Do You Need To Vacuum A Pre Charged Mini Split?

Mini split outdoor units have already been evacuated and charged with refrigerant at the factory. If you didn’t purchase a mini split with pre charged line set you will need to evacuate the line set and the indoor head.

MrCool makes a system that is completely charged with refrigerant, including the line set. It would be a plug and go installation for someone that didn’t have the resources or desire to mess around with evacuating a line set and indoor head.

They are a very convenient way to go for the average do it yourselfer. Put your equipment into its final location and connect the ends by simply screwing the quick connect fittings together. Hopefully you’re going to order the right length of line set.

It’s a great way to install a mini split without a vacuum pump. These line sets come with special ends that when screwed together actually puncture the line set as they are tightened. The seal is made at the same time. Care still has to be taken to keep the connections clean and dry.

I never use pre charged line sets because it’s not a very convenient way for me to select the proper length. What will you do if the line set it too short? If it’s too long then you have this ugly coil of line set to deal with. Where’s the extra line set going to go? If the line sets too short, well, your guess is as good as mine. You may need to move something closer or order a longer line set.

If you’re connecting raw ends to your mini split or even an air conditioner or heat pump, you don’t want to know what will happen if you don’t vacuum the line set. By raw ends I mean a line set that is not pre charged. Lines should be purged and leak checked with nitrogen.

In the 1970’s when I started in this industry we didn’t have the R-410A refrigerant that we do today. It’s a totally different animal. We never purged with nitrogen.

With todays systems, if you allow contaminates like air into your system, in time, sludge will begin to form in side the sealed system and your system will essentially be severely contaminated. Depending on the severity it could be cleaned up but the expense will certainly not be worth the short cut of not evacuating.

How Long To Vacuum A Mini Split?

I should only take about half an hour to draw a good vacuum on a mini split line set connected to one indoor head. I like to use a good micron gauge and get it down to at least 500 microns and then make sure it stays well below 1000 microns for at least 15 minutes. So make it 45 minutes so as not to be in a rush.

When working with new materials and being extremely careful to keep everything clean and dry, it’s not hard to beat those numbers. Mini splits piping systems are generally small in size and don’t take a lot of time to get down into a good vacuum.

So if you are hiring a contractor to do the vacuum part of your installation don’t argue with the poor tech if he charges you about an hour and a half or even two hours. You have to consider time to get all the tools out and hooked up and put back into the service truck. And don’t forget travel time.

What Would It Cost To Vacuum A Mini Split?

I would charge about $250 to just evacuate a mini split line set and indoor head. That’s prices in 2023. Inflation is killing us. Prices are going to vary between contractors even in the same area. That’s if I detected no leaks in the line. It would include start up of the unit and adjusting the refrigerant charge.

Most mini splits hold a small amount of refrigerant to begin with and require a small amount to add on start up. So any additional refrigerant would be an extra. Then you are going to run into those contractors that won’t want to hook up or evacuate someone else’s installation.

They feel that homeowners that are taking work away from themselves and that “do it yourselfers” sort of ruin the market for the industry. If you look around long enough you’ll find a hungry contractor that will do anything for enough money.

Chad Peterson

Chad Peterson is a veteran of the HVAC industry since 1977. "I like to explain heating and air conditioning problems in a way the average home owner can understand. "

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