Exposed Duct Mini Spilt

[ducatithunder]

I want to pose my plans of mounting an exposed mini split with ducted vents. This would be like a "loft style" install. My shop is 28x46 so just under 1300sqft. The ceilings are 12ft that slope to 14ft on the front. R38 ceiling and R23 rockwool on the walls. Currently the space is not conditioned but well insulated so it maintains temperature. The temperature inside the building stays between 50 to 70 deg depending on the season in Maryland. The main benefit of this install would be to cut the humidity in the summer months and take the chill off in the winter. I currently work in the shop as is and heat the space with a force air blower for 10 min if it is on the lower temp. I can't say I have had much issues with heat/summer months other then condensation formation on the floor in the summer when I'm running the large fan due to MD humidity.

I've attached pictures below, but my plan is to place the mini split in the corner hung from the ceiling joists. This location is based on the accessibility to the back wall for power and running the line set in the wall and out the back. It would run in one stud bay so no stud cutting required. Thinking about running 2 separate runs of 6" or 8" duct. The duct work would run along the back wall to the other wall forming a "L". I would also run a duct along the other side wall and it would run along the front just prior to the door opening on the front wall forming another "L". The duct would hang roughly 10 ft off the floor as to not affect the lighting through the window which is where the drywall stops prior to the windows. My thought is this would allow enough flow and draw the warm air back to the return above the work workbench. Im aware I could throw a couple wall units up and call it a day but there is some visual effects at play.

Does anyone see an obvious issue with my logic? Im open to suggestions.

 

[fitter30]

Even ducted minis have enhance coils be sure to add a premium pleated filter because they don't like dirt. Ton of cooling is 400 cfm. Minis have variable speed blower probably have to run the fan lock to manual to push air down the duct that might defeat the dehumidification.

 

[chinboys]

Why don't you install a conventional and drop-down centralized HVAC unit in the center of the garage?
Yes, mini splits offer "A" or flat coil options for installs on a duct, but it defeats the purpose of having their self-contained (evaporator, aux heating coil, and blower) head units installed on a wall.
Or get a 3-tonne single wall-mounted head being driven by a heat pump and perhaps plan on having an aux oil or natural gas Modine heater.

 

[ducatithunder]

Why don't you install a conventional and drop-down centralized HVAC unit in the center of the garage?
Yes, mini splits offer "A" or flat coil options for installs on a duct, but it defeats the purpose of having their self-contained (evaporator, aux heating coil, and blower) head units installed on a wall.
Or get a 3-tonne single wall-mounted head being driven by a heat pump and perhaps plan on having an aux oil or natural gas Modine heater.

Ceiling is insulated and finished. Opening it up to install a drop unit is not an option. Also there is a 8ft fan in the center of the garage. Just to either side of the fans reach is a 4 post and 2 post car lift.

I'm not a fan of the wall mounts. Given they work very well, Im after a certain "cleaner" look. I have a ton of wall space for dealer signs etc.
I like the idea of a heat pump based on simplicity and space. In hindsight I could have blocked out a corner for a conventional stacked HVAC but I think it would have been a wasted space. Worse case I can do a wall mount but I want to pursue the exposed duct split first.

I guess my question is if anyone has done something similar and if so did it work well? My other question is would ductwork 10ft off the deck worth on distribution of the conditioned air instead of a short cycle. I think the large 8ft fan would distribute the air well, but IDK.

 

[kaymccampbell]

They make ceiling mount mini split cassettes. You could put it right up there next to the BAF. Then all you'd need would be a longer lineset and a decorative line duct.

 

[ducatithunder]

They make ceiling mount mini split cassettes. You could put it right up there next to the BAF. Then all you'd need would be a longer lineset and a decorative line duct.

I just googled the cassette split. From my quick google search they are to big. The joist spacing is 12OC with a 30ft clear span. This is likely not an option based on the building specs. This suggestion did lead to finding a ductless hanging mini split unit. Thanks.

 

[Steve W.]

I just googled the cassette split. From my quick google search they are to big. The joist spacing is 12OC with a 30ft clear span. This is likely not an option based on the building specs. This suggestion did lead to finding a ductless hanging mini split unit. Thanks.

How far does your fan hang below the ceiling. The ceiling cassette mentioned was likely a 24x24 unit, which you said would not fit between your joists. What about adding a (decorative?) box between the ceiling and the fan? That would still centralize your conditioned air source, so it would spread around the room.

My shop is about half the size of yours (24x30), and I have been considering a Pioneer unit that can be mounted as a floor console or hung from the ceiling. Since you 'found' something somewhat similar, maybe consider two of them mounted near one wall?

Floor/Ceiling Mounted

www.highseer.com

.

 

[Yankeefarmer]

What you propose should work just fine- it’s very similar to my 26 x 48 x 15 shop in my avatar. I use a Mr Cool Universal with an L shaped duct arrangement. Based on my experience, you’d be fine with their 2-3 ton Universal model in MD. Mine is 5 ton for heating in New England, and it works wonderfully.

My air handler is standing on the floor and is not objectionable in terms of floor space occupied. You could mount the air handler on the wall if desired. I went with the floor configuration because I wanted to draw return air from the floor area for heating purposes.

Edited to add photo where the install is mostly visible.

 

[theoldwizard1]

Ducted or cassette mini-split air handler lose a LOT of efficiency.

Obviously more expensive, but multiple air handlers will give you better results.

 

[ducatithunder]

What you propose should work just fine- it’s very similar to my 26 x 48 x 15 shop in my avatar. I use a Mr Cool Universal with an L shaped duct arrangement. Based on my experience, you’d be fine with their 2-3 ton Universal model in MD. Mine is 5 ton for heating in New England, and it works wonderfully.

My air handler is standing on the floor and is not objectionable in terms of floor space occupied. You could mount the air handler on the wall if desired. I went with the floor configuration because I wanted to draw return air from the floor area for heating purposes.

Edited to add photo where the install is mostly visible.

Thanks for this. Do you mind posting some specs of the ducting?

 

[Yankeefarmer]

Thanks for this. Do you mind posting some specs of the ducting?

There’s no real specs. I used the 1600 cfm rating of the air handler from Ingram’s web site, then looked up appropriate sizing for round ductwork. Since I was splitting the flow two ways, that meant 18” for the main plenum and 14” for each of the two branches. I couldn’t get any local HVAC suppliers to quote me on any of the materials (because I‘m not a licensed HVAC co), so I bought everything on line. Home Depot had the best price on the 14” round duct, which I ordered online and got free delivery to my local store, IIRC.

I didn’t see any point in spending extra for spiral welded pipe over the simple round duct, and I’m happy with my choice. I spent a little under $5k for everything.

 

[ducatithunder]

There’s no real specs. I used the 1600 cfm rating of the air handler from Ingram’s web site, then looked up appropriate sizing for round ductwork. Since I was splitting the flow two ways, that meant 18” for the main plenum and 14” for each of the two branches. I couldn’t get any local HVAC suppliers to quote me on any of the materials (because I‘m not a licensed HVAC co), so I bought everything on line. Home Depot had the best price on the 14” round duct, which I ordered online and got free delivery to my local store, IIRC.

I didn’t see any point in spending extra for spiral welded pipe over the simple round duct, and I’m happy with my choice. I spent a little under $5k for everything.

Thanks!

 

[Jackfre]

Be careful with the amount of duct you put on a ducted mini evap. They have increased the static some but they don’t have a great deal of ability to move air through ducting. Make sure you are right if you go this way. I would look at a unit like a 36k suspended unit. Fujitsu makes one and I have good luck with it in a lot of locations.