8/11/2019 Unico HVAC Air Handler Replacement Guide Available from Unique Indoor Comfort Libertyville

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Unico, Inc. / 7401 Alabama / St. Louis, MO 63111 / Phone: 800-527-0896 / Fax: 314-457-9000 / www.unicos

UNICO’S GUIDE TO REPLACING OLDER SMA

DUCT HIGH VELOCITY AIR HANDLERS

NOTE: When replacing both the indoor blower and the outdoor condensing unit you MUST check the

matchup rating on www.ahridirectory.org

Equipment size. The modern AHUs are not exact replacements; they are better. They are

more efficient, quieter, and, for most applications, have more static pressure than the older

unit. In addition, the dimensions, although similar, are slightly different. Use the following

table to determine the closest match. 

Existing Unit Replace With

Tonnage Blower Coil

Unico

HP / VP 24362 M2430BL1-EC2 MC2430*

2.5 M2430BL1-EC2 MC2430*

MB2436H 3 M3642BL1-EC2 MC3642*

HP / VP 42603.5 M3642BL1-EC2 MC3642*

 4 M3642BL1-EC2 MC3642*

MB4260 5 M4860BL1-EC2 MC4860*

Spacepak

ESP18241.5 M2430BL1-EC2 MC2430*

2 M2430BL1-EC2 MC2430*

ESP30362.5 M2430BL1-EC2 MC2430*

3 M3642BL1-EC2 MC3642*

ESP4260

3 M3642BL1-EC2 MC3642*

 4 M3642BL1-EC2 MC3642*5 M4860BL1-EC2 MC4860*

* Can use either "C" or "H" coil

8/11/2019 Unico HVAC Air Handler Replacement Guide Available from Unique Indoor Comfort Libertyville

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Common Plenum Configurations:

Shotgun Pattern. For the 4860/3642 units, use 10-inch insulated metal or fiberglass duct for the f

cent of the outlets coming off the 10-inch plenum; then reduce to 9-inch if desired. For the 2430/

use 9-inch insulated metal or fiberglass duct for the first 40 percent of the outlets coming off the num; then reduce to 7-inch if desired.

40 %60 %

9-INCH DIA.

7-INCH DIA.

IL00124.CNV 

30% MAX.

 

Airflow - The older systems were designed for 200 CFMper nominal ton and often the actual airflow was 180CFM per nominal ton. The modern units are designedfor 250 CFM per nominal ton with a minimum of 200CFM for acceptable performance. It is very important tomaintain the minimum airflow. It is absolutely requiredif the outdoor unit is being replaced.

Plenum - Most of the older systems use 7 inch roundplenum. The modern units often use slightly larger duct

sizes. Therefore, you will need to adapt to the existingduct using reducer fittings. Be sure to seal the ducts andinsulate. It may be necessary to upsize the plenum insome applications. Primarily this will entail using alarger, 9 or 10 inch, duct up to a tee; then downsizingto the 7 inch. This is usually seen in horseshoe orperimeter loop configurations.

Common Recomendations

For the 4860/3642 - Replacing the duct work be-tween the AHU and the first fitting (in most cases it isa Tee) needs to be changed to a 10-inch I.D. insulatedmetal plenum for a minimum of 2 feet.

For the 2430/1218 - Replacing the duct work be-tween the AHU and the first fitting (in most cases it is

a Tee) needs to be changed to a 9-inch I.D. insulatedmetal plenum for a minimum of 2 feet.

24-inch 610 mm) Rule - Use at least 24-inch [610mm] of straight plenum before any fitting, such as anelbow, tee, or takeoff. Electric duct heaters require 48inches [1.2 m]. Avoid elbows directly off units.

Outlets - The older systems usually were designed with 4to 5 outlets per ton. The modern systems require 6 to 8outlets per ton. This does not mean that outlets automati-cally need to be added. Often the modern blower willhave enough reserve to compensate for the fewer out-lets. However, the increased airflow may create objec-tionable noise. If this occurs, or the required airflow isnot achieved, then you will need to add additional

outlets.

Space Takeoffs Evenly - Maintain distance betweentakeoffs as evenly as possible. Space the takeoffs atleast 6-inch [152 mm] apart and 12-inch [305 mm]from end cap.

Return Duct - Typically no changes are required. Use thefollowing table to determine if the return should be up-sized. (Downsizing is never required.)

Check Airflow - The EC motor makes it easy to check theairflow. Set the airflow capacity switch (high/low) to thecorrect airflow per the following table

Note: be sure that

the model switch is

set to the correct

model size.

*These are default

settings. These can

be customized if you

use a laptop and the

ECMconfig software.

Move the Aux (or Check Airflow) switch to the ON (orCHECK) position.

Count the flashes. Each flash is equal to 100 CFM. If yousee a half flash at the end, add another 50 CFM.

IF THE AIRFLOW IS LESS THAN 200 CFM PER NOMINAL

TON BASED ON THE OUTDOOR UNIT SIZE), THEN YOU

WILL NEED TO MODIFY THE DUCT SYSTEM. Either in-crease the plenum size or add outlets, or both. Consult

 with customer service if you need assistance.

IF YOU EXPERIENCE NOISE ISSUES BECAUSE THE NEW

BLOWER IS DELIVERING MORE AIR THAN BEFORE, YOU

WILL NEED TO ADD OUTLETS. If the unit is deliveringmore air than the minimum you can reduce the airflowusing the laptop. Consult customer service if you needassistance.

 Airflow in CFM Return Size

 400 12” 

600 14” 

800 16” 

1000 18” 

1300 20” 

Nom Ton Switch Setting Airflow*

1.5 M2430 (low) 500

2 M2430 (low) 500

2.5 M2430 (high) 625

3 M3642 (low) 750

3.5 M3642 (high) 925

 4 M3642 (high) 925

 4 M4860 (low) 1000

5 M4860 (high) 1250