Panasonic vs Mitsubishi ducted heat pump and ventilation solutions

Forums › Home Workshop DIY › Panasonic vs Mitsubishi ducted heat pump and ventilation solutions

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282 posts

Ultimate Geek
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#3451044 9-Jan-2026 11:44

timmmay:

4.16 COP is good. Smaller units tend to be more efficient. Our power bills are near zero with solar, but consumption would be about $200 worth, about 950kw, working from home as well as having an old house. The main way to reduce power usage here would be to have shade on the north side, but unfortunately not practical as the fence is about 0.5m from the house - I think the eaves go over the boundary. Very old house.

Oddly enough my Daikin is rated for 5kw minimum cooling, but sometimes is doing 350W power usage with a COP of 3.83 so 1.3kw. Very useful. We've had a few problems with the Daikin. The whole outdoor unit was replaced once due to weird noises like pressure releases very often. The new one does it occasionally during normal operation. The main board had to be replaced at about 4 years old. So nothing too bad. It is quite flexible, lets me do things like turn the fans off when it's up to heat or down to temperature which is useful in our case.

Yea shade would solve all my issues lol.

I guess can get a bad batch for anything. That does remind me though, I need to fix my outdoor units rattling. The compressor rattling against the chassis, and it's loud and annoying for the neighbours probably. Just need to open it up and move the foam around a bit. The installer already did that and fixed it temporarily, but noise is back...

tweake

2663 posts

Uber Geek
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#3451327 9-Jan-2026 16:53

I turned off the heatpump roughly between 9:30am and 12:30pm. As soon as I do that, the supply air (no airflow, as it's off) drastically climbs to the exact same temperature as the return air.

it will do that as room air will go up the outlet. especially with the sensor so close to the end.

keep in mind stack effect pushes upwards, so hot air is trying to go up through everything and will go up the heat pump ducts.

the other part of this is whats happening to the heat pump downstairs? i suggest turning that on first, set it a few degrees lower than upstairs. if you use upstairs first, all the downstairs hot air will go upstairs )and the upstairs cool air will go downstairs) and there is no way that unit will cool the entire house.

AlDrag

282 posts

Ultimate Geek
+1 received by user: 29

#3451330 9-Jan-2026 16:59

tweake:

it will do that as room air will go up the outlet. especially with the sensor so close to the end.

keep in mind stack effect pushes upwards, so hot air is trying to go up through everything and will go up the heat pump ducts.

the other part of this is whats happening to the heat pump downstairs? i suggest turning that on first, set it a few degrees lower than upstairs. if you use upstairs first, all the downstairs hot air will go upstairs )and the upstairs cool air will go downstairs) and there is no way that unit will cool the entire house.

Good point. I will give that a try tomorrow, usually only run both at night.

Thank you!

AklBen

136 posts

Master Geek
+1 received by user: 43

#3455094 22-Jan-2026 14:17

We've just had our ducted heat pump system installed by the team at Albany Heat Pumps (excellent). We went with a Mitsubishi 11kWh system, floor vented with 6x vents.

Wondering what other folks who have had ducted systems would say about operating tips?

timmmay

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#3455097 22-Jan-2026 14:26

AklBen:

We've just had our ducted heat pump system installed by the team at Albany Heat Pumps (excellent). We went with a Mitsubishi 11kWh system, floor vented with 6x vents.

Wondering what other folks who have had ducted systems would say about operating tips?

Turn it on before you need it. For example even though there's no one in our living area until about 6:00 p.m. we find it much more effective to turn cooling on as early as 11:00 a.m. to stop it getting hot rather than trying to cool it later. If you let it get hot the framing, the walls, all the room contents get hot then it takes hours to cool them down properly. The same goes for heating, although I find I don't need to turn it on quite as early.

Have a look at my ducted faq as well. Things like having appropriate return paths for air.

AklBen

136 posts

Master Geek
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#3455098 22-Jan-2026 14:32

^ thanks. Yeah, seems as if with cooling most people seem to just run the thing all the time (but at a fairly high temp like 20-22).

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boosacnoodle

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#3455106 22-Jan-2026 15:28

Had a technician from a different company come out to diagnose the cracking sounds I’d been facing with my Mitsubishi install. Turns out there was a flapping piece in the ducting causing a regular tapping sound, the vents on the roof were installed too tightly which causing a cracking sound plus there were a number of kinks and other issues all contributing to the noises.

timmmay

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#3455110 22-Jan-2026 15:47

AklBen:

^ thanks. Yeah, seems as if with cooling most people seem to just run the thing all the time (but at a fairly high temp like 20-22).

We turn ours off around sunset unless the temperature is really high, which is rare in Wellington. I don't like to leave it running overnight because it can make the place a little bit cold as it tends to run on really low power like 300W energy usage but that still makes the room feel really cold when you're in it. Instead I have home assistant monitoring temperatures and if it goes over a threshold turns the air conditioner on for 30 minutes, which is sufficient.

tweake

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#3455127 22-Jan-2026 18:09

AklBen:

^ thanks. Yeah, seems as if with cooling most people seem to just run the thing all the time (but at a fairly high temp like 20-22).

22c is recommended by WHO. but +/- for comfort. tho i warn against setting temp very low in typical nz houses, especially in the more humid aeras. (eg see above about condensation on the duct fittings)

if its properly set up and it hits set point, then just leave it running. it will turn on/off when required. keep in mind that a properly sized unit will fail to cool a house on the hottest days of the year when running constantly (by design). turning it on when its already to hot, its even worse.

