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Mini-Split heat pump for room in pole building?

Started by gspren, August 13, 2021, 07:41:56 PM

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gspren

  There's some talk about mini-splits in another thread but I have a different situation so I'll start my own. In the back corner of my new pole building I plan to build a 12'x24' room that will be my man-cave hangout with a workbench and just a place for tinkering and hiding from "her" during the day. No water to freeze or need to heat/cool all of the time but heat to mid 60s or so in winter and cool to mid 70s in summer would be nice, in extreme weather I could just stay in the house. Is a mini-split practical? 
Stihl 041, 044 & 261, Kubota 400 RTV, Kubota BX 2670, Ferris Zero turn

farmfromkansas

Mini split systems are supposed to be very efficient. Think I would double your shop space before you get it done and find it too small. Would affect your heating cooling if you have to add space.  Wood stove is great in winter, and you can get a mini split that is just AC.
Most everything I enjoy doing turns out to be work

gspren

Quote from: farmfromkansas on August 13, 2021, 07:48:51 PM
Mini split systems are supposed to be very efficient. Think I would double your shop space before you get it done and find it too small.
This is not for the main shop, just a room within, the main building at 46' x 64' will be the "shop" for both storage and working on stuff. I want an easy to heat/cool room for taking a break or just messing with little stuff like cleaning guns and sharpening chains, etc.
Stihl 041, 044 & 261, Kubota 400 RTV, Kubota BX 2670, Ferris Zero turn

metalspinner

Is it practical? What's your other option? A window unit?

I am in the same situation as you. My pole building is 40x60 and I made a room 10x40 that I'm installing a mini split for both heat and air. Its supposed to be very efficient. We'll see, I guess.
The one I'm having installed is good for up to 600sqft. But your space is half that.
I do what the little voices in my wife's head tell me to do.

SwampDonkey

If you're after AC mostly a modern AC unit in a window is way cheaper to buy and cheap to run. I have an 800 sq foot one, as big as you can get on a 110 outlet. And doesn't add $40 to the electric bill per month. A dehumidifier takes more juice to run continuous. Up here in winter at below zero a minisplit will really struggle compared to a wood stove. We had a large heat pump for the other house, they install an electric furnace along with it. $10,000 later. That should tell ya something. I never want to see another one again. :D
"No amount of belief makes something a fact." James Randi

1 Thessalonians 5:21

2020 Polaris Ranger 570 to forward firewood, Husqvarna 555 XT Pro, Stihl FS560 clearing saw and continuously thinning my ground, on the side. Grow them trees. (((o)))

btulloh

I've got a 12x24 standalone building insulated with R13 batts in ceiling and walls and it's pretty tight too.  Small window unit mounted in a cutout in the wall and a simple strip  heater with a fan that mounts between studs.  No problem getting it warm or cool.  The a/c is one of the newer units and is really efficient. The strip heater is what it is, but it supplies plenty of heat for the space. 2000 watt if i recall. I just use that space for reloading and a few other things like that. Less than $400 in the combo, and hardly a tickle on the electric bill. Just occasional use, but in the summer I'll keep it around 80 and turn it down if I'm going to be working in ther
HM126

gspren

I'm considering different options, need to ask insurance people about wood stove wouldn't want to go through the work and expense of putting in a stove and then paying too high of a premium to use it. I've also thought of the window A/C mounted on one of my interior walls exhausting into the main shop with a bucket to catch condensate and a small propane heater. This will not be used every day, just occasional use.
Stihl 041, 044 & 261, Kubota 400 RTV, Kubota BX 2670, Ferris Zero turn

hedgerow

I like mini splits and have put a lot of them in. Mostly for upstairs in two story houses. Don't forget to give the PTAC units a look will be less than a mini split. I have installed a lot of them in your type of applications. 

peakbagger

Its good application, especially if its sealed up from the rest of the building. Costco sells units with precharged lines that have a good rep. No need to hire an installer.  Not as efficient as the name brand units but still a lot quieter and more efficient than a window unit. Where any minisplit has issues is much below 20 F. Yes it will put out heat but it has rough time heating up a cold space. 

The tradeoff is they are not cheap compared to window unit but if you want heat hard to beat.

Al_Smith

I think for efficiency you have to factor in insulation and control of humidity for both heating and cooling .A little bit of insulation can save you a lot money over the long term .Otherwise you are just paying out a lot of fuel charges that could be avoided .For heating you might look into infrared heaters and just go with regular air  to air  air conditioning  for cooling rather than with the heat pump option which are not very good at temps below 40 degrees . 

