Variable Refrigerant Flow Zoning HVAC?

10 years ago

With our new house build after speaking with a buddy who is an engineer and designs commercial HVAC systems, his suggestion is to go with a Mitsubishi CityMULTI VRF system and still retain the ductwork. After reading and reading and then rereading his emails and watching countless Youtube vids and reading quite a few studies on these units, it just makes sense. Our house will be right around 2,600 sq ft with 2 stories plus a loft. There are only 2 of us. I work out of my home office which will be in the loft and the wife works and is out of the house for the day. It does not make sense to have the entire house cooled to say 75 when I am only really needing say 250 ft of it cooled and we can turn the tstat up in the other zones.

From everything I have read to the average lay person, it is something to consider. The only immediate downfall is cost since they're significantly more than a traditional HVAC. Anyone have any input or experience with these in the residential setting. We are in Pensacola, FL and 8 out of 10 people are using heat pumps for the cooler months and is does get down into the 20's here and there in the winter.

Here's a link: http://www.mitsubishipro.com/en/professional/products/heat-pump-systems/city-multi-vrf/city-multi-vrf-heat-pumps---outdoor-units/k-generation-y-series

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Austin Air Companie

10 years ago

The link you posted is for a 208/230 3 phase unit and some models include 460v 3 phase. It's unlikely you have 3 phase power at your home.

Additionally when it comes to zoning via mini split applications, the zones are done typically via refrigerant piping and 'heads' (air handling units) in which this piping is connected. VRF is one technology there are others with differences in piping requirements, circuitry to control the refrigerant flow among other things.

The complexity is within the refrigerant piping of the circuits, the other is that if you choose the Mitsubishi VRF technology over others you will be likely be bound to that when the system fails it would be extremely costly to change to any competing technology - there is no 'standard' necessarily when it comes to zoned mini splits. There are so many different models, configurations, piping designs, requirements that it's enough to make my head spin.

On top of all this is that the more equipment (multiple heads or air handling units) the more maintenance, more repairs, more problems not to mention specialty help to diagnose the system when problems develop.

Mitsubishi as well as other manufacturer's require dealers to be certified in working on their equipment. If your installing contractor goes out of business, you may be in dire straights to say the least choosing something that is considered the 'wild west' of air conditioning systems.

Foreign manufactured, short life cycles, short warranty periods, OEM required parts - if your particular model is no longer made - planned obsolescence, increased maintenance requirements --- IMO, there's not much to like with any mini split application other than maybe a single head type set up for 'non critical' function.

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Comments (7)

tigerdunes
10 years ago
this is a residential product?....

and still retain the ductwork...what does that mean?

TD
User
Original Author
10 years ago
last modified: 10 years ago
Yes residential and not a ductless system. Traditional ductwork will be installed. I.e., not a ductless system.
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fsq4cw
10 years ago
Keep in mind that while your friend is an engineer, he
designs commercial HVAC systems. This is not
exactly a ‘residential’ system. If
you were asking his advice about buying an SUV he’d sell you a Mack Truck!

At about 2600sq ft. I’d look to more conventional variable
speed zoned systems, such as Carrier Greenspeed.

Caveat Emptor

Careful what you wish for…

IMPO

SR
mike_home
10 years ago
I don't see why you can't accomplish what you want to do with a conventional residential HVAC system.

Don't start a new posting for every question. It makes it hard to follow for those who are trying to give you advice. If you do start a new posting, then add a link back to the original one.
ionized_gw
10 years ago
A VRR system might make sense if you need to simultaneously heat one area while cooling another, or you can heat a lot of water while cooling, or cool a lot of water while heating. I doubt that you have these characteristics. Otherwise, your bottom line might be improved by installing a mini split in the loft and a conventional system serving the rest of the house. The big system might overlap with the loft as well since you might not get enough heat out of the mini split for that area.
Mini-Split Warehouse
5 years ago
TYPICAL VRF SYSTEM STRUCTURE.

https://www.air-conditioning-heating.org/

A typical system consists of an outdoor unit (comprising one or multiple compressors), several indoor units (often and mistakenly called "fan coils"), refrigerant piping, running from the outdoor to all indoors, using Refnet Joints (copper distributors in pipes) and communication wiring.

VRV / VRF HVAC connectivity diagram

Communication wiring consists of a 2 wired cable, chained from the outdoor to all indoors, creating an internal closed loop network, that is an essential part of any VRF installation.

As for the Control, each indoor is controlled by its own wired control panel, while there are some possibilities for wireless remotes (IR) and centralized controllers, enabling controlling all indoors from one location.