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General Forestry => General Board => Topic started by: gspren on August 13, 2021, 07:41:56 PM

Title: Mini-Split heat pump for room in pole building?
Post by: gspren on August 13, 2021, 07:41:56 PM
  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? 
Title: Re: Mini-Split heat pump for room in pole building?
Post by: 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. 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.
Title: Re: Mini-Split heat pump for room in pole building?
Post by: gspren on August 13, 2021, 10:19:29 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.
Title: Re: Mini-Split heat pump for room in pole building?
Post by: metalspinner on August 13, 2021, 11:27:00 PM
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.
Title: Re: Mini-Split heat pump for room in pole building?
Post by: SwampDonkey on August 13, 2021, 11:39:37 PM
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
Title: Re: Mini-Split heat pump for room in pole building?
Post by: btulloh on August 14, 2021, 12:00:15 AM
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
Title: Re: Mini-Split heat pump for room in pole building?
Post by: gspren on August 14, 2021, 08:48:55 AM
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.
Title: Re: Mini-Split heat pump for room in pole building?
Post by: hedgerow on August 14, 2021, 09:43:44 PM
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. 
Title: Re: Mini-Split heat pump for room in pole building?
Post by: peakbagger on August 15, 2021, 05:44:33 AM
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.
Title: Re: Mini-Split heat pump for room in pole building?
Post by: Al_Smith on August 15, 2021, 08:14:41 AM
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 . 
Title: Re: Mini-Split heat pump for room in pole building?
Post by: Al_Smith on August 15, 2021, 08:38:21 AM
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---- 
Title: Re: Mini-Split heat pump for room in pole building?
Post by: scsmith42 on August 15, 2021, 08:28:28 PM
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.  


(https://forestryforum.com/gallery/albums/userpics/13296/Tool_cabin_C.jpg?easyrotate_cache=1629072770)




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.


(https://forestryforum.com/gallery/albums/userpics/13296/minisplit_outside_unit.jpg?easyrotate_cache=1629072814)



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.


(https://forestryforum.com/gallery/albums/userpics/13296/Lathe_in_cabin.jpg?easyrotate_cache=1629072884)



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.

Title: Re: Mini-Split heat pump for room in pole building?
Post by: 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.
Title: Re: Mini-Split heat pump for room in pole building?
Post by: beenthere on August 15, 2021, 10:07:09 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.
Title: Re: Mini-Split heat pump for room in pole building?
Post by: John Mc on August 15, 2021, 11:11:02 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.
Title: Re: Mini-Split heat pump for room in pole building?
Post by: Texas Ranger on August 15, 2021, 11:49:28 PM
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.

Title: Re: Mini-Split heat pump for room in pole building?
Post by: scsmith42 on August 16, 2021, 06:05:40 AM
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. 
Title: Re: Mini-Split heat pump for room in pole building?
Post by: gspren on August 16, 2021, 08:44:41 AM
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.
Title: Re: Mini-Split heat pump for room in pole building?
Post by: John Mc on August 16, 2021, 08:52:07 AM
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.
Title: Re: Mini-Split heat pump for room in pole building?
Post by: gspren on August 16, 2021, 08:59:38 AM
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. 
Title: Re: Mini-Split heat pump for room in pole building?
Post by: aigheadish on August 16, 2021, 10:15:14 AM
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...
Title: Re: Mini-Split heat pump for room in pole building?
Post by: Al_Smith on August 16, 2021, 10:20:40 AM
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 .
Title: Re: Mini-Split heat pump for room in pole building?
Post by: doc henderson on August 16, 2021, 10:25:26 AM
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.  :)
Title: Re: Mini-Split heat pump for room in pole building?
Post by: Texas Ranger on August 16, 2021, 11:06:14 AM

(https://forestryforum.com/gallery/albums/userpics/10007/aaaaapickup.JPG?easyrotate_cache=1629126201)



