Mini-split A/C and Hardwired TStat

[GadgetHome]

You can integrate any Mitsubishi or Trane (OEM Mitsubishi) mini-split or VRF indoor unit to HS with a T-Stat Interface adapter PAC-US444CN-1 + a 240Vac (primary) to 24Vac (secondary) Xformer + any third-party Z-Wave T-Stat. No cloud service is needed. See attachment.

I'm using a Trane XL624 t-stat (no need to connect to Trane's Nexia Cloud Services). It integrates with Alexa as any other ZW T-stat.

http://mylinkdrive.com/viewPdf?srcUr...-US444CN-1.pdf

https://www.amazon.com/Mitsubishi-El...0947442&sr=8-6

https://www.amazon.com/TRIAD-MAGNETI...0947534&sr=8-3

Hope this helps.

I recently installed a Mitsubishi split system. Here's what I learned.

I first went with the PAC-US444CN thermostat interface and had all Honeywell T6 z-wave thermostats on hand. I had spoken with Mitsubishi tech support several times to confirm that configuration would work. However, the three different people I spoke with at technical support always added that "not all features would be available," though none could tell me what features I would be giving up. That changed when the Mitsubishi rep showed up to check on the install that was in progress, he provided a little more information. While the configuration will "work," it will not work well, he said. As it turns out, most (perhaps all) wired thermostats perform binary on/off cycles with the Mitsubishi heat pump instead of adjusting the performance of the inverter. So instead of operating at variable rates, rising and falling based on temperature, the wired thermostats would operate the heat pump at either 0 or 100 percent--all or nothing--forfeiting a lot of the efficiency.

Well, that made sense to me. I gave in and went with the Mitsubishi RF thermostat with Mitsubishi's "Kumo Cloud" and returned the several hundred dollars worth of z-wave thermostats I had purchased. (I still use a couple of T6s for my heating system and love them.) Fortunately for me, the dealer agreed to eat the cost of the change because it had failed to advise me of, and had not been aware of, the limitations of a wired z-wave thermostat.

Here are the results:
The Mitsubishi RF thermostats are made by Honeywell and look identical to the T6 z-wave units. While HomeSeer is not yet talking with my Mitsubishi system, it turns out that the cloud solution with scheduling fulfills 95 percent of my automation needs. And my electric bill reflects the savings created by the heat pump inverter. Admittedly, I have trouble with being forced go to the cloud to control something in my own home, and I would like more control via HomeSeer. But life is full of trade-offs, and in the larger scheme of things, this trade-off has not been that bad for me.
--Dennis

[copras24]

Dennis,

The PAC-US444CN (T-Stat Interface) does NOT make the inverter system operate as a conventional system with 0 or 100% capacity. If proper settings are adjusted via DIP Switches on the PAC-US444, and the T-Stat is adjusted for 2H/2C, the system will operate with variable capacity as intended. The interface monitors the Y1/Y2 or W1/W2 signals simply to know how close to Set-Point the room-air temp is. if the Y2 or W2 signals are energized, the system will operate at full capacity. If only the Y1 or W1 are energized (meaning that room temp is close to set point), the system will modulate capacity to stay in that zone for as long as possible. If Y1 or W1 de-energize (no voltage), then the PAC-US444 just learned what the Set Point is on the third-party thermostat.

[silverton38]

I know this has been discussed before, but my question is a little different.

I am going to add A/C to my garage, and a mini-split is my preference because I'm not sure where I'd put an air handler for a regular unit. Plus mini-splits are cheaper!

While those remotes they include are fine, I also want to control it through HS4. Some of the manufacturers offer "smart" solutions which seems to always require using their proprietary app. Others allow a 3rd party smart wi-fi TStat, but they also require a cloud connection.

This is a new installation so I can use any brand I want, but the manufacturer websites aren't clear on adding a wired TStat.

Yes, I know I can use an IR blaster, but that doesn't provide 2-way communication.

Don't want to go the wi-fi route unless there's one that does not require an internet connection and will integrate with HS4. Another potential issue with wi-fi is the manufacturer messing with their API (like what just happened with MyQ last week that required days to get fixed!).

My preference is to find a way to use a Z-wave TStat like the Honeywell I use to control my Carrier central air unit.

I've also had an A/C contractor over and he's looking onto it for me, but it's been 3 days and no word from him yet.

