Will 24k mini split be large enough?

[GRivera]

I have a 30x40x12’ pole barn/work shop with scissor trusses - so center of ceiling is about 14’. The garage door is 8x18’ and insulated. Will be insulated with R38 ceiling, R19 walls. Will also have 2 - 60” 10k cfm ceiling fans. I just want to break chill in winter (60-65 deg) and make it tolerable in summer (78). In Maryland where low temps Dec-Feb can be 32 and high temps Jul-Aug can be 87. I only have a 100 amp panel to also operate a lift (30 amp breaker, large compressor (40 amp breaker).

Ingram’s recommends a 36k unit but it uses a 35 amp breaker and is $1k more than the 24k unit which uses a 25 amp breaker. I don’t mind supplementing with a kerosene heater but hope I don’t have to. If I do, will the Mini split pull moisture out?

 

[Fueler]

I have a 36 on a 40x40x12 but that is neither here or there.
Some things to consider.
1: While it may have a 35 amp rating it does not draw that much. That is more like if it happens to electrically jam up for whatever reason. Even if it took that much on the first fire up it uses way less in operation.

2: It is extremely unlikely that even though your compressor is the big draw always that all three things hit their maximum at the same time.
3: You will need the supplemental heat if it gets wicked cold. There is a limit to what these minis can withstand. Note that this is compounded if the outside unit it is exposed to open territory and prevailing winds. If other buildings (like located within a town) block/break up the wind then the problem is greatly reduced.

4: With your insulation goals the 24 will likely be fine. Particularly if you install a ceiling at the 12 ft level. If no ceiling and you have the money I would go for the 36. After a few years use I have not regretted it.

 

[strutaeng]

I have a 30x40x12’ pole barn/work shop with scissor trusses - so center of ceiling is about 14’. The garage door is 8x18’ and insulated. Will be insulated with R38 ceiling, R19 walls. Will also have 2 - 60” 10k cfm ceiling fans. I just want to break chill in winter (60-65 deg) and make it tolerable in summer (78). In Maryland where low temps Dec-Feb can be 32 and high temps Jul-Aug can be 87. I only have a 100 amp panel to also operate a lift (30 amp breaker, large compressor (40 amp breaker).

Ingram’s recommends a 36k unit but it uses a 35 amp breaker and is $1k more than the 24k unit which uses a 25 amp breaker. I don’t mind supplementing with a kerosene heater but hope I don’t have to. If I do, will the Mini split pull moisture out?

Yeah, the 24kBtu should work fine for those desired temperatures. I've got a space 22'x66'x17'high. Insulation is like yours, plus R5 rigid on walls, but I don't think that would make a huge difference. I've got a 22,000 Btu window shaker and has kept 75F even in 100F outdoor temperature all summer. I have a shop ceiling fan with 5' downrod. Will eventually install a second fan.

Window AC was temporary. I just ordered a 24kBtu mini split for permanent setup. Just locate it in the middle of the space, and should work.

 

[GRivera]

Thanks for responding. I will have a ceiling but it will follow slope of scissor trusses 2/12 pitch 12’ walls and 14’ peak.

 

[strutaeng]

If you don't mind the window shaker, it will save some money. Here's unit I'm currently running:

https://www.homedepot.com/p/LG-Elec...oner-with-Remote-Control-LW2217IVSM/309646824

It's an inverter like mini-split. No heat, though.

I've got a detached garage 25x25x12. I'm going to install it there eventually. I've got natural gas heater, so this is fine.

 

[MattT]

I have a 30x40x12’ pole barn/work shop with scissor trusses - so center of ceiling is about 14’. The garage door is 8x18’ and insulated. Will be insulated with R38 ceiling, R19 walls. Will also have 2 - 60” 10k cfm ceiling fans. I just want to break chill in winter (60-65 deg) and make it tolerable in summer (78). In Maryland where low temps Dec-Feb can be 32 and high temps Jul-Aug can be 87. I only have a 100 amp panel to also operate a lift (30 amp breaker, large compressor (40 amp breaker).

Ingram’s recommends a 36k unit but it uses a 35 amp breaker and is $1k more than the 24k unit which uses a 25 amp breaker. I don’t mind supplementing with a kerosene heater but hope I don’t have to. If I do, will the Mini split pull moisture out?

