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Mini-split - fact or fiction

2K views 21 replies 14 participants last post by  Knockonit 
#1 · (Edited by Moderator)
I'm looking for some feedback from members that have experience with Mini-Splits in their shops (preferably 5 years or more).

I have a mini-split that I've had an up and down relationship with. It's usually very efficient and does a great job for both heating and cooling.

The weather has turned warmer here in Virginia and it was doing a great job until yesterday. I could tell it wasn't keeping up and actually died on me when I was in the shop.

The technician told me today that mini-splits in wood-shops have a very short life because of the fine dust and there's not much I can do about it. Expect 5 years instead of the 10 years I was sold on.

My shop has decent dust collection on all power tools, 2 Air filters that I run after heavy tool use. I also have built a filter holder that fits quite snugly around the inside air-handler of the mini split so the air is filtered before it's drawn into that unit. I know I have to up my game on the kind of filters I'm using in that unit and run the shop air filters more often but I'm wondering if the technician's comment about the shortened life holds water.

Any experience or comments to share?
 
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#2 ·
i've an associate that has had a 2.5 ton mini in his shop for 12 years one of the first ones offered here in az. and in the last 7 years has been in his shop working on his lathe and other tools half the days of the week, and probalby about 5 - 6 days a week in summer months when its a tad too warm here to work without some air movement, his course of action is, clean it monthly pending on his work in shop, some months he claims little to nothing in filters and or coils, and occassionally he gets a whiff of dust when he uses a shop vac to suck and or blow dust out.

i have 2 ton in my shop approx 900 sq ft of shop space, its only been in for a few months, and just last month began using is, do have stand alone dust pick up, a festool vac for the ros, and misc. and large dust collector for saws, planers and big sanders, still assembling the big system for shop, took me forever to come up with a plan, but have a 4hp griz in a stand alone room to clean shop up.

Of course i would suspect geography has a lot to do with functionality and success of unit, with the almost lack of humidity here they tend to work simpler and easier, at least thats what one of my ac contractor claims, but like most things maintenance regularly can extend the life of most mechanical items.

i watched some youtube wood worker install a filter system in front of the intake on his mini splits, pretty simple, and was surprised at how little dust there was after months of working in shop.

any event, every thing breaks, and as murphy would have it do so, at the most inappropriate time, much like my pool pump, works all winter long, but once we hit the hundy a day mark it croaks, takes pool it seems like hours to turn swamp color much like DC is.

hope it is a simple fix, for sure they are a boon for small, even large shops pending your needs.
best for the fix

rj in az
 
#4 ·
I usually tell the A/C repair guys that if they can't fix it, that the guys I call to repair are never the ones that I will use to replace because it creates a conflict of interest. I also hint I have a friend who will install a new unit at cost but I don't like to bother him for repairs and maintenance. Gives them more incentive to try and fix it.

What brand and model do you have? That may help ID whether maybe you got a model that others have had trouble with as well. Other than not cooling, what other symptoms did it have. What exactly happened when it finally died?

I am curious how dirty the extra filters you added get? Does the internal filter get dirty? I have been wondering if the extra filters I have seen a couple of YouTubers add add any extra strain on the unit? Make sure the guy actually shows you what problems the dust actually caused. When I open up and clean my portable AC unit, it is pretty easy to tell that the dust had clogged it up (easy to clean too).
 
#5 ·
well one of the big issues on repair of mini's is a lot of ac contractors guys struggle with figuring out repairs, at least thats what my pal the ac guy says, claims a lot of contractors dont want to service stating, off brands, chinese, taiwanese, ect, ect.

they are how ever becoming all the rage in last half dozen years, seeing more and more, Mexico imports a gaggle here locally under the Mirage name, expats seem to go to mexihole and come back with truck loads of them and hawk them on offer up and craigslist, facebook market place, rumor is their life expectancy is limited due to workmanship in manufacturing. second hand news by the way, i have no experience with them.
good luck
rj
 
#6 ·
I've been using my mini-split for about a year. I built a frame around the intake to accomodate 4 12X24 furnace filters. This gives me 8 sq ft of air filtration which I clean every week or 2. My unit has a readout that comes on about that often. It says CF, I hope that means clean filter but if you ever see me work ya might think of something else. My son told me to be sure not to restrict the airflow on these units because they choke down quicky because of the size of their blower (that's part of the efficiency). Your unit might just need cleaning. He doesn't like installing them because he can't make much money off of them. Install them and just run'em. I'm not sure if he's ever had one break. He owns a HVAC business. As far as the filter addition, check out the Youtube video by Jay Bates. He's made some really good videos on varoius things in the shop. I've used his ideas on the minisplit and the elevator. That's where I got the idea.
 
