Mitsubishi ductless mini split: never shuts off?

[Flargen]

Hey all,

I recently installed a Mitsubishi 15k/18k ductless mini-split in my garage (now that the insulation, sheetrock, and electrical **** is finally done after nearly 4 years):

My vendor recommended the PAR-33MAA thermostat as part of the bundle, which ended up being ~$2,200 after taxes including everything except electrical wiring, line set covers, and a flaring tool (since none of my professional AC buddies have one?). Little did I know it's a freaking $300 thermostat, but I digress...

I guess I'm used to conventional central air systems, so my question is this: when I set the thermostat to cooling mode and set the target temp (leaving it at 78 degrees since I'm laid up after surgery for about a month), the system is ALWAYS running: both the condenser and cassette. The condenser seems to vary in terms of its load, so I guess these systems are meant to run 24/7 more or less?

Should I worry about setting the thermostat timer to shut the system off entirely for 10-12 hours per day? Even if it's a variable output compressor, part of me feels weird about the system operating 24/7. It's not an issue of holding temperature, either: it does this in "dry" mode, and will easily hold any temperature I've thrown at it (72 through 80).

Thanks in advance!

 

[Voi]

The condenser seems to vary in terms of its load, so I guess these systems are meant to run 24/7 more or less?

I think that ceiling cassette will ramp down to below 4000 BTU/hour so I wouldn't worry about it one bit. Better for it to be running that cycling on off is what I was told.

 

[PoorOwner]

Is it a m series or p series unit? P series have heavy duty components and are built to run 24/7. M series more meant for seasonal and occasional use.

On the cassette head and mhk1 thermostat there IS a way to shut the indoor fan off
Not sure on the PAR thermostat. There is a really big manual you should take a look closely.

The condenser at some point will shut off but it needs to be cold enough maybe 1-2 degeee more than your set point to do so.

 

[walta]

You just discovered why mini splits are so efficient. They almost never turn off they just speed up or slow down.

They are made to run nonstop, just get use to the hum of it running.

Walta

 

[yeldogt]

The P series is light commercial and extreme operation -- when you need to cool in cold temps or the unit is going to run flat out all year. The M is the normal residential.

My M will shut down when the temps have exceeded the set point --- leak when it gets cooler outside and the temp in the house is colder then the setpoint. Otherwise it's on.

The M comes in the smaller sizes .. the p goes higher.

... that looks like the P controller and unit .. they make a hyper in the P now.

The ceiling units don't function the same as the wall units --

 

[justinjoyal]

Let it run.

 

[Lelandwelds]

"Never " shut off is an exaggeration but if they're sized correctly they ramp up and down to almost not running. The evaporator stays cold so humidity is removed more efficiently.

My system isn't as fancy as yours. My install wasn't perfect. I am still pretty happy. Most days I have about 15 gallons of water removed. Pretty comfortable. I am unhappy with the filtration and air circulation. I plan on something free standing to fix.

 

[bobbyjean]

you love your cars alot...does the garage act as a shop as well?
you picked a great unit...Set it and forget it

 

[Jackfre]

Also, if you think about it, what is it that kills equipment? Starts and stops are not good for equipment. Also not good for the electric bill as you have that inrush current on start-up. Our conventional HVAC equipment has been single stage on/off, although we are beginning to see multi-stage equipment coming to market. Keep an eye on your electric bill and let the system run as it wants. Keep us posted on what you see and your comfort level.

 

[Tracs]

Inverter mini-splits are designed to pretty much run continuously, and ramp up and down as stated by the others in this thread.

As a side observation, I have a inverter 18,000 BTU Perfect Aire (I don't even know who makes them), and I keep my garage a 72F. Up north that is only 5 months of cooling, but it only adds maybe $20 per month.

 

[Flargen]

Thanks for all the input, guys. I'll keep an eye on it (along with my power bill).

you love your cars alot...does the garage act as a shop as well?
you picked a great unit...Set it and forget it

And yeah, I do love my cars a lot - the E39 M5 was a long-standing dream that's finally come to realization, and my XJ has been to hell and back with me (currently building a stroker after breaking a piston skirt at 240,000 miles). The garage is primarily a shop, but will only be seeing storage duties for another month (just had major surgery and can't really do anything til early August). This is actually the first time in 4 years of owning the house that it's housed 2 vehicles.

Oh yeah, and my old '67 Fiat Dino might be coming back into my possession in the next few months, so the garage will likely continue to see storage duties pretty regularly as well.