High Velocity (Unico) or Standard System

[hvacsteve82]

What would you put in your house? A High Velocity system like a Unico or Space-Pak, or a standard ducted Air Conditioning system? Why?

[TxTurbo]

Depends on the house and the budget. If I had a log cabin without any walls or floor to run ductwork through, Unico is the only way to go! The way they mix the air in a room is pretty cool and is great for installs where space is an issue.

Otherwise I personally would prefer a regular ducted system. The warranties are better and the equipment is more proven in the market. Specifically an inverter-driven system from Carrier (once they hit the market).

[hivacer]

I would go with a unico if I had a chilled water system like the one unico makes or a geothermal water to water unit, I just dont like how they run with standard dx a/c units, from my experience you will replace alot of compressors no matter how good the install. Also the blowers are noisy on startup but equipment isolation could prevent hearing this, I like how small the ductwork is though. Oh and you have to seal the ductwork reaaaaaallllly good. I just pretend its a water line when I seal it

[genduct]

Steve the special equipment (high velocity) means special Limited number of) contractors to service the equipment that has lower efficiency ( lot more fan horse power/ bigger motor ) that really effects the energy use at a premium price increase.

The original theory is thah the HV system would fit with less disruption smaller duct. But consider if you have to cut a hole for a small duct, what is the difference with a somewhat larger duct? You are still cutting a hole and adding drywall.

SO conventional is long term going to be less trouble and expense.

[DavidNJ]

Orange County...near me.

The HV systems are all heated with hot water coils. None can take advantage of the communicating thermostats, which all of the VRV compressors (current Nordyne iQ, future Carrier ICS) have. The hot water requires a mod-con boiler plus distribution plumbing.

All have very low latent ratios, under .7, which should make the air dry, possibly too dry in some climates.

Now the good. The hot water heat could be more efficient in practice; it gives the option of using radiators or radiant heat to supplement. They can use chilled water cooling. There aren't as many options as for DX compressors, but they are also probably more efficient. The system has only one fan coil, the plumbing of the boiler and chiller may be simpler. SpacePak has a boiler that I believe can hook up with few external pieces. Who knows, maybe they will have a chiller also.

Blowers are an issue. Unico has an ECM. The best, IMHO, is the VFD from High Velocity Systems. If zoning, they have an optional module that maintains constant pressure, dropping air flow as low as 150cfm. Of course, that couldn't be done with a DX coil.

The duct systems on all of them have less surface area, and use technologies (fiber duct, spiral duct, etc.) that have less leakage then conventional sheet metal ducts. All are installed to ensure mixing of the supply air, often overlooked in many conventional installations. The smaller ducts could be advantageous in a retrofit where space is at a premium or where basement height is an issue.

There are fewer installers, but most areas have more than a few. Because they sell for a premium price, from my observations these installers tend to be more quality than price focused. Since Unico sells its own chiller, all their dealers and most of the SpacePak dealers have a focus on hot water heating and cold water cooling with some experience in setting it up.

Net, the HV systems generally only compete in cases where price is secondary to some other installation issue or the homeowner is impressed by another installation. All have more dehumidification than conventional systems; whether that is good or bad, IDK.

[skippedover]

Nothing can beat a PROPERLY DESIGNED AND INSTALLED ducted system, IMO. The problem is, few of the systems are properly designed and fewer still are properly installed. Follow the attached guidlines and you'll get a very quiet, comfortable system. If either you or the contractor cuts corners, you could end up with a high velocity system no matter what brand or theoretical design it is.

[DavidNJ]

Nothing can beat a PROPERLY DESIGNED AND INSTALLED ducted system, IMO. The problem is, few of the systems are properly designed and fewer still are properly installed. Follow the attached guidlines and you'll get a very quiet, comfortable system. If either you or the contractor cuts corners, you could end up with a high velocity system no matter what brand or theoretical design it is.


Why would you say that? If you had an unlimited budget you'd installed a forced air system where the air flow was constrained by the stage of the furnace or AC guaranteeing inadequate air mixing?

Theoretically, a radiant floor/chilled beam setup with each space (room or part of room) zoned separately along with humdification/defhumidification/ventilation/filtration done separately (well, partly integrated into the chilled beams) should blow that away. The structure would basically have mild warm air rising or mild cold air falling, with air flows at a fraction of a forced air heating/cooling system.

Additionally, forced air provides limited expandability since the cooling system has to be designed tightly to the heat gain. There are no cost effective make up air scenarios. Hot/cold water allows easy expandability (there is a thread under chillers where the system was sized to handle an entire additional building to be build later!).

The HV systems force the homeowner to commit to hot/cold water; some supplying the equipment Unico sells their own chiller and SpacePak sells their own mod-con boiler. They also force duct placement and face velocity that ensures mixing. All use duct systems that are leak class 6 or better. With sheet metal how many residences are better than 12 or 24?

You may have hit the nail on the head: The HV systems may work better because they are residence specific installation is designed and installed better as much as any technology with the system.

[NCremodler]

Used unico as reccommended for a large remodel in an older home in NC. This has been a night mare and not worked. It does not heat and cool as needed and has continual breakdowns. It has been difficult to determine if a bad install, equipment or both. Factory has been involved but not corrected the issues. 2 years ago one of the units was replaced and now broken again and rendered "non site repairable". Would not use it again.

[George2]

What would you put in your house? A High Velocity system like a Unico or Space-Pak, or a standard ducted Air Conditioning system? Why?

It all depends (as mentioned by others) on the room that you have available.

I sell mostly the conventional low pressure systems because of the lower costs and rebates, etc.

However, when we don't have the room, we install the hi-velocity systems.

I've always had great results with either. But, if I may brag, I put a ton of thought into each installation.

I've designed systems (always on paper first) and then after "seeing" it more clearly, It's not unusual for me to redraw it until I'm satisfied.

[hedtedjr]

Personally I prefer a standard ducted system vs a high velocity setup. But that being said, I have never seen a properly installed HV system. They all seem like they were an afterthought to the builder, kind of a "just stick it wherever there's room" type of thing. I understand the idea and actually like the concept in some applications (renovations of old buildings without existing ducts), but because I work in service, I only see the problem children of the group.