Mitsubishi Mini-Split External Controller (MHK2)
Hi Folks,
I recently had a Mitsubishi 3-zone Hyperheat mini split installed in our 1440sqf home. When in heating mode, I cannot seem to find a way to reliably keep a set temperature. I have been playing around with the various vane and i-sensor settings. Every time I think I got something figured out, a few hours later it’s off again. Now, the room is by no means a uniform cube: it has partially cathedral ceilings, huge south facing windows, and it open to the kitchen/hallway. Makes sense that it would be hard for a inflow-vane temp sensor to figure out what the temp is.
Anyhow – I’d like to figure out what my external thermostat options are. At this point, I am only interested in upgrading the one zone. Sounds like anything that actually works for a Mitsubishi is quite expensive. (I did just try to use a Cielo Breeze that was over $100, only to realize that it isn’t a real thermostat.) Do folks have any experience with the new MHK2 system? In particular, with the MSZ-FH15NA type cassette? How difficult is the install?
[Edit] One more question. I see some sellers offering the MHK2 on ebay. $100 less than other retailers. Anyone has experience with going that route?
Thanks a lot for your responses.
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The MHK sensors are easy to install. You just need a philips driver to remove a couple screws to access the wiring connector to connect the wireless receiver. It really helps to stabilize things. The internal "room"/return air temp sensor is very prone to short cycling depending on the install, and air currents in the room. Before I had mine on my FH09 I could lay in bed listening to the compressor hunt, now it just settles into a steady capacity. (Note, don't wall hang the outdoor unit on a bedroom wall. Even though it seems silent when you stand beside it, there are vibration harmonics transmitted to the houses structure that get annoying.)
The setup is pretty easy to work thru if you can read the manual, with the key setting being making sure it is referencing the remote temp sensor.
Another option is the Kumo Cloud wifi receiver and remote sensors (might be around the same cost).
Personally I try and avoid wifi connected HVAC since it's likely to be obsolete due to changing standards long before the equipment service life is up. The MHK1/2 use the Standalone honeywell redlink protocol which doesn't have any external dependencies (like your wifi router).
Also, note the I-See sensor doesn't help with temperature feedback. All it does is help point the vanes toward or away from people/hot/cold spots, and act as an occupancy sensor. After playing with mine for a bit I disabled it due to the slight noise it makes when in a quiet room. It actually seems a bit gimmicky except for maybe the occupancy function which I don't use.
Thanks for the response Josh. That's encouraging to hear that you've had good experience with an external controller.
I do understand that the I-sensor is just for figuring out if there are people in the room, and/or where they are. I thought that by trying to avoid the people it would somehow spread the heat around more evenly? Anyway that wasn't the case. At this point I am starting to think the I-sensor is more of a marketing gimmick.
I am also not too interested in WiFi controls. Had a couple WiFi heater/AC units in the past, and after initially playing around with controlling them remotely, the novelty wore off and found myself just adjusting them directly. I could see how this would be useful for a second home or some other scenario.
Now I just need to decide if the ebay supposedly "New" MHK2s are legit. There seem to be quite a few of them for ~$180 shipped.
Does Mitsubishi not have the follow me feature on the remote? Both my Midea and Gree have it where it uses the remote as the temp sensor. It
constantly transmits the temperature from the remote to the unit. Works awesome as it bypasses the units sensor. I placed mine on the wall where a traditional thermostat would go. It perfectly maintains the temperature on the remote.
Unfortunately, the included controller for most m series Mitsubishi units doesn’t actually have a sensor in it. Hence the upgrade to a controller with a sensor like the MHK. At least it’s wireless so you can place it optimally.
Yea, it's a real shame. From the engineering perspective, this would literally cost Mitsubishi pennies to implement. The remote is already communicating wirelessly. All they would need is to add a sensor to the remote and some logic. Instead, you need to buy a ~$300 thing. It's nuts. (Oh, and that only solves the problem for one of your zones.)
I think the issue might be partially that it's IR so line of site, and one way (if I change the setpoint on my MHK the IR remote doesn't reflect the change, but the MHK will reflect an IR remote change.
If they used a RF remote then you could have, realtime space sensor feedback, two way comms and non-line of sight (like the MHK).
Right. I think the remote could still serve as a sensor, just sending the temperature info to the cassette.
Anyhow - there are plenty of simple engineering solutions that would work. I guess Mitsubishi has their marketing strategies and they must not care about this as much.
You can use Kumo cloud and the wireless sensor/reciever, it's less than the MHK's, same install, and you can still over-ride with the remote. Josh is right that the remote is one-way only, so it doesn't know if the unit is on/off or whatever, but as soon as you turn it on, it will over-ride the Kumo, but it's still using the remote sensor. I'm very happy with mine.
Its crazy that Mitsubishi makes you buy some few hundred dollar accessory for that feature. Even the $700 Pioneers have the follow me feature. They use RF not IR for communication as well. My Midea remote doesn't have a IR lens and will work without even pointing at the unit.
Agreed that it's silly. Especially when you pay top dollar for these system. Instead they put a bunch of features that are marginally useful (i-sensor, breeze mode, etc.)
Right. The Kumo cloud PAC-USWHS002-WF-2 is $175 and the sensor is $54. So you're out ~$230. The MHK2 is $280. With the MHK2 you're not dependent on WiFi and you have a real thermostat.
By the way - a question comes to mind: if you have the Kumo cloud interface with an external sensor, and you go to use the original remote to change something, will it still use the external sensor for feedback? Or will it revert back to the built-in sensor? This is important, because you don't want to always have to make your adjustments with your phone.
Also the MHK2 is available on ebay for $180. I spoke with a Mitsubishi tech rep, and it sounds like with the MHK2 and Kumo cloud can also be run together (connected piggy-back), if one were to get the MHK2, and later want to upgrade to cloud connectivity.
AKAIK it uses the ext. sensor. Others may varify.
So I found out the hard way that the MHK2 does NOT include internet access; for that you have to also get the PAC-USWHS002-WF-2, an additional $175.
:-((
I have tried a number of ways of running these and the conclusion I've come to is get a thermostat interface module and connect your own thermostat. It is still expensive but at least now you are outside of Mitsubishi land and you have a lot more options. Their thermostat module is actually pretty nice when connected to a two stage thermostat. Even better if you go with a thermostat that has multi speed fan control and wire in all the fan stages.
Just found this thread, it deals somewhat with the same issue as a question I just posted. But my client has already sprung for the costly MHK2 and it can't seem to adequately control its mini-ducted unit (sez-kd09na4). It seems content with an ambient temperature (as shown on its own display) up to 4 degrees different from the setpoint. How can you configure the MHK2 to be the boss? It's already set to "sense temp remotely" and I'm wondering if there are other settings onboard the main unit that are overriding the remote.
I have an mhk2 on every head. Light years better than the included remote. When you set it up, you have the option of relying on the temperature sensor in the thermostat, on the head unit, or both. I’ve had the best luck relying on the thermostat. Seems to affect heating more than cooling.
Out of curiosity, why didn't Cielo Breeze work?
I'm seeing overheating/overcooling issues with my 5 head-unit Mitsubishi mini-split (https://www.greenbuildingadvisor.com/question/is-my-mitsubishi-heat-pump-short-cycling) and was considering getting Cielo Breeze and try their Comfy mode settings to turn on/off the head units as needed based on a min/max temperature range. Cielo costs $114/unit vs MHK2 which is around $400 these days (and another $300 if I want WiFi/Kumo access).