(https://forestryforum.com/gallery/albums/userpics/10007/aaaaapickupa.JPG?easyrotate_cache=1629126338)
Title: Re: Mini-Split heat pump for room in pole building?
Post by: Tom King on August 16, 2021, 07:12:20 PM
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.
Title: Re: Mini-Split heat pump for room in pole building?
Post by: Texas Ranger on August 24, 2021, 03:37:46 PM
Addendum:  Put a serge suppressor in the line .  I found out the hard way.
Title: Re: Mini-Split heat pump for room in pole building?
Post by: gspren on August 24, 2021, 05:22:00 PM
Addendum:  Put a serge suppressor in the line .  I found out the hard way.
While surge suppressors can save a problem they can only handle so much, when the neighborhood had a major surge a few years ago those that had whole house protection got to add the cost of burnt out surge protectors to everything else, still blew out the modern appliances, tvs etc. only the old pre computer refrigerators that some of us had in our garages survived.
Title: Re: Mini-Split heat pump for room in pole building?
Post by: Tacotodd on August 24, 2021, 07:24:54 PM
The “surge” suppressors that I was thinking of were for a different kind of surge ;) NOW you know where I’m at, at least in my mind ;D
Title: Re: Mini-Split heat pump for room in pole building?
Post by: Larry on August 24, 2021, 09:58:36 PM
I got a bid on a Samsung 18k btu Single Zone Mini Split for the shop last week.  $3,800 seems high to me.

Right now I AC with a 18,500 btu window unit in 1,500 square foot well insulated tight shop.  Heat is 24/7 from a Vermont Castings wood stove.  First window unit lasted 7 years and I'm about that far along on the one I'm using now.  They work well and not much cost.

Still I would like to explore a mini split.  Have to contact a few more HVAC guys.  I'm also not afraid of a DIY unit. 
Title: Re: Mini-Split heat pump for room in pole building?
Post by: peakbagger on August 25, 2021, 09:13:44 AM
I installed my own Mitsubishi cold climate mini split but paid a tech to pump out the lines and charge the unit. It took them about 2 hours and charged me $250. It they had installed it complete it would have been about $2000. The Mr Cool units they sell at Costco reportedly come with precharged lines so its just plug and play (but the efficiency is lower than the name brands).
Title: Re: Mini-Split heat pump for room in pole building?
Post by: SwampDonkey on August 25, 2021, 02:32:52 PM
Still I would like to explore a mini split.  
Up here you won't get one for less than $6500 installed. That puts the brakes on the deal pronto. :D
Title: Re: Mini-Split heat pump for room in pole building?
Post by: Crusarius on August 25, 2021, 02:56:22 PM
3 zone unit for my house installed to replace the failed one is 15k. that is a 3.5 ton Gree unit. After this year, its worth every penny!

Of course install is scheduled for october sometime. 
Title: Re: Mini-Split heat pump for room in pole building?
Post by: Downstream on August 25, 2021, 10:26:35 PM
I just started researching these for my 24x24 detached workshop.  The MrCool units seem pretty easy to install and do not need ac tech to charge lines.  Has anybody installed these or another brand that was pre-charged?  Also the 12k btu ones say up to 500 sqft for heating and cooling so once again has anyone used that size for their 24x24x8 ceiling building?  I will be insulating the walls, ceiling, and garage door.
Title: Re: Mini-Split heat pump for room in pole building?
Post by: Crusarius on August 25, 2021, 10:28:45 PM
Be careful with the self install ones if you care about a warranty. There is fine print saying no warranty if you install it yourself on some of the units.
Title: Re: Mini-Split heat pump for room in pole building?
Post by: petefrom bearswamp on August 26, 2021, 07:29:28 AM
Mini split in the house, kind of a brand x I went with cause the company is in the US.
The system is of course imported from china.
Self installed, professionally charged.
Use it for AC only.
Have had 2 issues with it, the first mice got on the main board and built a nest causing it to fail.
$300 bucks later it ran OK for 2 seasons.
I took all the sheet metal off and mouse proofed it.
It now has been down about a month, the other board fried.
Part on order until late Aug, early Sept.
Probably wont have it operational until AC season nearly over.
Warrantee long gone with no issues.
My well insulated shop 32x56x 10' ceiling 4" concrete floor with no AC would stay cool but very high humidity.
Put a room dehum in and it now stays from 68 to 72 degrees with humidity around 40.
The unit runs continuously and I have no idea how long it will last.
cost about 275 bucks and I can buy a bunch of these as needed before it reaches the cost of a mini split system.
At my age the mini split is not cost effective.
I had thought about another self installed Mitsubishi system from AC direct costing about $3500 or so, but the dehum is working just fine with no great rise in elec cost.
My heat comes from a 55 gallon drum stove.

