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You often send us questions about pre-charged line sets, what they are, how they work, and which ductless mini-splits can (or can't) use them. Here are the answers you need to know.
What are Pre-Charged Line Sets?
During a normal HVAC installation, a professional needs specialized equipment and training to connect refrigerant lines. They must properly measure, vacuum, and charge the system. This is essential to effective and efficient performance.
Pre-charged line sets don't need any of that. They plug in relatively quickly and easily, because they come straight from the factory sealed and pre-charged (hence the name) with the appropriate refrigerant.
How Do Pre-Charged Line Sets Work?
Connect the custom lines to the custom condenser, tighten everything up, open the valves, and you're up and running. The specialized fittings on the condenser and line prevent any refrigerant from escaping during installation.
Which Mini-Splits Use Pre-Charged Line Sets?
To the best of our knowledge, MRCOOL DIY ductless mini-splits are the only ductless split systems that currently use this kind of line set. There could be some knock-offs out there. For right now though, no other company supplies pre-charged line sets on anything close to the same scale. Basically, if you want a ductless unit with pre-charged line sets, buy a MRCOOL DIY.
Now, we must specify that not all MRCOOL ductless mini-splits offer this capability. The MRCOOL Advantage, and Olympus products all use conventional line sets. An installer must connect, vacuum, and charge these models just like any other normal mini-split. So don't buy a MRCOOL Advantage to save a few bucks and expect it to be as easy to install as the MRCOOL DIY. Same brand, different products.
Questions or Comments?
Do you still have questions about these or other products? Or do you just want to tell us what you think? Let us know here, on Facebook, or on Twitter.
Thank you Kyle your response is very helpful regarding precharged will not work with the MrCool signature series central AC. It comes precharged for 15ft, but the distance between the condenser and evaporator coil is 35 ft Thru the attic (25 ft going under the house). So what are my options, please? Do I need to add refrigerant based on the extra 20ft?
Yes, additional refrigerant may be needed for that installation. Typically the installation manual for a condenser will tell you how much refrigerant would need to be added for a given amount of added line.
My 5 month old 4-5 ton universal outdoor unit is being replaced under warranty. This install used the No-Vac precharged 25' line set. Am I able to close all the valves on the compressor and air handler, and remove lines from old outdoor unit (in reverse order of install), and put the lines back on new unit without a vac and recharge?
Hi Kyle
If the lines are only 9 feet- on a mini split - how bad would it be to just secure the non vacuumed lines and open the Pre charged unit?
Thanks
Don
How bad would it be? That's hard to say. Some people do install them that way, and they will run. It's definitely not recommended, and might foul the warranty.
We had a new 5 ton A/C unit installed about 2 months ago. Last week it didn't cool down. The guy who installed the new A/C guy came out and after running tests said the line set was leaking somewhere which was under the cement and needed to be replaced. He quoted $1200 to install a new line set. Is this about normal what it should cost? The old line was under the cement, so he ran the new line through two walls and then outside the house, I wanted cleaner installation, but he said he could not bend the line set to a 90 degree angle or use elbows. So now we have a big black thing coming out our side of our house through a laundry vent with a bow in it connected to the new A/C. I can't believe the replacement line set has to look like this. If he used 2 90 degree elbows the line set could have run next to the house out of the way and look more professional;. Am I wrong?
A typical line set is not very expensive, but labor costs can vary. I suspect the majority of that $1200 quote is labor costs. Depending on the difficulty of the job, and you did mention cement, $1200 might not be out of line. In terms of bending, a 90 degree bend can be tough to pull off without kinking or stressing the line. There are tools that can help that sort of bend, but it is not a trivial consideration.
It sounds like you're looking for coupler kits. You can find an example here: https://iwae.com/shop/mrcool-diy-line-set-coupler-kit-for-9k-12k-18k-line-set-ha21479.html
If I get a MrCool Central air condenser that is precharged, can I connect it to a precharged 25ft mr cool set to connect to the evap coil or not? if the set is filled with the refrigerant and the condenser also has enough for 15ft, wouldnt that be too much refrigerant? if so what are my options? Also if I needed 35ft for the condenser and it only has enough for 15ft it means I need to add a refrigerant but how will I know how much more I need
MrCool has two kinds of precharged lines. One set is for the Universal and the other is for the DIY mini-split. The Universal prechaged lines would not be compatible with any other kind of central air system, MrCool or otherwise, without extensive modification. The DIY lines, of course, can also not work with a central system. If the central air condenser you're talking about is the Universal, it can work with the prechaged lines. If it is Signature Series or some other kind of MrCool condenser that isn't the Universal, then it can't.
