Why does this Mini Split Freeze up when I don't have it blasting?

[mpire]

So I have had this mini-split for more than 5 years, and its been great. I turn it on when I go to bed and turn it off when I get up in the morning.

Lately I have been leaving it on all day instead of turning it off like I used to.

I thought that cranking it up to 80 and just letting it run would help the larger house unit out a little bit.

So its been icing up, nothing too bad but last night it was a solid block of ice.

Levels all look right and I don't think its a leak.

The thing is, I can crank the temp DOWN on the AC to 70 and the ice melts off in half an hour or so.

I am guessing that its still running when I crank up the temp and the fan isn't putting enough air through the coil. More air through the coil seems to fix the problem.

Anyone seen this? Freezes up when set to 80, no problems at 70.

 

[soob]

Freeze up is almost always low freon. The ice melts because when you turn the temperature down because the evaporator fan spins faster, just like you said.

 

[larry4406]

I don't know if mini-splits use filters, but I have had conventional units freeze up due to poor air flow from a plugged air filter.

 

[LS6 Tommy]

Check your filter. If it's clean, you have a leak.

Tommy

 

[Jackfre]

Also, check the blower wheel. If the leading edge of the wheel has a bead of....**** on it your air flow drops. Also, after a couple years enough debris gets past the filter to **** up the coil. About 40% of the coil surface on the high wall units is hidden from sight on the back of the unit, and that is where they load up. Pull the whole cover and get a mirror to inspect it. I've used the New Calgon Evap cleaner to good affect on mine.

 

[mpire]

I think it was dirty, but I am still curious as it doesn't really make sense.

The levels look right, so I don't think it has a leak. I have had leaks before, and they never caused it to freeze up.

I have been running it all day on 80 degrees, then at night when I go to bed I crank it down to 72. The ice would melt off and it would be good to go. I would hear cracking and wonder what the sound was. So now I know.

The cooling differential is more than 25 degrees. So it is cooling like a champ and just as good as always. Actually, that's really impressive for a 5 year old minisplit.

 

[handymancanfixit]

Poor air flow or low refrigerant. If your inside and outside coils are clean and your filters are clean, then more than likely you have a leak.

 

[mpire]

Filter wasn't so clean. I cleaned it.

 

[justinjoyal]

High delta T does not mean all is good.

And what "levels" are you referring to ?!

 

[bazar01]

Is the compressor ramping down when room temp is close to set point?

 

[Jackfre]

Filter wasn't so clean. I cleaned it.

Over a period of time, the fine dirt carries through the mesh filter on your unit and at least some of it builds up ont he coil itself. When you look at the fin count on these things it does not take much to affect air flow. Yes, keep the filters clean, but periodically you need to clean the child itself and the blower wheel. I have good luck with the NulCalgon non-acid evaporator cleaner. Heavy plastic sheets into a large bucket and spray it down and then wash it clean. You will be surprised when you do it. Also, I once got a call on a job and the actual temperature sensing bulb on the evaporator had an accumulation of dust that was so heavy it wasn't sensing correctly. While these things are reliable there is a lot going on with the variable speed compressor, condenser fan and evaporator fan. Wish I had a silver vbullet for you.