Panasonic vs Mitsubishi ducted heat pump and ventilation solutions

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427 posts

Ultimate Geek

#3325965 29-Dec-2024 15:28

Kickinbac:
AlDrag: So I've had a quick look in the attic. Haven't looked at the unit itself yet, but might do tonight.

I think I can see that the intake and outtake for the ERV is right next to each other. Basically using the roof vents that are right next to each other, maybe 30cm apart. Surely that's a stupid idea?

I went back to look at the photo of your house gable. There are four cowls. At the minimum the supply and exhaust cowls should use the outer cowls which looks about 1 metre separation.
AS/NZS1668.2 prescribes that at less than 200 L/s the minimum separation between discharge and intake is 1 metre.
What are the other two cowls doing? I think you said the bathroom exhaust was now being done by the Lossnay?
A good design practice is to have the supply and exhaust on the same side of the building so that any wind pressure is the same. lol I didn’t do this on my home as it was not practical.

Ha, see we posted a couple of minutes apart!

AlDrag

247 posts

Master Geek

#3325967 29-Dec-2024 15:34

Kickinbac: I went back to look at the photo of your house gable. There are four cowls. At the minimum the supply and exhaust cowls should use the outer cowls which looks about 1 metre separation.
AS/NZS1668.2 prescribes that at less than 200 L/s the minimum separation between discharge and intake is 1 metre.
What are the other two cowls doing? I think you said the bathroom exhaust was now being done by the Lossnay?
A good design practice is to have the supply and exhaust on the same side of the building so that any wind pressure is the same. lol I didn’t do this on my home as it was not practical.

Right. So maybe I can keep move that right side bathroom exhaust to the other side of the attic next to the other bathroom exhaust (I assume I'll need a new duct to reach) and then move the Lossnay exhaust or intake (whatever it is) further to the right? And then it'll have the same wind pressure as you say? Which seems important. Then that avoids the possibility of having the bathroom exhaust going into the Lossnay.

I mean, I guess all this stuff is probably minorish? No matter what, I assume fresh air will get mixed with that stale air anyway. Just not ideal.

Kickinbac

427 posts

Ultimate Geek

#3325970 29-Dec-2024 16:32

AlDrag:
Kickinbac: I went back to look at the photo of your house gable. There are four cowls. At the minimum the supply and exhaust cowls should use the outer cowls which looks about 1 metre separation.
AS/NZS1668.2 prescribes that at less than 200 L/s the minimum separation between discharge and intake is 1 metre.
What are the other two cowls doing? I think you said the bathroom exhaust was now being done by the Lossnay?
A good design practice is to have the supply and exhaust on the same side of the building so that any wind pressure is the same. lol I didn’t do this on my home as it was not practical.

Right. So maybe I can keep move that right side bathroom exhaust to the other side of the attic next to the other bathroom exhaust (I assume I'll need a new duct to reach) and then move the Lossnay exhaust or intake (whatever it is) further to the right? And then it'll have the same wind pressure as you say? Which seems important. Then that avoids the possibility of having the bathroom exhaust going into the Lossnay.

I mean, I guess all this stuff is probably minorish? No matter what, I assume fresh air will get mixed with that stale air anyway. Just not ideal.

Yes the exhaust air mixes with the outdoor air fairly quickly. Still days and the wind direction will be the common cause for any short circuiting. But I wouldn’t get too concerned.

In your photos I can see daylight in three of the cowls and one flexi connected. Shouldn’t there only be daylight in two of them?
Do you have cowls at both ends of the roof?

tweake

2391 posts

Uber Geek

#3325973 29-Dec-2024 16:42

AlDrag:

Right. So maybe I can keep move that right side bathroom exhaust to the other side of the attic next to the other bathroom exhaust (I assume I'll need a new duct to reach) and then move the Lossnay exhaust or intake (whatever it is) further to the right? And then it'll have the same wind pressure as you say? Which seems important. Then that avoids the possibility of having the bathroom exhaust going into the Lossnay.

I mean, I guess all this stuff is probably minorish? No matter what, I assume fresh air will get mixed with that stale air anyway. Just not ideal.

yes, thats an ok fix for the situation. keep the bathroom exhausts away from the inlet.

you could also move the erv intake to other side and bring over the bath fan to its old spot. ie all outlets on one side and inlet on the other side. air pressure differences from the ends is pretty minor issue in a house like this.

