Panasonic vs Mitsubishi ducted heat pump and ventilation solutions

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#3436978 23-Nov-2025 14:42

Right. I didn't know you are supposed to run them all day, even though you ain't home or not using the rooms? But I'll try that. I'll see what power consumption is like and see if it can maintain a comfortable 21 degrees in all the rooms all day.

We do have blinds in all the rooms, but I can still feel the heat coming off them. It is a dumb design, like most townhouses in NZ. Such a massive waste of energy. Tempting to go solar, will probably keep my roof cool as well.

Apologies again for my ranting.

tweake

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#3436981 23-Nov-2025 15:06

where is the sensors located?

also does the system turn the fan off when its not cooling?

AlDrag

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#3436982 23-Nov-2025 15:09

tweake:

where is the sensors located?

also does the system turn the fan off when its not cooling?

The sensors are on the wall, next to the door. Above the light switch, so that typical place. However, in the given screenshot, that's my own sensor next to the bed on a table.

It never turns the fan off. I assume this is because it's synced up with the Lossnay, so it just cycles the air when the compressor turns off outside.

tweake

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#3436992 23-Nov-2025 15:57

whers mathew sensor compared to sensor 2 ?

what one is running the aircon and whats running the zoning?

you have the hallway has the spill zone?

just trying to get a handle on whats controlling what. the problem looks like its not turning on the cooling when its required, possibly because that sensor is already cooled or possibly misconfigured. i think the mitsi sensors can be adjusted from the control panel.

depending on setup, the spill can be returning enough cold air to trip the sensor even tho one room is still to hot.

also without using the zone system, how close in temp is each room. it may pay to tweak the airflows to favor that hot room, so the zoning doesn't have to do so much.

AlDrag

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#3437026 23-Nov-2025 19:32

tweake:

whers mathew sensor compared to sensor 2 ?

what one is running the aircon and whats running the zoning?

you have the hallway has the spill zone?

just trying to get a handle on whats controlling what. the problem looks like its not turning on the cooling when its required, possibly because that sensor is already cooled or possibly misconfigured. i think the mitsi sensors can be adjusted from the control panel.

depending on setup, the spill can be returning enough cold air to trip the sensor even tho one room is still to hot.

also without using the zone system, how close in temp is each room. it may pay to tweak the airflows to favor that hot room, so the zoning doesn't have to do so much.

Opposite side of the rooms basically. "Matthew Sensor" is on the wall next to the light switch". "Sensor 2" is a little zigbee sensor on his table next to his bed. Outlet is in the middle of the room on the ceiling (not ideal I know).

"Matthew Sensor" is running the zoning, as that's the Airtouch sensor.

I only just recently set the hallway as the spill zone last week to trial it. I figured that on a hot day in the attic, a bypass damper is less efficient, as it would be better to bring the cooling into my conditioned space, especially since I'm cooling downstairs as well.

In regards to the cooling turning on/off in that graph, that is just me closing the damper as I try things. So ignore that, sorry. I will try get better data with it on all day when it's a hotter day.

The hallway sensor (which is the airtouch tablet) is always very hot during the entire day, like 27 degrees most of the time. I think the hallway combined with the open landing/stairwell is just a big oven box that traps heat. I guess no curtain on that big window and the aircon doesn't touch the landing area, only the hallway as it travels towards the return.

Today I put a sensor in "Matthew's room" outlet and the return just above the filter in the ceiling.
Here's a graph: (ignore anything before 12pm).

The heatpump has been performing better today in comparison to yesterday. Possibly because it was cloudy for the first half of the day. Although Matthew's room can't seem to get below 22 degrees. Actually, I think I need to close the door, as that helps.

tweake

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#3437039 23-Nov-2025 21:16

how well is the downstairs heat pump working? one of the problems with multi level houses is heat in the bottom floor goes upstairs and cool air upstairs can drop down to the bottom floor.

whats interesting is the return temp flatlines like the heat pump is maintaining temps perfectly. are you sure the heat pump is not running off a heat pump sensor ?? because that looks like its been set to 27c.