I suspect that Carrirer or Mitsubishi has some sort of module that let's you hardwire a TStat but I can't find it easily on the interwebs. So before I call their tech support, wait 45 minutes on hold, then try to interpret what someone from another country with marbles in their mouth is mumbling, I thought I would see if anyone here has figured this out already.

Thanks in advance for any help!

You can install a regular Tstat for most split units. Check your installation manual for details.

[GadgetHome]

Dennis,

The PAC-US444CN (T-Stat Interface) does NOT make the inverter system operate as a conventional system with 0 or 100% capacity. If proper settings are adjusted via DIP Switches on the PAC-US444, and the T-Stat is adjusted for 2H/2C, the system will operate with variable capacity as intended. The interface monitors the Y1/Y2 or W1/W2 signals simply to know how close to Set-Point the room-air temp is. if the Y2 or W2 signals are energized, the system will operate at full capacity. If only the Y1 or W1 are energized (meaning that room temp is close to set point), the system will modulate capacity to stay in that zone for as long as possible. If Y1 or W1 de-energize (no voltage), then the PAC-US444 just learned what the Set Point is on the third-party thermostat.

How frustrating, then. Obviously, I am no HVAC expert, and based on what you are saying neither was my dealer and the Mitsubishi rep. This makes me want to scream. It is maddening when the folks selling a product don't know the product they are selling.

Would you share where did you find that info? I would like to present it to my dealer and have a little discussion.

Thanks.
--Dennis

[fresnoboy]

How frustrating, then. Obviously, I am no HVAC expert, and based on what you are saying neither was my dealer and the Mitsubishi rep. This makes me want to scream. It is maddening when the folks selling a product don't know the product they are selling.

Would you share where did you find that info? I would like to present it to my dealer and have a little discussion.

Thanks.
--Dennis

Dennis, your rep was mostly correct. Going with a 2 stage thermostat wiring and the thermostat adapter does give the system more than just on/off, but still not as efficient as the scroll inverter can operate. It's a matter of degree. For me, the benefit of maximum efficiency and comfort from a VRF style system is something I didn't want to compromise on. The kumo system gives you that.

[jgreenberg01]

You can install a regular Tstat for most split units. Check your installation manual for details.

This is not what I am finding. My recycle bin is full of downloaded installation manuals from various manufacturers that make no mention of connect external TStats.

Through speaking with the good folks on this forum, as well as the HVAC vendors my company uses to install the units in the homes we sell, I have only identified 2 manufacturers thus far that will absolutely do this.

They are: LG & Trane (Mitsubishi).

There are lots of manufacturers that will allow a "smart TStat" connection through wi-fi, which is what I specifically do NOT want to do. I am trying to avoid getting into a situation where the only external control is through a cloud service.

If you do know of another brand that does this, I would be grateful if you would share.

For now though, it will be LG or Mitsubishi, depending on what discounts - if any (there's some advantages to being in the new home biz!) can get me.

[jgreenberg01]

I'm still working my way through this, but has anyone actually used the PAC-US444CN-1 interface with a Mitsubishi mini-split?

I'm getting conflicting answers as to whether the RF remote will still work when using an external TStat. The manual has this:


But I've had others tell me otherwise.

This is incredibly frustrating!

[BeachBum]

I have an MXZ condenser with 5 MSZ wall units. I purchased 5 PACs and 5 Ecobees to automate each zone, but so far only have 2 zones installed at this time. I can tell you a few things:
- Don't use the remotes if you have the PAC installed on that wall unit. I can confirm - in my experience - they do not work together properly.
- I do use the remotes on the three zones that do not have the PACs installed yet. They work.

Overall, Ecobee/PAC works - mostly. I am having one problem that I'm still sorting through, I don't think it's related to still using the remotes on some units. I believe it's related to how the Ecobee is configured & PAC switches are set.

When it is first turned on everything works as expected - heating/cooling starts, if setpoint is not reached, stage 2 kicks in, setpoint is reached and it turns off. All fine and good. It's a vacation beach house & it experiences extreme temperatures both hot and cold, and the unit is a bit undersized. The problem - if it is very hot or cold outside, the unit struggles to reach setpoint and runs for hours. It drops back to Stage 1 after several hours, and then it will definitely never reach setpoint. I have not been able to pinpoint how long it runs at Stage 2 before 'resetting' to stage 1 - this happens overnight, or during the day while we are not home. Turning all units/stats to OFF, and then turning them back on solves the problem. It works as expected, with Stage 2 kicking in properly.

