Heat Pumps: Multi-spit vs 3x splits

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Handle9

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#3244084 3-Jun-2024 15:34

Scott3:

Generally seems like there is a lot of love for multi-spilts. I was expecting to be warned off them.

It's a mature technology that's been in the market for a long time. Multis and VRF multis have been around for more than 15 years and are really widely used in commercial applications so it's not a new thing that isn't understood by the industry. It's certainly a much better solution to control the space temperature than a ducted unit with zone "control".

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#3244090 3-Jun-2024 16:33

We’ve got 5 single splits installed at home (all Mitsubishi units, 4x AP25 and 1x AP 60). We were told by the installer that he doesn’t recommend multi splits from Mitsubishi for two reasons, the first being that the single outdoor unit can be a single point of failure, if it dies, then the whole house is without heating or cooling, but at least with single splits, if one outdoor unit fails, then it’s just that room that is affected.

The second I found interesting was the Mitsubishi single splits have both the indoor and outdoor unit mass produced in multiple worldwide locations, so bought together are quite cheap and Mitsubishi don’t mind if that technology is copied by an unscrupulous supplier. But the outdoor unit for ducted and multi splits contain some more proprietary technology so they only produce those in one factory in Japan and tend to be more expensive and a little harder to find parts for, so downtime potentially could be a bit longer.

Our quote for the 5 installed two years ago was $9,500 for the 5 multi splits (two were complex installs due to the outdoor units being installed on the opposite side of the house from the indoor units), $11,600 if we went multi split.

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#3244095 3-Jun-2024 17:01

@empacher48, with five separate areas to heat/cool, did you consider the option to install two multi-splits instead of five individual units or one single multi-split?

That would solve the redundancy issue, and would be interesting to see how prices would compare.

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#3244096 3-Jun-2024 17:06

Mehrts:
@empacher48, with five separate areas to heat/cool, did you consider the option to install two multi-splits instead of five individual units or one single multi-split?

That would solve the redundancy issue, and would be interesting to see how prices would compare.

No I didn’t look at the 2 multi splits. Since the 5 single units was about $2,000 cheaper to install it was what we chose. If we wanted to spend more money I may have looked at the 4 bedrooms off a multi unit and the living area a single split. But even then the bedrooms are in different sides of the house and they all have different heating and cooling demands.

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#3244125 3-Jun-2024 18:45

tweake:

i would use the 2kw models for the bedrooms.

i have two panasonic 2.5kw models in similar sized rooms and i wish they where smaller. both overshoot heating temps (probably due to being to big but possibly also temp sensor issues as i think they are designed for taller rooms than what nz typically has). noise of fans is an issue. the smaller units have slower quieter fans which is a lot nicer in bedrooms and office. with small rooms you tend to get blasted by the cool air.

also don't forget humidity. you want the aircon to run for long periods so it can work as a dehumidifier. heatpumps are usually tuned for best cooling and less dehumidification. with auckland humidity and air leaky homes, humidity control can be tricky. however reducing fan speed can increase dehumidification. this is also why smaller heatpumps can be better.

the office usage is probably a bit better if your using the office during the day. ie have aircon running early in the day rather than trying to cool down a hot room at the end of the day, which is what most tend to do.

upstairs may be a factor depending on how well the door is shut. cool air sinks. so if you leave the door open a lot, you will need a bigger model as your cooling downstairs as well. if so, seriously think about heating/cooling the entire house as one.

if you have a werid shaped room, check the required install height of the unit, and that you can actually install it at that height. (you might struggle to find that height in the specs, i only found it in the install manual.)

With the Panasonic & Fujitsu 2kW unit the minimum power (0.95kW cooling) is the same as on the 2.5kW so no improvement in minimum power.

For Mitsubishi The AP20 has a physically smaller indoor unit, and much lower minimum speed (1.1kW vs 0.6kW), but it is noisier, less efficient & costs the same if I want wifi control ($150 cheaper without)

Mitsubishi AP20

Mitsubishi AP25

Good point on the door open thing. We tend to leave our doors open, so yes a lot of cold will be draining down the stairs.

I suffer from dry eyes, and my child eczema, so prefer minimal dehumidification only.

also, our bedroom soaks up the full output from our 1.8kW portable aircon at the moment (doesn't get to set point) - assuming it is actually producing that, So I don't think a 1.1kW minimum speed is going to be an issue.

Also, with the fan set to the lowest setting & our long pipe runs, I doubt we will get full rated cooling.

In the downstairs room we may end up with the heat pump on a low wall, I will look into the minimum height.

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#3244126 3-Jun-2024 18:52

empacher48:

We’ve got 5 single splits installed at home (all Mitsubishi units, 4x AP25 and 1x AP 60). We were told by the installer that he doesn’t recommend multi splits from Mitsubishi for two reasons, the first being that the single outdoor unit can be a single point of failure, if it dies, then the whole house is without heating or cooling, but at least with single splits, if one outdoor unit fails, then it’s just that room that is affected.

The second I found interesting was the Mitsubishi single splits have both the indoor and outdoor unit mass produced in multiple worldwide locations, so bought together are quite cheap and Mitsubishi don’t mind if that technology is copied by an unscrupulous supplier. But the outdoor unit for ducted and multi splits contain some more proprietary technology so they only produce those in one factory in Japan and tend to be more expensive and a little harder to find parts for, so downtime potentially could be a bit longer.

