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Community and Q&A

Proper installation of 2 adjacent outdoor mini-split units?

pknutel | Posted in GBA Pro Help on

We just finished a major renovation project that included sprayfoaming, all new windows, and one new Fujitsu Halcyon mini-split on each of the three levels. The temps are now dropping here in Maine, so we’re finally getting a chance to experience the heating capabilities after a ton of research I did on this site and others (we do have backup electric heated floors and a propane fireplace ducted to the lower and upper levels as supplemental heat sources for brutally cold times).
Anyway, last week we had an error code on one of the units that made it quit, required a service call, and indicated an issue with an outdoor fan, according to the installer. I don’t know yet whether this was a fluke or may turn into a recurring issue, but I’m curious about whether anyone has thoughts on the configuration of the outdoor units.
For aesthetic reasons, we mounted two of the three units in one corner and the third on the other side of the house. They are all mounted several feet off the ground to keep them out of deep snow. We put a PVC fence and gate around the two that are next to each other, as you can see in the picture. The installer had reservations about this from an airflow perspective, and I told him we could always remove the door during the winter or possibly remove the entire decorative fence if necessary. We’re on the water and thus are subject to salt air and cold winds off the water that I thought the fence might help protect the units from both.
My questions are 1) should the units be blowing at each other at a 45 degree angle a few feet apart, and 2) will the the fence likely be helping to protect from high winds (Fujitsu said extreme high winds can impede fan blade rotation) or instead impeding proper airflow? I could always see if the installer could raise one or the other so they don’t blow air at each other at the same plane (they can’t be mounted one above the other, according to Fujitsu).
Thanks very much for any advice, and MANY THANKS for the wealth of information i’ve always found on the site!

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  1. GBA Editor
    Martin Holladay | | #1

    Good question. If I were you, my first step would be to contact a technical rep at Fujitsu. Give the company a call. Once you get a technician on the phone who sounds knowledgeable, explain the situation and e-mail the photo that you just posted.

    Common sense tells me that this set-up isn't ideal. But of course I don't have enough experience to know whether you will have problems in the future.

  2. wjrobinson | | #2

    Add some ribbons in the space and watch the air flow. stand on a ladder outside and reach in and feel with your hand, some air might be recirculating. Air out likes to move in a direction the air in is much different as it gathers air at much slower velocity from all directions off the back. You can feel this with your hand in front and behind any fan.

    Of course best case would be to not have what you have, the fence bouncing flows around and the outflows running into each other.

    You need the cold exiting air not to recirc. and for there not to be a lot of turbulent air whipping about the units from having the fence and cross flows.

    complex airflows...are complex. Check out this pic from Airbus

  3. pknutel | | #3

    Thank you, Marttin and AJ, for your quick responses! As the consumer and not the installer, I didn't know that I'd be able to get a technical rep from Fujitsu on the phone, so I'll first try that. I like the ribbons idea to let me be able to see just what's happening with the airflow in this situation. I'll mention that to the technical rep and see if he wants me to do that and send more pics that show what's happening with the airflows of the two units. They are certainly intersecting, but I don't know if the units are far enough apart for this to be significantly affecting performance. I'm hoping the first error code was just a fluke, but if it persists, that will provide the answer.
    If anyone has any other thoughts, please chime in. Otherwise, I'll post back after talking to the technical rep.
    Thanks again!

  4. user-659915 | | #4

    Whatever the concerns may be about conflicting airflows and turbulence etc. I think the fence has got to be a bad idea. These units undeniably work best with unimpeded free air access, the fence will restrict that and offers too many opportunities for further obstruction. I can already see a suggestion of the enclosure being used for equipment storage on the intake side of the left hand unit.

  5. GBA Editor
    Martin Holladay | | #5

    Kayak paddles... the camel's nose under the tent. Soon, entire kayaks.

  6. ohioandy | | #6

    Phil, I have two outside Fujitsu units also. I put them side-by-side, with no fence. We all choose these particular units for their high efficiency, and pay a premium for that. The way I look at it, energy efficiency is a game of inches. We do room-by-room heating load studies and size equipment carefully, to say nothing of the extensive engineering that goes into these devices and their controllers. Why would we do something so egregious as enclosing them in a high solid fence, an aesthetic choice that hamstrings them in their efforts to use less energy? Are the units that visually offensive that they need to be hidden behind a .... VINYL.... fence? I have no numbers, but just visualizing the air swirling around between those units would bother me every time I turned up the thermostat.

  7. Expert Member
    Dana Dorsett | | #7

    What Andy Chappel-Dick said. And...

    ... I can't imagine they are mounted high enough off the ground to eliminate snowdrift issues, since the fence also forms a snow trap. It's also not clear if they are sufficiently protected by roof overhangs against ice storm or roof-avalanche issues. (I'm guessing not.)

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