Shortening mini split lines

[bluedog225]

A question for you guys who have installed mini splits. I want to fit the lines to the install. No coils.

On the precharged units (not the precharged lines), do the instructions indicate how much you can shorten the lines without having to remove refrigerant?

I don’t mind making flares, pressure testing, vacuum etc, but I don’t want to get into removing refrigerant. Or having to trust someone else to do it right.

Or can I order custom lines so that the amount I cut off will not matter?

I see that many units have a reservoir so I suspect there are some instructions for this.

Thanks

 

[Balvar24]

Many mini splits specify a minimum number of feet of line set that is required. I believe some manufacturers are using this as part of the expansion device.

 

[fitter30]

Most minis shortest line is ten ft. Check your install manual.

 

[bluedog225]

Thanks. I’ll keep looking. I did not see in the Mr. Cool manual (non diy).

I am able to put one head unit very close to the compressor. The other can be 15‘ or so.

In a blinding flash of the obvious, I guess I could try to arrange it so I have a vertical drop and then a horizontal run to the compressor. Though I’d rather not.

 

[Balvar24]

I just left mine rolled on the wall.

 

[tdkkart]

I just did 2 24K Pioneers, their manual indicated you could shorten down to 10ft.

The units work great BTW.

 

[PCustoms]

Aren't the linesets evacuated and sealed?

How will you pull vacuum if you cut?

 

[bluedog225]

The mr cool diy are. Others, the main unit is pre charged. You install them pressure test and vacuum with a pump. Then release the refrigerant from the main unit.

My set up really needs custom lines.

No instructions on min length in Mitsubishi.

Will check pioneer. Thanks!

 

[bluedog225]

Well. I’ve read 3 installation manuals so far.

This is the only instructionI can find. Nothing about a minimum length that I can find.

This is the only instruction so far, the units should be “As close as possible.” This is from the Pioneer.

 

[Raisedonadeere]

I don't recall places I ran across min length requirements but do recall seeing 11' on a Mr Cool unit 12K and hearing a Senville rep saying conservatively stay above 15' on a 18K ceiling Cassette type. Several things I saw seemed to indicate that there is definitely a exposure to performance issues with too short a line. I have installed 5 different units over the past 5 years and researched each one and saw where one installer gave a warning to not get the line too short.

 

[Balvar24]

Usually included in the piping portion of the instructions.

 

[vavet]

MRCOOL Olympus ENERGY STAR 9,000 BTU 3/4 Ton Ductless Mini Split Air Conditioner and Heat Pump - 230V/60Hz O-ES-09-HP-230E - The Home Depot

Provide even air conditioning to your home with the addition of this MRCOOL Olympus ENERGY STAR Ductless Mini Split Air Conditioner and Heat Pump.

www.homedepot.com

There's a link from this page to an installation manual. It shows a minimum length of 9.8 feet (3 meters) for the 9k and 12k BTU units.

 

[Jackfre]

When the inverter units first came out we were told that to short a line set length would create a resonance, as in objectionable sound, from the evaporator. The following year at the AHR show I cornered one of the Japanese Engineers and asked him what the sound actually was. He replied, “It is the compressor slowly tearing itself apart.”

 

[mepstein]

I ordered my Pioneer with a 10ft line set.

 

[bluedog225]

Are you saying that you got a precharged condenser unit for a 10 foot line set?

I didn’t know I could order matched condensers and lines.

Thanks all. I’ll keep digging.

 

[bluedog225]

MRCOOL Olympus ENERGY STAR 9,000 BTU 3/4 Ton Ductless Mini Split Air Conditioner and Heat Pump - 230V/60Hz O-ES-09-HP-230E - The Home Depot

Provide even air conditioning to your home with the addition of this MRCOOL Olympus ENERGY STAR Ductless Mini Split Air Conditioner and Heat Pump.

www.homedepot.com

There's a link from this page to an installation manual. It shows a minimum length of 9.8 feet (3 meters) for the 9k and 12k BTU units.

Thanks. This is just the type table I was looking for (understanding that it is just for this unit).

 

[mepstein]

Are you saying that you got a precharged condenser unit for a 10 foot line set?

I didn’t know I could order matched condensers and lines.

Thanks all. I’ll keep digging.

Yes. It was an option when I ordered the unit.

 

[jjrbus]

Not an AC tech, another homeowner trying to get by. What I read was min 10 feet or can be noisy and only found specs for adding refrigerant for longer lines than 25 feet. I was told there was no need to remove refrigerant for shorter lines. I really do not like the look of the line coiled up behind the unit and also looks like an oil trap to me. For my short run I ran the line ( ???? can't think of word?) back and forth behind the unit, same as it would be in a coil and ended up with about 12 foot of lineset

 

[motterpaul]

With Pioneer you order a pre-determined line set (for example 10 feet) and the compressor will contain the correct amount of coolant for 10 feet. If you order 16 feet of line set it comes with more coolant. The amount is weighed at the factory to match the length of the line set you order. IIRC the two lowest options are 10 or 16 feet.

If you decide to cut off a couple of feet to avoid coils then I am not sure what the procedure becomes for determining how much coolant to use. I am hoping someone here has an answer to this question. I know there is a reservoir inside the compressor system to add or store coolant as needed to maintain a given indoor temperature.

I know each manual comes with tables specifying how many ounces of coolant you need for each foot of line set, but the process of pulling out the coolant and then weighing the correct amount back in is very complicated. I guess the question is "how much leeway is there for the right amount of coolant per foot?" - I see a lot of install videos where the "pros" just cut off three or four feet of line set and never even mention how that affects the R410a weight measurement.

IOW: I am also waiting for an answer to the OPs question - how much line set can you remove before you need to worry about how much R410a is in the system?

 

[motterpaul]

Just FYI - I was reading the Pioneer Support site and it says the leeway you have is really pretty high. I git the idea that most systems ship based on 16' lineset loads. It says...

"How do I know if my outdoor unit will require more refrigerant?"

"There is no need to adjust the amount of refrigerant for kits as short as 10 feet, and as long as 25 feet. If the kit length is outside of this range, the amount of refrigerant must be adjusted according to the accompanying manuals. Systems will show signs of low performance if the refrigerant amount is more or less than the required amount."

I also remember reading that if you change the lineset you can go shorter or longer by about 20% with no worries. There is a reservoir inside the condenser - the main thing is that you just don't want to overfill it. Check your PSI when you start it up again and make sure it is close to about 117 psi in cooling mode, but as low as 100 is not uncommon as long as it is cooling (although some would probably say that is a little low)

The main thing is having clean lines, no air or contaminants, and good flares.

 

[428PI]

I have the Pioneer triple outdoor unit and am running a 16 ft line to a 9k unit and 33 ft line to an 18k unit. Never adjusted coolant levels and is working fine. The outdoor units only come with a certain amount coolant. Doesn't matter what line sets order. Look at installation manual for details on levels for different lines.