4-5 Ton Vertical Plenum / Heating Module Air Handler

4-5 Ton Vertical Plenum / Heating Module Air Handler

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Availability: In stock

Model #: M4860R1
Brand : Unico

Availability: In stock

  • Unico Small Duct System

  • Same as MR3660

  • RAP

  • With Filter

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Unico 4 - 5 Ton Horizontal Return Air Plenum Module Air Handler M4860R1


The Unico System designed and built Return Air Plenum (RAP) is easily installed with the matching Unico System modular air-handling units. The RAP is designed specifically for multiple return duct systems. The plenum comes without any return openings so the installer can cut whatever openings are necessary for any number of return ducts. The top and all three sides of the RAP can be used for return air connections. Plus, it includes a centrally located filter accessible from either side of the cabinet.

The RAP is also ideal for bringing in outside air and combining it with return air, effectively changing the RAP into a mixing box. Return ducts can be any material so long as the duct is insulated, has acoustical properties, and is the correct size..

Packing List

Package Includes:

  • 1- Return Air Plenum Cabinet
  • 1- Hook Flange (to connect to Cooling Module)
  • 5- Screws for hook flange 
  • 1- Disposable 1 in Filter
  • 2- Latches
  • 5¾ ft- length of gasket tape


  • Blank sides and top allow for custom, multiplereturn openings
  • Centrally located disposable filter
  • Heavy-duty closed cell insulation (no exposed fiberglass insulation)
  • Filter access from both sides
  • Standard Unico System ‘latch’ system

Cabinet Construction

The cabinet is fully insulated with closed cell insulation. There is no exposed fiberglass inside the cabinet. The cabinet is constructed of 24 gauge (0.6-mm) galvanized steel with removable access panels on both sides for ease of service.

Providing Outside Air

The Unico System is designed to handle up to 100 percent outside air provided the air is filtered and all water coils are freeze protected if necessary. To accommodate outside air, the amount of required airflow must first be established in accordance with all local codes or ASHRAE Standard 62. Outside air is normally based on occupancy, square footage, and use. The Return Air Plenum provides a convenient plenum box for connecting and filtering the combined air streams from an outside air duct and the inside air ducts.

Return Duct System

Before proceeding with the installation of the Return Air Plenum, the design and layout of the return duct system should be completed considering the following factors:

  • If using return filter grilles, only use one filter. Use the filter that is most convenient for servicing.
  • For optimum acoustical performance metal ducts should be lined with fiberglass insulation and flexible duct should be the sound attenuating type that does not have a solid plastic inner liner.
  • Multiple returns should be used when conditioning two or more spaces that do not communicate with each other. This is particularly important when heating and cooling separate floors with doors separating them or office spaces with closed doors.
  • For multiple return systems, the duct system must be designed for static pressure drop no greater than 0.05 inches of water.
  • Be sure the number and size of the ducts, as designed for the job, provide sufficient area for the capacity of the system.This assumes ducts are no longer than 25- feet in length with generous or large radius turns.Where longer lengths and sharp radius turns are necessary, larger ducts must be used (adapters may be required).
  • To facilitate connection of round duct to the Return Air Plenum, consider using pre-fabricated connecting stubs or take-offs that are available from supply houses. These are available for connecting either rigid metal pipe or insulated flexible duct. Flexible duct may be retained at the connection stub using duct retaining straps such as the wire tie type. Be sure all return ducts are properly insulated with the required R factor for the application.

Additional Information

Brand Unico
Application No
liquid_line_connection_size No
Suction Line Connection Size No
amperage(amp0 No
Heating Capacity No
Cooling Capacity No
Warranty No