Mr. Cool Mini Split

[Tonty]

Wrapping up a Mr. Cool mini split install in my brother’s house. It’s the house I grew up in, and has never (at least since 1981) had any other heat than a wood stove. He and his family are out of country for a few years, and we want to rent the place out, so we needed a more user friendly setup.
We installed two outside units, a 27,000 btu feeding three 9k air handler units in bedrooms, and a 36,000 btu feeding a 24k air handler in the main living area, and also a 12k air handler in a bigger bedroom. This is in an old (1900 or so) two story farmhouse, that has been mostly renovated in the last 30 years or so. But would by no means be as tight as a newer house.
These were the DYI units, and we did all of the install work ourselves.
We’ve had the units up and running for a few weeks, but I don’t really feel like I have much to go on yet. So far, they’ve been heating it well, but we haven’t been running them all, or even some all the time, as we do not have anyone living there yet. They have a WiFi module, so I can keep tabs on the temps to make sure it doesn’t freeze.
I’ll try to update here as I know more. Feel free to ask install questions if you have them.

 

[EatenByLimestone]

These 7nits are pretty interesting. Did you have any trouble with the fixed length hoses? What did you do with the extra length?

 

[Tonty]

Here’s how it went. We thought we knew where we wanted to place the air handlers, so we did some measuring and ordered the line sets and units. Some runs were quite long, so we had to order some of the coupling sets used to couple two line sets together. When we got the units, we realized two things: some runs were too long (it appears like from the instruction manual they recommend maximum 49’), and also some of the air handlers wouldn’t fit where we had planned. So we did a bit of head scratching, and moved some units to different locations where they would fit, and to keep our maximum run to a 50’ line set. That worked quite well, and we didn’t have to use any of the coupler sets. But a couple of the line sets were just the wrong length so that we couldn’t coil them, but just too long that they needed somewhere to go. We made it work, though.
I can get some pictures if anyone wants to see them.

 

[EbS-P]

Here’s how it went. We thought we knew where we wanted to place the air handlers, so we did some measuring and ordered the line sets and units. Some runs were quite long, so we had to order some of the coupling sets used to couple two line sets together. When we got the units, we realized two things: some runs were too long (it appears like from the instruction manual they recommend maximum 49’), and also some of the air handlers wouldn’t fit where we had planned. So we did a bit of head scratching, and moved some units to different locations where they would fit, and to keep our maximum run to a 50’ line set. That worked quite well, and we didn’t have to use any of the coupler sets. But a couple of the line sets were just the wrong length so that we couldn’t coil them, but just too long that they needed somewhere to go. We made it work, though.
I can get some pictures if anyone wants to see them.

I’m haven’t read the specs at what line lengths does one need to add refrigerant?

 

[Tonty]

You don’t need to add refrigerant. The line sets are all pre evacuated/charged, as is the unit and the air handler.

 

[EatenByLimestone]

Probably more than 50ft, lol.

I’ve heard that come hvac companies don’t want to service them, but they have really good customer service. It may not matter. If it lasts 10 years and you have to replace it, you may be way ahead.

 

[semipro]

It's a little hard to imagine a precharged line set until you see them. There is an internal valve at each end of each line that contains the refrigerant and opens to allow flow when the connections are made.
You'd think that some refrigerant would be released while you're making the connections but I noticed none.

My only gripe about the universal MC units I installed is that the air handler fans are two-speed, and you have to configure either low or high even though I suspect the motors are DC. They are not variable during operation. The outside units have both variable-speed fans and compressors - very quiet.

 

[Tonty]

The units we put on have 4 different settings: low, medium, high, or auto.

 

[EbS-P]

Are the multiple head units the same as the single head? (I would guess so). Is this the new 4th generation that I keep seeing adds for?

 

[Tonty]

Are the multiple head units the same as the single head?

As far as I know.

Is this the new 4th generation

Yes, these are the 4th Gen series.

 

[Highbeam]

These 7nits are pretty interesting. Did you have any trouble with the fixed length hoses? What did you do with the extra length?

Here’s what I did with the extra. You can’t cut it and you can’t coil it vertically so I did this thing behind the outside unit.

 

[peakbagger]

The horizontal coils are definitely the way to go, there is a lubricant in the system and if the loops are vertical the lubricant can separate out and collect in a low point if the loop is vertical. That said its probably not that major of issue as my 12 year old minisplit(cooling only) was installed by a "trained" Mitsubishi rep and he had extra and coiled it up in horizontal loop. I had not researched minisplit installs at the time but he definitely did not follow standard practices and yet it still is running.

 

[EatenByLimestone]

I like the coil idea!

 

[EbS-P]

thought they were disposed to be install so gravity gets the oil back to the compressor??? So a flat helical shape is best????

 

[Highbeam]

thought they were disposed to be install so gravity gets the oil back to the compressor??? So a flat helical shape is best????

Correct, that’s why I did that. Horizontal coils are required by the installation manual for just that reason.

 

[stoveliker]

I think there is a misunderstanding regarding the naming of the orientation of the coil: its axis or the plane in which the coil lies.

I think you all agree.

 

[peakbagger]

Sorry for the confusion Horizontal coils are the way to go. I will correct the post. I swear its minor dyslexia sometimes, as I tend to transpose typed words on occasion.

 

[EbS-P]

I think there is a misunderstanding regarding the naming of the orientation of the coil: its axis or the plane in which the coil lies.

I think you all agree.

Last exam had a question where it said the coil was laying flat on the table. It was not clear enough but hid I said plane of the coil parallel to the table top plane there would have been more questions

 

[EatenByLimestone]

I think there is a misunderstanding regarding the naming of the orientation of the coil: its axis or the plane in which the coil lies.

I think you all agree.

Sheesh! Way to stop an argument where everyone swears they’re way is the right way!

 

[stoveliker]

Now if I only was able to apply the same method to myself...

 

[Highbeam]

Horizontal coil has lines stacked vertically? Ha!

That’s why I put up a picture. You can bet people argue about whether it matters because it’s a pain in the butt to lay the coil flat as directed and the manual even has a picture.

Even mrcool’s installation videos show the extra being coiled vertically behind the compressor which is contrary to the directions.

Minisplits have the expansion valve in the compressor so the lines should be moving gas, not liquid.

 

[Tonty]

Just a little update. We’ve been having some cold weather (for Kansas, at least). Low last night was -9.9*F with a wind chill of -32.3*F. The house we put these mini-splits in is currently an Airbnb and there aren’t renters there at the moment. So I’ve had one or two units set to 62* (lowest set point, unless you put it in freeze protection mode). I’ve been kind of surprised that they are still pumping out heat at that low ambient temp. We have been supplementing a bit with a wood stove, and I don’t think they’d get it up to 70*, but they do blow some heat even at this low temp. This is an old (for here) two story farmhouse that has mediocre insulation and windows.