I watched a ductless mini split install on a wood framed wall and I was surprised at the large amount of lines coming out of the air handler and through the wall. You had the electrical, refrigerant line, and condensate/drip line. They had to install a bracket over the lines to hide them. At least 3" circumference on all these lines.

On a new ICF build with 2.5" of EPS on the exterior and stucco finish, how does one hide these lines or is it not possible? I assume even if you stripped back the EPS down to the concrete, the 2.5" of EPS is not enough space to hide these lines. Not to mention the loss of R-Value.

After seeing it in person I believe they have to be exposed and run on the exterior of the stucco wall.

What kind of covers do they make besides those tacky looking white vinyl covers?

With my Mitsubishi units, I drilled a 2-1/2" hole for the the lines. I was able to just get the two refrigerant lines, the drain, and an electrical conduit through. I stripped the foam on the outside about 2-1/2" wide, and there was plenty of room to run everything down the side of the house and keep it below the surface of the foam. I will NOT be putting siding over them, though, as I would have to tear it all off if there was a problem. I attached a piece of the same 1X6 Hardi trim over it that I am using on the rest of the exterior, which I can remove for service. I used an air chisel to form a good sized radius where the lines come out of the wall so I could bend them without kinking. My other unit is on an inside wall, and I created an access panel behind it if the unit ever had to be disconnected or removed.

As for energy loss- I'm in a mild climate to begin with, and the small amount of loss might be offset by keeping my refrigerant lines better protected from temperature extremes.

As a side note- connect the wires to the indoor unit before you hang it on the wall, and feed them through with everything else. The Mits instruction say to hang the unit on the wall first, and then connect the wires, but this proved to be impossible, at least with my fat fingers.

Same thing with all penetrations. If you want them to line up to be buried parallel to the wall in the foam, they need to sweep through the entire wall thickness. A PVC conduit heating blanket is very helpful in making adjustments to the conduit.

On this install they wrapped the refrigerant lines with a black foam wrap. They said it was necessary to protect the line and to absorb any condensate that will form on the line. There is no way with that black foam wrap installed that it would it fit within the 2.5" spacing.

If the lines are buried behind the finished cladding (stucco, siding), it would be very difficult to find a leak or service the lines latter on.

So do the lines "sweat" within the wall? Condensation would be an issue if they were buried in the wall.

I think a 3" PVC sleeve would be the better choice in the ICF wall. The 2.5" might be cutting it close.

For a line to SWEAT, the exterior surface temp has to be below the dew point, and it has to come in contact with air. Wrapping it in insulation that is airtight, moves the temperature at the surface above the dew point (*hopefully). This is why in cold climates the cold water pipes are often insulated, or they sweat in the summer. Taken to an extreme I have seen a builder use thermostatic mixing valves on the supply lines to toilets, so the bowl does not sweat. Took me a while to figure out that one- and I still think that is kind of dumb. Cheers, Eric

Precisely, dry bulb temp and humidly (relative or wet bulb temp) determine the dew point temp. We have psychrometrics software to allow performing this calculation:

http://www.borstengineeringconstruction.com/Psychrometrics_Calculator.html

We also have building assembly moisture analysis software for sorting out what layer may be susceptible to accumulating moisture and estimate the accumulation rate:

http://www.borstengineeringconstruction.com/Building_Assembly_Moisture_Analysis_Calculator.html

Both are based on ASHRAE principals as explained in the software instructions.

Bear - any chance you could make the line set look like another downspout?

My lines were pre-insulated; they are about an inch in diameter with the foam. A 3 inch penetration would be much easier, but I hadn't worked out my plan well enough to make the penetration pre-pour. Trust me; drilling a 2-1/2" hole through a concrete wall is a LOT of work!

Posted By FBBP on 09 May 2014 12:16 AM
Bear - any chance you could make the line set look like another downspout?

I think I will go the route of just getting some pre-moulded sheet metal and cover the lines with that. This way I can paint the sheet metal the color of the stucco so it blends more.

Ripping apart exterior foam to run the lines is something that doesn't look too aesthetically pleasing and I have my doubts that the lines will sit flush within the 2.5" of foam. Plus the stucco will not adhere to that area unless there is EPS foam.

Posted By jdebree on 09 May 2014 06:56 AM
My lines were pre-insulated; they are about an inch in diameter with the foam. A 3 inch penetration would be much easier, but I hadn't worked out my plan well enough to make the penetration pre-pour. Trust me; drilling a 2-1/2" hole through a concrete wall is a LOT of work!

That is why I want to get the air handler locations pinned down so I can put in a 3" PVC sleeve in the wall prior to the pour. Drilling through reinforced concrete is not the easy task as boring through an OSB panel, especially if you hit rebar.

Precisely Lbear, you should expend the extra effort to sort out all the required building access points BEFORE the pour. We create the required enclosure space to address these sort of issues within the building living space when designing/constructing the walls or ceiling. For example, bring it through the ICF at a point adjacent to an interior wall that can host it.  You may need to gain access in the future and it is always much easier to open up sheet rock rather than exterior siding.

A couple of comments from my one time build. I had no problem hiding the lines behind the sheet rock. See the pics below. The only place where they didn't fit was the junction to split from the line going to main air handler and the wall unit in the garage. The junction is in the box that's near the ceiling and about 2" deep. As you can see in the one pic you really need to put a 16 gauge sheet metal nail & screw guard over the lines, whether they're inside or outside. These lines are for a 3 ton Daiken heat pump. The little gray cable is the controller (thermostat) cable from the outdoor unit to the indoor air handler.







