Mini split and "auto" mode inaccuracy

[ching0n]

I've got a 24k unit that doesn't seem to obey "auto mode" t-stat setting on the remote. It's got this "follow me" setting that updates the air handler if w/in line of sight of the remote. I don't recall it being an issue during winter but now in the summer it cools the space too much to the point where I have to go to heat mode to bring temp back up.

Has anyone had experience w/these generic Asian units and wonky hysteresis in auto? I'm considering hard wiring a wall t-stat since I'm not a fan of the IR remote but doubt it'll solve this auto issue. It's a "ductless aire" brand.

 

[jlv03]

Does your minisplit have a dehumidify setting? That might help you feel more comfortable without excessively dropping the temperature.

 

[ching0n]

Does your minisplit have a dehumidify setting? That might help you feel more comfortable without excessively dropping the temperature.

it does though I think it's just AC by a different name in this case. I don't recall it closing the louvres.

 

[BillK]

Does it have a thermostat on the unit that will work without the remote ? Has it worked properly in the past ? What model number is it ?

 

[ching0n]

Does it have a thermostat on the unit that will work without the remote ? Has it worked properly in the past ? What model number is it ?

There is a manual emergency defeat though I don't know if I can set the temp in that mode. The manual states that the unit will go into commanded temp but use the air handler sensor if the remote IR sensor is not detected past 7 secs. It almost seems like it's doing this or the hysteresis is set very wide for cooling. This is the first cooling season w/the unit. I just got a response:

When using the Auto mode, it is not unusual to experience a temperature fluctuation from the set point chosen. The AUTO mode allows the system to switch between heating and air conditioning automatically, but this setting may not always provide the most efficient and responsive operation. Instead, we recommend setting the system control to the HEAT mode during the heating season and to the COOL mode when you want air conditioning.
Do not think of the number displayed on the indoor unit as a temperature, but more of a "comfort set point". Raise the comfort set point up if you are cold and lower it if you are hot. What we typically suggest to the homeowner is basically this; if you set the thermostat to 68 degrees, for instance, but it feels much cooler, increase the temperature as needed until you find the “sweet spot”.
Do keep in mind that the temperature sensor on the indoor unit is located at the top, so it is going to read warmer air temperatures than what you feel closer to the floor, such as when you are sitting in a chair.

Basically they're saying our thermostat is useless so use your **** dyno and be your thermostat. Looks like I'll have to hardwire a wall t-stat and defeat the air handler sensor so it reads remotely. Here's the service manual (page 25)......I may have already gone through this and forgot come to think of it:

https://ductlessaire.com/wp-content/uploads/2019/06/ES-Service.pdf

 

[Jackfre]

What wall stat are you going to go with? It had best be theirs or you are in for a world of hurt and no warranty support. I used to get this all the time with the Rinnai wall furnaces. The stat thermistor is located two inches off the floor, the coldest place in the room. It would read that temp on the display. I would check the operation of the unit. It was doing fine. I would explain how the unit works as these folks have done for you and say that I do not care what the number is, and neither should they. What is important is whether or not you are comfortable in the space. I’d take a piece of electrical tape and cover the digital display and tell the customer that they could use the on/off button and the up/down arrows. I’d go back in a week and ask if they were comfortable. “Why, yes, yes I am.” I’d remove the tape and say that number, whatever it was in that space was best for them. Pay no attention to the number only your comfort. Relax and live with it for a bit. It will be better than what you are planning to do I think.

 

[ching0n]

What wall stat are you going to go with? It had best be theirs or you are in for a world of hurt and no warranty support. I used to get this all the time with the Rinnai wall furnaces. The stat thermistor is located two inches off the floor, the coldest place in the room. It would read that temp on the display. I would check the operation of the unit. It was doing fine. I would explain how the unit works as these folks have done for you and say that I do not care what the number is, and neither should they. What is important is whether or not you are comfortable in the space. I’d take a piece of electrical tape and cover the digital display and tell the customer that they could use the on/off button and the up/down arrows. I’d go back in a week and ask if they were comfortable. “Why, yes, yes I am.” I’d remove the tape and say that number, whatever it was in that space was best for them. Pay no attention to the number only your comfort. Relax and live with it for a bit. It will be better than what you are planning to do I think.

They don't offer one. Was going to get the closest one that worked w/whatever dozen other brands w/the same board that are out there. If I recall, it involves disconnecting the t1 sensor for the t-stat one. If I interpret the service manual correctly, it's a 4F delta from set point in auto before heat kicks in which seems about right (set at 70, start feeling chilly at 68 or so). Alternatively I guess I could just route the thermistor to another room if the voltage drop's not too much (mine's on the unit's air stream (wall mounted about 7 ft high)).

Just sounds like this auto is more tailored towards home w/o occupancy which is dumb that they'd let it work w/"follow me". Unit works fine if I use heat or cool function....just defeats the purpose of having a t-stat if you have to switch modes manually.

 

[Highbeam]

My minisplit has auto mode and then "auto" setttings for the blower speed and louver settings. Be sure that you and the manufacturer are all talking about the same "auto".

The stupid remotes need to have line of sight to work. That's dumb. Many installations don't allow that such as mine so I just depend on the wall unit's internal thermostat and adjust the setting to feel comfortable in the space. This setting will change as outdoor temperatures vary.

Like many thermostats for decades, there is a heat or cool toggle switch. It's not new to have to decide between heating and cooling.

 

[Jackfre]

In your space is it common to see cooling operation and heating in the same day and how much of a swing is ther in the space? Certainly it is your unit and your call, but I’ve lived with mini-splits for a couple decades and haven’t found auto to be a desirable setting. I am not familiar with your brand but but are you sure the “board” is the same. Sometimes temp irregularity in a space can be cause by installing the evap to high in the space so stratification and sensing get thrown off. I’ve also seen temp irregularity caused by air leaks through the wall affecting the temp sensor in the evap. I had one that was affected by direct gain to the point the room was like a freezer. Going back to your other comments the “thermostat is useless.” I sold the first successful modulating gas appliances starting in about ‘91 and probably 400k units and 15 yrs with Fujitsu splits. In the states we are used to heat or air coming on, running until the wall mounted stat is satisfied, shut down and wait for the single stage unit to be called on by the stat. I have had thousands of conversations with customers where once I describe the operation of a modulating appliance explaining that it wants to continue to run say that it was going to cost a fortune to run. They did not get the idea/benefit of modulation from both an economy and comfort set point. This operation gives a very flat temp curve in the space vs the big sine wave you get with single stage equipment. I have seen folks get into the units and install a wall stat and essentially turn a pretty cool piece of equipment into a single stage unit or blow the board and the warranty. Another thing is you say you do not have confidence in the IR function. The manufs recommend that prior to mounting the remote that it be tested in its location to ensure that it communicates with the evap. Prior to any modifications I would also suggest that you ohm out the thermistors to ensure they are functioning correctly. Perhaps it is best to run it in H or C for a while and see how the unit operates as suggested by the manuf before moving forward. I really think you are looking at a long rough road here with your current plan.