Ductless minisplit failures
CARL SEVILLE
| Posted in Mechanicals on
I have had 2 indoor coils fail in my Mitsubishi ductless heads within 3 years of installation. On top of that it takes the HVAC contractor more than a week to get the replacement part. Anyone have any similar experiences?
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Our Mitsubishi ductless system is about 2.5 years old. Apart from the interior distribution heads needing a deep clean soon, no issues so far.
Are you using one of their 'diamond' installers/contractors?
Yes, the initial installer actually screwed up some things although nothing that should have caused the failures. My new company is also a Diamond contractor. I'm concerned about 2 out of 3 units failing so soon. I have older models in another house without the same problems.
How sure you are the leaks were in the coils? Finding small leaks can be very default, frustrating and consume lots of time. All too often someone will just throw in a coil instead of locating and fixing the leaks. I am skeptic unless they show you the soap bubbles.
Were the 2 bad coils attached the same compressor?
Walt
Different compressors. Mechanic used a sniffer and found the leak in the coil. I was there when he found it on the 2nd one. Wasn't there for the first.
I call BS on leaky indoor coils. Unless somebody put a screw though the coil, there is no way that will leak.
Leaky flare, which would also show as a leaky coil since it is in the same area, definately happens. I've notice that most installers won't do a proper pressure test and you end up with the refrigerant escaping in a couple of years.
Whatever work they do, insist on doing a proper pressure test at 300psi, snoop all fittings and show you the system holding pressure after a couple of hours. Without this, there is no way to find the small leaks and you'll end up with needing these kinds of "repairs".
My Mitsubishi indoor unit failed in about 1 1/2 years. The coil had at least 3 leaks. So, the warranty kicked in and I was sent a new coil. My HVAC guy and I spent about six hours taking apart the indoor unit and putting it back together. It was ridiculous. Everything had to come out of the indoor unit to get full access to the coil.
The resulting cost was ridiculous too (and he did not charge me what he would have had I been "just another call out").
It would have been less expensive to buy another indoor unit.
I wrote to the company twice complaining about the product and received absolutely no response. As you may assume, I am not happy with the company and would recommend that people look into other brands.
This was less than a year ago, and so far it is working well.
There were lots of bubbles as he charges it with nitrogen.
Carl-
So glad to find this post of yours. I have a Mitsubishi City Multi multisplit VRF system that I had installed in a remodel and energy upgrade of my 1970s home 10 years ago. The system had one condenser/compressor outdoor unit and three ducted air handlers inside. First issue came 1 year after install. A coil leak. Replaced the coil under warranty. A year later, another coil leak. This time, the coil wasn't available so we had to replace the entire air handler, fortunately, under warranty. After another 18 months, the third coil leaked and had to be replaced. So, within 3-1/2 years, all 3 coils had been replaced due to coil leaks.
The story continues - in year 5, the compressor failed and I had to replace the condenser/compressor - covered under warranty. In year 7 and 8, two more coils had to be replaced due to coil leaks.
And then a little over a year ago, in year 10, two more coils leaked and I just shut down the system.
The installing contractor was an expert to the experts. He actually was one of Mitsubishi's "go-to" warranty support contractors for commercial VRF systems. I know that he designed and installed my system correctly. At each coil failure/replacement, he worked to isolate the system, purged and high-pressure tested the system with Nitrogen to ensure that no other leaks existed.
I worked directly with Mitsubishi to try to get a solution for replacing my entire system as it seemed as though I had a lemon. Despite much discussion and conversation, the discussion essentially ended when I answered one question - that question, "Does your house have spray foam insulation?" I did retrofit my cape cod home with open cell spray foam on the underside of the roof deck. I also added an ERV for ventilation. The folks at Mitsubishi said that they had had some coil failures in homes with spray foam insulation, but when I asked questions about what specific chemicals in the spray foam they found to result in coil corrosion, they didn't have any specific chemicals that had been associated with coil failures.
I'm definitely interested in anything that you learn or other ideas for possible causes for such failures in relatively new systems!
Todd - I heard some of the same questions about spray foam. My house doesn't have any, so it can't be blamed on that. I'll keep you posted on anything I hear from them.
Hopefully you'll get it sorted out. Keep in mind there's always the option of driving up to the Mitsubishi Electric Trane plant in Suwanee Ga staking out a protest across the street with a large banner about their poorly made coils. ;)
That spray foam excuse sounds like BS.