Al_Smith

I might add a little bit to the conversation .Recently my long term tenant on my rental passed away suddenly .Unknown to me the furnace plus the air conditioner were on the fritz .Somebody again unknown to me had replaced the blower motor and reversed the rotation .This threw the furnace into a high fire condition and cooked the compressor on the air . I had it figured out in about 10 minutes but it still cost me nearly $900 for a new 2 ton air unit .He had  two mini splits heating and cooling the house and never told me the problem for some reason .Plus the dehumidifier was out of commission and that caused a moisture problem in the basement which could have been prevented by a phone call .HVAC is not rocket science but it is  surprising the amount of people who have no idea of actually how it works .To get the most out of it you have to stay on top of it .---they  say a stitch in time saves nine---- 

scsmith42

I have two mini-split heat pumps in use here on the farm.  One is in a building that measures around 14' x 40', and the other is in a log cabin that measures around 18' square with a 12' wall height.

The 14 x 40' building is used by my wife's non-profit Veterinary practice as the inventory building.  It has a Mitsubishi unit with a ceiling cassette instead of a wall mount.  It works great; is extremely quiet and very effective.  This building has a tankless water heater inside it along with a stacked commercial washer and gas dryer, and the minisplit keeps up even with the heat generated by the commercial dryer.  Mitsubishi M series mini-splits have one of the best reputations in the industry.  We used to use them when we had to build a cell site inside a commercial building and were too space limited for a standard split HVAC unit.  The Mitsubishi units were the only ones that would last in that environment.

The log cabin has a Pioneer unit.  I use this building as a tool shed and machine shop.  It too works well but is not in the same league as the Mitsubishi.  It takes longer for the Pioneer to recover if the door is left open, and it does not do as well heating in the winter as the Mitsubishi, but it's still acceptable.  However the Pioneer was a $1000 unit versus $3k for the Mitsubishi, so I'm willing to cut it some slack!

Myself and my farm hands did both installations.

Below is the log cabin installation.  







Here is the condenser unit mounted on the back side of the cabin.  I painted it brown to blend in better and used wall mount brackets that are designed for mini-splits.  The box covers where the condensate drain and refrigerant lines exit the cabin wall.  The lower pipe is the drain; the upper pair is the refrigerant.






Here is a pic taken inside the cabin.  In addition to keeping the cabin nice to work in, the dehumidification features of the mini-split prevent rust build up on my tools and tooling, which was a significant factor in replacing the previous window AC unit with a mini-split heat pump.  The window unit was not cutting it in terms of dehumidification inside the cabin.






Both units are highly energy efficient, and a mini-split would be my first choice for the situation that you're in.  By all means insulate the room as well as you can; you will reap the rewards in terms of comfort and energy savings.

Peterson 10" WPF with 65' of track
Smith - Gallagher dedicated slabber
Tom's 3638D Baker band mill
and a mix of log handling heavy equipment.

John Mc

Has anyone seen a cold climate heat pump that will allow a heating set point down around 45˚F or so? My wife has a 24'x26' workshop that get used only occasionally in the winter. Most of the time all we need is to keep paint and other supplies from freezing.

I realize that recovery time isn't exactly the greatest with most heat pumps, but we could always supplement with a space heater if we needed to bring things up quickly.

When I looked a couple of years ago, all we could find were units with set points down to around 60. That's a whole lot warmer than we need to keep the place most of the time.
If the only tool you have is a hammer, you tend to see every problem as a nail.   - Abraham Maslow

beenthere

Quote from: John Mc on August 15, 2021, 09:14:18 PM
Has anyone seen a cold climate heat pump that will allow a heating set point down around 45˚F or so? My wife has a 24'x26' workshop that get used only occasionally in the winter. Most of the time all we need is to keep paint and other supplies from freezing.

I realize that recovery time isn't exactly the greatest with most heat pumps, but we could always supplement with a space heater if we needed to bring things up quickly.

When I looked a couple of years ago, all we could find were units with set points down to around 60. That's a whole lot warmer than we need to keep the place most of the time.
Use a mercury switch thermostat and mount it at an angle so the set point is changed to the degree that you want. Have my shop heater set at 45° for the heat to come on.
south central Wisconsin
It may be that my sole purpose in life is simply to serve as a warning to others

John Mc

Quote from: beenthere on August 15, 2021, 10:07:09 PM
Use a mercury switch thermostat and mount it at an angle so the set point is changed to the degree that you want. Have my shop heater set at 45° for the heat to come on.
I thought most minisplits had the thermostat built-in. If you can use an external thermostat with them, that's a great idea, though it may complicate using the AC in the summer.
If the only tool you have is a hammer, you tend to see every problem as a nail.   - Abraham Maslow

Texas Ranger

I replaced two window units with a split unit in office, 900 sq ft of not heavily insulated slab and metal building, about a year ago.  The split unit is more efficient and provides both heat and cool.  Unit cost $2300 installed, replaced about $800 worth of window units.  Electricity cost went down, humidity went down, and it is quite.  The split units come in different sizes so you can more or less fit your needs.  It has a hand held remote to handle the program, a hand held thermostat if you would.  Mounts on the wall in a holster.  It basically runs an internal fan 24/7 that you can barely hear, out side unit cycles on and off and is not heard inside the building.

