Mitsubishi M-Series vs. P-Series vs. City Multi
Can someone help me understand the differences between these different lines of products that Mitsubishi sells?
I understand that at a high-level, the M-Series is intended for Residential, the P-Series for light commercial and the “City Multi” for multi-family or more complex commercial. But what does that mean in practice? Is this one of those all-metal internals vs. plastic internals type of differences?
And any sense of price differences (just ballpark) between these lines?
We had a mechanical engineer design our HVAC, and they’ve come back suggesting a “City Multi” Multi-split set-up with ducted multi-position air handlers to handle different zones (floors).
But before even getting the system quoted, I’m afraid this is going to be outrageously expensive.
Is there any material downside to suggesting that we move to a series of M-Series HyperHeat units instead (i.e., combos like the SVZ-KP12NA/SUZ-KA12NAHZ) https://www.mylinkdrive.com/viewPdf?srcUrl=http://s3.amazonaws.com/enter.mehvac.com/DAMRoot/Original/10006%5CM_SUBMITTAL_SVZ-KP12NA_SUZ-KA12NAHZ_en.pdf
I can’t tell if I’m giving up something that I don’t fully understand or appreciate by asking for this “downgrade” or if the engineer has just overspecified the system because they more typically do commercial work and they’re more familiar with the City Multi family of products.
Thanks in advance!
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Yes, it sounds like your mechanical engineer is most likely specifying equipment from a commercial perspective. In general houses shouldn’t have loads big enough or complex enough to justify commercial equipment. If loads really are that big then somebody needs to design out that load.
It’s relatively rare to find mechanical engineers who work consistently on residential projects. You may be better off consulting a good installer. They will know their way around manufacturer product lines. Mitsubishi’s can be especially confusing.
I’ve never encountered a residential application for which a city multi unit would be appropriate. Are you sure you aren’t confusing “city multi” with “smart multi”?
Hyper heat P-series air handlers and m series air handlers have some differences: in one-to-ones m series maxes out at 36,000 kbtu, p-series at 42,000. Performance curves are different—look at COPs and min/max temperatures. If you want to cool below 68 then you’ll need p series for ex. P series will add some cost but not enough to be a consideration.
I don’t think there’s any quality difference to worry about between the two lines. And there is some crossover—the smart multi units are compatible with both p and m. Check the compatibility tables for specific units.
Be aware multi head outdoor units take a significant performance hit. Also make sure the equipment recommendation is based on an accurate load calc. Air source heat pumps don’t like to be oversized. A smaller ducted unit with back up strip heat is more efficient than a larger hp sized to meet the full load.
Good luck with your project.
Thanks -- super helpful!
The outdoor unit specified was the: PUMY-HP42NKMU2 (pg 129 of this catalog) https://cdn.agilitycms.com/mesca/new_city-multi_catalogue_fin.pdf
Indoor units are: PVFY-P12NAMU-E1 and PVFY-P18NAMU-E1
http://www.mitsubishitechinfo.ca/item/PVFY-P-NAMU-E1%20-%20Current
I think I'm going to request to downgrade to 1:1 M-Series or P-Series.
One additional question: for the P-series it doesn't appear they offer their Hyper Heat outdoor units in anything below 2T capacity. E.g., if I look at their submittals, they only pair the smaller indoor air handlers with "Standard" outdoor units like the PUZ-A12NKA7
http://www.mitsubishitechinfo.ca/item/PVA-A%2A%2AAA7
So does that mean for small pairings (I'd like a dedicated zone for each floor) I'm forced into the M-Series?
Thanks!
Not to open a can of worms, but if you have a well insulated shell and mechanical ventilation that is zoned and balanced (ala zehnder for ex) , you may be able to eliminate the need for the ducted system and used a single ductless head per floor. The ventilation system keeps the temps even enough that a point source for heating and cooling ends up getting well distributed. Cheaper and simpler.
Now I’m curious.. why the heck did my engineer specify the same?! I definitely remember getting bids, the installers were basically all like ‘ermmm, this looks like a commercial system, but ok….’
The architect coordinated the HVAC design, and this is what we got. I became interested in building an efficient home after hearing about the passive houses that only require a “hair dryer” to heat, obviously different in a Canadian climate but it is a long way from a heavy duty commercial system! Bad design (i.e. too much glass) or just crazily over-engineered HVAC?
Our load calcs are based on ASHRAE Heat Balance Method using dynamic building energy and performance modelling software IES VE 2022. Level 1&2 sensible heat load is ~ 26,000 Btu/h meanwhile the 2.5T AHU capacity is 34,000. Cooling load is 25,000 and capacity is 30,000. Meanwhile in the basement with 1T AHU the heat load is 11,000 but capacity is 17,000 and cooling load is 9,000 vs capacity 12,700. We also have backup heat strips.
" Air source heat pumps don’t like to be oversized. A smaller ducted unit with back up strip heat is more efficient than a larger hp sized to meet the full load."