Our quote for the 5 installed two years ago was $9,500 for the 5 multi splits (two were complex installs due to the outdoor units being installed on the opposite side of the house from the indoor units), $11,600 if we went multi split.

On the single point of failure thing, this has to be balanced against that more unit's means increased odds of an individual failure.

Same deal on multi-engine boats etc. Yeah, the consequences of failure are lower - you can get home on the other engine and don't need to call for a tow, but twice as likely to have an engine failure. And will statistically need to deal with twice the number of repairs.

For me the consequences of an air con failure are fairly low. I can either suffer in the heat, move my office to the lounge (with the old Panasonic unit), or go to the office.

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#3244127 3-Jun-2024 18:54

empacher48:

No I didn’t look at the 2 multi splits. Since the 5 single units was about $2,000 cheaper to install it was what we chose. If we wanted to spend more money I may have looked at the 4 bedrooms off a multi unit and the living area a single split. But even then the bedrooms are in different sides of the house and they all have different heating and cooling demands.

Great info. Currently I am in the opposite situation, with the multisplit being the cheapist option on the table, but I am asking that installer to price individual splits also.

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#3244128 3-Jun-2024 19:25

Scott3:

Also, with the fan set to the lowest setting & our long pipe runs, I doubt we will get full rated cooling.

In the downstairs room we may end up with the heat pump on a low wall, I will look into the minimum height.

make sure they adjust the gas charge for those long runs.

if you have to fit one lower than spec it might be a good idea to use a remote thermostat. (Panasonic make them for theirs). something i want to try out one day.

insane

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#3244200 4-Jun-2024 00:06

I went with a 4x Panasonic Multi-split for our upstairs bedrooms & office. 3x 1.6kw and 1x 2.0kw mostly due to price and having bought a Panasonic in a previous house.

I have another 5.4kw Panasonic single for my upstairs lounge, and another single Panasonic 3.5kw for downstairs lounge, and lastly another 3.5kw Mitsubishi for the downstairs bedroom (was my old lounge unit).
Panasonic has been only okay, but if I'd do it all again I'd probably go Mitsubishi. The Panasonic app looses contact with a wifi controller roughly every 6 months and you have to set it up again which just annoying as it's such a clunky process.

We had a earthmoving contractor hit our Multi-split compressor 3 times with a bobcat, leaving it scrap and having to be replaced... Single point of failure is a legitimate concern if your house is unbearable without heating/cooling.

When EES first installed the Multi-split I double checked that they had installed enough gas per the user manual, and they didn't! After the replacement unit was installed I was sure to get more gas included in the quote, and still they didn't show with the extra gas until I questioned the installers on site and made them go back to get it. With the extra gas it's been running much better, no more cycling between rooms when all 4 are running.

I'd happily go multi-split again.. 7 single compressors would be nuts. As it is 4 outside units feels excessive already and my neighbour probably agrees.

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#3244358 4-Jun-2024 12:46

insane:

I'd happily go multi-split again.. 7 single compressors would be nuts. As it is 4 outside units feels excessive already and my neighbour probably agrees.

yeah 7 is a lot. however this is really where ducted systems come into it. whole house heating is still relatively new for kiwis, but really cool to see so many here going that way. but you really need the house to be designed for it, something that is very lacking in the building industry today.

20 years ago we had people complaining that heat pumps cost to much to run to heat a single room, because they where so used to not heating.

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#3247696 11-Jun-2024 23:19

Yeah I'd really love some central heat exchanger contraption though for new or existing homes. Feels wrong, and very costly /inefficient to have multiple heap pumps for Air conditioning, Cloths dryer, Hot water, Pool heating etc all working in opposite modes.

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#3247700 11-Jun-2024 23:51

Thanks everybody for your help.

Ultimately selected 4x individual Mitsubishi electric AP25's.

Our house is going to end up surrounded by outdoor units, but 3x of them will be in what are essentially dead spots on our property, and won't be seen by anybody buy myself when I move the grass or pull weeds.

While Mitsubishi electric does cost more than the Panasonic and Fujitsu units I also had quoted, because 3 of 4 of the installs are complex installation is a relatively bigger proportion of our cost, I felt it was worth the money for a brand that seems to have consistently good feedback.

AP25 spec sheet is impressive (super quiet in the quietest mode, high efficiency etc). I gave very serious thought to going with the mini AP20 for our child's room (least thermally problematic of the three), mostly for the better turndown & better aesthetics of the smaller indoor unit. But ultimately decided that given the similar price to stick to stick with matching units

Turns out my initial impression that a multi split being cheaper was due to me comparing between different vendors (one vendor was about 60% higher in cost like for like). From the same vendor it was 22% cheaper to go with individual splits AP25 vs multisplit with AP20's in the rooms.

Ultimately decided against a ducted system as it was quite a bit more expensive (and I was concerned it would be less efficient with ducts in our very hot roof space, and struggle with minimum speed when feeding only one room).

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#3247703 12-Jun-2024 00:21

Sounds like you made a good choice then! Which installer did you/are you going with?

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#3248206 12-Jun-2024 21:25

Maybe too late for OP, seems to me some considerations are designing in fresh air turnover, and also I note the doors generally remain open. Did you consider a mix of ducting (for fresh air flow and distribution) and hi wall units?

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