24K should be more than enough for cooling, probably oversized if anything. Maybe not enough for heat though. Your 32* low number looks off to me. I'm not real familiar with the Baltimore area but I'd expect a heating design temp in the low 20s.

Don't worry about maxing out your 100A panel. If your compressor & lift are breakered correctly they won't be drawing close to the breaker capacity except momentarily when starting. So you could go to 36K if you want, but I wouldn't. Or add supplemental electric heat for less than a grand if it turns out you need it. No need to use kerosene for supplemental heat and no the mini split won't remove the moisture it puts out. They only remove moisture when cooling.

If you don't mind the window shaker, it will save some money. Here's unit I'm currently running:

It's an inverter like mini-split. No heat, though.

I've got a detached garage 25x25x12. I'm going to install it there eventually. I've got natural gas heater, so this is fine.

That would almost certainly cost the OP more. Between the installed cost of a heating solution and likely higher running costs.

 

[fitter30]

When minis are in heat and they go into defrost mode there is no heat coming from them till they come out of defrost 15-25 minutes.

 

[Fueler]

When minis are in heat and they go into defrost mode there is no heat coming from them till they come out of defrost 15-25 minutes.

Yup, there is that.
I keep my shop pretty much at the same temp year round.
No rust anywhere as a result.
Found it cheaper in the long run as opposed to reducing it at night.
As noted before a kerosene anything will fill the place with moisture and stink.

I have overhead propane tube heater as backup.
I fiddled with both thermostats so it kicks in if the mini fails to keep up.
That does happen when it gets in the 20s and the winter winds pick up.
A 200 acre field to the north of me does not help things.
Hence the need for backup, especially during the day when I am working.

It is cheaper if I run the mini as much as possible over the tube heater.
My propane guy can't figure out why I am using so much less over the winter.
Guess he works on commission. Too bad, so sad.

 

[dcg9381]

I'm in TX. 60x40x16 building. R15 walls, R17 ceiling. 3 x 14x14 insulated doors.
We cool with 2 x 24K BTU units (Daikin). They run off 20A breakers (actually off of 15A breakers currently).
They'll cool, but will lose ground when it hits triple digits.
For Baltimore, I'd expect that 24K BTU would be fine.
My cost on these was around $2400 for both units. It may be more economical to "split" units up.

 

[GRivera]

I'm in TX. 60x40x16 building. R15 walls, R17 ceiling. 3 x 14x14 insulated doors.
We cool with 2 x 24K BTU units (Daikin). They run off 20A breakers (actually off of 15A breakers currently).
They'll cool, but will lose ground when it hits triple digits.
For Baltimore, I'd expect that 24K BTU would be fine.
My cost on these was around $2400 for both units. It may be more economical to "split" units up.

Great info- thanks. How high on walls did you install the air handlers?

 

[outdoorspace]

Cooling will be no problem with 24k. Heating is another story, and this will depend on the specs of the particular unit you get, but 24k is probably not enough. Check the BTU spec at your design temps.
Personally I would not consider supplementing with kerosene heat.

My walls are 16' and I installed the indoor unit at 9'.

 

[Bert_]

Breaker size means absolutely nothing. Motor loads often have the breaker sized 2x or more than the actual current draw.

Example a 5 horse compressor would often be put on a 50 amp breaker. Most only draw 22 to 23 amps.

 

[outdoorspace]

My 24k mini split has a 25A breaker (and 12 ga wire). I measured the draw at 9A running full out.

 

[dcg9381]

Great info- thanks. How high on walls did you install the air handlers?

I installed them at about 8'. They have "directional" vents and about 12' away from them I have a couch...

Note, in a 16' building in Texas, there is big temperature difference between the eve and the floor..

These have (in the manual) minimum set-backs required from the ceiling and sides. But I'd set them to "point at" what you want cooled (if there is such a thing).

 

[polizei1]

My 24k mini split has a 25A breaker (and 12 ga wire). I measured the draw at 9A running full out.

DIY manual calls for 10awg on the 24k. I used 10/2 on a 30A breaker. At least HD/Lowes don't sell 25A breakers for my (new) box.

