Nest Thermostat Install with Mitsubishi Split System (PAC-US444CN-1)

Parts needed: Mitsubishi PAC-US444CN-1 Adapter & 24V 40VA Transformer with 208V input.
Amazon link for the transformer I purchased: a.co/d/4r5ZYGh

[@mattpatt01]

Thank you for this. There I very little info out there on these things and even though the video was hand held, it was very helpful

[@richardjefferson4958]

Can you still use your remote control? I bought a similar adapter for my Gree and the display on the blower is no longer visible and I cannot use the remote (there are 2 functions that I can not utilize with the Nest thermostat).

[@jamesishere6630]

i thought i had successfully done it but last night i heard the fan unit trying to turn on & off and it would shut off in 10 to 30 seconds and try to turn on again(repeating cycle) . it would mimic the action as a struggle car trying to start up and then shutting off after a few seconds, Does anyone know why?

[@thehpw]

Great info. Thanks. How did you set up your thermostat? Im using a nest, do you set it up like a standard unit or do you set the thermostat settings to heat pump?

[@ejbarrios]

Awesome vid, thanks for uploading this. Only call out is that I think it's recommended to connect the two stages to thermostats that support it like the Nest, I believe it runs more efficiently that way.

[@jamesishere6630]

can you explain why, i have the same system and want to go for simplicity , thank you in advance

[@ejbarrios]

@@jamesishere6630 The inverters are most efficient running at lower speed, it consumes less power to run it continuously slowly than at full power on and off. If you look at the manuals for the PAC 444 you'll see that when the you have the two stages connected, the first stage only adjusts the temperature setpoint of the internal computer such that the cooling/heating rate is changed slowly and more efficiently, only running it at full power when the second stage kicks in. When you only have a single stage, it runs at full power when the thermostat signal comes in, there's no gradual temperature changes.

[@jamesishere6630]

@ejbarrios ah makes sense thanks bud...I appreciate your insight...I'll try to figure out the wiring I am hoping is not that more difficult

[@TAGUPNBLUE]

The service disconnect is not a breaker

[@allent1034]

Thank you for putting that together. I see five wires from your thermostat to the connector box. It looks like you have another wire from the thermostat but it is not used. Is that correct? I only have five wires from my thermostat so it should work?

[@charliecobb12]

Yes you only need 5 wires. I bought 6 conductor wire but only needed 5 so one wire was unused.

[@Champabay]

Does this bypass the Mitsubishi remote control? My system keeps blowing fan for 90 minutes after the Nest turns off and I can't use any modes on the remote.

[@charliecobb12]

Do you have a system similar to mine, or a wall mounted mini split?

[@ejbarrios]

I'm not an HVAC anything but I've been forced to look into how all this worked because I had aux heat strips that weren't working. So with that said, take the following with a grain of salt! The Air Handler has its own thermistor (reads temperature) of the return air, when you use a Mitsubishi thermostat on CN105 it communicates to the control board a desired temperature (set point) and the control board decides how to run the blower and inverter based on the temperature it is reading and what the set point is. Presumably, once the temperature reaches the set point, that's when the variable speed of the fans and inverter kick in to make it efficient (heat pumps are more efficient when they're only having to maintain the temperature.) What the PAC 444 does is try to emulate that set point configuration by interpreting the signal from the Nest and converting it into a desired temperature with the calls for cooling and heating, so to answer your question more concretely: the operation of the fan and the heating is controlled by the control board on the unit, the Nest doesn't directly control the fan or anything (and this is a good thing, that's how the efficiency is maintained.) However, if you look at the manuals on the PAC 444 and 445 (not sure which you have) there's some DIP switches that control how long the fan runs after the call to cool/heat ends, if you want more control over how long the fan runs you can probably try changing those, but it's probably less efficient to run the system that way. -------------------- On PAC 444: DIP Switch Definitions (Factory default is OFF for all switches): Delayed Off SW1-1/2: After reaching thermostat set point, the unit will continue to run for a set period of time in order to improve efficiency. The period of time is set by adjusting SW1-1 and SW1-2 according to the following table: SW1-1 SW1-2 Result OFF OFF 5 minutes (Default) ON OFF 10 minutes OFF ON 30 minutes ON ON 0 minute ---------------- On PAC 445: 4.2. Functions of DIP switch Zero delay timer SW1-1: Chooses the fan/off delay mode following heating or cooling mode. SW1-1 Delay timer OFF Stay in heating or cooling mode for 2 hours once W1 or Y1 is no longer active, which provides more efficient operation but does not respond to fan request changes (G) during the 2 hours. This setting allows more time for defrost timers in the outdoor unit to run (default). ON Once heat or cool request W1 or Y1 is no longer active, the system turns off or goes into fan mode immediately depending on the G signal. This is less efficient operation but responds more quickly to fan request changes. This setting operates most like the previous Thermostat Interface with zero hold time after achieving set point.

[@montiesingh-d9s]

Your system is not a single stage This is why you should call a mitsubishi trained technician You just made your system single stage 🤣

[@chrisfernandez5030]

Thanks

[@jamesishere6630]

great job and video curious any updates or issues that you would do differently? please advise thanks!

[@charliecobb12]

It is still working well! Some comments prefer to keep it in two-stage mode for efficiency, however mine is working just fine as-is.

[@jamesishere6630]

@@charliecobb12 i noticed the comments on the second stage I wonder if it would make a HUGE difference in cost saving on electricity.

[@jamesishere6630]

@@charliecobb12 i was able to successfully get it done, (i have a smart panel monitor by breakers(Emporia) ) but wanted to let you and everyone know that this unit draws an average phantom power wattage of 25 to 30 watts (at times 40) throughout the day when its off. i need to shut off the breaker itself at times to conserve some energy and save on my bill.

[@eduardoestrada4275]

Excelente video!

[@matthewlancieri]

Thanks so much!!