Mini split question- possibly a little technical......

[Boundertom]

I have 3 Pioneer mini splits. I installed them all myself. I love them. The oldest, an 18,000 BTU is about 4 years old. It has started giving me a little trouble. I have noticed the compressor and condenser fan shutting down, even when the thermostat is stilling calling for cooling. Example, room temp 74 degrees, thermostat 68 degrees, compressor not running. It has always kept up fine before. Normally, the compressor just slows down (inverter style unit). I started paying closer attention today to what was happening. The compressor would run for 2 to 4 minutes and stop. If would be off for 2 to 2.5 minutes then restart. Over and over.

I was thinking it might be a bit low on refrigerant, and was about to put a gauge on it. (Only one service port) Then, I was looking at the indoor unit and noticed that the fan was fairly dirty. I started cleaning the fan with a bottle brush. Kind of a PITA. I am not even done and needed a break and decided to turn on the unit for a while. It has been running for about 30 minutes now, and compressor has not shut off at all. I am showing about a 25 degree differential between room and outlet air.

So, here is my question: What about a dirty fan (reduced airflow over the evaporator) would result in the compressor cycling on and off? My knowledge of air conditioning systems is a little rudimentary, and I don't get this. It has only been a little over a half hour, but I think I may have solved the problem. I appreciate any wisdom from those more knowledgeable.

Thanks!

Tom, in AZ (100+ degrees today) (Again!)

 

[Raisedonadeere]

Poor air flow over evaporator coil will result in excess pressure on high side. Some units have a high pressure cut off. As soon as pressure bleeds down enough the compressor is turned on . Or the low pressure side is pulling too low as can happen with low refrigerant. The clean blower fixing it makes sense.

 

[Kaizen]

Might want to do a complete clean in on all of the units if you haven’t yet.


Sent from my iPhone using Tapatalk

 

[jjrbus]

Google cleaning mini split blower fan. 1 of my 3 was really bad after a year, it was easier to remove the blower fan and clean.

I spent a ridiculous amount of time trying to clean in place and after I was done the fan was vibrating. Could not see or hear it but could feel it by putting hand on case.

 

[Jackfre]

Your internal unit has the thermostat bulb mounted on the evaporator coil itself. It is constantly feeding to the primary board on your outside unit. Based upon the setting and the reading of the stat the condensing unit ramps up or down the compressor and the evaporator fan. This is a very tight spec and the dirty unit creates a situation where the unit is fighting itself and in frustration finally goes into a safe mode. Do completely clean the fan. Otherwise it gets out of balance. Also, if the fan is that dirty, the coils, indoor and out need service as well. You will be amazed at the difference in operation.

 

[yeldogt]

FYI: The mini's work a little different vs a typical split found in most homes. The expansion valve is outside .. the indoor unit is like a car radiator. That's why you need to insulate both lines to a mini. There is some more expansion after the coil ...that's why the return is a bit larger. This confuses people.

There is a thermostat that maintains the indoor coils temp -- I had the OP's problem when I did my first mini back in the mid 00's. LG "Artcool" .. The whole front pivots on those models. Installed in the previous owners writers cabin that we use as a guest room. The unit had defect and we did not understand that the front was not opening all the way. The space was not used often -- it needed to run on high when first turned on ... unit would shut off. Took us weeks to figure out what was going on.

Some units must have different filter types -- I have never had this dirt buildup problem,

 

[jjrbus]

FYI:

Some units must have different filter types -- I have never had this dirt buildup problem,

It is not dirt, it is mold, I have read everything I can find to figure out why some get it and others do not, although it is more common in humid areas. In my case I have 3 Daikins, 2 9k and 1 12k, the 12k is the only one that had the issue;

Blower wheel was caked and coils are clean.

 

[Raisedonadeere]

It is not dirt, it is mold, I have read everything I can find to figure out why some get it and others do not, although it is more common in humid areas. In my case I have 3 Daikins, 2 9k and 1 12k, the 12k is the only one that had the issue;

Blower wheel was caked and coils are clean.

there is a lot of good information in this thread that still needs sorting out. I hope the manufacturers can come around to being more helpful in the future. but I doubt it will happen. It is going to take us folks living with these things a while to sort it all out and get it down to where it is just another thing we are familiar with and can deal with.

I have two Mrcool Hyper heat units and they have simply blown me away with their performance. I love these things but it was hard getting information I was confident in for doing the install. To much was mixed in with conventional HVAC theory.

Any way one thing hasn't changed. Good airflow is critical to the performance. What ever clogs things up will cause problems. I don't relish dealing with cleaning my coils, because of where they are loacated in the house and their accessability is still a mystery.

yeldogt and jackfre if you have any links that explain the theory of operation it sure would be appreciated. I winged some things knowing these units are not the same as standard split systems and good a good install but inevitably I will need to charg one of thse

 

[LS6 Tommy]

Poor air flow over evaporator coil will result in excess pressure on high side. Some units have a high pressure cut off. As soon as pressure bleeds down enough the compressor is turned on . Or the low pressure side is pulling too low as can happen with low refrigerant. The clean blower fixing it makes sense.

A dirty evaporator or low evaporator air flow does not cause high head pressure. It will cause low suction pressure. It can also cause a flooded compressor or slugging in extreme cases without a LPCO.

Tommy

 

[Boundertom]

Thanks for all of the responses! Some good information and I appreciate it all.

I don't think my blower was super dirty, but cleaning it sure made a difference. It is working great. The coils look very clean, but I am sure they would also benefit from cleaning. I have always been pretty careful about cleaning the filters. The filters must not be really effective. Since I have 3 of these to maintain, I will have to figure out a better way! I probably spent 2 hours with a bottle brush and vacuum, and it is not perfect. It looks like a pain to get the blower out, but I will have to give that a try. It is now apparent that these mini splits will require periodic thorough cleanings. My other two don't look too bad. I will deal with them when it is a bit cooler.

Searching on the web, I found the Speed Clean Bib Kit. It is pretty pricey for what it is, but looks like it will make this a lot easier. It allows cleaning of the coil and blower with cleaning solutions, in place. There is a very good video on Youtube of a tech cleaning a mini split with this system.

I have an interesting side story that I left out of the original post. Just last week, I helped a friend with his Pioneer mini split. I had helped him install it about 18 months ago. He was having a problem with water dripping out of the indoor unit. He thought that the evaporator was freezing up. His fan was really filthy, 3 times worse than mine. And his is much newer. The only thing we can figure is that his is very close to his kitchen area and is picking up grease from cooking. After a time consuming manual cleaning, that one is also working well again. Anyway, the interesting thing to me, is that a dirty fan produced 2 different symptoms.

Thanks again for the responses!

Tom, in AZ

 

[coyotehunter]

rectorseal sells a citrus based product kit called Desolv that is made to clean indoor units for mini splits. it works pretty good. i have 3 mini splits in my house and i cleaned them a few years ago. i had dirt beyond the blower wheel and this kit actually worked it loose and was not very messy. it has a cheesy frame and a bag with a chute that you put into a bucket to catch the solvent and water. but if you can get the unit loose enough at the bottom and tuck the bag up it does catch the mess. rectorseal has a video tutorial on their website and you can probably find it on youtube also. i just read the last section of Boundertom's post and the speed clean bib kit is almost the exact same kit as the desolv kit. ill have to look up the rectorseal kit and see if there any changes to it now.