 

[fatjay]

I just installed a 24k btu mini split on my first floor. AC only, no heat. I heard that they're very inefficient in the heating department, I already have a wood stove, fireplace, and oil furance, so $300 saved.

I paid $900 on ebay for an innovair 24k btu. The compressor was pre-charge, so I just had to run the lines, electrical, vacuum the lines, then release the freon.

My first floor is a living room, dining room, kitchen, foyer, and den, pretty decent sized. When I first fired it up it was 85F. In 30 minutes it was 75F, and shortly there after it was 70F when it was 92F outside. I couldn't be happier. Very easy to install myself, watched a few youtube videos documenting it.

 

[MattT]

I just installed a 24k btu mini split on my first floor. AC only, no heat. I heard that they're very inefficient in the heating department, I already have a wood stove, fireplace, and oil furance, so $300 saved.

If you are burning oil in cool weather, when it isn't cold enough to light the wood stove, then a heat pump would likely save you way more than $300 over the life of the unit. Even below freezing it'd likely be cheaper than burning oil.

 

[outdoorspace]

DIY manual calls for 10awg on the 24k. I used 10/2 on a 30A breaker. At least HD/Lowes don't sell 25A breakers for my (new) box.

My unit is an ECOX 22 SEER model heat pump. Different units will have different requirements.

My example was showing that the full load current is often not close to the circuit breaker rating.

 

[polizei1]

My unit is an ECOX 22 SEER model heat pump. Different units will have different requirements.

My example was showing that the full load current is often not close to the circuit breaker rating.

I thought I was still on the Mr. Cool DIY thread.

 

[GRivera]

I ordered the 24k from Costco for $1589 after tax/free shipping- it arrived this past Monday. I went with Costco over a less expensive vendor due to their unlimited return policy- hopefully I never have to use it.

I plan to use a portable kerosene heater for auxiliary heat.

 

[dcg9381]

Great info- thanks. How high on walls did you install the air handlers?

About 8'. Above that and they are operating in "hot air".

 

[cwbag1]

I am finishing up a 30 x 40 with 10 ft ceilings. Just had it spray foam insulated this week with open cell. I had originally thought I would need the 24k mini split but now am concerned it will be oversized since the workshop will be insulated so well. The 18k is the next size down. I live in San Antonio so heating won't be much of a problem but the brutal summers are a concern. Any thoughts?

 

[dcg9381]

I'm in Texas. I don't know your R values, but my shop is 2400 sqft and with 2 x 24k units, I'm in no danger of over-cooling in the summer. I am taller than you. I'm also open cell insulated, but I have big doors.

The deal is with these inverter based mini-splits - they can throttle down and not have to run at full capacity on/off like a ducted system. Much more OK to over size.

I've installed an 18k in as little as 500 sqft (poorly insulated).

If it was mine, it'd be 24k all day long. Only think better than manual-J is finding the same sized shop, same geography, and asking about the heating/cooling. 18k may work just fine.

The other thing to consider is use case. My shop is really weekend and odd evening only. I don't keep it cooled all the time, so there needs to be enough capacity to bring it down to temp.

 

[Gravedigger]

ANY update ?

 

[GRivera]

I bought the 24k from Costco but ended up returning it and buying a 36k to replace it. The cold weather is my concern. Hope to good install within next 60 days.

 

[wanderer]

It is very common with heat pumps to supplement with electric resistance heat which happens to be very cheap. I would size a load for the cooling load and supplement with an electric garage heater for the few days a year you need more out of your heat pump.

 

[GRivera]

I hope to get mini split installed while still cold out- will be a good test in cold weather.

 

[GRivera]

Ingram’s ships fast! I ordered on 12/13 and received 12/19! Just need time to install! For those who have installed Mr Cool- the hole for The line-set sleeve is supposed to be at a slight angle. Does this result in the sleeve’s flange sitting cockeyed on wall?

 

[shade]

Ingram’s ships fast! I ordered on 12/13 and received 12/19! Just need time to install! For those who have installed Mr Cool- the hole for The line-set sleeve is supposed to be at a slight angle. Does this result in the sleeve’s flange sitting cockeyed on wall?

No it will still fit fine. Double check the drain line coming off the unit. Make sure the clip is tight.
Mine from the factory wasnt very tight and slipped off after a month. I just tightened up the clip by bending a bit.

