Setting Fan Speed

Jeb1

I have multiple Mitsubishi SEZ-KD12NA4 indoor units. They are controlled by 5 Nest Thermostats. Is there a jumper or a way to set the fan speed to high or medium on the unit when the thermostat calls for cooling?

pecmsg

What happened to the Mitisubishi controllers?

You couldn’t pick a worse t-stat then NEST to control that system!

Jeb1

That is what they installed

GW

Most Mits guys will use the MHK2 stat,which allows you to select different fan speeds. I’m sorry I don’t have an answer for a very simple question. The Nest can’t handle any real communication other than “give me heat or give me cool” 

pecmsg

THEY installed NEST?

Ask for the Mitsubishi controllers that came with the equipment. 

Jeb1

My wife only wants one unit for each as we also have zoned oil water heat

pecmsg

Good luck then. 

ratio

Mitsubishi tech support has always been helpful to me. Also, AFAIK ALL Mitsubishi documents are available online at mylinkdrive.com.

Jamie Hall

Jeb1 said:

My wife only wants one unit for each as we also have zoned oil water heat

The Nest isn't much good for that, either.

If you only want one thermostat for each unit (how is the oil heat zoned by the way? Is it zoned? Do the zones correspond to the heat pumps?) and you want variable speeds on the fans... you are basically going to be designing and building your very home, custom purpose built control system. The interface with the oil heat won't be that much of a hassle, but you will find you need to figure out what control signals the Mitsubishis are expecting. Have fun...

GW

Oh— you have integrated controls? That’s the only semi-logical reason for having a nest(s in this situation. 

As you may have picked up, not many nest levers on this site

Jeb1

Are there any Qualified Mitsubishi AC companies in southern New Hampshire that can help correct this issue?

GGross

@jeb21
https://www.mitsubishicomfort.com/find-a-contractor

3rd party stats never work well with mini splits. The thermostat needs to communicate with the system to actually get what you paid for. Many contractors don't know this, many more just install whatever the homeowner asks for whether it will give full functionality or not. Luckily I ran into this problem early on. The best thing to do is use the little remote controls most mini splits come with, if thats not your bag, you really need to purchase the brand specific wall controls, and sometimes those are really ugly. All of the technology that is in your thermostats, which cost extra money, was already included in the unit and the built in controls actually work correctly.

Jamie Hall

Jeb1 said:

Are there any Qualified Mitsubishi AC companies in southern New Hampshire that can help correct this issue?

There are only two possible "corrections" for this.

First, and best, as has been said above, is to use the controls which are designed to communicate with your minisplits. Either your installer should still have these, if you don't, as they are packaged with the units by the manufacturer, or he or she may be able to source them independently. Other Mitsubishi dealers may be able to source them for you as replacement parts.

The second is to determine -- possibly from the manufacturer, but unlikely as the systems are proprietary -- exactly what the communication protocol for the minisplits is You may have to find an electronics engineer to do this work. Then, once you have determined that, design and build your own control system, including a bespoke temperature sensors and a computer with the appropriate software and peripherals, to control the minisplits and the boiler.

Not that this can't be done. It can, and there are people out there who do this sort of work. You might even find a hobbyist who would be interested in doing it -- for a reasonable fee,, of course, say a few large. Yor Mitsubishi dealer is not going to be equipped to do it, nor will any other normal HVAC person. Oddly such an individual may not be all that hard to find, as you have a couple of very high end defence electronics contractors in your area who have staff who are qualified.

BlueGreen

My kitchen mini-split I had installed to run when needed since the heat gain is so variable and the central AC could not keep was always a pain to keep running at the right times and fan speeds and temps etc. I finally tamed it with a wall mounted Cielo Breeze control/thermostat that talks to the mini-split over IR and makes it so the mini-split is only on when it needs to be with the daytime schedule I programmed it for.

It talks to the mini-split like a remote and works with about every min-split out there.

I think Sensibo is another brand that does about the same thing.

In a perfect world all mini-splits would have a wall mounted thermostat instead of a remote.