Replies

1. Expert Member
   Dana Dorsett | Apr 17, 2019 02:02pm | #1

   The SHR of either is probably not going to be satisfactory in normal cooling mode for the muggiest-stickest of days, but the SHR improves latent cooling dramatically putting it into "DRY" mode. The down side to DRY mode is that it doesn't cool to the temperature setpoint in that mode, and has to be manually returned to normal cooling mode to keep it from overcooling.

2. 
   Esmond | Apr 17, 2019 02:03pm | #2

   Thanks Dana. Do you have any advice about the difference between these two units?

1. Expert Member
   Dana Dorsett | Apr 17, 2019 03:07pm | #5

   >"...any advice about the difference between these two units?"

   I reckon it's about $400. ;-)

   Either one will handle the load with some margin, at about the same efficiency.

   From an as-used SHR perspective I would presume them to be identical, or nearly so. The coils & blowers appear to be identical, so the primary difference is the compressor. If appearances are reality on the coils, at a given load, the coil temps and blower speeds would be the same, delivering the same SHR. The published SHRs are at the nominal "rated" cooling values.

   If more latent cooling is desired in normal cooling mode set the blower to stay at the lowest speed rather than modulate up/down. At the lower speed it delivers cooler coil temps for the same amount of sensible cooling for an improved latent cooling.

1. 
   Esmond | Apr 17, 2019 04:06pm | #6

   Thanks Dana and Josh,

   These were extremely helpful replies!

3. 
   joshdurston | Apr 17, 2019 02:18pm | #3

   Is there a reason to go floor mounted? If it were for heating, then floor mounts make sense with the low return to keep the inlet temps low and efficient, but for cooling dominated application, a wall mount will be cheaper, probably have better air distribution, have a lower min modulation, and a bit more efficient.
   The FH09 modulates down to 1700 btu in cooling (1600 in htg), and the seer rating is 30. But most significantly it's about $1000 cheaper.
   I know because I wanted a KJ09 (floor mount), but went with the FH09 (wall mount) due to cost/cosmetic constraints in my living room.

   FH09 has a disappointing 0.92 SHR, but I suspect slowing the fan down will reduce it significantly, and there's always dry mode. With the modulating fans and compressors, and expansion valve the SHR is not fixed.

   http://meus1.mylinkdrive.com/M-Series/R410A+Systems/Floor+Mounted+/index.html
   According to the data sheets it looks like the 09 and 12 floor mount units use the same compressor (not the same outdoor unit model though). SNB140FQUMT , so I'm not surprised the min capacity is the same on both. I would probably go with the smallest unit that meets your load calc, since you'll save a couple dollars by going down a size.

1. 
   Esmond | Apr 17, 2019 02:24pm | #4

   Indeed. The primary reason to go with floor-mount is that we have no exterior wall to mount it on (the exterior wall is sloped above the knee-wall). We'd have to mount it on an interior wall, and route the lineset on the interior wall. If I knew of a way to make that look ok, I'd be eager to save the $1000 as you suggest.

   The secondary reason is that the floor mount position happens to point towards the stairway, and will facilitate pushing conditioned air towards the floor below. The interior wall position requires the conditioned air to turn a corner. I'm not at all sure how much this matters.

4. 
   gusfhb | Apr 18, 2019 08:17am | #7

   All my wall mounts are on interior walls, but I had the luxury of having the walls open in this house. That said, sheetrock work is cheap.

   years ago I mounted one in a hallway and popped through to a closet to run the lines down into a garage and out. I also had a room with a large window on every wall, so the unit ended up over a window. I ran the lines to the edge of the window frame, cut the sheet rock down to the floor[I also dislike the external lineset] and out. a 4 inch by 7 foot strip of sheetrock was nothing to fix.

1. 
   Esmond | Apr 18, 2019 01:25pm | #8

   Thanks Keith. My interior wall is a fairly thin fire-wall separation between townhouse units, so I think opening it won't be practical. But this thread has led me to reconsider built-in bookcases to either side of a wall unit, and I could hide most of the lineset behind them. The MSZ-GL12NA or MSZ-FH09NA would be a pretty good match for our loads, and the savings would pay for the bookcases, which we need anyhow. ;)

5. Expert Member
   Dana Dorsett | Apr 18, 2019 01:50pm | #9

   >"MSZ-GL12NA or MSZ-FH09NA would be a pretty good match for our loads..."

   The GL12 has "only" an SEER of 23 and an HSPF of 12.5 but it's HEATING capacity at your outside design temps in Toronto is less than an FH09 (9,790 BTU/hr @ -15C compared to 10,900 BTU/hr @ -15C for the FH09):

   http://meus1.mylinkdrive.com/files/MSZ-GL12NA-U1-MUZ-GL12NA-U1_ProductDataSheet.pdf

   https://nonul.mylinkdrive.com/files/MSZ-FH09NA_MUZ-FH09NA_Submittal.pdf

   If you can see your way to upgrading to an FH12 instead of a GL12 you'd have significant heating backup should the gas burner fail, and higher SEER / HSPF efficiency too:

   http://meus1.mylinkdrive.com/files/MSZ-FH12NA~MUZ-FH12NA_Submittal.pdf

   The list-price up-charge from a GL12 to an FH12 is less than CDN$500, but the FH12 may actually come in cheaper in Toronto than a GL12 due to the higher sales volumes of the FH series in your relatively cold climate.

1. 
   Esmond | Apr 18, 2019 02:18pm | #10

   Thanks Dana.

   Hopefully the emergency backup heat is a low-probability event. (Knock on wood). Our main heating use would be to raise a 12x13 ft room (connected to the rest of the house - it's open concept) by 3C, once in a while. At -20C, the GL12 still puts out 7920BTU, which would be more than sufficient for that purpose, would it not?

   But for cooling, wouldn't you prefer the min 1500 BTU cooling of the GL12 vs the 2500 BTU of the FH12? I can't guess how much cycling that really avoids.

1. Expert Member
   Dana Dorsett | Apr 18, 2019 03:11pm | #11

   Unless it's an extremely lossy room like an attached greenhouse or something the GL12 should be able to fully heat a 12' x 13' room at -20C.

   The 1000 BTU/hr minimum modulation difference is the equivalent of 2 active adults or 3 sitting adults. When the load is already down to 2500 BTU/hr it's probably after sunset and going to near-zero anyway, but it's a difference. The SHR at only 1500 BTU/hr (or 2500 BTU/hr for that matter), operation in DRY mode at least some of the time when the sensible loads are lower is a given no matter which you went with.

   Are you sure you need the full cooling capacity of a GL12 over that of a second FH09?

   The max cooling of an FH09 is only 1600 BTU/hr less than a GL12, (13,600 BTU/hr vs. 12,000 BTU/hr) and the difference in minimum cooling is less than the heat emitted by one sleeping human.

   A couple years ago on another forum I talked a guy in North Carolina to go with an FH09 for his attached sun room (of comparable size to your room) instead of an HM09, which had been the most reasonable among several (much worse) proposals, primarily for minimum modulation and efficiency reasons. When his heating system crapped out during a cold snap he was pretty glad to have gone that route, since it became his primary source of heat for the whole house for a week. The whole exchange, including the cold-snap/no-heat report can be found here:

   https://terrylove.com/forums/index.php?threads/yet-another-mini-split-sizing-question.70906/#post-563684