 

[3rdgendslmech]

Ingram’s ships fast! I ordered on 12/13 and received 12/19! Just need time to install! For those who have installed Mr Cool- the hole for The line-set sleeve is supposed to be at a slight angle. Does this result in the sleeve’s flange sitting cockeyed on wall?

I did mine with a half inch drop through a 6" wall....the outside flange sits flush on the metal ( you have to make sure that it's going to land completely on a flat if you're using ribbed steel. The inside sleeve you can tell is at an angle but mine is going to be hidden by shelves so you wont see it. What I should have done is drilled it straight, put the line into the top and rolled it around a little as it exits.

Anyhow, mine has been working great...on days when its around 35-40 it keeps the temps around 50 degrees....without a ceiling! The couple days it got real cold I didnt stay out there long but used a diesel torpedo heater to warm things up quick and it held about 47 degrees once I shut off the torpedo heater.

I'm wrapping up a few things then I'm going to be putting in foam boards to help keep the heat from going right out the ridge vent.

 

[GRivera]

I did mine with a half inch drop through a 6" wall....the outside flange sits flush on the metal ( you have to make sure that it's going to land completely on a flat if you're using ribbed steel. The inside sleeve you can tell is at an angle but mine is going to be hidden by shelves so you wont see it. What I should have done is drilled it straight, put the line into the top and rolled it around a little as it exits.

Anyhow, mine has been working great...on days when its around 35-40 it keeps the temps around 50 degrees....without a ceiling! The couple days it got real cold I didnt stay out there long but used a diesel torpedo heater to warm things up quick and it held about 47 degrees once I shut off the torpedo heater.

I'm wrapping up a few things then I'm going to be putting in foam boards to help keep the heat from going right out the ridge vent.

Thanks - what size unit and shop? Also, when you say no ceiling, no ceiling or wall insulation? where in Maryland?

 

[3rdgendslmech]

Thanks - what size unit and shop? Also, when you say no ceiling, no ceiling or wall insulation? where in Maryland?

No ceiling or ceiling insulation yet. I've got all but the back wall insulated. 24x32x10 pole barn in Gambrills

 

[GRivera]

Cool- I’m just west of you in Jessup (AA County).

I started the install of the 36k air handler today. I bored the 3.5” hole and it is about 1/2” lower to the outside like yours - the template also has to be slightly off center to land on flat spot between the metal ridges. Was a PITA with long drill bit drifting but got it done. Need a 3rd person to feed the lines through the wall so maybe New Year’s Day. Since I have 12 foot walls with scissor truss ceiling I put the air handler 8 feet up on eave (40’) wall. I plan to run the line along outside wall to the condenser which will be mounted on wall brackets 2 feet off the ground. I will use all the 25’ line as it’s on the long wall.

 

[GRivera]

Installed the air handler and pulled the line set through wall. Once I start installing the hide a line cover I’ll settle on location of condenser unit. My goal is to not have any coiled up line. I will install the 90 degree elbow of the cover just above the wainscoting and do the 20’ horizontal run to end of barn.

 

[Roothawg]

Installed the air handler and pulled the line set through wall. Once I start installing the hide a line cover I’ll settle on location of condenser unit. My goal is to not have any coiled you line. I will install the 90 degree elbow of the cover just above the wainscoting and do the 20’ horizontal run to end of barn.

I am curious why the long run to the unit? Did I miss that somewhere? I am thinking of trying one of these.

 

[MattT]

I am curious why the long run to the unit? Did I miss that somewhere? I am thinking of trying one of these.

The Mr Cool DIY series he's installing comes with a pre-attached 25 foot lineset. Running the line along the outside of the building is an just an easy way of dealing with it.

 

[GRivera]

Installed the hide-a-line cover today. Drilled a hole at bottom of one section for the drain line. Hopefully get to the condenser brackets tomorrow

 

[GRivera]

Installed the wall brackets today. Inside, I added a 6' long 2x6"s, vertically attached to the purlins. The grade 5 bolts go through the 2x6's and out to the brackets. This should help carry the load of the condenser.

 

[SALIV8]

Lookin good!

 

[GRivera]

Thank you