Sizing my Mini Split w/ Heat pump for MI

[NWOhioChevyGuy]

Yes here is another Mini Split sizing thread

Looking at options for supplying my new garage's Attic Space with A/C & Heat

14'x40' w/ 8' ceilings inside the truss's - thus only 8' in center of room.
Will have R30 Insulation, ceilings, side walls and floor, two end walls will be R19. Each end wall has a single double hung window.

This space will be finished off w/ 1/2" sheet rock and utilized as a home office and storage.

Live in Southern MI (right at OH border)
Would like to do a DIY installation

From what I see a 12000btu unit is the correct size, is this correct?
Where would be a good place to source?
Linesets will be run in wall cavity to exterior unit.

See link to my build in signature

 

[shurkai]

I am also installing a mini-split in a new construction...how are you going to run the line-set in the wall cavity? Particularly how will you make the connection to the unit as those usually have ~24" of line extending out.

Thanks

 

[NWOhioChevyGuy]

Those 24" lines will be installed/assembled the same way as if inside the outside "raceway". Just interior to the garage wall.

Outside would look like this. Although my install will be on a pad next to the garage.

 

[shurkai]

Those 24" lines will be installed/assembled the same way as if inside the outside "raceway". Just interior to the garage wall.



Outside would look like this. Although my install will be on a pad next to the garage.

So how do you make that connection behind drywall or similar interior wall finish? Or do you put drywall (wall finish) behind the unit only, leave a stud cavity open, make the connection and put the wall finish on later?

I saw this on another post and wasn’t really sure how he finished it.

 

[NWOhioChevyGuy]

So how do you make that connection behind drywall or similar interior wall finish? Or do you put drywall (wall finish) behind the unit only, leave a stud cavity open, make the connection and put the wall finish on later?

I saw this on another post and wasn’t really sure how he finished it.

Yes the connections would be behind the finished wall in the wall cavity. Line sets and electrical would will be run before wall is finished.

If it concerns you put a piece of plywood over that space, like one would for a shower access panel.

Got thinking more about your question.
In my case the inside cassette will be mounted on a 5' knee wall so access for that line connection will be in the truss webbing behind that wall.

 

[shurkai]

Thanks for he further description.

What I am unsure about is how do I make the connections and then "push" that into the finished wall cavity without kinking the lines or totally messing up the insulation in the wall. That's why I had thought about mounting the cassette on a sheet of drywall, finishing the mini-split install then finishing the wall.

The way you have your installation it seems that's not so much of a concern.

 

[NWOhioChevyGuy]

Looking at one of these two units.

https://senville.com/12000-btu-floor-mounted-mini-split-air-conditioner-heat-pump-sena-12hf-if/

https://senville.com/18000-btu-floor-mounted-mini-split-air-conditioner-heat-pump-sena-18hf-if/

I see comments on NOT oversizing - as too large can cause issues.
On a new construction TIGHT, build properly insulated, would not the 12000BTU unit be sufficient?

Plus - in a room with full 8' ceilings it is 4480 cubic foot of volume, my attic trusses would equate to 4300 cubic foot.

The heat side of things would likely be utilized more here in MI.
These units have a very efficient heat pump so can work down to -22F, which is below our normal lows by 10+ degrees.

 

[ericm]

This is supposedly an easy to use version of the Manual J heat/cooling load calculation: https://loadcalc.net/

there's also a Manual S sizing calculator to be used after you get the results of the Manual J.

 

[PoorUB]

A 12,000 will be fine for cooling. These days most mini splits are inverter units and will run only as hard as they need to. I would see if you can find specs for heating BTU output at various temps. They all will say they will heat down to a certain outdoor temp, but they all fall off performance wise at some point. If it will heat to -22F chances are you will peak out at full output right around zero and fall off from there. At -22F you might be 60% of rated. You may need to over size slightly to get the BTU you want in severe cold. 12,000 might cool it just fine, but you might have only 8,000 BTU available at -22F. Going to a 18,000 and you will have 12,000 BTU at -22F

The other option is to put a small electric baseboard heat strip at each end and use it only if the heat pump doesn't keep up in severe cold.

 

[glennm]

I have that exact floor mount unit in my loft. Here is my install thread

https://www.garagejournal.com/forum/showthread.php?t=469270&highlight=Glennm

I have been using it for a few months and it works great. The comments about falling off at cold temperatures seem to be right, when the temp is down in the teens it works fairly hard but still stays reasonably comfortable. At temps around freezing or higher it is super efficient. The unit makes no noise, is nice looking, easy to install,etc. I have found that the temperature setting is not too accurate, I set it for 66 and it feels like it’s quite a bit warmer than that. I’m sure the AC will be excellent as well. If you have any questions ask away, it looks like your install is very similar to mine!

 

[NWOhioChevyGuy]

I have that exact floor mount unit in my loft. Here is my install thread

https://www.garagejournal.com/forum/showthread.php?t=469270&highlight=Glennm

I have been using it for a few months and it works great. The comments about falling off at cold temperatures seem to be right, when the temp is down in the teens it works fairly hard but still stays reasonably comfortable. At temps around freezing or higher it is super efficient. The unit makes no noise, is nice looking, easy to install,etc. I have found that the temperature setting is not too accurate, I set it for 66 and it feels like it’s quite a bit warmer than that. I’m sure the AC will be excellent as well. If you have any questions ask away, it looks like your install is very similar to mine!

glennm
Your post is the one that got me thinking the floor mounted unit. MUCH easier installation for me as my end walls lack the space to install a wall mount unit as recommended. I like the looks of this and install will be a breeze due to it being on a side wall with service from behind in the trusses.