Title: Re: Mini-Split heat pump for room in pole building?
Post by: Larry on August 26, 2021, 11:14:53 AM
The MrCool units seem pretty easy to install and do not need ac tech to charge lines.  Has anybody installed these or another brand that was pre-charged?
Along about 1980 I walked into the local Sears Roebuck store.  Remember them?  I gave them the size of my house, window location, and insulation.  They figured out the size central air conditioner I would need.  Gave them some money and walked out with a central air conditioner, A-coil for my furnace, thermostat, and pre-charged lines.  A week later I was cool doing all the work myself with no experience.  Sears sent out a HVAC guy about a month later to check out my work.  Think he added a little Freon and that was it.

So, the DIY technology is not new, and I suspect its improved.  I would think a mini-split might take half a day to install.

 
Title: Re: Mini-Split heat pump for room in pole building?
Post by: hedgerow on August 26, 2021, 04:41:52 PM

Along about 1980 I walked into the local Sears Roebuck store.  Remember them?  I gave them the size of my house, window location, and insulation.  They figured out the size central air conditioner I would need.  Gave them some money and walked out with a central air conditioner, A-coil for my furnace, thermostat, and pre-charged lines.  A week later I was cool doing all the work myself with no experience.  Sears sent out a HVAC guy about a month later to check out my work.  Think he added a little Freon and that was it.

So, the DIY technology is not new, and I suspect its improved.  I would think a mini-split might take half a day to install.

 Over the years I have repaired a ton of these type of units. Those screw together connections start leaking on the high side and leak the charge out. We just cut the screw type connections out and solder in new connections add a filter, pump the system down and charge back up and your back cooling again. A lot of mobile and modular homes around hear had this type of units installed in them.  
Title: Re: Mini-Split heat pump for room in pole building?
Post by: petefrom bearswamp on August 27, 2021, 11:28:46 AM
Larry, took my friend and I a half day as you stated above
That was just putting the units in place and connecting the lines.Had an electrician friend hook up the electric end, took him an hr and a half.
Title: Re: Mini-Split heat pump for room in pole building?
Post by: scsmith42 on August 29, 2021, 01:29:42 PM
To my knowledge all of the mini-split units come pre charged with Freon. With respect to DIY installation, The issue is not so much charging them as it is the need to remove all of the air and purge any moisture out of the line set.

Charging them is a simple matter of opening both valves on the compressor / condenser unit to let the Freon into the rest of the system.

All things being equal, a system that has been properly evacuated (draw a vacuum) after installation will cool better than one that was not.
Title: Re: Mini-Split heat pump for room in pole building?
Post by: Tacotodd on August 29, 2021, 10:58:22 PM
29.5” of mercury for a minimum of 30min is supposed to be the shiznit, at least that’s what “I” was taught in our automotive ac classes that I was “allowed” to attend :D
Title: Re: Mini-Split heat pump for room in pole building?
Post by: metalspinner on September 21, 2021, 09:07:41 AM
Mine is up and running! This was installed by my HVAC guy and inspected by the city. 

A mechanical inspector and the electrical inspector came out to look. This was installed on a 20 double pole breaker. But the electrical inspector made him change it to a 15 amp double pole. 

 I wanted the outside unit up high so it would be out of the way. It is amazingly quiet. 

This room is about 400 sq/ft. 


(https://forestryforum.com/gallery/albums/userpics/12750/E2D9F526-ECFA-4833-BC90-C86D011B32C5.jpeg?easyrotate_cache=1632229527)
 


(https://forestryforum.com/gallery/albums/userpics/12750/5970FC7B-1CB9-4DA1-B3D4-42C268E1422A.jpeg?easyrotate_cache=1632229528)
 


(https://forestryforum.com/gallery/albums/userpics/12750/A56100DD-4F36-47F4-969E-92183FCDECE9.jpeg?easyrotate_cache=1632229564)