Since it's a vacation home, it has not been a priority to figure this out, but I'm working on it. I suspect DIP switch settings on the PAC may correct this problem.

[strikvid]

I have a multi-zone LG and use the HS plugin as well. One head unit is in the garage and the other is in the bonus room over the garage. I've setup a serious of events to monitor and control. vidmate 2019i insta downloader

[jgreenberg01]

Update:

I went with a Mitsubishi mini-split: MSZ-WR24NA & MUZ-WR24NA

The PAC-US444CN-1 board does indeed work as expected and it is being used to allow a Honeywell Intrusion TH6320ZW2003 TStat to operate the mini-split.

The downside is that:

• The remote that comes with the mini-split can't be used to control the A/C - the external TStat does all the work
• Some of the mini-split features may be lost - in my case the Honeywell TStat does not support the variable fan speeds that the mini-split is capable of

The upside:

• The mini-split can be controlled by HS4, allowing for total HA control (potentially minus a mini-split feature or 2, depending on your TStat)
• It can now be controlled anywhere WITHOUT REQUIRING A CLOUD CONNECTION!

My control screen looks like this, and I have total WAF because she really dislikes those little TStat screens, especially when trying to set schedules:

[Guest]

Just for the record, Fujitsu mini splits also offer a 3rd party thermostat option. The UTY-TTRX works similarly to the PAC-US444CN described above. I have 7 mini splits controlled by 6 Fujitsu UTY-TTRX. The fan control is solely by the head unit, and the mini split essentially has two stages of heat and two stages of cool per the thermostat.

My systems are in an Airbnb 2 hours away so the loss of some efficiency is outweighed by the ability to control it remotely.

[outbackrob]

Something to consider is the Remotec ZXT-600US. I have a very (VERY) old split system that I am shocked even had a remote, but it has no other app or other interface capability. I didn't think I was going to be able to remotely control it let alone get it to function via HS. Without much more than adding it as a z-wave device, I can control MOST of the functions of my old Mitsubishi. I can turn it on or off, change the temp, change the mode, and change the fan speed. And, it just works. I have had it for a few years now and it is still on the same two batteries. It was the last major system in our house I had to automate and the Remotec made it happen.....

PS: You can still buy them on Amazon: Amazon.com: Remotec ZXT-600 Z-Wave Plus - IR Extender for AC Conditioner : Home & Kitchen

[Tomgru]

Just for the record, Fujitsu mini splits also offer a 3rd party thermostat option. The UTY-TTRX works similarly to the PAC-US444CN described above. I have 7 mini splits controlled by 6 Fujitsu UTY-TTRX. The fan control is solely by the head unit, and the mini split essentially has two stages of heat and two stages of cool per the thermostat.

My systems are in an Airbnb 2 hours away so the loss of some efficiency is outweighed by the ability to control it remotely.

I've been looking for someone that has messed with these. I have the Fujitsu with 2 zones controlling my 3rd floor bedrooms... and the tstat batteries are dead in each unit. total pain when the power flickers. apparently the only way is to replace the entire unit.

I Looked into these .... So i'd use 1 for each zone, right? then I'd replace the tstats with a Next or Ecobee (i actually already use Ecobee for my other Hvac system).

So i'd need two of these at 200 a pop. Two more Ecobee tstats, the 24v transformer, and install costs? all to get HS4 integration?

[Guest]

Correct! It’s not cheap. As a general contractor I used my account with a local wholesaler. The UTY-TTRX still cost about $140 each. I also bought my thermostats in bulk on eBay. I got RCS Zwave stats that look as simple as possible because it’s a rental and we didn’t want guests asking how to use it.

I should also mention Fujitsu instructions for configuration are not the clearest, but once set up they’re great.

[Tomgru]

Correct! It’s not cheap. As a general contractor I used my account with a local wholesaler. The UTY-TTRX still cost about $140 each. I also bought my thermostats in bulk on eBay. I got RCS Zwave stats that look as simple as possible because it’s a rental and we didn’t want guests asking how to use it.

I should also mention Fujitsu instructions for configuration are not the clearest, but once set up they’re great.

Thanks! So why 6 of the units for 7 minisplits?