Mini split preference

DC123

Hello,
We have a 10 year old multi-zone ducted Fujitsu minisplit (which covers two zones on the 2nd floor) that just crapped out on us. Acknowledging that the contractor remains the most important part of the equation, I was wondering if you all had a preference on brand? Cooling requirement for the two zones is likely around 15k BTU. Also, not sure if it's possible to just replace the outdoor unit, or if this would require replacing all the indoor components as well (assuming it was replaced with another Fujitsu model).

thanks!

NY_Rob

My AC guy likes Daikin or Mitsu.

Here's what he recommended for my upcoming install this spring:
https://www.ecomfort.com/Daikin-D3H36W09092400/p66139.html

5 yr parts, 7yr compressor warranty on the Daikin.

GW

General opinion is they’re all quite similar. I’ve done Mitsubishi for 15 years or so. We have a local vendor with a really good field tech. We don’t need him often but when Ductless systems act up, you gotta have some ducks in a row because the labor can get jacked up with some of the glitches we have ran into.

Do yourself a favor, hire a guy with a solid history. Or, roll the dice with a cheap guy if you’re feeling like you need a quick break on costs.

DC123

Thanks, all. One other question that may be tough to answer - AC guy thinks the issue is in the outdoor unit and recommends replacing the unit with the newer model (AOU36RLXFZ) but thinks it may be possible to keep the indoor air handlers since they are in fine shape. It's a AOU36RML1 (about 10 years old, uses r410) outside attached to three Aru12 indoor units. It's not clear to me that the new unit will communicate correctly with the indoor units. Does anyone have any experience with this?

ratio

The manufacturer would be able to tell you definitively. FWIW, Mitsubishis will work one generation in either direction, but not further. Too bad our Guestimator didn't know that when he quoted a new indoor head on a system two generations old...

GW

Yes I concur. The labor can quickly over run the costs of cutting the bait and getting a new system installed. No one said life was fair. I’ve replaced units in the past at no charge for our good customers (some psychology kicks it, if someone expects a free install, I charge them!)

Not knowing the answer isn’t a crime, which contractor knows everything . I call the rep all the time with questions.

You may wish to ask for a price to simply swap the indoor units too, now you’re good to go with a new warranty. Or you could kick the can down the road, yet at some point the indoor units will require work.

Big Ed_4

Why does it has to be replaced , did you look in to repairing ?

DC123

I don't know enough to know how to diagnose these things, but the diagnostic approach of the tech was as follows:
Initially told by the Fujitsu support that the system was not functioning because of a high pressure issue and recommended cleaning indoor coils and/or replacing the pressure switch. However, when the tech looked at the air handlers, they looked pretty clean. The main board and PCB of the outdoor unit had a couple spots that looked a little fried though, so he's assuming that may be the major issue. However, he can't be 100% sure and recommended replacing the outdoor unit at a minimum as the unit is 10 years old and he didn't think it was worth putting too much work into it. He also noted the wiring from the outdoor to the indoor units was a little funky (I think he mentioned too many splices) and recommended re-wiring.

I'm a little leery of paying a couple thousand to replace the boards if there's no guarantee that there isn't a problem somewhere else in the system. But if I can't just replace the outdoor unit and need to redo the whole system, that may change things...

I'd love to hear any thoughts, thanks.

GW

I think you’re on track, meaning, you need to decide what’s best.

High pressure? Can’t the tech check pressures on the service valve in heating and also cooling, and then repeat the process one more time. The second time on the high and low side of the compressor. And if this is two zones, he needs to check this entire sequence 3 ways: each zone and both zones on together. I would think this would be A few hours though. Perhaps it’s a sticking reversing valve or something else causing pressure issues. A reversing valve change is a bit of a pain, could be a full day of labor

Repairs can get costly so choose wisely

Jack

Splices in the control wiring is a no-no. A loose connection in the wiring will send that unit into orbit. You have 1-2 & 3 connections plus ground. 1 & 2 are 120v legs. 3 is a comm leg and makes its circuit through 2 & 3. Anything but clean power and no splices is unacceptable. I have your model condensing unit on my home and my daughter has one in her home. I just put the new 24 k tri in my other daughters home. I do not know if the evaps can be kept. Call Fujitsu with models and serial numbers. They will tell you. Ask your contractor to check the parts pricing. You just have to look at the numbers and make a decision. Setting a new condensing unit and evaps is generally not a huge issue...then again you have the ARU’s. Whatever you do, pull new wire.