I am satisfied it works better and more efficiently than the window units.

Will it pay for itself?  At some point.  But dryer office and uniform temperature is a good results.

The Ranger, home of Texas Forestry

scsmith42

Quote from: John Mc on August 15, 2021, 11:11:02 PM
Quote from: beenthere on August 15, 2021, 10:07:09 PM
Use a mercury switch thermostat and mount it at an angle so the set point is changed to the degree that you want. Have my shop heater set at 45° for the heat to come on.
I thought most minisplits had the thermostat built-in. If you can use an external thermostat with them, that's a great idea, though it may complicate using the AC in the summer.
My Pioneer included a remote control with thermostat. The Mitsubishi has a wall mounted thermostat. 
Peterson 10" WPF with 65' of track
Smith - Gallagher dedicated slabber
Tom's 3638D Baker band mill
and a mix of log handling heavy equipment.

gspren

I'm fairly certain I will go with the mini-split, room will be under 300 Sq Ft and will be easy to insulate. I am more concerned with cooling than heating but I do want both, there will be times in winter where it isn't used for a few weeks while we are away and then when we return I could use a portable propane heater for a few hours at start up.
Stihl 041, 044 & 261, Kubota 400 RTV, Kubota BX 2670, Ferris Zero turn

John Mc

One thing to keep in mind on the portable propane heaters: If a propane heater is not vented, it adds a lot of moisture to a room. If you are just running for an hour or so, or if you have some kind of outside air exchange/ventilation it may not be a big deal. We found out the hard way just how much moisture it can add when we heated my wife's very tightly sealed shop for several very cold days. The walls were dripping.
If the only tool you have is a hammer, you tend to see every problem as a nail.   - Abraham Maslow

gspren

If and when I used the propane it would just be a kick starter to get the room up in the 50s then the mini split would be used alone. I guess next question is size and brand recommendations. 
Stihl 041, 044 & 261, Kubota 400 RTV, Kubota BX 2670, Ferris Zero turn

aigheadish

My shop is about 14'x23' or so and is a drag to heat. I'd love to cool it also but I have a giant set of doors to open that give a nice view. This winter I expect it to be a bit more insulated but last winter it was common to fire up both a propane heater and a kerosene heater. Both got expensive and the room, when it was legitimately cold, never got warm. The room does high a cathedral style ceiling, probably 16-18' high that is uninsulated and the big doors aren't insulated either, so lots of spots for leaking...
New Holland LB75b, Husqvarna 455 Rancher, Husqvarna GTH52XLS, Hammerhead 250, Honda VTX1300 for now and probably for sale (let me know if you are interested!)

Al_Smith

On unvented infrareds I have an old "Ember Glow " propane mounted on a cart that holds a 20 pound propane tank in the bottom .It works just fine in a 24 by 24 garage and will burn about 4 days on a tank full .It's seldom I use it in winter which BTW is not my favorite season of the year but it will crank it up to about 50 degrees after a few hours of run time .It's certainly a better option than trying to work in temps from 10 above to 10 below .Work ten minutes and take 20 minutes to warm back up again, no thank you . I have no desire to live in North Dakota or Alaska  in the winter time .Ohio is cold enough .

doc henderson

My shop has floor heat with a boiler, and after about 4 (not cheap) Lowes widow AC units, I acquired a home unit to install in the shop.  I like the mini splits for a small room.  quiet, efficient, and all in one.  I keep the heat at 55 to 60 in the winter, and start the wood stove when I am working.  I like the idea of tilting the thermostat to get a lower temp (mercury switch).  my shop has a basement and is full insulated.  the shop including the basement is 4500 sq. ft.   many folks I know get the Mitsubishi brand.  the size depends on the room size and insulation.  can be sized by the company selling the unit.  heat pumps do not tend to works at the extremes of temp.  If only we could find things to heat in the summer and freeze in the winter.  :)
Timber king 2000, 277c track loader, PJ 32 foot gooseneck, 1976 F700 state dump truck, JD 850 tractor.  2007 Chevy 3500HD dually, home built log splitter 18 horse 28 gpm with 5 inch cylinder and 32 inch split range with conveyor powered by a 12 volt tarp motor

Texas Ranger

The Ranger, home of Texas Forestry

Tom King

The difference between a mini-split, and a window AC is like riding in a new Cadillac, or a 65 Chevy that's gotten low on Freon.

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