Directing Minisplit Air Flow with a Ceiling Fan
This website has been a fantastic resource for my remodel, but I’ve searched these and other forums for the past few months and have been unable to find a good answer. I’ve also talked to about 5 contractors who have provided different solutions and figured I’d throw the question to you folks to see what you think.
Info: Am installing an 18K mini split will unit (and removing the window unit) to cool down a first floor in a 1920s rowhouse in a very hot/humid Zone 4A location. Attached is a picture with my current plan (looking South to North, from Sunroom to Living Room). The first floor is an open floor plan. It is about 40 feet long and 15 feet wide. The mini split location is constrained due to brick party walls shared with neighbors and few exterior-facing walls. I’ve looked into a variety of options and I’m pretty confident I want to stick to a mini split wall unit (of course, I’m open to feedback on that front if a bad decision).
Question: If I can place a ceiling fan in the room the mini split is located in, will I be able to get cold air across the entire open floor plan even though the mini split’s air flow is directed at the opposite wall? Or do I need to reconsider this placement since the air flow (either from the split’s internal fan and/or the ceiling fan) will not be powerful enough to push the cold air across the entire floor?
Thanks again for this awesome website and any help you can offer!
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Replies
A ceiling fan will help, since it will stir the air. Having the only minisplit at the far end of a long and skinny space like that isn't going to get you optimal temperatures across the entire space though -- it's going to be colder near the unit and warmer at the farthest end of the space. If you can't get the minisplit more centrally located, at least try to position it so that it can blow down the long axis of the space and not across the narrow dimension of the space.
Bill
It's ok if temperatures are not optimal, but I'm worried that it will be a stark and noticeable temperature difference b/t sunroom and living room and that the living room may not even cool down on a very hot and humid day.
It's worth mentioning that there will be a 9K placed at the top of the stairs on the second floor and that may move some cold air down to the living, but I feel like most of the work is going to be down by the 18K.
Agreed on long axis. The windows impede a location allowing it to blow down the long axis. Quite the conundrum b/c that's where I ideally wanted to place it.
I think your purposed location is far from ideal for your building.
A single mini split head will often work well in a large open space with good windows if it is well insulated and air sealed but that does not seem to be your case.
Do you have a basement or crawlspace?
Would you consider hiding the refrigeration line behind a crown molding or bulkhead near the ceiling?
How tall are the ceiling 12 feet?
Walta
There's an unfinished basement below the first floor.
I've considered hiding the lines and that may be an option. There's lath/plater over brick so I may be able to put the mini split centrally located in the dining room and then lines down into the basement and then out the back.
Ceilings are 10 feet I believe.
Locate the unit centrally and hide the lines. The problem is not just ariflow, but because of the airflow, it will not sense the temps properly.
If you use a condensate pump, you can run the lines any which way to minimize their looks
Sensor will be in the remote, but I'm definitely concerned that the air will not travel the long axis in the current direction.
I have a pump, but was not planning on using. Trying to do it as simply as possible, but maybe there is no other way.
prioritize. Simple is not simple when it doesn't work properly. Condensate is about the only problem I have with mini splits. Even ones with a 16 foot drop and good drain right out of the unit can give trouble, so in the end, a pump might be simpler
What kind of mini split is it? If it’s Mitsubishi, don’t be fooled by their advertising leading you to believe the “thermostat” (hint: it’s not one) in the remote will do bupkis. You’ll need to get the MHK2 or similar if you want a temp reading anywhere other than the head.
I've been assured the temp reading for the remote should suffice. Can also hook up to the smart thermostat, but that may take a bit more work.
Best if cooling is well distributed - for example, with ducts or a fan. But "magnitude matters", so how bad will it be? Say the sun room is 75F and it's 95F outside. Despite the distance and poor insulation, the living room will be much better coupled to the sun room than outdoors. So under 80F in the living room? But solar gain and wind direction could effect this significantly.
Thanks for the info. This is exactly what I'm concerned about. If 75 in sunroom, and 79/80 in living, then it's no good. One saving grace is that I will have another minisplit above the stairwell on the second floor so some cold air will be falling down towards the front door (bottom left of the picture) and make its way to the living room.
I definitely know a lot of cool air is going to get caught in the sunroom, and I'm worried about what the differential will be. At the end of the day, I guess I'll just have to install and see. Been quite a tricky installation.