Big Ed_4

I assume the evaporation coil was not cleaned and the pressure switch was not replaced ? So we don't know ...

DC123

Thanks! This is all very helpful.

Dennis

The outside unit has dirty coils. They may appear to be clean but I have found the dirt can get deeply imbedded between the fins with the surface looking clean. Other issue might be the condenser fan motor. The tech should not be guessing what is wrong. 10 years is not old, I have a few installed well over 20 years ago and all working fine.

One of my customers recently fell for the "$49 limited time only inspection and maintenance agreement". Their tech claimed the 5 year old 4 zone unit I personally installed had a bad compressor. Coupled with a quote of $25k to replace the system, or $6k for the compressor. I was the second opinion, to my own customer. A good cleaning was needed due to the neighbor having major construction done next door (row house) and the unit was back working perfectly.

Very important with mini splits, the flare joints, are critical. A special flare block is needed, we use a digital torque wrench for accuracy. After we switched to the digital torque wrench our incidence of leaks went to zero. I would also suggest pressurizing the lines to 500 psi while leak checking, and then pull a vacuum and let it sit for a couple of hours or overnight before giving the lines a leak free status. On VRF systems we pressurize 150 psi for an hour, 300 psi for 12 hours, and 600 psi for 48 hours. If the pressure does not change by more than 5% we know the system is leak free. Leaks will kill mini splits.

Big Ed_4

You found the torque wrench was worth the investment ... Thanks I will add that for my next install ... I have been adding the surge protector .. Figuring it could not hurt and I hate changing boards in these units ... My last one I had to change was on a ladder ... Ugh!

NY_Rob

A lot has changed since I installed my 4-head Panasonic mini-split in 2013... No nitrogen purge, no 24 hour 550psi test, no triple evac, no micron gauge needed, etc.... back then.

My 2013 Panasonic factory install manual suggested connect lines, draw down to -30 inHg for 1-2min, check the manifold gauge for return- if no return you're done/ready to power up unit. Use soap/water mix to check for pressure leaks while running.
They did however note the importance of deburring before flaring and the importance of using a clutch/eccentric type flare tool (they even suggested using Rigid brand tool). They also suggested lubricating the flares and applying correct torque with a torque wrench.

I have read that down in Mexico, South America, etc... they simply install the indoor unit- connect the line set to the outdoor unit and fire it up. No pressure test, purge, evac, etc.. and they still run for 5-10 years! Up and running in 1/2 an hour!

DC123

Ended up getting rid of the outdoor unit (AOU36RML1) and replacing the one zone comprising two indoor units with a single ducted 12k BTU Fujitsu 12RLFC that had a SEER of 20. Re-routed the lineset for the other ducted zone, with an attic indoor unit, to another functioning AOU36RML1 on the other side of the house (since they are from the same era). All working great so far. Fujitsu now has a 12 year warranty, which is much improved from prior.

bob eck

What is the average life of a ductless HP unit like Daikin, Fijuitsu or Mitsubishi. Is it 5, 10 or 15 years?
What type of maintenance is required on this type of system?

SuperJ

I'm thinking of putting a Mitsubishi mini split in my kitchen but, the cleaning videos on youtube are scaring me off. Looks like they get pretty nasty inside and are a pain to clean. The disassembly process looks like a recipe for broken parts over time. An annual professional cleaning is likely expensive enough to offset the savings versus a conventional central air system.

https://www.youtube.com/watch?v=2e6by0tV8h4

I don't want to mister negative but I haven't seen an easily end user serviceable mini-split yet.

SuperJ

I wonder if UV or some other sterilization systems might reduce the dependency on regular disassembly for cleanings.