# Mini-Split lineset insulation



## Marty S. (Oct 31, 2009)

The metering device is in the outdoor portion so both lines can sweat so they both need insulated. Not sure why the instructions say not to run the lines together but it does. Always best to follow the instructions.


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## ggold (Mar 19, 2012)

keeps the insulation tight on each line. Any gaps would create puddles.


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## Curious_George (May 22, 2012)

Well, I guess we'll see what happens... recently I ran my lineset through the attic and I insulated both lines together. I did not feel like paying for a prefabricated extended insulated lineset (50 feet), so I made my own with copper tubing from Home Depot. 50 feet of 1/4" and 3/8" cost me $100, which was bad enough. I ended up cutting the lineset to 45 feet for my application. 

Not thinking about the mini-split traditionally having each line insulated separately, I insulated both lines together. I added additional R-410A as indicated in the IM at 0.2oz/ft, which is about 4ozs. The system is running and appears to be Ok. The air temp coming out of the vent on high speed is about 57*F. On low speed it is about 50*F. 

These readings are similar to another mini-split I have in my bedroom with a 15 foot lineset.


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## joecaption (Nov 30, 2011)

Hold on untill one of the real HVAC guys come on.

I have two mini splits and the lines are not insulated together, reason being one lines is cold and one is hot. One in, one out.


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## Curious_George (May 22, 2012)

joecaption said:


> Hold on untill one of the real HVAC guys come on.


I am sure to get a firestorm of opinions either way. Unfortunately, people in all trades come in two different groups... those who have been doing the same thing for 30 years and learned something everyday and those who have been doing the same thing for 30 years and not learned anything after the first 2 years.


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## joecaption (Nov 30, 2011)

And what does the manufactuer say about it?
They have the last word.


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## carmon (May 8, 2010)

the lines must be insulated seperatly....... will it work togehter .... sure .... follow what the install instructions say


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## beenthere (Oct 11, 2008)

What did you put between the lines so they don't rub together, and rub a hole in one or the other.


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## Curious_George (May 22, 2012)

joecaption said:


> And what does the manufactuer say about it?
> They have the last word.


I emailed Fujitsu and they actually replied... the "application guy" said it should be "Ok".


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## Curious_George (May 22, 2012)

beenthere said:


> What did you put between the lines so they don't rub together, and rub a hole in one or the other.


Before I insulated the lines, I taped them together every 4 or 5 feet, so I could easily slide the insulation over the lineset. I used the Armacell Polyethylene foam (solid one piece, not split down the middle) from Home Depot and "glued" the pieces together with the recommended cement. Worked great and smelled good too. :yes:

The 1/4" and 3/8" lines fit nice and snug in there.


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## clocert (Oct 14, 2010)

Ideally you should separate them, the large line is very cold which must be insulated to avoid condensation or water damage, also, when it goes into the compressor, the cold gas won't work the compressor too hard (or too hot). the small liquid line is at room temp. if it is too cold, it may affect the metering device. But this is all theory, the real effect should be small.


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## HVACDave (Oct 16, 2007)

There were some manufacturers of ductless splits a few years ago that recommended pairing the lines together and insulating as you have done. I installed a few at that time and they worked fine. 

The metering device is at the outlet of the condensing unit, so technically both lines are part of the evaporator. You may loose a bit of capacity, but it has been done before with success.


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## Curious_George (May 22, 2012)

HVACDave said:


> There were some manufacturers of ductless splits a few years ago that recommended pairing the lines together and insulating as you have done. I installed a few at that time and they worked fine.
> 
> The metering device is at the outlet of the condensing unit, so technically both lines are part of the evaporator. You may loose a bit of capacity, but it has been done before with success.


Based on the mini-split design, I don't think that having the lines together will affect the performance that much. Will there be an affect? Certainly, but I don't think it will damage or be a detriment to the system as a whole. 

There are 3 or 4 thermistors that sense temperature on most mini-split systems. One at the rear of the condenser, one at the inlet to the evaporator, one (sometimes) in the middle of the evaporator and one at the outlet of the evaporator. If the evap inlet sensor detects to high or to low of a refrigerant charge (based on the temperature of the suction line affecting the "smaller" line), the TXV valve will compensate. Once the system is on for awhile, everything should reach an equilibrium.

This is my logic.


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## 205HVAC (Mar 22, 2010)

Curious_George said:


> Well, I guess we'll see what happens... recently I ran my lineset through the attic and I insulated both lines together. I did not feel like paying for a prefabricated extended insulated lineset (50 feet), so I made my own with copper tubing from Home Depot. 50 feet of 1/4" and 3/8" cost me $100, which was bad enough. I ended up cutting the lineset to 45 feet for my application.
> 
> Not thinking about the mini-split traditionally having each line insulated separately, I insulated both lines together. I added additional R-410A as indicated in the IM at 0.2oz/ft, which is about 4ozs. The system is running and appears to be Ok. The air temp coming out of the vent on high speed is about 57*F. On low speed it is about 50*F.
> 
> These readings are similar to another mini-split I have in my bedroom with a 15 foot lineset.


What type/model mini-split do you have?


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## Curious_George (May 22, 2012)

205HVAC said:


> What type/model mini-split do you have?


Fujitsu AOU9RLFW outside unit and ASU9RLF indoor unit.


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