New air conditioner doesn't hold stable temperature at night
July 27, 2020 2:58 PM Subscribe
My wife and I recently bought a new 6,000 BTU window air conditioner (model LG LW6017R). It cools the room in the evening, but doesn't hold the temperature at night.
We've had the air conditioner for about three weeks, and we have it set to 65 degrees F. We turn it on a few hours before bed, and the bedroom feels really comfortable at bedtime. But then it felt like the temperature would rise at night. At first, we thought this was just our imagination, but we confirmed it with a Bluetooth thermometer that records the temperature in one-minute intervals. See this graph (the top line is temperature, the line under it is relative humidity).
Is this normal behavior? It seems odd. Our old unit didn't do this. I suppose we can try lowering the temperature by five degrees just as we get into bed, though it's a hassle.
We've had the air conditioner for about three weeks, and we have it set to 65 degrees F. We turn it on a few hours before bed, and the bedroom feels really comfortable at bedtime. But then it felt like the temperature would rise at night. At first, we thought this was just our imagination, but we confirmed it with a Bluetooth thermometer that records the temperature in one-minute intervals. See this graph (the top line is temperature, the line under it is relative humidity).
Is this normal behavior? It seems odd. Our old unit didn't do this. I suppose we can try lowering the temperature by five degrees just as we get into bed, though it's a hassle.
Have you tried running it down to 65 (or whatever it can reasonably handle) during the day to observe what happens? Check to make sure it isn't freezing over, has proper airflow, etc.
posted by hankscorpio83 at 3:16 PM on July 27, 2020
posted by hankscorpio83 at 3:16 PM on July 27, 2020
My old window AC had a mystery button on it for energy efficiency or some bullshit. In AC terms "energy efficient" apparently means "shut off the compressor at night, when you want it the most." I didn't even know that setting was activated for the first two weeks I had the thing.
Read your manual--if there is any kind of setting for energy efficiency turn it off. I think mine had the image of an electrical plug with a water droplet on it: mystery.
posted by phunniemee at 3:21 PM on July 27, 2020 [7 favorites]
Read your manual--if there is any kind of setting for energy efficiency turn it off. I think mine had the image of an electrical plug with a water droplet on it: mystery.
posted by phunniemee at 3:21 PM on July 27, 2020 [7 favorites]
My portable (not window) AC has a "Sleep" mode that gradually increases the temperature. So that might be another thing to look for.
posted by kbuxton at 4:15 PM on July 27, 2020 [1 favorite]
posted by kbuxton at 4:15 PM on July 27, 2020 [1 favorite]
On my comparable unit ‘econ’ mode at 73F does far less effective cooling and dehumidifying than 76F on ‘cool’ mode, YMMV.
posted by SaltySalticid at 4:20 PM on July 27, 2020
posted by SaltySalticid at 4:20 PM on July 27, 2020
This happened to me with an AC that defaulted to efficiency mode. Efficient mode would shut down the circulator fan and chiller (compressor motor) once thermostat setpoint was reached. It would then cycle both motors on for a bit, cool a very small local area of the room, and then shut off again.
In normal mode the circulating fan is on constantly and the chiller motor cycles on when temp rises above setpoint and off when temp is below setpoint. The constant fan stirs the air in the room and maintains a more constant room temp.
posted by sol at 4:22 PM on July 27, 2020 [1 favorite]
In normal mode the circulating fan is on constantly and the chiller motor cycles on when temp rises above setpoint and off when temp is below setpoint. The constant fan stirs the air in the room and maintains a more constant room temp.
posted by sol at 4:22 PM on July 27, 2020 [1 favorite]
Response by poster: Note: The air condition has an economy/efficiency mode, but I don't use it. When I look at the unit in the morning, the economy mode is still shut off, so I know it's not activating itself overnight. There is no sleep mode on this model. While the unit is running, the fan is always on, regardless of whether the compressor is operating. There are three fan speeds. I typically use the middle one. I can try using the faster speed to see if that makes any difference.
posted by akk2014 at 4:31 PM on July 27, 2020
posted by akk2014 at 4:31 PM on July 27, 2020
This used to happen to me. It sounds like it's freezing over, as described in this article. If you can get a look at the outside of the unit when this is happening, and see ice on it, that would be a good smoking gun. That article has a few fix-it tips and now you have a new search term to try.
posted by phoenixy at 6:18 PM on July 27, 2020 [2 favorites]
posted by phoenixy at 6:18 PM on July 27, 2020 [2 favorites]
What’s the duty cycle of the compressor when it’s at your desired set point? Is it running constantly or is it shutting off for significant periods?
If you’re at the unit’s capacity, adding two sleeping people to the room would increase the room temperature.
posted by mr_roboto at 7:03 PM on July 27, 2020
If you’re at the unit’s capacity, adding two sleeping people to the room would increase the room temperature.
posted by mr_roboto at 7:03 PM on July 27, 2020
How far away from the AC is your thermometer? It does look like it’s keeping a constant temperature (which your thermometer is reading as 70), kicking on when it raises two degrees.
If it’s too hot in the room, I’d just turn it on at 60 and leave it rather than adjust it before bed. In theory this would cause your thermometer to read it as going down toward 60 and rising back to 65, which is what you want.
Alternatively, you might try a fan to circulate air in the room more. It would probably be a lot cheaper than making the AC work that much harder.
posted by cali59 at 10:22 AM on July 28, 2020
If it’s too hot in the room, I’d just turn it on at 60 and leave it rather than adjust it before bed. In theory this would cause your thermometer to read it as going down toward 60 and rising back to 65, which is what you want.
Alternatively, you might try a fan to circulate air in the room more. It would probably be a lot cheaper than making the AC work that much harder.
posted by cali59 at 10:22 AM on July 28, 2020
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If there’s an option to leave the fan on but cycle the compressor, it might help keep the room temperature more even and sidestep the problem.
posted by doomsey at 3:08 PM on July 27, 2020