AlDrag

247 posts

Master Geek

#3326009 29-Dec-2024 19:55

Kickinbac:

Yes the exhaust air mixes with the outdoor air fairly quickly. Still days and the wind direction will be the common cause for any short circuiting. But I wouldn’t get too concerned.

In your photos I can see daylight in three of the cowls and one flexi connected. Shouldn’t there only be daylight in two of them?
Do you have cowls at both ends of the roof?

Yea I have 4 cowls at both ends of the roof.

AlDrag

247 posts

Master Geek

#3326010 29-Dec-2024 19:59

tweake:

yes, thats an ok fix for the situation. keep the bathroom exhausts away from the inlet.

you could also move the erv intake to other side and bring over the bath fan to its old spot. ie all outlets on one side and inlet on the other side. air pressure differences from the ends is pretty minor issue in a house like this.

Right. Minor issue in a house like mine due to the fact my house isn't a fancy, passive house, super airtight house? What would an air pressure difference make for the lossnay? Just make it not perfectly balanced? Slightly positive or slightly negative depending on the day?

tweake

2391 posts

Uber Geek

#3326013 29-Dec-2024 20:19

AlDrag:

Right. Minor issue in a house like mine due to the fact my house isn't a fancy, passive house, super airtight house? What would an air pressure difference make for the lossnay? Just make it not perfectly balanced? Slightly positive or slightly negative depending on the day?

exactly. when its windy, which would unbalance the lossnay a bit, there is most likely more airflow through the house via leakage than through the lossnay. in that situation it doesn't matter what the lossnay is doing.

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AlDrag

247 posts

Master Geek

#3326399 31-Dec-2024 00:31

tweake:
also check/ask if they gased the heat pump properly. i did a quick look in the install manual and those units only have enough gas for a 7m long pipe. after that they have to add extra gas, otherwise you will get reduced performance.

Can you provide a link to that manual? Assuming it's for the PEAD 50? So I can ask them about the gas if needed. I couldnt find any reference, but I'm probably blind.

AlDrag

247 posts

Master Geek

#3326400 31-Dec-2024 00:54

If outside of the house is 17 degrees, and my room is currently 22 degrees, then running fan mode only shouldn't then start slowly increasing the temperature right???......only reason I could think that might be happening is that the incoming air is getting reheated by the outgoing hear, but I thought the erv has a bypass damper for that situation?

tweake

2391 posts

Uber Geek

#3326572 31-Dec-2024 14:00

AlDrag: Can you provide a link to that manual? Assuming it's for the PEAD 50? So I can ask them about the gas if needed. I couldnt find any reference, but I'm probably blind.

google suz-m50va installation manual. but please check that is your outdoor units model number.

i have "Mitsubishi_Electric_SUZ-M_VA_Installation_Manual_Eng.pdf" page 7, 5. Refrigerant piping work, "Refrigerant adjustment ... If pipe length exceeds 7 m, additional refrigerant (R32)
charge is required.
(The outdoor unit is charged with refrigerant for pipe length up to 7 m.)"

i had a look at similar models and they also have a 7m charge. if you have the install manual that came with the unit its probably written in that.

tweake

2391 posts

Uber Geek

#3326573 31-Dec-2024 14:12

AlDrag: If outside of the house is 17 degrees, and my room is currently 22 degrees, then running fan mode only shouldn't then start slowly increasing the temperature right???......only reason I could think that might be happening is that the incoming air is getting reheated by the outgoing hear, but I thought the erv has a bypass damper for that situation?

several things at play here.

first is heat soak. the rest of the house is going to pour heat in until that cools down. i notice that a lot because i run bedrooms a lot cooler than i run the rest of the house. so all of the house heat is trying to escape via the bedroom. plus you also have all the heat in the roof and walls. remember that air holds very little heat compared to the house structure.

how much effect the pipes and unit have on the temps i don't know. you could be picking up heat from the hot ceiling.

finally i think bypass on the erv is a silly idea. you don't want to bring in all that humidity from outside as it defeats the point of having an erv in the first place. so i would leave the bypass off. its all set by the dip switches in the unit, including what temp it opens etc. hence need a pic of the dip switches to know how its setup.

if you get a pic of the dip switches and connectors, let me know what size house it is (and garage size), the evr's model number, and if they installed the downstairs vent. then its easy enough to check they set it correctly.