All evaporators have an aluminium coil, whether it is a mini split or an AC system. If using a bit of spray foam in a house could cause coils to fail, we would have heard about it a long time ago.
The problem is not spray foam. It is poor quality control.
Todd, you must have paid a fortune for repairs since Mitsubishi only covers the parts under warranted. If mine fails again soon, it is going to be removed, and another brand us going in.
Just to be certain, I recognize that only folks that have had problems are likely to post here, but It is good to hear that not everyone is happy - even if we are a small minority.
Formicary (aka "ant nest") corrosion is known to attack AC coils. Could be some VOC in a building product, but it's hard to nail down. Google it - it's fairly well documented (but not widely known by many) in the HVAC industry, including ACCA, Carrier, and other groups.
https://www.achrnews.com/blogs/17-opinions/post/114802-formicary-corrosion-on-the-rise
Why would it attack these AC coils and not typical central air heat pump coils? What's different between the two?
It attacks both.
Sorry to be waking up an old thread. One of the minisplit coils inside my ICF home has developed pinhole leaks. Has anyone had success with preventing formicary corrosion using any sprays/coatings. TIA.
Our service department finds formicary corrosion leaks in all manufacterers copper coils, some worse than others but they all have the problem. Seems to have started about 10 years ago, probably because the copper is much thinner and lower quality now? Ive been in the business 36 years and it never happend in the NE prior to that although it was a thing in the south in certain areas I believe. Coils where heavy copper compared with this new junk. Most coils are all aluminum now but those leak too, but less often (thin, poor QC?). We find no connection to homes with foam insulation, it happens everywhere. They do tell us its an IAQ problem LOL, its not the paper thin copper! Outdoor coils leak too, usually at the u-bends in the steel end plates- vibration abrasion, not formicary. Manufacterers won't usually help with labor or materials on a warranty coil. A large dealer can add some leverage to help you get something but a small contracter probably can't. This is going to get tricky with the refrigerant change next year, they say they will stock older coils but we will see...
I understand many of the Central Ducted system manufacturers offer "all-aluminum" coils, but on my Fujitsu RLS3, the inside coil is actually copper on the end loops even while it looks like aluminum all thru the fins area, which makes me believe they are actually tin-plated copper, not aluminum, per the below video. I wonder if there are any mini-split manufacturers that actually offer "all-aluminum" coils instead of tin-plated ones. The below explains formicary corrosion and other factors: https://www.youtube.com/watch?v=sHNF7SKU4Cc
I had a single zone mitsu 18k BTU failure due to poor installation by the first contractor I hired.
I replaced it myself several years ago and it has been working fine, although the new evaporator coil is already showing corrosion inside on either end. I clean the blower wheel and pan once or twice a year and haven't had a need to steam clean or use a coil cleaner on my indoor head yet.
There is much debate about the durability of these micro coils. If you pop on any of the manufacturers pages or on a few of the popular HVAC forums youll see this topic is hotly debated. Many manufacturers do not recommend any coil cleaning products on their coils. slightly acidic cleaners are a no. Slightly alkaline cleaners are a no. Ph neutral cleaners are a no. Some even argue the build up of organics, oils and greases from normal use on the coils do just as much damage. Depending on the end user and their habits, these coils can become pretty dirty or plugged in short order.
These micro coils have thinner copper and significantly thinner connections between the aluminum fins and copper tubing. My personal unit is in dry mode most of the year and I just have a feeling electrolysis is taking place as the coil is wet and condensating most of the year and there are the sections off to the sides where the coil sits pooled with condensate.
While I have had good success since I went out of my way to acquire my 608 cert, purchase the tools, and read as much technical documentation around these units, they are not a turn key solution they are made out to be.
They require deep cleaning once or twice a year, essentially fully disassembling the indoor units which isn't very difficult but it is time consuming and can make a mess if the unit is installed in a difficult location like over furniture, counter tops, etc.
After personally experiencing a failure in the winter, its hard to recommend a multi zone unit. I have a single zone and I think most would benefit from several single zone units vs a multi-head unit for redundancy. If one experiences an issue you won't be left in the cold so to speak. However if a leak or failure occurs with these units, the only proper way to recharge is with a fully evacuation and to weigh in the proper charge after repair or after locating and fixing the leak.
