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Community and Q&A

Installing a Minisplit System

JFink | Posted in Mechanicals on

Hi all,
Can editors step out from behind the curtain to ask opinions, too? I’m planning to redo my garage shop this Fall and although my primary heat for the space is a woodstove, I’d love to have some supplemental heating, and cooling in the summer would be great, too. I’m no schlep when it comes to remodeling work, but have never installed or seen a mini split install. Would I be a fool to try the install myself or have the kits gotten streamlined to the point that its basically plug and play, complete with factory-charged units and quick connect line sets, etc?

Let me have it – am I being over ambitious or is this within grasp for a general remodeler?

Edit: I should mention I’ve been an editor at Fine Homebuilding for 9 years, have run my own remodeling company for 7 years, and in terms of mechanicals I’ve done all of my own plumbing and electrical installs, including a gas tankless water heater.

Thanks, Justin

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  1. GBA Editor
    Martin Holladay | | #1

    I haven't done it. As far as I know, the trickiest part is charging the refrigerant line, which apparently requires a vacuum pump. If I were you, I would call local HVAC contractors to see if a contractor is willing to help you if necessary -- if only to charge the line and commission the equipment.


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  2. homedesign | | #2

    Hi Justin,
    I would be inclined to hire a professional.
    There are "Kits" available with pre-charged lines....
    and plenty of do it yourself videos on YouTube.

  3. user-460363 | | #3

    Perhaps a silly question, but have you downloaded and read an installation manual for a proposed unit?

    I think around here you need to have a special license to do the refrigerant charging part, if it needs that.

    If you've installed a gas tankless water heater completely on your own, then how could a mini split be beyond you? Aside from the refrigerant charging.

  4. dsmcn | | #4

    I've been remodeling for almost 40 years, and two years ago I bought a mini split for my rental—confident I could install it myself (fully knowing this would void the warranty). Well it didn't seem to work as it should. So I called around and found that professionals wanted $300–$400 just to re-connect the pre-charged lines. I finally found someone who worked for an HVAC company to come out after hours and do it for less than $100. The next time it got hot, I had to hire a real professional to re-do the work a third time. Maybe I should have made a youtube video of me being an idiot. : -)

  5. jinmtvt | | #5

    If you are internet whizz a little, it is very easy to find quality units at around half price of what dealers charaged intalled ..

    then you have to weight the cost difference of no warranty and equipement cost,
    VS warranty at higher cost.

    I diy because i plan on getting refrid license neway and wanted to get my hand dirty,
    and i had to buy the equipement neway .. so was a simlpe choice on my part
    ( saved near 8000$ on the first 4 installs )

    but if you are to do it only once ..might not be worth it

    minimum tools required :

    - torque wrench ( open type or adapter ) ~ 80-100$ for a pro kit
    - vacuum pump and lines /adapters ( ~ 200$ ebay ..~400$ pro pump )
    - vacuum gauge ( digitals ~150$ ...dial ones you can get when buying a pump kit with manifold )
    - thread sealer ( MUST ) 10$

    you will need to purchase pre flared line sets and live with the extra length

    disconects ( 60A siemens @ HD usually runs under 30$ )

    Best way to check out flare connection leaks is bubble soap ,
    if bubbles pop up u tighten a little bit more the flares.

    At worst u'll need a tech guy to fixe up things. .probably under 300-400$ call

  6. Expert Member
    Dana Dorsett | | #6

    If you have installed and commissioned a split-system air conditioner or heat pump a mini-split installation is a walk in the park.

    If you haven't, you have to buy the tools and pay close attention to the instructions. There are lower cost tools for doing the one-off job that a pro reefer tech would never want to own, but even with those the cost-adder is usually more than what it takes to get a qualified tech to come out an do it right, preserving the warranty, and somebody to call back should it not be working well enough.

    While 95% of the job can be done by decently handy person, it can still be worth the up-charge to pay somebody who has the experience and tools to take the final commissioning step.

    The pre-charged line sets can work fine, and is the most common way to install them in the third-world. But pre-charged line sets don't always have exactly the right volumes, and any leakage issues with the initial installation can reduce it even further. I know of one such DIY in WA (IIRC it was an LG) where the line set had (apparently) lost nearly all the charge prior to installation. The think kinda-worked, but at a heating COP of about 1 at 40F outdoor temps, which means the same performance could have been had with a $100 worth of baseboard. Unable to diagnose it himself, he hired an incompetent refrigeration tech to help him out, who couldn't figure it out either, but since it happened to be one of the NEEA Northwest Ductless Program test installations, an engineer from Ecotope whose job it was to measure the performance pointed him in the right direction, and he eventually got it running hiring yet another refrigeration tech to fully charge and test it. YMMV.

    For a mini-split that you only intend to use intermittently in a garage there's nothing wrong with going with a cheap third-tier no-name mini-split and precharged line sets. Odds are good that it'll work-mostly if you pay attention to the details. (If it usually works for folks in Afghanistan, your odds probably won't be any worse than theirs.) For something you really need to count on for both efficiency & capacity it's worth buying a better unit, and let a qualified tech commission the beast even if you did the other 99%.

    BTW: If you live in snow country don't make the all too common mistake of ground mounting it or putting it where it can get hit by roof avalanches/cornice-falls. Ideally there will be a place to mount it where it's protected by an overhanging roof (rake is better than eaves), and above the historical high snow-depth. Wall mounted and building a small protective shed roof/awning works if you don't have sufficient roof overhang. More than once I've managed to see people digging up their mini-split after a winter storm.