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mudguard

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#3438125 28-Nov-2025 10:36

Rather than create a new heat pump thread I thought I'd ask in here.

We have two heatpumps running off a single external unit. Not really discussing that, however the upstairs unit is located in our bedroom, directly above the downstairs lounge unit so the external capping is a single run and nice and neat.

Both units have performed flawlessly, our bedroom runs all night through the year on cool as I run a bit hot and we live in Auckland. The downstairs unit gets mostly used on heat and occasionally cool when it gets really sticky. I'm pretty diligent about keeping the filters clean however given the upstairs unit is run 99% on cool, the fan itself got a bit grotty. So we had the installers come out and do a pretty thorough clean. The units we have require reasonable disassembly to get the fan unit out for a steam clean, so it's put me off doing it myself.

I've set it up so that it will run on fan for a few hours in the morning to help dry the unit it out better.

Long story short, the cleaning was done in July and now in the past ten days that it's got very humid, the upstairs unit is leaking water. Now as far as I'm concerned it's not rocket science, the water isn't draining and is tipping out.

So either the drain is blocked or the hose is kinked. I've booked them to come out and clean the unit again and check the hose. I have the install manuals from when I purchased everything however I suspect the hose is blocked going into the wall.
Problem is the hole in the wall is very small and I can't really do much about the hose orientation?

Thoughts?

tweake

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#3438298 28-Nov-2025 17:02

if thats the pipe there, looks like it just need to be pushed back into the wall to straighten out that kink.

also worth checking the tray. i've had a couple of times where mice has gone up and died in the tray.

AlDrag

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#3450954 9-Jan-2026 09:59

Warning: Lots of text incoming, I apologise. But maybe someone will find this investigation interesting.
Tl;dr: System definitely struggling when there's no cloud cover on a hot summer day. Rooms get above 23 degrees, despite target temp of 20/21. Planning to try lots of small improvements to the system such as adding insulation and redoing duct work (and better window treatments) to see if any noticeable difference occurs.
Massive window facing east in my landing has no window treatments and maybe that's a big contributor!
Would love feedback on my findings about the ducting installation quality.

Ok I've done a lot of investigation through this summer, by way of going through the attic and understanding my system, researching online, trying different settings and watching temp sensors in my supply/return ducts.

NOTE/IMPORTANT: If I close all my windows and blinds and turn off all heatpumps, my rooms can reach 28-30 degrees on really hot days.
NOTE/IMPORTANT: Room measured in the graphs below is on the west side of the house, with west facing windows. Its northside facing wall shares a wall with the neighbours townhouse.

Temperature sensor results on the 7th of Jan (HOT day)

I've been leaving the heatpump on all night for a couple of days.
This day is probably the hottest we've had so far this summer, and no cloud. Seems peak outdoor temp was maybe around 25 degrees (according to Metservice), but obviously my attic would have been a scorcher.
I'm pretty sure I actually had my Lossnay turned off, as its temp sensor was reporting 35 degrees on all its internal sensors.

NOTE: the supply temp sensor was placed just above the supply grill in the ceiling. The return temp sensor was placed just above the return filter in the ceiling, just at the beginning of the return flex duct.

So based on the graph above, you can see that as the return air supply temp increases, the supply air increases as well. This makes sense obviously, but I assume it needs to be well below those readings to effectively cool the room at the target temperature of 20/21 degrees.
You can also see that it starts to go up basically as soon as the sun rises and hits my roof/windows.

The fluctuations of the supply temperature at the beginning the graph (early morning of the night) are fluctuating as I think it's the target temp being reached, then the compressor turns off, Lossnay interlock causes the airhandler to keep the fan circling air (I like this, I think).

Temperature sensor results on the 8th of Jan (Similar outside temp, but more cloud cover)

Now these stats are an interesting one. You can see in the graph below, 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.
This suggests to me that maybe the attic air is influencing the efficiency of my system dramatically. But perhaps this is just normal if there's no airflow. The heat will penetrate the ducting insulation eventually, just by how long that is supposed to take, I don't know.

