Mitsubishi City Multi System

[ajpackman]

Anybody have any experience with this system? It seems like a great option for an historical renovation project I am designing, but there don't seem to be many installations in the US.

 

[tombmech]

A couple of things:

1. Mitsubishi ductless split systems are absolute jewels. A large part of my career has been introducing these units wherever I can. The only problem with their units these days is trying to control the purchasing departments. There are too many cheap knockoffs with atrocious quality. The originals are as good as any refrigerant-based A/C unit ever made.

On the other hand,
2. There is an obvious predisposition of some foreign cultures against chilled water systems. I have seen million+ sq. ft. non-American auto plants go with DX rooftop units, only - when even the worst chilled water system would've saved money on first cost, much less decades of savings from energy and maintenance.

The fact that Hitachi makes the world standard for absorption chillers only makes this observation more bizarre!

Nevertheless, the extremes of engineering and design that go into some of these refrigerant systems are incredible, especially when a simpler chilled water system is inherently superior, cheaper, longer lasting, and more reliable. That's not to say that some American firms are beyond doing the same thing. I have seen outrageously complicated 8-stage DX systems quoted in an effort to keep a project in the "refrigerant only" umbrella of a preferred vendor.

For your specific case, I don't have all of the information needed to make a decision. However, if your application goes beyond 20-30 tons, I would think it a nightmare for future maintenance. Whatever small benefit may be obtained from the heat recovery traits would pale in comparison.

Only Mitsubishi could have the expertise to make a system like this work in the first place.

DISCLAIMER: Please accept my apology if I've offended anyone. An opinion was solicited, and this is simply my own based on my experience and observations.

 

[Wolfie82]

A few weeks ago I attended a seminar about the Mitsubishi City Multi Variable Refrigerant Flow Systems. They mentioned this type of system is particularly well suited for historic buildings, especially buildings located in urban areas. The indoor units can be surfaced mounted if necessary and everything serving these units (refrigerant piping, electrical conduits, and condensate piping) can be run together through a hole as small as 3" in diameter. The outdoor units are relatively small and can be installed out of sight on the roof. They said this type of system has been installed in various buildings listed on the National Historic Register.

 

[KiwiMace]

See also Daiken VRV systems, recently introduced to the US. Daiken, Hitachi, Mitsubishi all good names in VRV and split ductless systems. Multizone splits are great replacements for central air.

Typically rooftop DX units aren't used so much outside US, and I can't understand the fascination here.
I've worked in Asia and don't think the use of DX systems by asian companies here is driven by a love of packaged DX, efficiency or even first cost, so much as the ridiculous labour cost in the US needed to maintain central plants.

 

[tombmech]

Labor cost for a central plant is a "ridiculous labour cost" compared to dozens, if not more than a hundred, separate compressors at an exposed, elevated height? I don't think so.

Wolfie82 does make a good point about historical items, and there may be another - leakage of refrigerant will have zero impact on the preservation of valuable property. However, a leak of chilled water can have disastrous effects. In normal practice, that's an acceptable minor risk - considering the benefits. On the other hand, that may be too much of a risk to contemplate with historical artifacts.

 

[KiwiMace]

Tombmech: My point on labour cost being that a large firm with good salary for direct employees and ongoing benefits packages 'til death do you part' and often union issues... the outsourcing of all these burdens through equipment selection can be an attractive proposition. Personally, I'm all for central plants - just trying to understand it all myself. I was also thinking that the first cost of redundancy can be a lot higher with water/water chiller systems, where multiple RTUs have a kind of inherent redundancy in open plan industrial settings.

 

[tombmech]

CinciMace:
Yes, it is too bad that labor issues can "infect" what would otherwise be a simple life-cycle cost judgment.

If the existing unionized work force is in a central plant, then the unitary approach might allow an outsourcing to a cheaper maintenance contractor.

If the existing unionized work force is in the buildings with unitary systems, then a central plant might allow an outsourcing to a cheaper maintenance contractor.

I have experienced it both ways, in fact. Yet as you say, I'm all for central plants.