Frequently Asked Questions
1. What is a Small Duct High Velocity (SDHV) system?
2. Are both sides of the system considered high pressure high velocity?
3. What pressure and velocity are we talking about?
4. How many cfm per ton is the Unico system designed for?
5. What types of cooling or heating methods can Unico provide?
6. What types of refrigerant are Unico coils rated for?
7. How many air handler sizes does Unico offer?
8. What configuration and orientation?
9. What voltages are available?
10. How do you set airflow?
11. How is cfm measured?
12. How do you refrigerant charge a Unico system?
13. Will 250 cfm per ton affect my suction pressure?
14. Will 250 cfm per ton in heating on a heat pump effect head pressure?
15. Will 250 cfm per ton change my discharge clg air temperature?
16. Will 250 cfm per ton affect my discharge air temp in htg with heat pump?
17. How many supply outlets per ton do I design for?
18. How do I size my refrigerant piping?
19. What is and why use sound attenuator tubing?
20. When should I use the aluminum supply tubing?
21. How far can you run the supply tubing?
22. How many styles of finished outlets does Unico have?
23. How many types of outlet boots are available?
24. Can any condenser or heat pump work with a Unico system?
25. How high a seer rating can I install with a Unico System?
26. What is aspiration or induced flow?
27. Are there install kits for rough in?
28. How do I handle changes in altitude?
29. Where did 33 cfm per outlet come from?
30. What is a FRO (Full Rated Outlet)?
31. Is the 1218 a modular model?
32. What is a high ambient heat pump kit?
33. Can the Unico system be zoned?
What is a Small Duct High Velocity (SDHV) system?
The product is so unique in its application ability and principles of operation that the air conditioning industry identifies the Unico System with a separate classification called "SDHV" Small Duct High Velocity. There are only 2 companies in this classification, Unico and SpacePak. There are other companies that call themselves SDHV but cannot fall within the definition listed below.
- 220 - 350 cfm per ton
- 1.2 inwc or greater supply plenum pressure
- Supply Outlet velocity of 1000 fpm or greater
- Less than 6 sqin of supply outlet opening
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Are both sides of the system considered high pressure high velocity?
Only the supply side of the system has relatively high pressure high velocity. The return side is the same as a conventional system. This means you can apply accessories to the return side of the system the same as a conventional system. Humidifiers, UV lights and Electronic Air Cleaners. Do not use a bypass humidifier.
Only the supply side of the system has relatively high pressure high velocity. The return side is the same as a conventional system. This means you can apply accessories to the return side of the system the same as a conventional system. Humidifiers, UV lights and Electronic Air Cleaners. Do not use a bypass humidifier.
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What pressure and velocity are we talking about?
A conventional duct system is designed for .1 or .2 inwc (inches of water column) of duct pressure. The Unico system operates at approximately 1.5 inwc duct pressure. A conventional system will have supply duct velocity of 500 to 700 fpm, the Unico system is 1500 to 2000 fpm and the outlet supply velocity will be 1000 to 2000 fpm.
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How many cfm per ton is the Unico system designed for?
The Unico system is designed and tested at 250 cfm per ton. 200 cfm per ton could be applied in very moist climates if necessary but 250 cfm per ton is a must in dry climates.
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What types of cooling or heating methods can Unico provide?
Cooling:
- Refrigerant using outdoor condensing units
- Chilled water supplied by existing chiller or Unico reverse cycle chiller
Heating:
- Standard air to air heat pump
- Hot water from a boiler or Unico reverse cycle chiller
- Electric heater
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What types of refrigerant are Unico coils rated for?
R-22 / R-410A / R-407C
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How many air handler sizes does Unico offer?
There are 4.
| 1218 |
1 or 1.5 ton |
12000 btu or 18000 btu |
| 2430 |
2 or 2.5 ton |
24000 btu or 30000 btu |
| 3642 |
3 or 3.5 ton |
36000 btu or 42000 btu |
| 4860 |
4 or 5 ton |
48000 btu or 60000 btu |
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What configuration and orientation?
The 2 thru 5 ton units can be mounted Horizontal, Up flow, or Down flow. The 1218 can only be mounted up flow and horizontal.
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What voltages are available?
(208 / 230 single phase) & (208 / 230 three phase) (460 / 480 three phase)
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How do you set airflow?
CFM is initially set using the blower restrictor plate on the outlet of the blower. You move it up or down to set motor amperage listed on the side of the blower module. CFM and mass flow (pounds of air per minute) are related. As the cfm goes up so does the mass flow and amperage.
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How is cfm measured?
CFM is measured with a Turbo Meter. The meter is positioned over the outlet opening and is measured in knots. A knot to cfm conversion chart is provided to determine cfm. The Turbo Meter is the only method we tested to measure air flow. The Turbo meter is sold by Unico for about $125.
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How do you refrigerant charge a Unico system?
Unico uses a txv for the refrigerant metering device. TXVs are normally charged by measuring sub cooling at the outdoor unit. Lift and line set length will change this value. UNDERSTAND SUBCOOLING.
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Will 250 cfm per ton affect my suction pressure?
Measured suction pressure will approximately 10% less than a conventional. For example, instead of 75 psi you will read about 67 psi.
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Will 250 cfm per ton in heating on a heat pump affect head pressure?
Measured head pressure can be 30 psi higher than listed on your charging chart.
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Will 250 cfm per ton change my discharge cooling air temperature?
The outlet air temperature in cooling will be colder than a conventional system. Normally on a conventional you will have 15 to 20° drop across the coil, on a Unico you will have 25 to 32° temperature drop.