With modulating heat pumps this isn't so much of an issue. If you look at the spec sheet on the M-Series, at temperatures above 17F the COP is higher at minimum modulation than at maximum or rated output. See https://ashp.neep.org/#!/product/34583/7/25000/95/7500/0///0
Ok that is what I thought before, but wasn’t sure if I understood! You mean since it is VRF right? So it’s not running at high speed, the condenser is modulating the speed and able to perform even at a very low demand since it can just regulate as needed? The fan just goes very very slow if it needs to?
The compressor has a variable speed motor. Typically it can go down to 20-25% of rated capacity, if demand is below that it has to cycle on and off. This is where it gets tricky, cycling tends not to be as efficient. So you want the compressor to be running at a level where it can run slowly but not cycle.
The M-Series are further complicated that they have vapor injection to boost output at low temperatures. In vapor injection mode they have highest COP at full output. But that's probably OK because at those temperatures you should be running near full capacity anyway.
Hmmm. Performance data doesn’t support this. The spread between minimum and maximum output for multihead compressors is much much less favorable than one-to-ones., especially ductless. Check out the NEEP website or the Mitsu submittals. Multiple small heads on a large compressor means any time there’s a load from a single head, the compressor is likely below its minimum output. There have been a number of threads on this subjects here—graphs from energy monitoring software showing the short cycling etc.
In the case of the S-series outdoor unit, which both OP’s engineer and mine have specified, it would seem that it is designed to operate better than the others with multiple heads and at lower outputs…? That being said OP’s seems more oversized as the AHUs are 12 & 18 vs mine which are 12 & 30 (totalling the 42k Btu capacity of outdoor unit).
Is vapour injection mode what Mitsu calls Hyper Heat?
In any case, I was under the impression that the City Multi outdoor unit (“S-series”) can handle low loads well below the total capacity whereas the other residential units that are better 1:1 for the reasons described above with cycling on/off. I am curious if there is any data showing specifically for the City Multi units running low loads to see at what point they are cycling.
Great success, I found the submittal for the PUMY-HP42NKMU2 outdoor unit finally! http://www.mitsubishitechinfo.ca/sites/default/files/SB_PUMY-HP42NKMU2_202404.pdf
As well as this lovely 63 page data book: http://www.mitsubishitechinfo.ca/sites/default/files/DB_PUMY-%28H%29P-NKMU%282%29%284%29_M-P0891A_202309.pdf
Our architect told the engineer to do 3 zones with this equipment (same as yours but larger capacity). And yes it was outrageously expensive. You can ask the engineer directly how it might be simplified, that’s what I did and he was able to save us $10-$15k by removing 1 zone.
Just want to mention with these fancy VRF heat pumps you have to use their archaic controller. Don’t get Kumo cloud, visit Reddit to learn why. So you cannot have EcoBee or Google nest or any other smart thermostat.
The SM series are essentially the small commercial unit with different software for the lower capacity units, physically they are all the same.
The issue with these is that it is impossible to tell how well they will turn down with different combination of indoor units. The was a post here about somebody that installed the SM with a single ducted unit and and even there it would not modulate down. The data sheet does look good, so maybe just a software issue but that doesn't help the end costumer when the system doesn't run as expected.
The P series are semi commercial. Usually the M series is a much better deal with similar performance. Some P series do run in a couple of degrees colder outdoor temp, so might be worth it if you in the north edge of zone 6.
If you want zoning, I would go for separate one to one units for each zone. You can also do zoning with a single unit and dampers but it does require some careful design.
If you want regular thermostat, most will take a thermostat interface module (PAC-US445CN-1). These are not too bad if configured properly and used with a two stage thermostat.
Properly configured, the first stage would slowly ramp the unit and will keep it running at last setpoint after the first stage heat/call is satisfied, close enough to modulating performance. Stage 2 is full power. Important part is setting it up properly which is harder than it sounds for an installer that has never used one before.
I sort of regret not getting them to switch it to 1:1 but I hardly know what I’m talking about so just had to let it be. I would think the cost is higher to do 1:1 (maybe not?) but at least there is resilience if one malfunctions. The OP still has time to switch to 1:1 though. Space might be a consideration being in TO, lots can be tight and the outdoor units are unsightly. The city multi being stacked is efficient, not sure if the single units could be stacked.
I posted separately about smart thermostats a couple days ago, thanks for the info. The key seems to be finding an installer who knows about this, but it does not seem to be something most installers have experience with.
“So does that mean for small pairings (I'd like a dedicated zone for each floor) I'm forced into the M-Series?”
I say get one outdoor unit for every zone. Yes it will cost more but you gain redundancy. Soon or later some part will fail and when that happens the multi head system is 100% off line and you have a crisis that requires immediate action. With 2 or 3 smaller systems when one goes down it is an inconvenient that can wait tell Monday.
My opinion avoid the multi head option. If you read the threads from unhappy mini split owners to me generally, they have a few things in common 1 multiple heads on one unit 2 they are oversized and lately the word Mitsubishi
Now the posting bias is going to be bad, as people with problems will post for help, but......
The number of posts for problems with multi units does not bode well
It seems that the number of setup and installation issues would scare me off.
I have 3 single units in my house and have had very few issues in 14 years.
Perhaps my house is setup oddly, but I think visitors to my house would be challenged to tell you where the outside units are.
As Walta mentions, all of these units are standard in stock with free shipping replacements if they should fail.