  7. user-1115477 | | #7

    I watched two ductless minisplits go into my place, and I would do it myself if I had to do it over again. The labor was too expensive, and all the quotes were that way, even though the work is considerably less than installing a traditional ducted heat pump. The licensed electrician (required for code in my location) my hvac contractor brought with him tried to cut corners and I didn't like him.

    The work is almost all DIY stuff, but Jin, and others, makes a good point about specialized equipment needed. I do just about everything myself, but the cost of tools/equipment/specialized expendables is not trivial. Just two other comments:
    1.Plan your layout and keep regrigerant line length within the capacity of the pre-charge.
    2. The inside units are made to be so compact that it's a p.i.a. to get the refrigerant/power lines crammed into the space they give you in order to get the unit to end up mounted tight against the wall--too compact in my opinion. My crew struggled and never did get either unit perfectly tight--I didn't see where I could have done any better than they did, in that regard.

  8. jinmtvt | | #8

    Sonny: what brand of minis ?

    Fuji are precharged for up to 50' .
    If you can't fit a mini with a 50' hose, find another installation area or product.
    And no need to take out any if the hose is longer than 10-12' either which it should be.

    One could get away with approx 150$of toolins if going the cheap route "c'est a dire " :
    - vacuum pump from ebay @ 125$ and a 10$ hose

    just let the pump run for 2-3 hours to make sure it is down ..but then u don't know if you have a leak before releasing the refrigerant

    hand tighten the flare ( easy to over torque or undertorque though )

    verify leaks as soon as in fuction with soap and retighten as required...

  9. user-939142 | | #9

    Yes you can, in most cases, exceptions apply. I just did this myself a month ago.
    I did my own as I tend not to trust or hate to fight with getting people to do the job right; I know of all the materials I bought, and I installed it the way I wanted it to look, no surprises.

    Like many DIY things, I look at it as giving it a go and having back up funds and time to hire in a pro if needed.

    [correction to prior comment] There should be no pre-charged linesets; it wouldn't make sense as there would be no way to keep a charge in the copper tube and connect them.

    Go and download the install instructions for a few of the units you are looking at and you'll get an idea of what is involved.

    First you want the unit to be new, so it already has a known charge and oil, and you want the standard charge to be within the length of a lineset that you are going to use (so you don't have to add any charge).

    You can buy pre-assembled linesets or try to find a resource to flare the copper tubing yourself. I was surprised that my unit came with the flares. The new 410a flare spec is different so it can be hard to do. I was able to save a good chunk of money by getting a standard order lineset at my local building supply, rather than special order or internet ordering.

    You'll need flare wrenches to tighten the nuts, and to do it right, you'll need a torque wrench and flared head sockets to use it (cheap ones can be found). Having done it once, I wouldn't bother with the torque wrench as it clicked about the time I would have stopped anyway. For he indoor unit it is almost useless as tube out hangs so you can't really overdo it as far as torque, but you can be careless and not hold it steady
    You'll need a dab of refrigerant oil or similar for the flares and maybe a thread locker of some sort.

    For vacuuming I used a little device avail on harbor freight that cost less $20. It requires you have a sizable air compressor handy otherwise you are buying a vacuum pump you'll never use again - shipping weight makes it unrealistic to try to make back the cost of this. For leak testing I brought the vacuum down and then left it set for over a day to see if it held. It also helps to do this on a hot day.

    Ideally you have a micron gauge and do a pressure test with nitrogen, but heck many hack companies will do even worse. I accepted that if I ran into problems, I would have to pay a professional. They are going to want about $400 just to bother with the vacuum.
    If you buy a new lineset that wasn't dropped in the ocean, sealed ends, and a new mini with sealed ends, their isn't going to be much moisture to worry about.

    I used a guageset common for auto needs. You have to spend a lot to get some thing real.
    For 410a units, you'll need an adapter found on ebay.

    Running the copper linesets was easy. Buy the stiffer more expensive drain line tubing. If you order online they will often carry accessories for running the lines through walls, or an outside cap, etc.

    You'll need some electrical knowledge and want to go slow. You may have code issues in your area or choose to follow them if not, like a GFCI breaker, or a secondary shutoff inside.

    If it is going to heat, you'll need a foundation and stand to keep it out of the snow and up from drainage. You may also need to build a small roof to keep blowing snow from getting sucked in, or other vent designs for other issues, sometimes mention in the instructions.

    And as mentioned, getting the install tightened up can be a challenge with the copper lines, electrical, drainage, etc. You have to plan out ahead of time the steps you'll take and the access you'll need, but it's not hard.
    Because I don't like having the linesets snake outside the walls of the house, I ran mine inside the wall down into and through the crawlspace.

    Probably the biggest issue for us DIY is being able to appropriately size the units to need, as well as being limited to the single head models in most cases. If not sized well, you lose the efficiency.

  10. user-1115477 | | #10

    I have Fujitsu units. In my case, the layout was easily planned so that refrigerant line length would be under 50 feet, so that no additional charging was needed. The problem with "fit" that I was talking about was physcially fitting the lines, so they stay hidden, in the immediate area behind the inside units. The lines come in from outside and run parallel to the wall , between the wall and a tiny space in the back of the unit, for a short distance, before reaching the connections on the unit. It's a ridiculous cram-job, and there are some other ridiculous design features of these inside units that make it too hard even to clean filters.