AlDrag

282 posts

Ultimate Geek
+1 received by user: 29

#3455214 23-Jan-2026 07:57

So my main issue at the moment is that even during the night, I get a lot of overshoot. My return air is always around 21 degrees, despite my rooms being lower. So I set my room to 21 degrees, during the night the room gets colder and colder until about 16/17 degrees when I wake up. The return sensor reads 20/21 all night basically. Even though the bypass damper is open.

Either the bypass damper is not sized correctly, I could play with the settings in Airtouch to open it more, or maybe I need dedicated returns for my small PEAD50? I also wondered if the bypass duct should be directly ducted to the return plenum instead of the ceiling return box?

For context, I'm using "Auto" in Airtouch setup with a bypass damper and my Mitsi is in Mode 02/01, so it's using the internal sensor of the unit, not the controller.

timmmay

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#3455271 23-Jan-2026 08:59

@AlDrag what do you have "control sensor" set to? Details in my Airtouch FAQ. It should be "economy". This tells the system to stop heating / cooling when the rooms reach temperature rather than looking at return vent temp.

When you say you're using "auto" in Airtouch setup, where exactly have you set that?

I wouldn't think you need separate returns, just need to work out why this is happening. Is it integrated with home assistant, and are you familiar with HA?

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AlDrag

282 posts

Ultimate Geek
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#3455372 23-Jan-2026 09:59

timmmay:

@AlDrag what do you have "control sensor" set to? Details in my Airtouch FAQ. It should be "economy". This tells the system to stop heating / cooling when the rooms reach temperature rather than looking at return vent temp.

When you say you're using "auto" in Airtouch setup, where exactly have you set that?

I wouldn't think you need separate returns, just need to work out why this is happening. Is it integrated with home assistant, and are you familiar with HA?

I've been on the Unofficial Airtouch Facebook Group and supposedly "Economy" should only be used if you have a spill zone while "Auto" if you have a bypass damper.
Reason being, "Economy" will fall back to the spill zone sensor once room set poitns are reached. While "Auto" will fall back to the A/C sensor (usually internal return sensor by default), as the Bypass damper should give it the colder air quickly once room dampers start closing, triggering the heatpump to turn off sooner, avoiding overshoot.

Despite all this, the Airtouch documentation is so limited in the regards of what it actually does and maybe contradicts what I've been told above.

I'm a little confused on what the difference of "Sensor turned Off" versus reaching "Set Point" is though. Makes me believe Economy runs forever unless you manually turn the sensors off, but that seems extremely unlikely.
If my bypass damper isn't efficient enough, and I don't think it is because it isn't plumbed directly into the return plenum, it would be mixing with too much unconditioned air and not affecting the A/C sensor enough.

I do have my room dampers set to have a minimum % opening always now because of my Lossnay. I like airflow. But maybe that's throwing off the algorithms. Hmmmmm.

I do have it all connected with Home Assistant and very familiar with it. Was thinking about making my own automations to make it more efficient, but I assume turning it on/off is a bad idea. Can't set it to fan mode directly after reaching set point, as that dumps all the coil moisture in. Maybe I can automate it setting the Set Point really high when my "desired" set point is reached in the rooms.

I could just use a spill zone instead. If it works well for you in economy mode, maybe it's worth me to give that a try.

timmmay

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#3455416 23-Jan-2026 12:42

I suspect your minimum opening could be another suspect. Turn that off first, that's definitely going to overcool particularly when combined with auto mode. You don't really need fresh air 24/7, we just run the old ventilation system which has an outlet near the ducted system inlet 4 hours a day with the system on fan mode, that's good enough.

I have no experience with bypass dampers unfortunately. If turning off minimum opening doesn't work I would suggest giving economy a try, based on the description above you probably don't want the AC sensor used at all, just the room sensors. I think Economy will just turn the outdoor unit off when the rooms reach temp, which is what I find. With a spill zone, system set to economy, when the room sensors reach target I can confirm the outdoor unit turns off. I was directed to do this by Polyair support, but for my system with a spill zone. It's definitely worth a shot IMHO.

I'm guessing "Sensor Off" means a zone being disabled.

Third option, consider whether direct damper control could help. With a spill zone, I find the dampers get closed way too early causing spill and overheating / overcooling. I directly set dampers in some conditions and it helps hugely. I can provide sample code - PM me if you want it.

Fourth option, which I don't like, but you could set the setpoint high like you say based on HA and room temperatures, then put it back down when you need additional cooling. I do a variation of this as we don't often need overnight cooling. I have HA monitor room temperatures, when they go over my threshold they turn air conditioning on for 30 minutes, then turn it off again. That usually only happens once or twice on a hot night.

The other configuration I changed on my Daikin heat pump directly is to prevent air circulation when the system is up to heat or down to cooling temp. I didn't like the breeze it put through the rooms constantly.

I also change my spill zone based on whether I'm heating or cooling, just because of the layout of our house.

I'd be interested to hear how you get on.

AklBen

136 posts

Master Geek
+1 received by user: 43

#3456880 29-Jan-2026 09:06

Which smart home automation/assistant stuff works with the Mitsubishi ducted system with wifi control?

Anyone have any experience with it?

AlDrag

282 posts

Ultimate Geek
+1 received by user: 29

#3460925 12-Feb-2026 10:45

AklBen:

Which smart home automation/assistant stuff works with the Mitsubishi ducted system with wifi control?

Anyone have any experience with it?

Home Assistant. I have the wifi controller from Lossnay working great with it. I think it's the same controller. I just bought and installed it myself.

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