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Old 07-01-2009, 01:48 PM   #1
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Mini split lineset question


Is there any disadvantage in using liquid lines and gas lines that are one size bigger than the manufacturer calls for? I am having a quad zone Mitsu system installed right now and the installers used 3/8" and 1/2" lines one each 9K BTU unit when the installation instructions call for 1/4" and 3/8". They also cut the flare fitting off the inside units and are going to braze the lines together(1/4" to 3/8" and the 3/8" to 1/2") instead of using the flares. Is this an OK practice or should I start to worry? I have no idea what they're going to do when they connect the lines to the condenser. The three 9K units have 1/4" and 3/8" connections and the 15K unit has 1/4" and 1/2" connections.


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Old 07-01-2009, 01:58 PM   #2
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Mini split lineset question


I would call Mitsu and ask them what the heck these guys are doing. Those units have a measured/critical freon charge (to the ounce) and it depends on the proper line size or it won't work properly

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Old 07-01-2009, 02:03 PM   #3
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Mini split lineset question


I believe the unit is precharged for 130' of lineset. But, that is measured with the suggested lineset sizes. I will be around 110'-120' with the four units. I think they are going to have to adjust the charge no matter what, but I'm concerned about the performance of the system and them brazing eight fittings when they didn't need to.

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Old 07-01-2009, 02:12 PM   #4
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Brazing is not real good unless they purged nitrogen thru the lines while doing it. Otherwise you get carbon buildup inside the lines. Minisplits have very little or no filter driers so that can be a big problem.
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Old 07-01-2009, 02:37 PM   #5
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Mini split lineset question


Geez.

Considering that what your calling the liquid line. Really isn't the liquid line.
CALL mitzu and ask them if it will work ok.

The oversized vapor line, can hiner oil return to the compressor.
The ovesized small line(its actually part or the metering device on min's) may screw up the system from also having too slow of a velocity. And allowing the rerigerant to [ick up too much heat before it reaches the evap coil(even though its insulated).

There was no reason to cut the lines and braze.
If using the larger lines is ok, they make reducing flare fittings. Including 3/8 to 1/4, and 1/2 to 3/8.
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Old 07-01-2009, 02:43 PM   #6
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Mini split lineset question


Just called Mitsu. Their tech guy says they shouldn't have done either of those things. I'm waiting for a call back from the Mitsu area manager now. Not looking good. I'm ready to make a big pile in the front yard and let them pick it up. They have three of the inside units hung and two of the linesets ran.
Been- Is it not consider a "liquid" line since it's beyond the expansion valve and therefore part of the evap?

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Old 07-01-2009, 02:49 PM   #7
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Mini split lineset question


Yep.

A liquid line feeds liquid refrigerant to a metering device.
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Old 07-01-2009, 03:01 PM   #8
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Mini split lineset question


Quote:
Originally Posted by beenthere View Post
Yep.

A liquid line feeds liquid refrigerant to a metering device.
Ok. The instuctions label them as "liquid" and "gas." Some pics. I'm just sitting here wondering what to do. I'm ready to call the company's install manager and tell them to come pick up the pile of equipment that will be sitting in the front yard. They already have to bring out a new outside unit tomorrow since the one they tried to install had a big dent in the side.
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Old 07-01-2009, 03:08 PM   #9
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Mini split lineset question


That small line carries refrigerant in a saturated liquid state.
A true liquid line carries liquid refrigerant in a subcooled liquid state.

So its not a liquid line, in the full meaning of liquid line in regular A/C and refrigeration.

You might want to call the install manager, and tell him what mitzu said.
See what he says in return.
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Old 07-01-2009, 03:11 PM   #10
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I would document everything for the lawyer you may need. Doubt if it will ever work properly as they did not follow the manufacturers procedures and most likely will void the warranty.
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Old 07-01-2009, 03:18 PM   #11
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I would document everything for the lawyer you may need. Doubt if it will ever work properly as they did not follow the manufacturers procedures and most likely will void the warranty.
I'm trying not to let it get to that point. If I need to put a stop to this now, I will.
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Old 07-01-2009, 04:40 PM   #12
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Mini split lineset question


I spoke to the Mitsu area rep then the company sales rep. The Mitsu rep didn't want to say anything negative until I found out the reason they used oversized lines, but said there was no reason they should have done that. He said they may be brazing the lines because they are more comfortable doing it that way. It sounded like he didn't want to take sides just yet. I then spoke to the sales manager of the company. He said if there was a mistake in the line sizes it was because he spec'ed out the material using the wrong book. Sounded like BS. He said they braze the connections because it is less likey to leak that way, and the flares are prone to cracking. He said any contaminants would be removed during the evacuation.
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Old 07-01-2009, 05:06 PM   #13
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Mini split lineset question


If you have ever seen the inside of a fitting after brazing you will be shocked to see the carbon residue which can only be removed by a flush kit not a vacuum pump which they may use. They are BSing you. Flares if done properly with a high quality flaring tool are not a problem, just requires a skilled installer. I would document everything as I have seen lots of jobs gone wrong and without names, dates and times of who you talked to they will deny everything. Hopefully Mitsu is a reputable company. I work with Lennox and they are very good that way. The eccentric cone flaring tool is the standard for R410 flares for minis:http://www.yellowjacket.com/HVACRPro...9&t=HVACR&c=84
They never crack flares.

Last edited by yuri; 07-01-2009 at 05:11 PM.
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Old 07-01-2009, 05:23 PM   #14
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Mini split lineset question


Quote:
Originally Posted by yuri View Post
If you have ever seen the inside of a fitting after brazing you will be shocked to see the carbon residue which can only be removed by a flush kit not a vacuum pump which they may use. They are BSing you. Flares if done properly with a high quality flaring tool are not a problem, just requires a skilled installer. I would document everything as I have seen lots of jobs gone wrong and without names, dates and times of who you talked to they will deny everything. Hopefully Mitsu is a reputable company. I work with Lennox and they are very good that way. The eccentric cone flaring tool is the standard for R410 flares for minis:http://www.yellowjacket.com/HVACRPro...9&t=HVACR&c=84
They never crack flares.
I am documenting. I'm still trying to decide what to do. That's the flaring kit I was going to buy if I did the install myself. I thought I was doing the right thing by hiring professionals, but this sucks. I should have saved the four grand and did it myself. If they flow Nitrogen when they braze do you think it would be OK?
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Old 07-01-2009, 05:41 PM   #15
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Mini split lineset question


It is DIFFICULT to do that procedure. I myself have a hard time with it. Too much pressure and it blows the weld apart. Only a skilled tech can do that and it is primarily used for medical gas lines etc. Most AC installs have a good size filter drier. Minisplits are a lot more finicky/precise and flaring is the best way to go. The problem is the weld cools quickly then carbon forms faster and you need to wrap a wet rag around sensitive areas etc etc. Doubt if those guys have that kind of welding skill but anything is possible. If the weld is cold or bubbly then it may leak slowly later. I hate telling you all this negativity but some people think what we do is real simple and easy. There is a lot to it for a proper long lasting install. There is a extra strong type of solder called StayBrite:http://www.harrisproductsgroup.com/c...loys.asp?id=32
which is almost as strong as silfoss and does not require the extreme heat of silfoss (silver solder) which they may use. I don't like it for vibration or high temp jobs but some guys use it.


Last edited by yuri; 07-01-2009 at 05:52 PM.
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