Am still exploring centrally located in the dining, but the run through the walls and down the basement will get complicated.
Since it is a row house, most of your cooling load comes from solar gain and air leaks.
The plans don't show orientation, but if any of the windows are south or west facing, I would install the unit above the west/south facing window blowing along the length of the place.
Center mount works and usually the best location for a long place.
An 18000 BTU is a pretty big head with a lot of flow. It is also ludicrously oversized for a 720 sqft place. Assuming the place is somewhat air sealed, and those are not curtain windows, you are probably around a 9000BTU. You oversize the unit a bit as these do modulate a lot but you won't get good humidity control with an oversized unit.
Appreciate all the info. We've been doing lots of different calculations and loads with the HVAC specialists. Historically the space has had an 18K head; whether it be a window unit or two portable 9Ks. I'm feeling ok on the load, but you definitely raise a concern that's been in my mind.
Another option to consider: the short hall between the stair and living room seems a decent spot for a low-static ducted unit if there's space for a ceiling furr-down. Short duct runs could throw at the entry, into living and the kitchen/dining rooms.
Yep! One of the options provided to us by a contractor!
>"An 18000 BTU is a pretty big head with a lot of flow. It is also ludicrously oversized for a 720 sqft place."
That's what I was thinking... Unless those windows are very large and facing due west without obstruction the design cooling load of that place is probably less than 12,000 BTU/hr, maybe even less than 9000 BTU/hr.
First, do a room by room load calculation using Loadcalc (dot net) or Coolcalc (dot com).
Is this for both heating & cooling, or cooling only?
If this is a cooling-only application you might do better with pne or even a PAIR of Midea - MAW08V1QWT U-shaped window units, one where the old window unit was, the other in one of the windows near your planned location for the 1.5 ton mini-split. These units are pretty much a "3/4 ton mini-split in a can", with a significant modulation range, good throw (20' at high fan), and decent CEER 15 efficiency. The window closed down into the slot of the U shape to an open height of ~3" (5-6" if you have exterior storms with frame higher than the window sill to deal with.)
FWIW: I recently bought the 1-ton version (MAW12V1QWT) to deal with a hot-spot in my home's loft-office overlooking the kitchen & open stairwell to the living room. It's a (still minor) bit of a PITA to install compared to most window ACs but modulates quite well, drawing only 200 watts a minimum modulation and nearly as quiet as a better 3/4 ton mini-split. At max speed it's pulling in the 900 watt range, but still quite a bit quieter than a typical half-ton window shaker. (I've been considering writing an in-depth product review for this site, TBD.) Internet pricing and availability on the 8K unit (the one I was originally intending to install) is all over the place, with a lot of price gouging going on, but MSRP list price is $360 or so- not cheap for a window unit, but it's way nicer than any window AC that I've dealt with previously. The 1-tonner is available for the list price of ~$460, which is less than the street price for the 8000BTU/hr version from those who actually have it in stock.
The remote that comes with it is identical to the ones shipped with most Midea or Carrier minisplits It (tantalizingly) even has a "Heat" mode selectable on the remote, but with no reversing valves, or strip heat- it's strictly a cooling unit, not a heat pump, and doesn't respond to attempts to set Heat mode from the remote.
The single 1-ton in the loft is doing a good job of cooling both the loft and the entire first floor rooms (open to the kitchen with archways) at outdoor temps in the low to mid 80sF outdoors. (It's 85F outside with a dew point of 63F, 73F at an RH of 50% indoors, and it's been loping along modulating between 300-400watts of power draw all afternoon.)
Dana,
I'm considering this unit for our tiny nursery that won't have a ductless head. I read a review that water can get into the pan on the outside unit and has no ability to drain. Have you experienced this? How are you air sealing/insulating around the unit?
It's 18 b/c the windows are indeed very large and facing south/sough-west without obstruction and getting a TON of direct sunlight. I think 18 may be slightly more than required, but figured I'd stick with what has historically been in there BTU-wise.
We've done the loadcalc, coolcac, all manual J/S/etc etc calculations.
I've seen those window units and think they are pretty fantastic, but I really want to get things out of my windows and feel like minisplits have a much cleaner look as compared to the window units. Regardless, appreciate the heads up.