#8 · (Edited by Moderator)
Before I would spend any money on a repairs or a new min split, I'd take the cover off and expose the coils and vacuum them off thoroughly, then if you have an air compressor, blow off the coil thoroughly. Clean everything out really well then turn it back on. Same with the blower motor if you can get to it.

I still need to build a furnace filter frame around it to keep it cleaner.

I have a mini split that I've been using for ~3 years and I do this every couple months.
 
#9 ·
I have a grizzly G0738 air filter running at the same time and after the split.

Gadget Gas Technology Electronic device Wire


- Madmark2
I have 2 of those in the shop. One is down under my assembly table and one is above the assembly table. I also have a "filter box" like the Jay Bates video around the unit.

It definitely still gets a fair amount of dust inside the unit which turns into a kind of sludge and runs down the unit.
 

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#11 ·
I also have 2 of that Griz air cleaner. I just move them around so I am where the dust is, and those air handlers are too. I don't have a mini split, but a conventional furnace. You still don't want any kind of heating/cooling unit bathed in sawdust. I've found on those air handlers that they are more efficient closer to your head, than above it, so I sit them on benches, and work surfaces.
 
#13 ·
I see the dust intake making the unit a little less efficient maybe but I don t think that will cause premature failure unless you never clean the filters. Leaving them plugged would place a strain on the fan motor.

- controlfreak
I doubt that would strain the fan motor. Think of it like a DC, closing the blast gates reduces the load because the impeller isn't moving air. But I'd bet it's still not good for the system, the compressor will be told to run by the thermostat, but there's little air to exchange the heat.
 
#14 · (Edited by Moderator)
I see the dust intake making the unit a little less efficient maybe but I don t think that will cause premature failure unless you never clean the filters. Leaving them plugged would place a strain on the fan motor.

- controlfreak
My thoughts too.

The filter should keep the (most of) dust out of the unit. You want to keep the dust out of the coils. It will clog up the fins, lower the air flow and kill the cooling ability.

Getting out of my wheel house but I think if the fins get clogged enough it can cause some issues with the pressure of the freon in the system? Seems I remember learning that somewhere.

It would also collect on the fan but I can't imagine it lowering air flow that much.

If you keep the filter clean and they are doing there job I have trouble understanding how it would cause a failure. If the coils are getting stopped up then I can see why you have problems.
 
#15 ·
I've seen several videos recommending using one of these bags when you need a thorough cleaning using a foaming cleaner.

I m thinking that relocating the low one to the ceiling near the mini-split head unit would help. Or maybe just buy another unit to place up near the mini-split.

- bh1710
One thing that I thought about doing instead of making a filter box is instead running the output from my air filter systems into the intake of the mini-split. Not sure that I would want the noise all the time but feeding pre-filtered air might reduce maintenance at least. I would probably want a way to bypass the air filter when I am not making much dust in the shop.
 
#17 ·
+1 RJ comments: Mini-split servicing and repairs are a PITA.

Not surprised by your tech's lame excuse.
Mini-split units are high tech compared to old school HVAC unit. They are also a lot cheaper than furnace mounted units, where an equivalent high efficiency furnace mounted 'smart home' HVAC with variable fan/compressor speeds will cost $8-15K new. This reduces technicians interest in make repairs. Most HVAC techs don't repair enough mini-split units to be comfortable with repairs. Big OEM brands require a laptop/tablet and special mfg diagnosis programs to be a fully authorized service provider. Due cost of training and all the off brand units; finding true authorized service for mini-split can be impossible.