But due to cloud cover, and even when I had the heatpump off for a few hours, compared to it being on all day on the 7th, you can see it handled the room temperature easier. Not as good as it should be still, but good enough perhaps.

Heatpump/Ducting/Lossnay installation quality investigation (I have lots of questions)

So with the help of some reading, and querying my Dad (who works in commercial ducting in Australia), I've noted some potentially bad quality workmanship (probably the norm) and improvements I could make to my system.

Potentially undersized unit?

My neighbours, who have the exact same house as me, actually have 7kw ducted units. No ventilation. One of them chose and installed their own unit (electrician), while the other was quoted a 7kw unit from a company they work for.
My unit is 5kw (cooling)! However, checking my previous quotes from other companies before I got this installed, they also quoted me 5kw or 6kw (panasonic 6kw unit is also 6kw heating, where my Mitsi can do 5kw cooling, 6kw heating) units.

Return air box (ceiling)

So my return air box has NO insulation on it at all. It's not even properly sealed (the mounting of the box to the ceiling gib has gabs and there's a few holes from screws they obviously messed up), so perhaps under certain high static pressure loads, it would be pulling in attic air into the return!
Whether that makes much of a difference, I don't know, but it seems to be an easy thing to insulate, so I'll just do it.

Air supply plenum

The air supply plenum metal box that's attached directly to my air handler, also has NO insulation. It has 3 spigots supplying my rooms and the box is very cold to touch when the unit is running. I assume this is the worst and should be fixed, so I'll definitely sort that out somehow.

No backdraft damper on Lossnay supply

So my Lossnay is interlocked with my heatpump. Basically, the supply duct goes into the heatpump's return plenum, the lossnay gets its own dedicated return vent (although it's the same return box used by the heatpump and bypass duct).
However, it has NO BACKDRAFT DAMPER installed on its supply. So in theory (based on my readings), if I turn off the Lossnay (which I started doing during the day as it gets super hot, which would be potentially reducing my cooling efficiency), but leave my heatpump on, it would actually still pull in fresh air and positively pressurise my home?
This seems like a very easy fix, so I'm just going to do it, again, maybe won't make much noticeable difference, but I really enjoy learning about this stuff and improving things.

Sweating on Polyaire dampers (and duct joins)

Some Polyaire dampers are sweating moisture. Not all, but I think just the ones sitting on top of the insulation.
There's also sweating on one of the ducting spigots from a Y-join that splits one main duct to 2 rooms (and a bypass). I think this is because they didn't fully cover the spigot with the ducting insulation.

Ducting bends galore

My ducting has sharp bends all over it. Some of it held by wire or through trusses, potentially crimping airflow. Will definitely fix this, as it seems like an easy job.

Ducting insulation not sealed off/taped

Supposedly I've been told that insulation from a flex duct should be fully sealed off with tape? Otherwise moisture ingress can occur? It seems they just zip-tied the outer duct to the end of the spigot, leaving lots of insulation exposed. Maybe this is actually a non-issue?

Supply ceiling grills not insulated enough?

The supply ceiling grills are just pieces of plastic, exposed to the attic. Obviously the flex duct insulation covers most of it, but some of it is still exposed, and the ceiling insulation isn't really covering the area around it much anymore.
Worth fixing this? Maybe miniscule.

Unused room supply

I have 4 supplies. 3 rooms, 1 landing/hallway. I don't use that landing/hallway duct at all. Trialled it for spill zone, but think I prefer bypass.
So maybe removing that unused supply could provide a bit more airflow/static pressure for my unit?

Shitty window treatments

Typical with NZ new housing, all my windows are massive and the fact east and west, no awnings, no eaves and thus let in SHIT loads of heat despite having a see-through white inner blind and roman blind.
Just sitting next to the window, I can feel the heat radiating off of it, so this might actually be one of the major contributors. Even the aluminimum framing is super hot (why no thermal-break for a 2023/2024 build?, ffs fletchers).

I'm thinking that these blinds are just too thin and might change the internal blinds to a double honeycomb. Could make a massive difference.

