Mini split line set is one foot too long - fix it or ignore it?

[DrVlikhell]

I'm finally installing my 3rd mini split. The first two went fine and have been working great. With the third one I'm going to need to put the outside unit farther away than expected. The unit came with a 16ft line set and is precharged for up to a 25ft line set. However, the shortest extension I can get is 10ft, which would make a total of 26ft of line set. Is the extra 1 foot enough to make a fuss about? A line set calculator says it needs an extra 0.23oz of refrigerant for the extra foot. The specs for the unit say it already has a precharge of 40.56oz.... will the extra 0.23oz, or lack of, really make a difference?

I could possibly shorten the line set by one foot, but I don't have flaring tools and have never flared copper line, so I don't know if I trust myself to make new flares that don't leak. I got the mini splits directly from Pioneer in Miami and I believe they make, or at least cut and flare their line sets in house because all of the flares look really good. So I don't really want to go that route unless absolutely necessary.

Thoughts, opinions?

 

[nadogail]

Make a "Dog Leg" in your new line, the extra length won't hurt you and may be enough to allow you some flexibility in relocating the equipment.

 

[PCustoms]

How long do you need?

Is there a more appropriate "extension" you can use as THE line set instead of trying to build onto what you have?

 

[DrVlikhell]

I'm not sure what you're referring to by a "dog leg" in the line. 26 feet is plenty to put the outside unit where I want/need it to go, I'm only concerned about it being 1 foot over the 25 foot limit for the precharge.

I would put the outside unit closer, but it would be blowing hot air directly onto a car, and I'd rather not slow bake the car. Plus the instructions say you're not supposed to have anything placed within 80 inches of the front of the outdoor unit.

 

[DrVlikhell]

How long do you need?

Is there a more appropriate "extension" you can use as THE line set instead of trying to build onto what you have?

I could use a single 25 foot line set, but those are at least twice as expensive as a 10 footer, and they're out of stock from the manufacturer. I'd have to get a 25 footer from some other company, which would mean more researching of which parts/brands can be trusted in the sea of Chinesium. Also it would leave the 16 foot line set that I already have useless.

 

[pcmeiners]

They have engineers working on minisplits, engineers always have give and take figured in. If the length were 5 foot over I might be concerned,.... .23 ounces, 1/4 ounce, basically is nothing, that is less than a tablespoon, 1/162th of the charge. Absolutely nothing to worry about.

 

[chinboys]

The best indicator of a correct refrigerant charge is to reference the manufacturer's specs but to measure the superheat or supercool temperatures during the peak cooling season and when the system is under full load.
A rule of thumb is 5 to 10 degrees of superheat or super cooling.
The exact charge weight matters on those hydrocarbon refrigerants (R290) measured in grams or ounces.

 

[nadogail]

I'm not sure what you're referring to by a "dog leg" in the line. 26 feet is plenty to put the outside unit where I want/need it to go, I'm only concerned about it being 1 foot over the 25 foot limit for the precharge.

I would put the outside unit closer, but it would be blowing hot air directly onto a car, and I'd rather not slow bake the car. Plus the instructions say you're not supposed to have anything placed within 80 inches of the front of the outdoor unit.

A "Dog Leg" ls a deviation from what would ordinarily be a straight line.

 

[pcmeiners]

"The exact charge weight matters on those hydrocarbon refrigerants (R290) measured in grams or ounces."

It is not a refrigerator or water cooler, it is a minisplit running R401A, <1/4 once is minuscule for a minisplit. Put the book smarts away, it is common sense.

"A rule of thumb is 5 to 10 degrees of superheat or super cooling."

Let not get carried away for <1/4 once of 410A

 

[MadScientist3019]

"The exact charge weight matters on those hydrocarbon refrigerants (R290) measured in grams or ounces."

It is not a refrigerator or water cooler, it is a minisplit running R401A, <1/4 once is minuscule for a minisplit. Put the book smarts away, it is common sense.

"A rule of thumb is 5 to 10 degrees of superheat or super cooling."

Let not get carried away for <1/4 once of 410A

I'd agree with this as an engineer. The amount referenced that's "off" here is probably within the measurement accuracy that you could get from the scale used by most HVAC techs trying to charge the system anyway. I'd say stick with the original proposed lineset option of adding 10' to make 26' total.

 

[micromind]

Worst case would be very slightly reduced performance, slight enough that you likely couldn't measure it.

If the reduced performance is noticeable, have a HVAC company come out and properly charge the system.

 

[pcmeiners]

"If the reduced performance is noticeable, have a HVAC company come out and properly charge the system."

At a couple hundred for the service charge and a <tablespoon of 410A, my advise, buy the wife really expensive perfume, it will be cheaper and the best bang for the buck.

If the OP could possibly notice 1/162th of the performance (considering the engineers did not add a teaspoon of 410A to the systems extra as a margin), for his next miracle, walking on water would be right up there.

 

[dscheidt]

The best indicator of a correct refrigerant charge is to reference the manufacturer's specs but to measure the superheat or supercool temperatures during the peak cooling season and when the system is under full load.

How do you do that on a system with an electronic expansion valve, and no way to force it to full load? And for which the manufacturer doesn't provide subcool or super heat targets for, because it's expected to run at 0 degree superheat a lot of the time?