I'm purchasing the 2 Ton 15 SEER MrCool Signature Central Heat Pump Condenser - MHP15024A. It looks like it comes with 15ft of charged interconnecting tubing. I need to go 30ft. What should I buy?
I realized I undersized my 12k BTU unit and need to replace with an 18k unfortunately. It's a studio cottage that is 450sf that is super well insulated, so it seemed like the right size. But it has three french doors, a sloped ceiling that reaches 11 feet and a dozen or so windows. It does not get warm enough or cold enough in outdoor temp extremes. So I want to fix it with a new 18k unit and sell or donate the smaller unit. I was told by a dealer that I can buy the 18k BTU unit and just disconnect the compressor and indoor unit and I would not lose the charge in the 25ft line that is already embedded in the walls. Does that make sense? Any other suggestions are welcome.
Yes, that is correct. The DIY series units with pre-charged lines will reseal themselves when disconnected at both the condenser and the indoor air handler.
Do you think the pre charged line set connection is superior to the standard line set flares? Can they leak at the indoor and outdoor unit if not properly installed?
They are prone to leaking if not properly installed like any line set would be if not properly installed. While one fitting is not necessarily more superior than another fitting, there are pros and cons to each. Some people prefer pre-charged line sets with Quick Connect fittings because they are much faster to install, and others prefer a more traditional installation.
We are looking into a MR. Cool DIY Dual Zone Minisplit. The first level will work with 16ft line, however the 2nd level needs a 25ft line. I’ve read that I can’t fix and match different line sets but can the two 16ft ones be attached together and work for both downstairs and upstairs as one line or do I need 2 separate lines.
You would need two separate lines. They would each need to connect to the condenser and one air handler. The DIY multi-zone mini-split systems come with one 25 foot pre-charged line set per air handler.
It really depends on a number of factors, including insulation, sun exposure, and the climate you live in. We cannot say for sure, but you may want to look into a 12k BTU system.
what does pre-charged line set mean? does it mean the line-set has only been vacuum? Or is there refrigerant in the line-set? Or both, vacuumed and refrigeration performed on the line-set ?
My MrCool was supposed to have precharged lines. It stars right on the unit lines must be evacuated. I know the system is charged but I thought the lines already had a vacuum on them. I just purchased it from you 2 wks ago.
Can you connect two precharged line sets together?
My current installed mini split is a 9k BTU Sanyo with flare nuts on the line set the length is right at 35'...If I buy a 12K BTU 115V Mr. Cool DIY with an additional line set will the line sets connect together?IE are the connections male female on the line sets?
MrCool is coming out with coupler kits that will allow two pre-charged lines to be connected together. However, the MrCool DIY pre-charged line is only compatible with MrCool DIY units. It would not work on a Sanyo mini-split.
I am installing an 18k DIY Mr. Cool and the linear distance from the indoor unit to the compressor is approximately 12 feet. The line set has a fixed length of 25 feet. What Is the best method to coil the extra 13 feet of length? Can I leave in a vertical coil? But if I do won't the refrigerant oil get trapped in each coil? Should I mount to the exterior wall bending the line horizontally for 4 feet (with a slight down grade) bend down vertical for a foot and then bend again horizontally back to the compressor? And lastly should the entire line set be higher than where it ties into the fitting on the compressor? Thanks for getting back to me.
The manufacturer recommends coiling the excess and storing it nearby the condenser. Like you, we think that keeping it horizontal is the best option. If you can store it above the compressor, then do so.
Can I connect the pre charged line set and let it sit for a week while I wait for the electrician to come connect the power? Or do I need to operate the system immediately after hooking up the lines???
I am installing a 24k diy kit and don’t have access to go directly out the back of the unit. There is a knockout at the side. I need to run the lines thru this knockout and then 90 degree bend the line set out the wall. Should I have any concerns bending a precharged lineset?
I'am going to purchase a 36K BTU mr cool DIY 2 ZONE 2 - 18K Air Handlers Split System. Would 16 foot line sets be sufficient enough for the 36 K BTU
Condenser ? 25 foot line sets would be to long.
Is it possible to move mr. Cool DIY unit after installation? Can the precharged lines be closed or does the refrigerant need to be evacuated prior to disconnecting the mr. Cool DIY precharged lines for moving of the unit.
After 5 years of use of a system, if I want to test the system for any refrigerant leaks, are pre-charged line sets more or less difficult to test for leaks compared to sweat line sets?