There have been a lot of changes to mini-split market as the state/federal gubermint's increased minimum efficiency standards for AC. This made a lot of 'not so old' lower seer models instantly obsolete in USA. Techs are less prone to want to bother with repairing older units, as parts are less common. AKA another reason for lame excuse.

+1 Always tell repair tech, no conflict of interest: you never use same outfit for repairs as a new install. And if you need a new unit, will get 3 quotes and pick best one, including your certified friend/cousin/etc. :) The repair story always changes when they might not get business to replace a unit.

BTW - If your tech did not remove covers to access the maintenance buttons on control boards, you need a new tech and are getting a total line of BS.
Buttons on both condenser & evaporator control board will remove the efficiency crap, allowing a 'normal' check of unit pressures/temperatures (like a normal HVAC). It's impossible to check operation without turning on the maintenance mode(s). Top of line units even have indicator led that signal when there is low/high Freon, or control error to make repair a simple parts replacement.

Degree of difficulty with repair will be determined by model, and what is BORK'd.
Hard to DIY troubleshoot and repair mini-split as mfg are very tight with distribution of service manuals. Can often find a generic service manual for base units made overseas, as the core components are common to many brands. Mini-split mfg is similar to WW tools or appliances, I.E. lots of common internal parts with different skin out outside. There are 3 high volume mfg of mini-split that cover majority of OEM in US. For example; Midea in China makes MR. Cool, Panasonic, Mirage, Carrier, York, and many other brands.

Despite the high tech complexity, there are not that many serviceable parts inside mini-split; 2 control boards, 1-3 valves, 2 fans, sensors, and compressor. Fans will fail when units always have dirty filters. If the control boards are bad, usually won't go into maintenance mode. Most common failure on DIY installed units is condenser proportioning valve, which helps create the work shop mini-split short life expectancy myth (IMHO). The valve is a precise instrument, and key to performance. If unit was not properly evacuated with all moisture removed during install, residual moisture and modern Freon corrodes internals; clogging the valve in half the normal lifetime. This valve is not expensive, but Freon removal/replacement and opening system can be. On unit less than 18K BTU; many repair techs charge more in labor, then cost of new unit. If don't have Freon loop failure, repair can be pretty simple; often just leak fix with top off, or swapping out a $50-$100 PCB (that tech charges you double to install).

Still with me? Thanks for reading this far.

+1 What mfg and model?
If can post or PM the make and exact model information on either/both condenser and evaporator unit tags; Can try to find the service information for you? No promises for success probability.

Best Luck.
 
#18 ·
+1 What mfg and model?
If can post or PM the make and exact model information on either/both condenser and evaporator unit tags; Can try to find the service information for you? No promises for success probability.

Best Luck.

- CaptainKlutz
Thanks for the detailed response. Very helpful.

Unit is a CARRIER- 40MHH. Not sure which size it is. I'll check.

The manual never once mentions Carrier anywhere. I wouldn't know if it's a Carrier if I hadn't heard the tech on the phone with them during the 5 months it was down this winter. That's right… 5 months. I had a Chinese beetle get in and fry the main board and then it was off to the races with one excuse after the other. Turned out the replacement board they sent after the "beetle-board" fried was defective. They had replaced just about everything else before going back to the replacement board.. I never got an invoice for any of that. Parts are covered with warranty but I'm sure there was at least 30 hours of labor.

That tech no longer works there. The new tech I met yesterday told both my wife and I separately he was "the best mini-split tech in Virginia". That makes me happy and worried. He as also the one that told me mini-splits in woodshops are doomed.
 
#19 ·
Unit is a CARRIER- 40MHH. Not sure which size it is. I ll check. - bh1710
Lol, Medea and Carrier have huge joint venture in appliances. Medea/Carrier service manuals are easy to find, and often used to diagnose off brands. Size does not matter.
Finding your service manual took 5 seconds on DuckDuckGo:
https://www.shareddocs.com/hvac/docs/1009/Public/02/SG-40MHH-01.pdf

Navigating issues when a unit has had numerous warranty service calls is tricky. Most carrier shops use refurbished control boards as that is all warranty policy reimburses. Refurbished boards have been used by someone for up to length of warranty, and may not last as long as new. They also don't get updated if there is a design change that improved performance or reliability. Carrier has several 'grades' of AC units. The lowest cost commodity versions, tend to lose support sooner than high end models mostly installed in business locations.