Massive east facing window in my stairway landing

I still have no window treatments on my massive window in the landing area. This brings in a lot of heat and is really not going to help the system.
Will definitely get this sorted, just bloody expensive to do so (basically requires scaffolding to install blinds on it).

Final picture of the kraken

timmmay

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#3450958 9-Jan-2026 10:07

That's a really detailed investigation. It sounds like you've identified some areas that might improve efficiency. I guess no residential installer will help with this unless you're paying by the hour, it would be far too much work and not sure many have the knowledge.

My main suggestion is that if you want a cool house in the evening, turn the air conditioning on in the morning. My 9kw Daikin runs at 1500kw (measured power use not cooling power) then settles down for most of the day to run at 300W to 700W, so quite low - lower than it's officially rated for I think. I find if I do that I can turn cooling off around sunset and the house stays fairly cool. I have home assistant automations that turn cooling back on at night if the bedrooms get too warm - the automation run it for half an hour or so at a time as otherwise even at low power the rooms feel really cold.

We have 9kw or so cooling which we use to cool 2 - 3 bedrooms. When the air conditioning is running the room feels really quite cold. I think our unit is too large. Too small is ok, you just run it for longer, unless it's really badly undersized.

This is all based on experience. I have no training or qualifications in this area.

AlDrag

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#3450962 9-Jan-2026 10:14

timmmay:

That's a really detailed investigation. It sounds like you've identified some areas that might improve efficiency. I guess no residential installer will help with this unless you're paying by the hour, it would be far too much work and not sure many have the knowledge.

My main suggestion is that if you want a cool house in the evening, turn the air conditioning on in the morning. My 9kw Daikin runs at 1500kw (measured power use not cooling power) then settles down for most of the day to run at 300W to 700W, so quite low - lower than it's officially rated for I think. I find if I do that I can turn cooling off around sunset and the house stays fairly cool. I have home assistant automations that turn cooling back on at night if the bedrooms get too warm - the automation run it for half an hour or so at a time as otherwise even at low power the rooms feel really cold.

We have 9kw or so cooling which we use to cool 2 - 3 bedrooms. When the air conditioning is running the room feels really quite cold. I think our unit is too large. Too small is ok, you just run it for longer, unless it's really badly undersized.

This is all based on experience. I have no training or qualifications in this area.

I agree. Like I could complain about all these points to my installer, but I'd just be laughed at or annoy them, and I can understand why.

For the past week, my unit has been basically running 24/7 (obviously the compressor won't be running if set point is reached, in theory). It does have a COP of 4.16, which I think is really good. Powerbills have been around $250 a month, but we are still on a cheap plan with Frank Energy (not sure when they'll switch us over, that company isn't supposed to exist anymore, so I thought, but I won't poke the bear).

300w to 700w is really low! That's great! Honestly, if I started over, I'd be very tempted to go with Daikin. Mitsi seems a bit old fashioned (so I've been told).

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timmmay

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#3450967 9-Jan-2026 10:28

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.

boosacnoodle

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#3450979 9-Jan-2026 11:01

Anyone had issues with the ceiling air diffusers (round circle things) making a cracking sound intermittently?

Mine does it infrequently during the day, which is fine - but in the guest bedroom overnight it can crack every 10 seconds to a minute, which is very annoying.

timmmay

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#3450987 9-Jan-2026 11:31

Mine are square MDO diffusers. They seem to make that noise occasionally in cooling mode. We tend to cool during the day and turn it off at night other than running for short blasts so we're not often in the room when air conditioning is running, so can't say for sure. Every ten seconds seems very high, even every minute seems high.

AlDrag

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#3451043 9-Jan-2026 11:42

boosacnoodle: Anyone had issues with the ceiling air diffusers (round circle things) making a cracking sound intermittently? Mine does it infrequently during the day, which is fine - but in the guest bedroom overnight it can crack every 10 seconds to a minute, which is very annoying.

Is this only in heating or cooling? What are they made of? Assuming plastic?

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