  11. jinmtvt | | #11

    Sonny: i have to admit that the lines at the rear of the fujitsu could be longer, was that your problem also ?

    installed 3 of the units on ~14" thick walls where the connectoins would have to be in the wall
    ( concrete = not possible )
    i ended up making space for the hoses within the walls so the connections could be accessible for tightening and leak tests once the unit was installed ( the walls are not finished yet )

    I believe that the intend the installer to run the hoses either straight through the back wall and connect outside, or paralell to the unit inside and connect the unit from under with the bottom cover removed.

    Easiest way on a thin wall is to make the hole and poke everything through to connect to lines at the exterior point, even if that means you need to sharply bend the hard connected lines.

  12. apmachine | | #12

    Hi Justin, not all units are plug and play systems. Also mostly all machines are quite good these days as before entry in North America, they have to pass certification and testing - not to mention that a handful of companies have a monopoly on the parts. If you need long linesets, -- lets say above 20 feet -- youll need to go into the custom installs (like fujitsu, gree, etc) but if your install is under 20 feet, there are available plug and play systems on the market. Something like the caribou mini split system ( is extremely easy to install

  13. gusfhb | | #13

    I have installed 5 units myself, but I know a guy who knows a guy who is a refer tech, and pay him to show up nitrogen pressure test, then vac down the system. He also reflared the lines just because. Cost me about 100 per unit, less when I had 3 done at once.

    the hardest part is getting the condensate drain right, there is very little depth to the tray so even a small mistake can cause water coming out the vents. If you are doing a straight up through wall install, getting power to the compressor needs some thinking, as it may be a 10 ga wire from wherever your box is.

    The problem with HVAC companies is they view these as a threat. If you have a 2000 sq ft house, they want the money to install AC in that house, so you get ridiculous install quotes. They also frequently have antiquated supply chain, so they are paying significantly more than online prices and then need to mark it up to you, so what should be a $2300 unit will become a $3000 unit plus install. They probably hire an electrician, where you might do your own wiring. So in the end, you pay a big bill, and no one in the entire deal really made a lot of money

    Do it yourself, absolutely

  14. MrWawa | | #14

    I have been following this conversation with interest since I just installed a Fujitsu mini-split in my home. I was surprised to see that not one person mentioned the importance of the quality/level of vacuum.

    I bought my unit online before I knew about several details regarding installation. What I discovered from research on line is that a deep vacuum is better than a poor vacuum and means a lot for any efficiencies you hope to achieve. I may be wrong, but my understanding is that these new high SEER pumps need a deep vacuum. The Fujitsu installation instructions say -76 cmHg, or -1 bar.

    That's where the problems start. Finding an affordable vacuum pump that can do that is not easy. Every pump lists different vacuum figures (cmHg, bar, microns, etc) And from what I can see, it is difficult to find out how much of a vacuum these affordable pumps can do. The pump might list an "ultimate vacuum" of 5 Pa but then if you read the comments people say that the best vacuum they achieved was -26 inches Hg. From what I understand, even -29 inches Hg is not enough.

    In order for the heat pump to achieve its rated efficiency a higher vacuum is necessary. If you just use any old vacuum pump and assume you did it and all is well, you might be mistaken since you will not be saving as much on your electric bill as you think.

    And if you don't buy a digital vacuum gauge you are really just guessing by using regular gauges. I think many DIYs just let the vacuum pump run for some time and Bob's your uncle.

    Or maybe I am wrong about all this, and really, all we need is an average vacuum that any affordable vacuum pump can achieve? Perhaps someone can address this?

  15. jinmtvt | | #15

    Good enough quality digi gauges are available on ebay or AC tooling resellers starting from around 100$ .
    Deep vacuum pumps specially made for AC installations are available on ebay etc.. from around 150$.
    They are enough for a homeowner simple installation but may be slow for a professional.
    A fast 2 stage reliable pro pump is worth approx 300-400$ .

    Then, torque wrench set is required to properly connect most line sets, that's another 100$
    ( i've seen some at lower prices in usa stores )

    If you can't afford to purchase those tools as the minimum,
    you can't afford to DIY a mini split install.

    If you plan on using the tools more than once,
    it is almost a no brainer investment.

    you do not need the 3 gauges manifold sets to install a precharge mitsu/fujitsu unit
    if you've planned your line set length according to installtion manuals
    ( at worse if too short, just make a few loops somewhere in the attic or free space in the ceiling )

  16. MrWawa | | #16

    Regarding my post in #14, and in reply to Jin Kazama, perhaps I wasn't clear enough. I will ask more directly.
    1. What pressure to professionals apply when doing a vacuum on the new high SEER (27) mini splits?

    2. Which inexpensive vacuum pump can actually achieve the vacuum needed? Will a single stage pump that sells for $53 and lists an ultimate vacuum of 5 Pa actually do it or is it a waste of money? Many pumps list higher vacuums then they actually manage, according to the commentators. Of course, unless someone actually had experience with one of these cheap pumps and knows it will do the vacuum required then it is very difficult to know which pump to choose. Perhaps someone on this site can give a good answer.

    3. Is it better to buy a $350 pump to get a 500 micron vacuum possibly only one time. Or is it better to buy a cheaper vacuum pump for $100 and maybe only achieve 10,000 microns?

    And by the way, anyone who has done a fair amount of plumbing knows how to tighten flare nuts enough without breaking them. I use Nylog sealer and tighten to a point, check for leaks, and tighten a little more if necessary. Works fine.