AlDrag

247 posts

Master Geek

#3326575 31-Dec-2024 14:56

tweake:

several things at play here.

first is heat soak. the rest of the house is going to pour heat in until that cools down. i notice that a lot because i run bedrooms a lot cooler than i run the rest of the house. so all of the house heat is trying to escape via the bedroom. plus you also have all the heat in the roof and walls. remember that air holds very little heat compared to the house structure.

how much effect the pipes and unit have on the temps i don't know. you could be picking up heat from the hot ceiling.

finally i think bypass on the erv is a silly idea. you don't want to bring in all that humidity from outside as it defeats the point of having an erv in the first place. so i would leave the bypass off. its all set by the dip switches in the unit, including what temp it opens etc. hence need a pic of the dip switches to know how its setup.

if you get a pic of the dip switches and connectors, let me know what size house it is (and garage size), the evr's model number, and if they installed the downstairs vent. then its easy enough to check they set it correctly.

That does make sense. I was observing the issue at midnight though. Ran cooling all night, then when I went to bed at midnight, switched to fan mode and noticed the temps going up. I didn't go up by much though. Could also just be the fact the hallway (where the return is) is hotter than the room.

Would you mind helping me determine where I can access the dip switches? I managed to open the panel where the ERV core is, but don't see any control panel there, despite the door having the picture of it.

It's a LGH-25.

Maybe it's on the otherside of the unit, just more of a pain to get there due to all the ducting.

AlDrag

247 posts

Master Geek

#3326576 31-Dec-2024 14:58

tweake:

google suz-m50va installation manual. but please check that is your outdoor units model number.

i have "Mitsubishi_Electric_SUZ-M_VA_Installation_Manual_Eng.pdf" page 7, 5. Refrigerant piping work, "Refrigerant adjustment ... If pipe length exceeds 7 m, additional refrigerant (R32)
charge is required.
(The outdoor unit is charged with refrigerant for pipe length up to 7 m.)"

i had a look at similar models and they also have a 7m charge. if you have the install manual that came with the unit its probably written in that.

Yep that's my model number. Outside the house, I can see there is at least 4m of conduit going from the unit to the ceiling wall.

Then in the ceiling, there is at least another 3-4m. So maybe it really is undergassed. I'll ask them "nicely".

tweake

2391 posts

Uber Geek

#3326581 31-Dec-2024 15:31

i would expect the dip switches are in the box to your right, probably has the wiring going to it. please don't electrocute yourself.

8m pipe length is ok. tho i kinda expected it to be longer. but i have no idea how long the house is and where the units placed. if its any longer i would certainly be getting the gas right to make sure you get full performance. if the unit is border line in spec (which is a good thing in many ways), the last thing you want is anything that downgrades performance.

AlDrag

247 posts

Master Geek

#3331268 14-Jan-2025 10:42

Ok so the installers came over today.

2 of the dampers were not fully closing, the bypass damper and one of the bedroom ones. They contacted Polyaire and it seems like it's a bad batch of dampers (basically has play in the switch when closed).

They indeed didn't give it enough coolant. The system is rated for 7m, as pointed out by tweake. They calculated the pipe is about 10m, so they added 70grams of coolant. I don't know if that would make much of a difference? But I guess we will find out. They incorrectly assumed that the Mitsubishi was precharged for 15m like Panasonic (seems most installers in Auckland focus on Panasonic. Must be a good rebate).

They wanted to max out the static pressure as well. I luckily told them to hold off on that for now to see if these are other 2 variables make a big difference. After hearing from you guys and reading about increasing static pressure, it seems like a bad idea in all but the rare cases. The installer even stated the airflow currently is already really good, so idk why they wanted to increase it.

I also enquired about getting the Lossnay controller installed separately. As it would be nice to be able to adjust those settings myself. Like being able to adjust the bypass damper etc. Not sure if this is a good idea though, maybe it'll interfere with the heatpump? As I think even with native Mitsubishi, if you couple the lossnay with a heatpump, they replace the Lossnay controller with a single heatpump controller?
Installer seems to think it's fine though. He's gonna look into it.
I do still want to take a look at the dip switches though and get a picture from the Lossnay.

So fingers crossed these variables make a big difference.
The main annoyance that's still unresolved for me is the fact the Lossnay is useless at night. If it's colder outside, it'd be nice to bring that coldness inside without having to use A/C...but it just heats up the room instead. Doesn't make any sense.

Despite all these problems, they have been really accommodating and willing to help.

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