With the comments on heating capacity above - I may lean towards the 18000BTU unit, so that I don't have to run back up heat as often.

 

[PoorUB]

Get the specifications for the unit you are interested in. My comments on heating output were fairly general, but I believe them to be reasonably accurate.

I sold Gree mini splits and that heating outputs were typical of that brand and also I had compared to Mitsubishi at one time and the specs were similar.

 

[NWOhioChevyGuy]

Get the specifications for the unit you are interested in. My comments on heating output were fairly general, but I believe them to be reasonably accurate.

I sold Gree mini splits and that heating outputs were typical of that brand and also I had compared to Mitsubishi at one time and the specs were similar.

Your numbers look fairly accurate as this is the AHRI Cert for this unit.
https://senville.com/content/certificates/SENA-18HF-AHRI.pdf

 

[PoorUB]

I am not very impressed with the heat output of that unit. It maxes out at 47F and 10,000 BTU at 17F. what is it doing at 0F? or colder?

 

[theoldwizard1]

14x40. You will need 2 air handlers.

 

[NWOhioChevyGuy]

14x40. You will need 2 air handlers.

The office will be at one end of the space, occupying roughly 1/2 of it so 14 x 20. I could care less if the storage space gets "comfortable".

I have yet to decide if I'm doing built in closets, or open shelving. This will make a difference in my load calcs / square footage. If I build them in I will have roughly a 4' x 20' hall from the house to the office space.

I am still finishing the bath & mud room on the garage level, the attic area is after that. Just trying to plan ahead with that part of the project.

 

[BrianPK]

Pioneer mini split. Call them give them your specs and they will recommend a size. EZ install for a do it yourself.

 

[Jackfre]

560 sq ft with a 12k unit will be fine. In ME, NH & VT, we used a 600 sq ft per ton, Rule of thumb. Do the calcs, but don’t go nuts on over sizing. I would strongly suggest that you not put the unit on a pad. Mount it on the bracket you show. The unit will be cleaner and it will drain better in the defrost mode, which it will run in regularly in the heat mode. What can happen, and I have seen this is that in the defrost mode the moisture off the coil can freeze in the bottom of the unit. That ice can build up and damage the fan or simply fault out. I assume you are getting a -20* unit. It will likely have a base heater in it, but you will be happier with the unit hung on the wall

 

[justinjoyal]

Yes the connections would be behind the finished wall in the wall cavity. Line sets and electrical would will be run before wall is finished.

If it concerns you put a piece of plywood over that space, like one would for a shower access panel.

Got thinking more about your question.
In my case the inside cassette will be mounted on a 5' knee wall so access for that line connection will be in the truss webbing behind that wall.

FYI the connections on floor consoles are directly at the unit, not extended behind it or in the wall like a regular wall unit.

Also, for those who may be wondering, you can install a wall unit in such a way that the flare fittings and drain connection end up between the unit and the wall (basically right behind the drain pan), instead of going straight into the wall.

The lineset comes in from the left instead of the right :

 

[metlmunchr]

I am not very impressed with the heat output of that unit. It maxes out at 47F and 10,000 BTU at 17F. what is it doing at 0F? or colder?

Agreed. I'd be surprised if it will do more than 5 or 6 thousand at zero. In the same output range as a 1500 watt electric heater

 

[glennm]

My unit ( same as he is looking at 12,000 senniville floor model ) was installed in December. I am in Ontario and it can be very cold here. On the below zero days it still kept my 640 sq ft space in the mid to low 60s ( 12 ft ceiling ). It did work hard to do that. At freezing temps and higher (32 f) it can easily and quickly heat the area to any temp I want ( too hot). I’m sure the ac will work even better. I am very happy with mine, I would have liked the wifi ability but it’s not necessary and wasn’t available on the floor unit.

 

[Phuckin' Jim]

https://support.senville.com/hc/en-...ing-and-cooling-performance-data-for-my-unit-

 

[dneiding]

I have a 24X40X12 with a 10X16 office on the side. I used https://www.alpinehomeair.com/ . They are super friendly and helpful and will size it for you. I have 36k BTU outdoor unit and three indoor air handlers (two in the shop, one in the office). Two years ago, I also installed three outdoor and six indoor units in my house also from Apline Home Air and have been very happy with them so far.

 

[NWOhioChevyGuy]

I have a 24X40X12 with a 10X16 office on the side. I used https://www.alpinehomeair.com/ . They are super friendly and helpful and will size it for you. I have 36k BTU outdoor unit and three indoor air handlers (two in the shop, one in the office). Two years ago, I also installed three outdoor and six indoor units in my house also from Apline Home Air and have been very happy with them so far.

Thanks for the reference - I will look them up

 

[NWOhioChevyGuy]

Talked to Alpine Home Air and they recommended this unit for my space.
Very helpful.

https://www.alpinehomeair.com/produ...ini-splits/single-zone/blueridge/bmhh18y20fcc