  17. wjrobinson | | #17

    Buy best tools use resell done.

  18. jinmtvt | | #18

    Bill : AJ has a valid point tools have the highest resale value

    I would not consider my job done at anything higher than 100 microns,
    but 125 would be suitable for most installation.

    I was able to get less than 90 microns on all of my installs.

    Usually, if you can get it to less than 100microns, it means that there is no leak in your installation,
    but, the pressure experienced by the operation is much higher than the pressure excerced by the vacuum operation.

    Checking for leaks is mandatory, use a very soapy solution .

    Minuscule leaks could also be present and be very hard to detect through soap test though,
    and would result in loss of operation within a long period of time
    ( often i hear 6months- 1 year )
    and then you need to call a pro to recharge and check up.

    So tighthening to specs is a must, this is not water plumbing.

  19. SausageLuvR | | #19

    Hope I am not hijacking this post but this subject is very interesting to me. I was all set to hire a professional to install 2 mitsubishi hyper heat units in my home in eastern MA but was shocked at the first two quotes I received.

    Seemed like a very easy installation to me. Bolt the interior unit to one side of exterior wall, bolt the compressor to the other side of the wall and go. Based on comments, both contractors were planning on a day long job with an experienced tech and a helper. Labor (above price of units) was over $3000 excluding electric. Both contractors wanted me to hire my own electrician and coordinate the installation.

    I was wondering about installing the units myself but hiring a qualified HVAC professional (preferably someone certified by Mitsubishi) to charge it. Specifically I wondered:

    1. For folks that have gone this route, what was your experience ? How did you locate someone willing to do this (seems like folks that are making $400 an hour doing full install might be resistant to getting $400 an hour for only part of the job) ? If it was in MA, would love to know who did the work.

    2. Were you able to maintain warranty coverage with this arrangement ?

  20. jinmtvt | | #20

    What was the price of the units by themselves mr FOO ?

    It is pretty simple

    diy = save some money
    diy = no warranty

    you have to compromise
    if the DIY saves you near the price of a single unit
    and you are confident in your capability to install them correctly
    then why not.

    if you are going to save 4-500$ ...let the pro do it

    This is only worth it with good units that have low problems rate though.

    Aslo, i read somewhere recently that Friedrich is out with a model destined for DIY
    and the warranty is valid ? might want to check that out ..

  21. SausageLuvR | | #22

    Thanks Jin,

    The Friedrich is interesting. I can see how this could be very a popular option. Looks pretty straightforward to install.

    I am looking for a mini-split for heating and it gets pretty cold where I am so I really need the Mitsubishi Hyper heat. Not sure the Friedrich unit is set up for heating in colder climates (<0F).

    Not having a warranty is not necessarily a deal breaker. I would be OK with this- not ideal but as you say, if the savings on the installation is great enough then you still come out ahead.

    I still am interested in having a pro charge it. Given enough time and the right equipment, I think I could probably handle this myself but I am certain that a pro would be more efficient. Might be money well spent to pay for this part of it. My concern is finding someone who is both qualified and interested in doing this. I have consistently had troubling finding competent folks willing to do smaller jobs for a reasonable price. Seems like that might be the case here.

  22. KeithH | | #23

    I wrote to Friedrich about that unit, though I've already been convinced to go another direction. Here is the reply I received:
    "Thank you for contacting Friedrich Air Conditioning. I do apologize, but I have to inform you that our Breeze units (the DIY install mini splits) are not available at this time. Unfortunately, there is not an ETA on when these units will be available again. If you have further questions, please call our Consumer Assistance Department at 1-800-541-6645 ext. 260 for further information.


  23. jinmtvt | | #24

    Keith: woa, not a good sign.

    FOO - i have no experience with Mitsubishi, but the equivalent RLS2H from Fujitsu comes pre-charged
    for 15' to 50' of line length.
    You do not need to remove or add any refrigerant if you work within the length limits.

    I've installed one unit on a 50' long lineset and a 25' or so raise ( head unit is 25' higher than exterior unit ) and it seems to be working just as good as the others.
    ( there are several rules to follow when doing this kind of extreme , need advices from pros )

    So i could say it does have some tolerances built it for working with different possible setup situation, it may affect the efficiency though..

    younits dot com have great prices if you wish to try MIT or FUJITSU diy

  24. gusfhb | | #25

    re: Warranty issues

    The newest of the units I have installed are over 4 years old now, and not a peep. So buy good quality units.

    At the price of the installs quoted, buy a spare it would be cheaper

  25. GBA Editor
    Andy Engel | | #26

    Justin, since I plan to do this too, as do Rob and Patrick, we can split the cost of the tools and maybe leverage a bulk purchase of mini-splits. When we're all done with the tools, we sell them and go out drinking with the proceeds. What think?

  26. wjrobinson | | #27

    Group purchase, I'm in.

  27. jackofalltrades777 | | #28

    On the exterior plumbing portion, I noticed they use those white vinyl covers to hide the lines as they go to the outdoor compressor unit. Those white covers look tacky so I was wondering if they offer another alternative or if they can be painted?

  28. jinmtvt | | #29

    Peter : you can also use gutter plastic/metal products..usually cheap and offered in different colors.

  29. CanAmSteve | | #30

    I've noted that friends outside the US (South Africa, UK, Canada) have installed these units years before they became popular in the US. In some cases they have run ten years (with annual service) without issue. LG, Panasonic, Fujitsu, etc. - all the big names have something.

