Outdoor mini-split unit shutting off

[DIY Engineer]

I bought a 9k BTU 3/4 ton 115V Mr. Cool 3rd Generation Advantage Series mini-split unit and installed it myself.

After installation, the unit ran on cooling mode for over 24 hours before the outdoor unit shut off with the indoor unit still running, but not blowing cold. Every time I turn it off with the remote, then back on, it starts running again and blowing cold. After a couple of hours, the condenser shuts off, then the room warms up.

There is approximately 20 feet of elevation difference between the indoor and outdoor units and 30 feet of copper lines. I bought a small can of R410A to top off the refrigerant since I was using slightly longer than the standard (25ft) line length. When running, the refrigerant pressure is 120psi with the ambient temperature at 76 degrees, which seems to be in the normal range (in the green zone on my gauge).

The unit is powered by a dedicated 20A breaker with a local shut off and supplied by 12 gauge wire.

Before opening the refrigerant valves, I used a Pioneer Kwik eVac system to remove all air from the lines and pressurize the system to check for leaks. All connections in the copper lines were torqued to specification using a torque wrench.

I’ve been trying to troubleshoot why the outdoor unit is shutting off.

Any help you can provide is much appreciated.

 

[fitter30]

Did u turn the Led on on the indoor unit? A fault code should show up in a failure.
Install book page 40 for codes. Other codes page 7. You purchased a 50' line set or did u cut it and added on. If purchased 50' lines it had the proper charge in it since their precharged.

https://mrcool.com/wp-content/dox_repo/mc-diy-3-es-im-um-en-01.pdf

 

[DIY Engineer]

There are no blinking LEDs or error codes. I purchased a 25 ft line set and I attached the 16 ft line set to that. I then cut and flared the ends to attach them to the condenser unit.

My guess is that I’m still low on refrigerant and the coils are freezing up after it runs for a couple of hours, but I’m not sure about that since the pressure is reading 120psi when the condenser is running.

 

[justinjoyal]

Why would you be low on refrigerant ? You mentionned you pressure tested the system.

(Most newer units will show a low pressure/refrigerant leak error code.)

 

[shade]

Mr Cool provides how much oz of refrigerant needed for 25 ft.
So if you do the math it's X OZ per foot.
The amount you need to add for an additional 16ft is next to negligible.
I dont think the system is low unless it's leaking

 

[WildBill]

I don't think you can pressure test heat pumps like you would a regular AC system, they have variable compressors so unless you can trick it into going to full max power its not going to read correctly. Plus I thought they were much higher pressure, like 250-400. M y understanding is the only way to properly check the amount of freon in the system is to pull it out and weigh it, or just very slowly add a little at a time while watching the pipe and air temps.

 

[HamAndEggs]

What's your communication wire look like? Sounds VERY similar to an issue I had with my Daikin Unit

Dual Zone Daikin Mini Split Problems

Any Daikin experts? I have a dual zone Daikin Mini Split, its an 18K BTU outdoor unit and 2 x 9K BTU indoor units. Generally the install sucked, I paid a pretty penny to an HVAC company, and as time goes on I notice more and more things that were done wrong. Should have just done it myself...

www.garagejournal.com

 

[Highbeam]

These things measure room temperature oddly. Are you using the "follow me" feature on the remote? It is common for the outdoor unit to shut off and inside unit to keep blowing. That's the normal cycle when it thinks it has reached setpoint. Oh and all of the remote thermostats are line of sight.

It is possible that the area right around the indoor unit is cooled to setpoint and the rest of the room just hasn't caught up yet. That happens when you try and cool a hot room instead of just keeping the room cool.

Set the desired temperature lower than you think you want it and let it run for a couple of days doing whatever it wants. See if the room becomes comfortable enough. This isn't ducted central HVAC.