New Mitsubishi system set up

rconkling · January 2

Hello all and thanks in advance.

I just moved into a new construction condo with a pretty nice Mitsubishi HP city multi system and I want to make sure its settings are correct for best performance/efficiency.

The outdoor unit is the M Series - MXZ-4C36NA2-U1, with 1 PEAD A24AA7 or A15AA7 servicing the 3 rd floor bedrooms, and 2 M-Series - MLZ-KP09NA or MLZ-KP12NA-U1's servicing the main living area. Indoor unit sizing is unconfirmed because they list both as installed on the web portal.

Each indoor unit has a honeywell TH6320WF2003 thermostat with a PAC-US444CN-1 interface controller.

My understanding of the city multi MXZ is that is really a commercial VRF unit. Info on the system is quite limited online.

The thermostats are set up as a single stage gas system. Which just seems strange to me. But maybe thats where the interface controller comes in?

Is there a way to gain access to the system and see how the controllers are working or how they are setup?

My only other experience with a HP is a Daikin FIT, which I really like.

Im trying to find out what contractor installed the system and get info from them, but I also would like to verify what Im being told by them.

Cheers and Happy New Year!

Ryan

pecmsg · January 2

mitisubishi has a contractor locator site.
punching in the serial #’s may give the installing contractor information.

Choose your service provider wisely.

Kaos · January 2

Generally with modulating units, you want to use the factory communicating thermostat. These don't have the easiest user interface, so I can see why people would opt for a regular thermostat.

You can get the regular thermostat working reasonably well but it does need to be configured properly.

The themrostat should be set to 2 stage heat and cool (so lots of wires to the PAC) and the PAC configured properly. Without this, the units are simply on/off at full power which defeats the purpose of a modulating unit.

For the PAC,

you want to enable delayed off (30min is the best), fan to auto, stage1 operation to ramp (not full).

Make sure the thermostat is also configured for two stage heat and cool.

If they didn't run all the wires, there are wire expanders that allow you to have 7 wire control over regular 5 wires.

GW · January 2

Hi Ryan

M Series - MXZ-4C36NA2-U1 is not a City Multi, it's an M series (residential)—-someone has their wires crossed somewhere. It's not a Hyper heat either, in which climate zone do you reside?

PAC-US444CN-1thermostat interface—-that's a bummer, maybe the GC speced that and the installer had his hand tied. The MHK-2 is what you want. But what you have does the job

rconkling · January 3

Sadly I wasnt given any options on the HVAC side of things and I have no idea who designed and spec'd the system. But I have no doubt that keeping costs low as possible were the priority.

Based on what ive seen so far in the rest of the house, it will require some tinkering or replacing of parts to make it work as designed.

I do know they plumbed a make-up air duct from outside directly to the PEAD, but I dont see any way to control it. The super mentioned no one uses it. I now see why.

I live in Northern CA, Novato to be precise. Hyper heat is not required.

Where would the PAC likely be installed?

I do have 7 wires going to the thermostat.

Kaos · January 3

It will be in or near the electrical panel of the indoor unit.

You are in warm enough climate that fresh air without recovery is fine. Pretty much all new construction is tight enough that you do need mechanical ventilation. I would keep the fresh air feed open or if you have a CO2 monitor, adjust the opening to keep CO2 under 1000ppm. During wildfire season, you do want to closed.

rconkling · January 3

https://forum.heatinghelp.com/discussion/comment/1831541#Comment_1831541

Looks like the MHK-2 is a wireless thermostat. It appears to have a lot more functionality but I think Id prefer a wired connection since the wires are installed. Unless this can be modified to connect to the wires. But I dont see that in the install manual.

GW · January 4

what you state is correct

one rep once told me the Kumo adds more flexibility and functionality. They aren’t terribly expensive

rconkling · January 4

https://forum.heatinghelp.com/discussion/comment/1831802#Comment_1831802

Thank you.

I spoke with someone from the company that installed the system. They installed it to the plans they were given by the builder.

He agreed that its not ideal and recommended a wired T-stat but said it would also need a interface module for it to operate.

I may cave and use the MHK-2 since it comes with the interface module.

Cheers

pecmsg · January 4

so the builder speced the equipment.
that doesn’t work out well.

GW · January 5

@pecmsg all new construction is spec’s by someone, isn’t it? Unless it’s a custom build but isn’t that getting rare these days?

Everything has a pro and a con. Buying a condo- less decision making. Some people like it that way

GW · January 5

interface module—-it doesn’t come with that.

What you have now is called the interface module

Well it does have a little dongle thingie, but most people wouldn’t call it an interface module.

Kaos · January 5

There are wired thermostat options as well:

https://mylinkdrive.com/USA/M_Series/R410A_Systems-3/Outdoor_Equipment/R410A_Outdoor/PEAD_A24AA9?product&categoryName=R410A_Outdoor

I remember those being a 3 wire connector but could be wrong, either way you have enough wires with the existing setup. The cost of a thermostat, never mind two, is high enough that it isn't really worth it. I would get the existing thermostat and PAC-444 set up the best you can and see how it runs first.

pecmsg · January 5

https://forum.heatinghelp.com/discussion/comment/1832028#Comment_1832028

The GC doesn’t give a flying F#%k about the buyers energy usage or Comfort. ALL he cares about is HIS bottom line.

really!

pecmsg · January 5

https://forum.heatinghelp.com/discussion/comment/1832028#Comment_1832028

So that justifies being wrong?

GW · January 5

I’m unsure what you are asking, it’s not right or wrong, it’s just the way it is.

rconkling · January 15

https://forum.heatinghelp.com/discussion/comment/1831540#Comment_1831540

I think I figured it out.

On the PAC-US445 I have all the dip switches off. The installers had SW1-1 on which caused major short cycling.

T-stat is set up for conventional electric 2 stage heat and cool, with T-stat fan control.

Seems to be running lower fan speeds initially now which is nice.

I may still end up with the MHK-2 in the near future.

Kaos · January 15

There are screws that hold on the cover. You unscrew those to open and adjust the dip switches.

rconkling · January 15

https://forum.heatinghelp.com/discussion/comment/1834900#Comment_1834900

Thanks I finally figured that out. I thought they would be on the side, easily accessible.

The system is definitely running differently. Ill see how it goes.

rconkling · January 15

Well so far its a complete failure to have SW1-1 turned off.

Not sure what climate zone this is supposed to operate more efficiently, but it cant be mine. Although I guess efficiency and comfort dont always go hand in hand.

The Ceiling cassettes never turn off, the fan runs off and on, but mostly stays on, even with no call for heat. So the room feels a lot colder due to the cold air movement.

EDIT:

I put SW1-1 back on and lowered the CPH from 9 to 6 during heating mode.

Kaos · January 16

Multi splits have a nasty habit of not modulating the indoor unit properly, sometimes have to play with the settings and find one that gets you decent comfort.

New Mitsubishi system set up

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