    The installed cost elsewhere seems to be about US$1500 for a "room" size unit (10- 20K BTU). I've considered one of these for my intermittent-use cottage in Maine, but installed cost looks to be about $3000 - $4000 for the same size unit. Obviously someone is making quite a profit somewhere.

    My install would be very straightforward - it's a SIP post & beam, so as long as you miss the posts, the lines can go anywhere. It would also be within 20' of the electrical entrance (plenty of space for its own circuit). The exterior unit would hang on the wall above snow level on a gable end (no falling ice/snow damage).

    I think part of the problem is that there are some gov't grants available to encourage the use of high-efficiency heat pumps, and the installers increase their prices to take a larger slice of the money.

    I will report back but wish these threads had a "subscribe" link like many other forums.

  30. jinmtvt | | #31

    Steve P: i dare you to find a canadian installer that would sell you a 12K heat/cold from the large brands under 3K$ installed.

    Mitsu and Fuji are really the only one you should consider at this point for Maine ( if you've been following here ) and you probably won't find any units installed for under 3 000$
    keep in mind that the unit pair costs between 1800$ and 2300$ + linesets and accessoires.

    20K BTU is far from a "room size " .

    Some people here and around are using a single 12K BTU for hole house heat/cold.

  31. shaferlabs | | #32

    My answer may vary from some of the technical advice already given here, which I would definitely not dis. However, I am sort an a "third world" inhabitant. Therefore, if I may I will just tell you what I did on two Shinco one ton units that I installed myself on two separate occassions. They were supplied with 15' linesets. In my ignorance I thought "pre-charged" meant "plug-and-play." Ha! So I followed the instructions to the best of my ability, and did a clean and thorough job... except for the vacuum process. I tightened the prefab fittings well, opened the system into the lines, bled the air until I started to see and smell signs of refrigerant, and immediately closed the bleed valve. Both systems heated and cooled efficiently for years with no problems whatsoever. Now, whether I had maximum efficiency I cannot say. Only that the heating and cooling capacity was plenty impressive to me, and was far less expensive in terms of energy than the window units I was previously using. I am not advising anyone to follow my example. I'm just a "third world" kind of guy.... Cheers

  32. jinmtvt | | #33

    Mark : some refridgeration guys might answer correctly, but i believe that the vacuum serves 2 basic purposes here ... remove any trace of air/humidity in the lines
    ( were the line sets end sealed with a valve or just capped off ? as some are nitrogen filled )
    and to verify that you do not have a bad leak mainly in your conenctions,
    before releasing the refridgerants ( so you do not have to recharge, and they do not exit to atmosphere )

    that's what i understood from my searching.

  33. Bdgray | | #34

    I find this post extremely relevant as I'm in the middle of determining how to replace a very antiquated HVAC system at my home. My preference for many reasons is to go with a VRF/minisplit. I've priced a complete installation from a minisplit HVAC contractor vs buying the materials online and doing the work myself. Here is the delta in costs:
    1) HVAC contractor: LG Mini-Split Quad-Zone System: $16,150
    2) Buying parts only online: $6,386 (note: this just the VRF system and does not include line sets, drain pipes, or electrical)

    Obviously for a nearly $10K "rebate" there is a strong motivation to slog through this myself. Further, I've been unimpressed with most of the HVAC contractors who do this. What I want is a ducted VRF that conceals the interior air handlers. My plan is to steal overhead space from closets and hallways to create very short duct runs which I believe should work well. The contractors with whom I've met have clearly never installed this type of VRF system. Their minisplits installations have all been straightforward wall units. Do I really want to pay a contractor an additional $10K to do something they have never actually done? Further, can I trust that they will do the work correctly?

    Going from there, my question is this: Practically speaking what are (and where are) the best online resources (instructional videos, best practices, step-by-step processes, design support, technical explanations, etc) to walk a DIYer through the design and installation of a multi-zone minisplit system? As a DIYer I've found Fine Homebuilding and to be great resources for many projects that I've tackled myself - insulating basement walls with rigid foam, air-sealing my attic floor, feathering in hardwood floors for an addition, building a deck, etc. I would love to find a similar level of design/installation detail for minisplits that comes from a trusted resource. My experience with most DIY work is that these types of online resources can make even very complex projects attainable/realistic for intelligent people who are both diligent and detail focused. The only exception I've seen is where a project requires specialist tools that may be cost prohibitive (and cannot be rented).

    I would welcome any online resources that can help guide a skilled DIYer through the steps of a VRF installation.

    Thank you,

  34. KJM-NH | | #35

    No answer, but I am in the same boat as FOO. I have two Mitsubishi split Hyper heat AC/heat pumps showing up in a few days. Calls to local HVAC folks haven't been returned; is anyone willing to simply evacuate the lines, or do they only do full installs? My longest run is ~20 feet, and pre made but uncharged line sets are in my online order. The condenser is recharged for up to 25 feet. I have experience with vacuum systems and could borrow a micron gauge from work, maybe also a pump. What I don't quite get, despite reading the install manual, is how I pull a vacuum on the stop valves, and then disconnect the vacuum line without air rushing back in before I use an allen wrench to let refrigerant from the compressor into the lines. Since I won't have to add refrigerant, I could probably get by with just a single tube with a tee for the micron gauge instead of a manifold. I would also happily pay someone instead of doing this myself. Any leads on a willing HVAC guy or company near Haverhill MA, or detailed guidance on the sequence of actions should I do this myself? Thanks!