In my case the lines come in from the outdoor unit through a 3" PVC sleeve that is sloped at 45° through the wall. They then are run up the wall to near the ceiling where you see the junction box. The main lines run near the ceiling toward the corner and then go down to a long turn conduit sleeve to go into the crawl space and then to the main air handler. My main air handler is in the crawl space which I use as the supply plenum. The 3" sleeve to the outside has the two refrigerant lines, the condensate line for the garage wall unit, the power cable to the outdoor unit, and the controller cable. I didn't get pics of all that before it was covered with drywall.

I think it would be better to run all the refrigerant lines inside the house, as much a possible in whatever cavity space you have available like in the ceiling space, crawl space, attic, or wherever, and then under the drywall in the foam.

I took a couple pictures of my install, although I was too lazy to drag out a ladder to get a pic where it comes out of the wall 12' off the ground. My mini-split lines easily fit in a 2-1/2" wide slot, along with the drain and flex conduit for the wires.

[URL=http://s84.photobucket.com/user/flgargoyle/media/025-2.jpg.html][/URL]

[URL=http://s84.photobucket.com/user/flgargoyle/media/026-1.jpg.html][/URL]

In that one photo it looks like someone punctured the refrigerant line with a nail or screw. Is that accurate?

I was told that the longer the line run, results in a drop in efficiency. That all lines should be under 25' and the SEER rating is determined based on a short line run. Is this true?

Shorter is always better when moving fluids and heat through a pipe…less friction head loss and less heat loss. However, you need to locate these units where you need to locate them, so I wouldn’t expect the performance loss to be too significant if you stay within the maximum length limit recommended by the manufacturer. I don’t know what length is used for the determining the SEER rating…likely very short to maximize the rating.

Posted By Lbear on 10 May 2014 12:09 AM
In that one photo it looks like someone punctured the refrigerant line with a nail or screw. Is that accurate?

I was told that the longer the line run, results in a drop in efficiency. That all lines should be under 25' and the SEER rating is determined based on a short line run. Is this true?

That's why the drywall was opened up there and why the caution about using a guard plate! I, the HVAC gang, and the drywall crew, all missed the need for them. HVAC contractor didn't charge to repair the line and refill the system, and I twisted the drywall contractor to do the drywall repair without charge after I installed plates. Shared negligence.

I just looked at the installation manual for the Daiken VRV system which I have. Total length of pipe for all branches is to be greater than 33' and less than 1000'. Max distance from the outdoor unit to any indoor unit is 492'. Max distance from the first branch in a line to farthest indoor unit on that branch line is 130'. Part of the design will be to be balance the size of the units with the number of units with the distances from the outdoor unit. The more smaller units you have, the closer they collectively need to be to the outdoor unit.

Another thing to keep in mind, because of a mistake I made, is design the system to minimize the probability of only one or two small units running at one time, thus being the only load on the outdoor unit. My system is 36k Btu. The main indoor unit is 36k and the garage unit is 9k. What I figured out from the mfr data sheets is if the garage unit is running by itself, the outdoor unit will run at 9000 Btu output. In cold weather the COP of the outdoor unit drops close to 1 at that load, which is hardly any better than straight resistance heat. I solved the problem by installing a pellet stove in the garage. Plus, a 9k unit isn't enough to lift the garage temp from 50° in winter to 70° in a reasonable length of time when I want to work out there.

The 25' distance you cite is impractical and a figment of someone's imagination.

Posted By dmaceld on 10 May 2014 11:33 AM

I just looked at the installation manual for the Daiken VRV system which I have. Total length of pipe for all branches is to be greater than 33' and less than 1000'. Max distance from the outdoor unit to any indoor unit is 492'. Max distance from the first branch in a line to farthest indoor unit on that branch line is 130'. Part of the design will be to be balance the size of the units with the number of units with the distances from the outdoor unit. The more smaller units you have, the closer they collectively need to be to the outdoor unit.


The 25' distance you cite is impractical and a figment of someone's imagination.

Wow, that is quite a lengthy line. Mitsubishi Mr.Slim Mini Split states the following:

Refrigerant Piping Max Ht. Difference (ft.):	40
Refrigerant Piping Max Total Length Each (ft.):	65
Refrigerant Piping Max Combined Total Length (ft.):	65

1,000' of line is pretty insane and even 490' is high. Are you sure you are reading that correctly? 1,000' is the length of almost 3 football fields.

The SEER that is advertised on the units are determined by using a 25-30' line. After that the SEER #'s begin to drop, hence the reason why they use 30' or shorter lines to test and rate the SEER.

Posted By Lbear on 10 May 2014 12:01 PM

1,000' of line is pretty insane and even 490' is high. Are you sure you are reading that correctly? 1,000' is the length of almost 3 football fields.

Correction! The max total length in the current installation manual is 3280 feet!

Go to page 53. http://www.daikinac.com/content/assets/DOC/EDUS391004-N%20VRVIII%20Installation%20Manual.pdf

Actually, the above is for the 6 ton plus sizes of the VRVIII system.

The 3 ton unit, like I have, installation manual is this one. It also applies to the 4 ton unit. http://www.daikinac.com/content/assets/DOC/RXYMQ-P%20Install%20Manual.pdf.

The piping lengths are on page 10. Max total is 1000'.

Goofed!

There is no way that 500'+ of line will be at the optimum efficiency level stated on the unit. Maybe some HVAC techs can speak up about this but I wouldn't be surprised to see a 30% + reduction in efficiency in longer run lines.

The Daikin installer who just installed 2 units on a commercial job I was at told me that a mere 25' extra length will reduce output.

Something doesn't make sense here. If the Mitsubishi engineers state that max length is 65' on a mini split, how then can Daikin claim 1,000'+ ?