Unico high-vel AC: how to reduce airflow

Nom_Deplume

Hi...our Unico AC system has a box of misc. parts, including some perforated metal pieces that I understand are intended to reduce the airflow from individual ducts.

What I can't figure out is how to mount them in the ducts. There are some round metal "holders" that the perforated metal pieces drop into, but I can't insert any of this into the duct opening.

There are also some soft white plastic stoppers that can be inserted into the openings after some struggle, but these completely stop up the ducts rather than allowing partial flow.

Many thanks!

Kybeans403

The cheese graters get installed at the main trunk line where each individual tube is connected at the "take-off" 

You need to remove the jet tubing from the take off by snipping the clamp ring. Once duct is off, slide the plate onto 2" round take off, then put the disc with the lip on top if that. I would then tape the edges to the take off as it's not a super tight fit. Jet Tube slides back onto takeoff.....

Before adding a bunch of these I'd check a few things.....Unico systems work best and sound quite good (quiet) when you have at least 7 outlets per ton.....2 Ton air handler.....you should have at least 14 runs, if not a few more.

Also there shouldn't be any take offs installed  close to the air outlet of fan module...need at least 36" and after the first Tee or Elbow. There should not be any takeoffs installed within 2 feet of end of trunk either.

Back to top, if you don't have enough outlets,  or your trunk duct is insufficient,  adding the restrictors can adversely affect performance.  

Nom_Deplume

Wow. many thanks! I didn't realize it was not a casual homeowner install.

PS I have 12 outlets for a 2-ton, the minimum number, which means I probably shouldn't use any restrictors anyway.

GW

way back in the old days it was 5 per ton. You could hear it!

Ironman

Are you trying to reduce the air flow because of air velocity noise or because certain areas are over cooling?

Nom_Deplume

Overcooling. When you can have 1, 2, 3...ducts per room, i.e. round numbers not fractions, it is hard to balance south-facing and north-facing rooms exactly. It's too bad the system does not have some kind of variable flow restrictor driven by individual room stats.

GW

Nom that’s getting more into the commercial world of hvac. 

You might be able to slow the flow down in that one room, without affecting too much of the refrigeration cycle.

Kybeans403

If a room is over-cooling you can install one of the white plugs into the white donut outlet.  BUT, since your short on total outlets anyway it might not be a great idea. It won't break anything per se, but the systems need a specific air flow across the coil. If you start restricting that you can run into coil icing issues. The coils do have freeze stats but they aren't installed in the best spot and the fins will ice up substantially before the freeze stat shuts compressor off. 

You can zone these systems, but you'd have to redesign the entire duct system. 

Jon_blaney

Can you add outlets in other rooms to decrease the proportional airflow?

mattmia2

That would be my suggestion, to add outlets in the rooms that are too warm.

Nom_Deplume

I'm a homeowner, so adding outlets is not realistic (or cheap). However, I now understand that there exists a set of plugs for the outlets (UPC-36-15). These are apparently not recommended because noise is better controlled if the airflow restriction is upstream rather than in the room; but they will work OK for my purposes. I am only going to cut the flow 50% in one outlet, which leaves 11-1/2, and I will assume that the system will survive this since the old recommendation was for 10.

PS I was able to connect via USB and see that the airflow rate is set at 500, even though the max allowed is 750. (Unico 2436 with 2-ton AC). So presumably the fan is capable of pushing out the required airflow even with 11.5 outlets?

Many thanks for all the expert responses!

Ironman

What make and model outdoor unit do you have?