  35. jinmtvt | | #36

    Kevin : there is a port on the 3 way valve exactly made for connection to manifold/pump.
    You pull the vacuum through the lines and then close the valve while the pump is still working.
    There is no open to air ever.

    Then you open the valves to let the refridgerant flow and open the loop from the ext to the indoor unit.

  36. KJM-NH | | #37

    Jin: Thanks! I saw the allen wrench valve, but didn't see any other valve actuator. Does turning the allen wrench close off the vacuum pump side before it opens the refrigerant into the line, or is there an actuator that I don't see? On another front, I called the heating oil company that we do business with. The person there said that they don't evacuate lines, but they know folks who do on the side. So a few leads. I wouldn't mind the guild of all or nothing if they charged a reasonable amount per hour. But they don't... Thanks again.

  37. mackstann | | #38

    Tracking down those "on the side" guys is the key, I think. Maybe you have a shop like this in your area:

    "Can I do a Heat pump or A/C Myself? YES!!!
    You can save $$. As the homeowner, you can do the majority of the work yourself. We can refer you to qualified contractors in the Portland area to help with the refrigerant related portion of the install."

  38. marco485 | | #39

    There is a Mitsubishi training course in Southboro Ma.

    2014 Schedule (Classes available for purchase at this time): 08/26/14 - 08/27/14 | 09/03/14 - 09/04/14| 09/16/14 - 09/17/14 | 10/07/14 - 10/08/14 | 11/18/14 - 11/19/14 | 12/02/14 - 12/03/14

    This 2-day M- and P-Series Service Course is for installation and troubleshooting of M- and P-Series systems. The concepts and theories of M- and P- system operation including a study of the unique technologies employed. The theories of properly applying, installing and troubleshooting M- and P-series systems will be discussed along with practical hands-on exercises. Laptops are not required for this course.

    Class Attire for all training classes: Please do not wear shorts or open-toed shoes for safety reasons.

    Location of the Boston (MA) Training Center: 150 Cordaville Road, Southborough, MA 01772. Phone: 508-281-4095

  39. kevin_in_denver | | #40

    If installed cost is the most important consideration, I humbly suggest that a PTHP can be installed much more cheaply than a minisplit.

    You must cut a 16"x26" hole in the wall vs a 3" round hole, which could be a deal killer.

    Anyone with basic carpentry skills can cut and air seal that hole.
    PTHPs are very quiet nowadays, but they are less efficient than some minisplits. Low temperature operational limits aren't as big a deal as you might think. YMMV

  40. marco485 | | #41

    1. There is a cheaper internet price at plus they provide guides for all the components for your system.
    2. The installation instructions tell you what you need to do to install the unit.
    3. The most critical parts of the installation are the refrigerant line connections and the line evacuation.
    If the line connections are not properly done and checked for leaks you will lose refrigerant and eventually malfunction. If you do not evacuate the lines, the system will lose some efficiency.

    According to Mitsubishi "Refrigerant adustment... If pipe length exceeds 33 ft.(10 m), additional refrigerant
    (R410A) charge is required"

    Kevin McCarthy, I am very interested in your installation. I live in the Marlboro area in Ma and would love to help and learn on your installation. Please let me know at [email protected]

  41. schuelerj | | #42

    I too have found this post very relevant and the answers above extremely helpful. I'm an avid DIY'er. We are in the middle of planning our future home, while at the same time trying to 'limp' our 'temporary' mobile home through till the new home is to be completed. I'm looking at dirt cheap heating & cooling solutions for the current house since the the furnace is 100% dead (ac is still operational). Cost of a new unit into a short term house with leaky under-floor ducts is just not an attractive option anyway I look at it. DIY mini-splits are definitely on my short list of options. There are cheaper options out there, but mini-splits seem to bring the total package I'm looking for: high efficiency, heat & cool in one unit, relatively unobtrusive install, reasonable cost, and doable as diy project.

    Yes, PTHP's are a viable option, lower cost, and simpler install. I would think people's issue with them is they are just one step away from a window unit. I would probably wake up in the middle of the night for the first year thinking I was in a motel. Unit efficiencies for PTHP's are getting better and decent units are out there to be had. I have not experienced a PTHP (or PTAC for that matter) that is as quiet as a good mini-split indoor unit though.

    In response to Brian about ducted indoor units: You may have to look at commercial contractors to find anyone with experience with this type of install (of course most commercial contractors just aren't geared for small residential work). I do commercial mechanical design for a living, and have designed a number of these type systems - smaller multi zone mini-splits all the way up to the Mitsu City Multi systems. Architects around here tend to favor the ducted units, and are especially not keen on wall mount units. In this area at least, most commercial installers have sort of had to go through a trial period figuring out multi zone VRF systems, but most who are willing to do the work are getting really good at it now. I still see fear in the eyes of a lot of the residential installers I've talked to lately when bringing up the subject of multi-zone mini-splits and VRF.

    The comments above about finding the "on the side" guys is definitely true. They are most likely out there in your area - the key is finding them. I'm fortunate that I have connections I could call upon if my diy install went south or if I wanted to have a pro do the commissioning. Usually though, the guys at the supply houses (I'm not talking about big box stores like Home Depot) will have a good idea of who is willing to do this type work. They may be reluctant to talk to you on a cold call though. Ask around - most likely, you already know someone who knows someone that can help you out.