If unit is out of warranty; suggest you attempt DIY diagnosis before considering a new unit. Manual is decent, and has troubleshooting logic trees.

Your tech is not totally wrong when saying wood shop is harder on mini-split. Wood workers should add a pleated pre-filter to indoor unit. But as long you have an extra filter, keep the filter screens clean, and blow out the fine dust from evaporator coils annually; a wood shop is no different than any other room for a mini-split.

FWIW - Mini-split HVAC units are a dominate format in Asia, and other countries due high energy costs. Can see entire apt buildings that have walls covered with 100's of condensers hanging outside a window. This might sound strange, but replacement fans and control boards for most common models are sold in local hardware store.
Since our gubermint requires HVAC techs to be certified to work on AC systems thanks to hazardous gases; US folks have to much harder time finding parts for DIY mini-split repairs. Note to DIY HVAC: It is illegal to intentionally vent Freon into atmosphere. Which means anyone repairing HVAC need expensive Freon salvage equipment. Freon venting fines are more expensive than owning the proper tools.

Cheers!
 
#20 ·
Thanks for your quick response. I should amend my initial post to state that I feel I m being prepared to be recommended a new unit instead of finding the trouble with this one and simply blaming the wood-shop environment.

- bh1710
Before I would spend any money on a repairs or a new min split, I d take the cover off and expose the coils and vacuum them off thoroughly, then if you have an air compressor, blow off the coil thoroughly. Clean everything out really well then turn it back on. Same with the blower motor if you can get to it.

I still need to build a furnace filter frame around it to keep it cleaner.

I have a mini split that I ve been using for ~3 years and I do this every couple months.

- EarlS
I have had my Mr Cool DIY mini split since 2018 and it is still working great.
I have had the same repair experience with other appliances as you are having with your mini split.
More and more trying to sell new vs repair not so old. It is a pain, but keep searching for a repair guy, that will actually repair it if need be. But as others have stated, deep clean it and see what happens.

I have not tried to build anything around the air handler. But I do pull the screen filters every month and vacuum them clean. And I do take my compressor to the coils at the same time. Then also a couple times a year I go outside a gently wash the condenser coils off. Las Vegas desert dust is a killer in itself.
I do run a Jet air cleaner, and a Powermatic DC, or shop vac depending on the tool in use.

So I keep up with this monthly cleaning. And I am a part time hobby woodworker, who gets so busy at my real job that I may only get out there on the weekend here and there. And I still get a bunch of crud out of my air handler.
Coming into summer now, the A/C system will run 24/7. winters are mild here, so it runs part time then.
Where I work, we have Lenox branded systems in several construction offices/trailers. We have to clean those filter screens weekly.
 
#21 ·
When I had my shop built I got a Mitsubishi mini-split installed. It's a larger compressor with three head units for the shop, the upstairs portion of the shop and a third head unit in an all seasons room that was once a breezeway between the house and garage. It's very efficient and inexpensive to operate. It is also a reverse cycle heating system which works in our Gulf Coast climate but probably wouldn't be good in areas that have very long or prolonged winters. We normally don't have more than a handful of days that dip below freezing and even then it is rarely colder than the upper 20s. The unit in the woodworking shop has a thick fiber filter over the intake on top of the head unit that catches a lot of dust. Both the filter material and the head unit and its internal filter are cleaned regularly.
 
#22 ·
well so far been almost a month and half' i've had ac units running in both shop and office, and have been in shop average of a few hours a day during week, and almost daily on weekends. table saw, ros sanding, router work, drum sander
each have dust collection, but i still have some dust in air, and filters are sparkly clean, i do have one air filtration unit hanging a tad in front of one head, the other has none.
i'm happy with units, i only crank them on when i'm headed out to shop, place stays in the mid 80s without ac, the foam at roof line sure make a huge difference here in desert. any event, it cools the joint down in about 30 minutes with the ceiling fans running.
im a happy old wood worker
rj in az
 
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