Mini Split Reliability

[Sigarms]

I have a 30k BTU fujitsu halcyon as our main A/C and backup heating. The unit and system itself has been perfectly reliable for 6 years now, BUT, we did have a refrigerant leak that no HVAC company could find. Got a few opinions before spending $1k just to evacuate and recharge it. Working well again now, but we'll see for how long.

As far as heating efficiency goes - it does really struggle when the outdoor temps go below ~20f. We never use it when it's that cold out, since our primary heat is the woodstove. But I've tested it during cold snaps, and it really struggles. It kinda makes sense though, you are trying to extract heat from frigid outdoor air and add 50-60 degrees into your house. Versus A/C mode when you max out at around 30f of temperature difference.

You probably have a 30RLXB unit. 2.5 ton of air conditioning.

The question is, if you needed 30k of cooling, exactly how much heat did you need at what outside air temperature design condition?

Since you already have a primary heat source other than a mini split, I can only guess that the installing contractor gave you a lower price on a system that could produce less heat vs a system that could produce more heat, but being more expensive.

If you had a refrigerant leak and the HVAC contractor could not tell you where the leak is coming from, but still charged you 1k to evacuate and recharge it, I would never use that contractor again. You don't spend a thousand dollars to just roll the dice and hope for the best IMO when the leak is either coming directly from the equipment coil (indoor or outdoor) or line set and or connections.

 

[LouNY]

I have two 36,000 btu Mitsubishi units with 7 heads rated to produce heat down to 25F.
They are going on 6 years old, my AC cost in the summer are significantly lower then with multiple window units.
They do a good job of heating in the fall before I light up the coal insert, and in the spring when it goes out.
My primary heat is an oil fired boiler the split units are a bit less costly then the oil.
Here is a link to a very good heating cost calculator for most any fuel;

Fuel Comparison Calculator for Home Heating | Coalpail.com

You enter the cost of your available fuels and the actual efficiencies and see the actual cost per million btu

 

[IXLR8]

I have a 12K Btu Mitsubishi unit, only thing I have done to it in the 8 years we have had it is to clean the fan 3 times. Doesn't provide much heat below 20dF outside so we fire up the wood stove anytime temps get below 25dF. Newer units will provide heat to 0dF.

 

[deezler]

You probably have a 30RLXB unit. 2.5 ton of air conditioning.

The question is, if you needed 30k of cooling, exactly how much heat did you need at what outside air temperature design condition?

Since you already have a primary heat source other than a mini split, I can only guess that the installing contractor gave you a lower price on a system that could produce less heat vs a system that could produce more heat, but being more expensive.

If you had a refrigerant leak and the HVAC contractor could not tell you where the leak is coming from, but still charged you 1k to evacuate and recharge it, I would never use that contractor again. You don't spend a thousand dollars to just roll the dice and hope for the best IMO when the leak is either coming directly from the equipment coil (indoor or outdoor) or line set and or connections.

Yep I think you pretty much nailed it. We had three repair opinions from HVAC folks around here, at $100 a pop, and they all quoted me exorbitant prices just to find the problem before even possibly correcting it.

The final company we went for repair with pressurized the system and it held for hours, so it's a little confusing how we could have lost all our refrigerant. Maybe it was under filled from the start and just limping along? We knew and agreed that we were taking a gamble by simply refilling it and hoping it holds. But I was a bit tight on cash and it was a heat wave in July, we needed it working, and thats what we got. I think it was actually only ~$800, but that still felt like a lot.

I think our original installing contractor just didn't really know what he was doing. We probably don't need 30k of air conditioning, heck, some summers we hardly use it at all. Our house is super insulated and partially earth-bermed, it stays nice and cool unless a multi day heat wave comes along, which isn't every summer in Michigan. And we only use it for heat during the shoulder seasons (fall/spring) when its too warm to justify firing up the woodstove. So it's always running well below its full capacity, not ideal.

 

[Sigarms]

Yep I think you pretty much nailed it. We had three repair opinions from HVAC folks around here, at $100 a pop, and they all quoted me exorbitant prices just to find the problem before even possibly correcting it.

The final company we went for repair with pressurized the system and it held for hours, so it's a little confusing how we could have lost all our refrigerant. Maybe it was under filled from the start and just limping along? We knew and agreed that we were taking a gamble by simply refilling it and hoping it holds. But I was a bit tight on cash and it was a heat wave in July, we needed it working, and thats what we got. I think it was actually only ~$800, but that still felt like a lot.

I think our original installing contractor just didn't really know what he was doing. We probably don't need 30k of air conditioning, heck, some summers we hardly use it at all. Our house is super insulated and partially earth-bermed, it stays nice and cool unless a multi day heat wave comes along, which isn't every summer in Michigan. And we only use it for heat during the shoulder seasons (fall/spring) when its too warm to justify firing up the woodstove. So it's always running well below its full capacity, not ideal.

The realtiy is that 30k unit would run fine for only needed 10k of air conditioning if that is all the load that is required.

With mini splits and inverter compressors, as long as you know what you low range is for cooling and that will work for cooling, you generally oversize the AC to hit what you need for heating. One reason why a load calculation (if done properly LOL) is important, particularly with mini splits. Point being, capacity use to be rated arund 50%, so you're fine not wasting anything running below it's maximum capacity.

If the system had the "leak" within the manufacturers warranty, I would of nailed the installing contractor. Leak is either in the indoor coil, outdoor coil, or line set or line set connections to the indoor and outdoor unit. Charge could of been off depending on line set run as contractor HAS to add additional charge generally by the foot after 15' . Other issues if going down that rabbit hole, but IMO the installing contractor should of been able to figure that out at worst case, talking with technical.

 

[rademamj1]

Minisplit AC systems first started out in the Asian market by Mitsubishi in 1960, and was called the ductless AC systems. Central Air Conditioning, which is very common in the US, is just not utilized in Asian homes. Typically each room has it own minisplit, and you only operated the minisplit in the specific room your currently in. My house there has 5 Mitsubishi minisplits installed in 2007, and they are still working very well 14 years later. Only maintenance required was an occasional refrigerant recharge. In the long run, I found they were significant electric power savers and reliable.

After finding there way to the US, heat pumps are now incorporated into the minisplits.

 

[Sigarms]

Central Air Conditioning, which is very common in the US, is just not utilized in Asian homes.

You will find most of the world does utilize ductwork in the home to distribute conditioned air other than North America.

 

[herm0016]

3 heads on a mitsu hyperheat. we ran it when it was 20 below and it was still heating when our boiler could not keep up. about 2 years in and no issues. it was the only way we could really add AC to our house and its so nice in the summer.

 

[Sigarms]

3 heads on a mitsu hyperheat. we ran it when it was 20 below and it was still heating when our boiler could not keep up.

Either your boiler / radiant tubing was undersized or your mini split was oversized if a mini split could out perform a boiler for heating

Mitsubishi did a great job with that marketing term. The reality is other mini split manufacturers have the same heating performance, and in some cases outperform the Mitsubishi. No different than Carrier with Puron and hybrid heat.

When it comes to heat in very cold weather, nothing can be hydronic/radiant IMO.

 

[Popgadget]

I have a 3 head Sanyo system in my shop that is 20 years old. It still works great.
The only issues that I have ever seen are all installer induced. Poorly executed flare connections are very common. But the equipment is very reliable. I would definitely stick with the “big” names for parts and support in the long run.