  42. kevin_in_denver | | #43

    Response to Jeff Schueler,

    You said "Yes, PTHP's are a viable option, lower cost, and simpler install. I would think people's issue with them is they are just one step away from a window unit. "

    Comparing them to a window unit emphasizes their best advantage: easy replacement.

    I for one would love to own a car with an easily changed engine. Imagine owning a home where you can replace or upgrade the HVAC system for $700 per zone, by yourself, in one hour.

  43. jshima | | #44

    In a recent build of a 600sqft cottage I looked into the PTHP and chose the mini split because the PTHP does not have variable output. The mini split can put out between 3800 and 12000 btu's. The PTHP will cycle on and off all the while making a lot more noise than the mini split. The mini split is VERY quiet. The outdoor unit is so quiet that the only way you can tell it is running is by looking at the fan spinning. The cottage is a rental and spending the extra $1800 on the mini split was well worth it.

  44. tnsoftailrider | | #45

    Hey guys, I know the original question is a year and a half old, but this is good info anyway. there is a company, IdealAir, who makes a complete DIY mini split. The lines are connected at the factory to the indoor unit and vacuum sealed. After running the lines out to the outdoor unit you only have to connect the two lines, open the valves and the pre-charged outdoor unit fills the lines. Hook up the AC power and the four wire to the indoor unit and it is done. Check out the Youtube video
    I plan to install one of these this spring in my house as I removed the old, and dead, central system.

  45. chessgames56 | | #46

    Definitely hire a contractor who has EXPERIENCE installing mini splits. I didn't and I'm paying for it. I hired an HVAC certified mechanic, and he did not use the proper torque or torque wrench, and there's a slow leak outside where the (larger) line connects to the compressor. I called another contractor in who claimed they experience with mini-splits. He recharged the system with coolant, then tightened the connector even more. Now it has slow leak again. What I did to try to patch it is wrap a latex exercise band very tightly around the leaking joint and secure it with tie wraps. Don't know if this will work, but thought it was worth a go. So if you hire someone, ask for references and make sure you get a warranty in writing for the install. Don't make the same mistake I did.

  46. iLikeDirt | | #47

    That if anything sounds like a good argument for doing it yourself if after hiring two separate pros (one of whom claimed relevant experience), the job still wasn't done right. I bet for the money you spent hiring them, you could have bought first-class tools to do the job right yourself, and then re-sold the tools, recouping most of the cost.

  47. Expert Member
    Dana Dorsett | | #48

    It never ceases to amaze me when refrigeration techs don't bother to use the right flaring tools when installing refrigerant lines. As long as the thing is still working when the truck rounds the corner disappearing from sight after the job is done, it's good enough?

    R410A is a powerful green house gas, and it's a crime against the planet to not repair it reliably. Rather than wrapping it in a latex band to slow the leak, find a factory certified tech for the model you have, tell them the problem you have had with other contractors, and promise to pay them well if they do it right, and to wring their bloody neck if they don't use the right flaring tool for the fix! :-)

  48. iLikeDirt | | #49

    The problem is that nobody cares as much as you do, that and people in skilled trades who are used to feeling like experts are slow to adapt to change and admit that their expertise may be stagnating. Instead of paying hundreds of dollars to teach someone their own job, pay that amount of money to learn how to do it yourself right the first time!

  49. charlie_sullivan | | #50

    Recall Marc Rosenbaum's recent blog post on the value of thinking about handprint as well as footprint. To minimize your footprint, you might do it yourself and do it right (if you have the right skills and care more about it than a tech might), and not risk the R410A emissions. To maximize your handprint (how much good you do) you might actually do best by "paying hundreds of dollars to teach someone their own job." At least that's what I tell myself when I end up doing that.

  50. SteveR_79 | | #51

    Since this thread has resurfaced, are there any reports both good and bad on the DIY installation of a mini-split?

  51. newyorkductless | | #52

    Hello Nick,

    You will need a vacuum pump, nitrogen manifold and tank, micron gauge, R410 ready gauges, metric torque wrenches and pipe bending tools. Let's not forget an EPA refrigerant certification! I've done Ductless Split installs for professional builders and plumbers in their own homes and after completion they said they were glad they didn't do it themselves! What make it look easy is that the installation of the indoor unit only takes 15 min. The entire project takes 5-6 hours by a good ref. tech! There's a lot to know. Feel; free to contact me via with any questions you have! I have over 30 years experience in HVAC!

