We're having some temperature control issues with the new 2014 HyperHeat models (MSZ/MUZ FH09/15NA).
With the goal of both A/C and reducing our usage of our oil burner as much as possible for winter heating, we purchased three individual units. Due to the layout we have terrible airflow between rooms, even if we set up fans, and our home is not well insulated. Since electricity is *much* cheaper than oil and the price difference between a multi-zone and the individual units was very small, with the individual units having much better efficiency, we went with individual units. Our contractor promised us that they are a bit oversized but that short cycling shouldn't be an issue for us, and definitely not when things are very cold out. Two are are the smallest we could get -- 9k BTU models that are in ~350 sqft. rooms. The third is a 15k BTU model heating about 800 sqft. I'm not sure if those details are relevant, but just in case.
The problem we are seeing is that in cooling or heating modes, the units (all of them) seem to cycle on too often. This does *not* happen in auto mode, however.
For instance, if I close the door to one of the bedrooms with the 9k unit and set it to 70 degrees on auto mode, it'll maintain a temperature between about 69 and 72 degrees -- exactly what you'd expect since it tries to keep things within a 4 degree swing.
However, on heating mode with the remote (which has a temperature sensor on it) in the exact same location, the temperature will climb and climb and climb...up to 77 degrees or higher. It turns on when the room is already too hot instead of waiting for the temperature to drop to an appropriate level.
I also found this problem in cooling mode, where the temperature would end up dropping below the set temperature slowly but surely. Again, switching to auto mode with the remote in the same place makes this behavior stop.
Why does this matter? Because I'd like, for energy savings, to allow the temperature to drop during the day when nobody is around. The problem is that auto mode allows it to switch to (in this case) cooling when the set temperature drops low enough. So if I have it set to 69 degrees overnight but then want to allow it to drop down to 64 during the day, setting it to 64 will actually cause the cooling to turn on, even if it's 20 degrees outside. I guess it wouldn't be on long, but this still makes little sense. Worse, because even in auto mode the temperature can fluctuate, I've found that even having a two-degree difference in set temperature can cause cooling to kick in, if the room was higher than the original set temperature to begin with.
So I want to use the cooling/heating modes as the ceiling/floor they're designed to be, but I can't when they keep making rooms too hot/too cold (and wasting energy as they do it).
I called Mitsubishi about this, and the useless person on the phone suggested that all of my units were defective and I should have a contractor come out and inspect them. Outside of an actual design flaw in the new model line, I have a very hard time believing that all three brand new units are defective in exactly the same way and pay for a contractor to come inspect them all.
So, I hope somebody here can give me some suggestions on how to avoid/fix this problem.
Thanks!
With the goal of both A/C and reducing our usage of our oil burner as much as possible for winter heating, we purchased three individual units. Due to the layout we have terrible airflow between rooms, even if we set up fans, and our home is not well insulated. Since electricity is *much* cheaper than oil and the price difference between a multi-zone and the individual units was very small, with the individual units having much better efficiency, we went with individual units. Our contractor promised us that they are a bit oversized but that short cycling shouldn't be an issue for us, and definitely not when things are very cold out. Two are are the smallest we could get -- 9k BTU models that are in ~350 sqft. rooms. The third is a 15k BTU model heating about 800 sqft. I'm not sure if those details are relevant, but just in case.
The problem we are seeing is that in cooling or heating modes, the units (all of them) seem to cycle on too often. This does *not* happen in auto mode, however.
For instance, if I close the door to one of the bedrooms with the 9k unit and set it to 70 degrees on auto mode, it'll maintain a temperature between about 69 and 72 degrees -- exactly what you'd expect since it tries to keep things within a 4 degree swing.
However, on heating mode with the remote (which has a temperature sensor on it) in the exact same location, the temperature will climb and climb and climb...up to 77 degrees or higher. It turns on when the room is already too hot instead of waiting for the temperature to drop to an appropriate level.
I also found this problem in cooling mode, where the temperature would end up dropping below the set temperature slowly but surely. Again, switching to auto mode with the remote in the same place makes this behavior stop.
Why does this matter? Because I'd like, for energy savings, to allow the temperature to drop during the day when nobody is around. The problem is that auto mode allows it to switch to (in this case) cooling when the set temperature drops low enough. So if I have it set to 69 degrees overnight but then want to allow it to drop down to 64 during the day, setting it to 64 will actually cause the cooling to turn on, even if it's 20 degrees outside. I guess it wouldn't be on long, but this still makes little sense. Worse, because even in auto mode the temperature can fluctuate, I've found that even having a two-degree difference in set temperature can cause cooling to kick in, if the room was higher than the original set temperature to begin with.
So I want to use the cooling/heating modes as the ceiling/floor they're designed to be, but I can't when they keep making rooms too hot/too cold (and wasting energy as they do it).
I called Mitsubishi about this, and the useless person on the phone suggested that all of my units were defective and I should have a contractor come out and inspect them. Outside of an actual design flaw in the new model line, I have a very hard time believing that all three brand new units are defective in exactly the same way and pay for a contractor to come inspect them all.
So, I hope somebody here can give me some suggestions on how to avoid/fix this problem.
Thanks!