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Will 250 cfm per ton affect my discharge air temp in heating with heat pump?
Because of a lower air flow the Unico heat pump outlet air temperature will be approx. 25° warmer than a conventional.
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How many supply outlets per ton do I design for?
Six outlets per ton at Sea Level and a moist climate, 7 or more as you go up in altitude or a dry climate. Starting with a minimum of 7 per ton is recommended.
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How do I size my refrigerant piping?
You must follow your outdoor unit manufactures recommendation for refrigerant piping size for the outdoor tonnage. Basically the pipe sizing is the same as a conventional.
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What is and why use sound attenuator tubing?
The sound attenuator tubing core is made of spun nylon, covered with insulation and an outer jacket of Mylar. The Mylar is a vapor barrier and maintains internal duct pressure. The sound attenuator must be used if the outlet sound level is important. You must use at least 3 feet of sound attenuator tubing before the outlet to prevent air noise. Attenuator tubing comes in 12ft lengths; you can use the full length if you choose. You must cut a little off of each end to dress up the connection for proper fit and taping.
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When should I use the aluminum supply tubing?
Aluminum tubing is more rugged. If the outer jacket is torn air will not escape. You can use it on long runs where you are going up walls and across attics with sharp corners. Aluminum comes in a 25 ft length and is a little less expensive than sound attenuator. You can run aluminum and sound attenuator if you choose but the last 3 ft must be sound attenuator. There is a coupling for joining or extending lengths in the install kits.
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How far can you run the supply tubing?
You can run the supply tubing up to 30 ft if required. If airflow is reduced from length so will the delivered btus delivered. To compensate you may have to add more outlets to that area to heat and cool properly.
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How many styles of finished outlets does Unico have?
There are two styles. The round outlets you are familiar with and slotted outlets. Both styles can come in plastic, metal and a variety of woods.
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How many types of outlet boots are available?
There are round outlets and angled round outlets in case you are installing in a vaulted ceiling. There are straight slotted boots and a slotted boot with a 90° bend. The 90° boots can be used in a 2" x 4" wall with side wall air discharge.
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Can any condenser or heat pump work with a Unico system?
Almost all makes of condensing units will work quiet well. You will loose about 2 points on a 13 seer and 5 to 15% Btu capacity at certain conditions. This is because we are operating at 250 cfm per ton instead of 400 which lowers Btu capacity. Unico operates at a higher duct static which lowers cfm per watt. SEER = BTUH / WATTS. The Unico duct system is much more efficient at delivering btus to the space that we regain the efficiency and capacity.
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How high a SEER rating can I install with a Unico System?
If the highest rated unit efficiency on paper is what is required by the homeowner then Unico will not equal a conventional systems matched combination. Even though the Unicos delivered efficiency can be higher, sometimes it is what's on paper that drives the sale. A 13 SEER to a two stage 19 SEER will work very well with Unico air handlers. Be sure the control scheme is compatible. Some units have communicating indoor and outdoor sections.
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What is aspiration or induced flow?
At 1000 fpm a low pressure develops around the air stream. The low pressure promotes room circulation. A return air in the same room is generally not needed to create circulation but a path must be provided to get back to the return air intake.
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Are there install kits for rough in?
There are rough in kits available for the round and slotted outlets. The rough in kits look like a light receptacle kit. A metal bracket will expand to fit between the joist spaces.
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How do I handle changes in altitude?
You must adjust your air flow design as you change altitude. Increasing altitude reduces air density and increases cubic feet per pound. Reducing air density reduces poundage of air crossing the coil. The higher you go the more cfm you will have to move to equal the same mass flow as at sea level. For example at sea level 1 lb of air occupies 13 cubic feet, but at 5000 ft it takes approximately 16 cubic feet. At sea level you would move 250 cfm per ton and require 7.5 outlets per ton and at 5000 ft you would move 300 cfm per ton and require 9.5 outlets per ton. Call Unico about high altitude installations, you may exceed the capabilities of the blower because of air density.
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Where did 33 cfm per outlet come from?
Unico used to recommend 5 outlets per ton, (200 cfm / 5 = 40 cfm per outlet. An outlet was noisy at 40 cfm. The cfm was reduced until the outlet became quiet which is approximately 33 cfm. 200 cfm / 6 = 33 cfm per outlet. The Unico system is designed for 250 cfm per ton. 200 cfm per ton is possible only in moist climates where the condensing moisture yields heat into the coil to keep suction pressure above freezing.
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What is a FRO (Full Rated Outlet)?
When we talk about the number of outlets per ton we really mean the number of FRO outlets per ton. An FRO means 10 ft long and 33 cfm.
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Is the 1218 a modular model?
The M1218 air handler is not modular it is one piece. You have to order it with the heating and cooling options factory installed. The 1218 in the standard configuration has a three speed motor without a restrictor plate. The 1218 with the Advanced Circuit Board comes with a two speed motor. CFM is set with by selecting one of the speed taps not by adjusting a restrictor plate.
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What is a high ambient heat pump kit?
If a heat pump is operated in mild weather meaning 60° plus you may have a head pressure problem. In mild weather the heat pumps capacity can exceed the cooling capacity. The mild weather kit cycles the outdoor fan off if head pressure gets to high. Stopping the outdoor fan reduces outdoor coil load which drops suction pressure and in turn lowers the head pressure. The outdoor fan will cycle on and off on head pressure.
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Can the Unico system be zoned?
The Unico system can be zoned. A number of design scenarios can be applied. Please call Unico with your design application and they will select the proper system configuration.
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