    Regards, Larry

  52. scorrpio | | #53

    I have done two dual-zone DIY installs so far, both rather complicated setups. The kits described in this thread are only good for simplest installs - indoor unit on the outer wall, single zone, lineset running through the wall to the nearby outside unit. If you got anything more complex, such as indoor unit on the inside wall, with lines routed through ceiling or such, things get a lot harder. Special care needs to be given to the condensation lines. Also, if you can help it, do not mount the outside unit to a wall, unless it's a masonry/concrete wall that will absorb vibration well. Best option is a nice concrete pad that goes below frost line and raises the unit at least 6-8 inches from the ground.
    Take great care with tubing. Never bend it in way that can twist the tube. Use a bending tool for tighter bends. And go real slow and careful, cause if you kink it, you have to cut a section out, flare the ends, and put in a coupling, which is a potential leak point. This is the beauty of DIY - hired pro working on a fixed fee wants to finish as quickly as possible, He will not bother to get the lines just right. Also, flaring: Go careful and slow with the cutter, ream thoroughly, always pointing the open end down, make sure the end is nice clean and square, and extends a proper distance from flaring clamp, there is no reason not to make a perfect flare every time. And do not forget to get that flare nut on BEFORE you flare!
    Next, the connections. A friend HVAC pro recommended this blue stuff called Leak Lock, look it up on Amazon. This stuff is awesome, and a 4oz jar will last you a lifetime. Get a bit on the threads and on the flare fitting mating surface (not on the tube) and it seals perfectly.
    Next step, charging. Gotta do it right, and gotta have the tools, no going around it.. I estimate I spent about $600 on vacuum pump, manifold, vacuum gauge, nitrogen tank with regulator and various brassworks. Still less than cost of labor on an install like that, and I get to keep all those tools. Make sure you get a proper gauge set, one that is good for R410A. And you do need a decent electronic vacuum gauge. Your manifold gauge might be down to zero, but you are still nowhere near the needed level of vacuum. Oh, and a tool that can make things real easy is a valve core remover, like Robinair 18560. Just make sure you get a properly sized one. This tool lets you remove and replace the schrader core from the service port without breaking the vacuum, and with core out, your pump has to work a lot less to get the vacuum needed.
    My procedure is: Get the core out, pressure test the lineset with about 150 psi of dry nitrogen from a bottle, if gauge needle doesn't drop any lower for an hour, you are good. Now, pump it down to maybe 800-900 microns vacuum, connect the nitro tank again and put about 15 psi of dry nitrogen into the lineset. Now, get the pump going again, and take it down to under 500 microns. While the pump is still going, open the extractor valve, reinstall the core, retract extractor shaft and and close off the extractor valve again. Close off pump connection. Keeping the extractor attached, open the liquid and gas sides. Now, extractor can be removed and service port capped off.

  53. ScorpsRock | | #54

    One point I would like to make, having researched these things to death, is don't fail to factor in efficiency if you are using the click and go units such as idealair. Most I have seen are in the 13 -20 SEER. Whereas the Fujitsu is up to 33 SEER. Also note it seems Mitsubishi (about 30 SEER) does not go so far as to say no warranty if you do it yourself, but Fujitsu makes no bones about the fact that the warranty is void if you buy online.

  54. BrianHarkins | | #55

    Justin (And all others),
    I realize this is an old post, however, someone may stumble across it later.
    As a career HVAC installer, and having installed over 200 mini-splits, I can answer your questions.
    The overall installation of a ductless system is extremely simple. Anyone can do it. But there are deeper processes to the install for proper operation.
    Once the flared fittings are connected, how can you tell if there are leaks? By injecting dry nitrogen to a minimum of 100 psi and observe if there is a leak. Gauges are required.
    If no leak is found, then the nitrogen is released and the system placed on a vacuum pump. Once the system is in a vacuum (300 microns), the refrigerant may be released from the outdoor unit. But an EPA certification is required for that final step.
    Therefore, due to certain requirements and specialty tools, just get a professional HVAC contractor to do it. Plus you keep the warranties.

  55. tomk358 | | #56

    Good informative comments, great work from this community as always. In my research, the best website I've found that explains the DIY process (including tools and supplies) is this one:

    I have yet to attempt a DIY commissioning. On my first house build, I put in a minisplit, ran the lines, and then hired an HVAC contractor to commission it. I didn't know then that I shouldn't have left my lineset open to the atmosphere for 4 months, which meant that he had to do a triple round of pull a vacuum, fill with dry nitrogen, and test for leaks/remove moisture. It ended up costing me ~$2k for his time, which was the single largest (and by far most expensive mistake on my entire project). I vowed to do better next time, and I'm currently in the permitting phase for a 2 unit townhouse, I'll have a good excuse to get the equipment for DIY since I'll be putting in 2 units with extended linesets (requiring extra R410).

    1. AlexD2022 | | #57

      I installed my own mitsubishi unit this spring - it wasn't terribly complicated, but bending the copper without kinks was tough. All in all it cost me about $700 in tools I didn't have, you could end up spending more if you don't already have things like a torque wrench or vacuum pump (some auto parts stores loan these out for free though).
      I would check into if you're allowed to buy refrigerant in your state (might even be a federal law?) as I believe the general public is not allowed to buy refrigerant.

      1. tomk358 | | #58

        I think it's actually an EPA certification that is required, so should apply to all states. 608 is the certification number, and there are various types as explained here:

    2. charlie_sullivan | | #59

      Have you considered going with air-to-water heat pump systems? The unit comes pre-charged and the only lines to run are water lines.

      1. nickdefabrizio | | #60

        Interesting. Are there any units Air to Water units that are reasonable and efficient ? Allso, are there any that can be used with baseboard for those who do not have in floor radiant?

    3. nickdefabrizio | | #61

      Thanks for this link. Iwas thinking about giving up on mini splits because the install quotes I am getting are too high to make them worth while ($16k for two outdoor units-5 heads). I helped install a number of units and it only takes a few hours. I have even replaced the motherboard in a 36,000 unit when my HVAC guys said it was too complicated (it wasn't). But the vacuum/refrigerant aspect seems daunting to get right. It is difficult to find an HVAC guy around me willing to do just this part however. So I am starting to lean toward simple electric baseboard heat and window air units with adding additional PV panels on my system. However, I would much rather figure out how to do the vacuum/refrigerant part if I can, especially since between my home and my dad's there are four or five units that could be installed over the next year or so.

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