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Moving a mini-split

Darren Wright

Darren Wright

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Springfield, Missouri
I have a mini-split that was hail damaged about a year ago. I need to replace that unit and will do a refrigerant recovery of it before disconnecting the line set. While watching some youtube on the process of doing that, I came across the following videos showing how you can vacuum down the refrigerant into the outdoor condenser unit as they do from the factory.

This could come in handy for someone that needs to move or remove a mini-split. Using this process vacuums the refrigerant into the outdoor condenser, you then shut the service valve(s) manually when reaching 0 pressure. The lines and indoor unit can then be disconnected, moved or removed, then go through the vacuuming of a reconnected line set and indoor unit and leak test before releasing the refrigerant back into the line set.

For a single zone:

For a multi-zone unit:

In the case of my damaged unit, I think the bent fins caused some over pressure and refrigerant conditions. I'll need to recover the refrigerant since I'll be replacing the unit, so I'll be pulling the refrigerant out with a recovery machine to a tank. Should I decide to re-use the unit I'll need to pressurize it with nitrogen, leak test and fix any found, and reload with new refrigerant (R410a) by the weight required, which is listed on the outdoor unit label.
 
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Yes, that's how to do it, but don't let the gauges read even one pound below zero is best. A little outward moving gas as the lines are broken will be better than any vacuum that draws air/moisture into the system will be best way to avoid getting air and moisture into the lines and evaporator, but follow up with a check to see that you haven't lost any refrigerant over time, or when doing this pump down and recharging. Seal the ends of the open lines quickly after you break the connections. Do your best to keep any oil that might be in the evaporator and lines from leaking out while the units are separated, since the amount of oil in these systems is quite critical and difficult to replace accurately. Only the exact replacement refrigeration oil will be required too. Moisture entry from humid air entering the open lines is very important to keep out. A nitrogen flush of the lines and evaporator with compressed dry nitrogen is a quick way to get moisture out before pumping the system down, but if the lines and evaporator are sealed quickly when broken and kept well sealed you should be able to get away without this nitrogen purge. Just pulling a vacuum doesn't get moisture out unless you can pull a near complete vacuum and hold it at that level for an hour+. Watch the low side vacuum level reading with the vacuum pump valve closed and the vacuum pump off. If it creeps up, but then stops, moisture is present and additional vacuuming is needed. If it continues to creep up you have a leak allowing more air/moisture to get in and a repair will be necessary.

Usually a check of the operating pressure/temperatures will work good enough for determining if additional refrigerant is needed, after you are certain that you have no moisture or leaks and have opened the valves to let the refrigerant from the outdoor unit circulate again and the system has run long enough to stabilize. Be prepared with some of the same refrigerant to add a little if needed, and add it a little at a time as a gas to the low side for accuracy. Purging your gauge lines before connecting them with a small amount of this refrigerant before connecting them to the system is recommended too. Watch the temperatures and pressures for a while after each time any refrigerant is added, for them to stabilize, before making the decision to add more. If you don't get al of the moisture out of the system, it will freeze and block refrigerant flow, making the system stop cooling until it is turned off for a period. When turned back on, it will work for a while, until the refrigerant flow is blocked by ice again and it will again stop cooling until off for a period and the ice melts again. Only a complete removeable of refrigerant, vacuuming to remove this moisture, and then replacement of the correct new refrigerant will correct this.

These small systems loose efficiency if not charged accurately. For leak testing, you really need a sniffer designed for the refrigerant being used to detect tiny leaks. A soap bubble test isn't near good enough.

You should be certified to work on refrigeration systems before doing this too. I am, but I'm a bit too far away to be of any help to you.

Charley
 
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