A set of gauges and a top off is not feasible. Finding a contractor to setup in the winter to tarp or enclose the outdoor unit and heat it to get a quality evacuation is going to be a challenge. Most residential contractors wont want to be bothered or will say its not possible to evacuate in sub 40 degree temps. Nor would they want to leave their pump running for a day or more on a unit then have to come back to finish the job if they choose not to heat the unit.
With the requirement to weigh in the proper refrigerant charge as the only method, this could leave owners without primary heat. Hopefully then they have a backup heat source.
As for costs, I am in the camp of these being disposable when it comes to repairs. Maybe if you're doing the work yourself but if the average owner looks at the price of a board or compressor or coil, something large with labor added, you might as well just have a new single zone put in and then not have to worry about again for a few years. Its sad to say. But with the single zones being at such a low cost and if you're paying for labor for either a repair or a replacement on a single zone unit, I would be tempted to guess that the replacement (assuming you can reuse the existing lineset) would probably be faster and or cheaper.
Not to mention most of these mini split manufacturers drop warranty if any on site brazing occurs so I can't see anyone brazing a pin hole leak shut. And if they do, do they want the headache of a call back if it fails or the unit fails later and they get the blame?
Again, I came onto this board a while ago with no experience with these units. Now that ive personally had one running since 2018? and now that I am wiring these up on almost every school retrofit job and in every data closet and deal with some of the trouble shooting I think mini splits can be a good choice for those with the tools, skill and DIY upkeep. And for those who can order a new head or outdoor unit offline and have it delivered in a few days, accept the lack of warranty and swap it in if they have a failure.
Im personally not sold that these are dependable long term units for non skilled homeowners. The additional evaporator cleaning alone (if having to pay a tech to come out once a year after cooling season to clean the mold off the blower wheel and the interior spaces of the unit) is cost prohibitive and makes any energy savings (money wise) a moot point. Might as well install a much more robust low efficiency forced air unit that can handle the abuse and neglect of the average home owner.
I personally think most of the HVAC equipment on the market is over priced, poorly made and doesn't hold up like the equipment of even the 90's and early 2000's. Ive been doing HVAC control work on commercial projects for about a year now which inst very long but the overall equipment just doesn't seem very durable any more. The additional electronics and sensors add complications and failure points. Building automation, integration and the overall drive for "efficiency" seems to have lead to less robust products. I'm sure there are others here who will disagree. But the older units ive worked on just seem to have thicker metal enclosures, larger gauge wiring, and less overall things to fail. VFD's and variable speed motors seem like great fixes and points of energy savings but at least in my short experience now, seem to not last anywhere near as long as single speed motors.
Again, I can only offer anecdotal input.
Just now saw this very interesting news from Fujitsu. Apparently they have been using "ProCore" copper tubing since 2019 with good results and they seem to be going to town with this news just recently. Anyone here that has installed a Fujitsu system in the last 5 years and still ended up with a leaking evaporator coil? https://www.youtube.com/watch?v=ZD5wLd58YYY
Fujitsu's "ProCore" copper page has the below suggestion. Anyone know what off-the-shelf cleaners might fit the bill? FROM: https://www.fujitsugeneral.com/shared/us/pdf-fcus-residential-technologys-procore-catalog-01.pdf
Coil Cleaning
Standard Copper Tubing
Oxygen-Free Copper Tubing
ProCoreTM Copper Tubing
In extreme environments, it is recommended that a contractor or installer follows industry preventative maintenance procedures and clean the coils of the indoor unit on an annual or bi-annual basis using a spray cleaner. Fujitsu recommends specially formulated alkaline detergent with the strength to dissolve grease, oil, dirt, tar, lint, nicotine, etc. without attacking aluminum fins. When mixed properly and when used in conjunction with a chemical neutralizer, this combination will ensure your system is properly cleaned. Mini-Split Neutralizer is used to neutralize the alkalinity of mini-split cleaner after cleaning and to prevent possible damage to aluminum fins from improper rinsing.
It's also intriguing that Fujitsu and many other minisplit manufaturers tout "all-aluminum" coils in their multi-position air handlers but continue to offer copper coils with what appear to be tin-plated/aluminum fins. If they moved toward all-aluminum coils in MERV-filter-protected units, shouldn't they have moved to all-aluminum coils for ductless units that don't have proper air filtration as well?