all the duct leakage in a 25 year old house...
(Sealing/insulating/conditioning the crawlspace is on my list for the future)