Floor Mounted Air Handling Units (AHU) – Centralised Cooling Units

Modern floor mounted AHUs use double skin panels with insulation sandwiched between an outer and inner sheet. This construction reduces heat gain, prevents condensation on the outer surface, reduces noise, and gives the unit strength and a long service life.

The mixing box combines return air and fresh air. Motorized dampers with actuators allow automatic control of fresh air, return air, and exhaust air quantities based on temperature, CO₂ levels, or BMS commands.

A multi-stage filter section improves indoor air quality. A pre filter AHU stage (G4) protects downstream components, fine filters (F7/F9) remove finer particulates, and a HEPA filter AHU configuration provides very high filtration for hospitals, operation theatres, and cleanrooms.

The air handling unit cooling coil is typically made of copper tubes with aluminium fins. Coil rows, fin spacing, and circuiting are selected to achieve the required cooling capacity, dehumidification, and pressure drop. Both chilled water cooling coil AHUs and DX cooling coil AHUs are available. A well-selected air handler coil is the key to reliable cooling and humidity control.

Where reheat or winter heating is needed, a hot water or electric heating coil can be added, allowing the same unit to work as an air handler for both heating and cooling. Humidifiers are used in pharma plants, laboratories, and hospitals where relative humidity must be held within tight limits.

The fan section includes the AHU blower, motor, and drive. Options include forward curved, backward curved, plug fans, and EC fans, with belt or direct drive. Air handler fan selection directly affects airflow, static pressure capability, noise, and energy use.

A sloped stainless steel drain pan collects condensate below the cooling coil. Stainless steel resists corrosion and makes cleaning and sanitization easier, which is essential for hygiene.

Spring or rubber vibration isolators prevent fan vibration from travelling into the building structure. Hinged access doors with proper sealing provide easy entry for inspection, filter changes, and cleaning.

In horizontal AHUs, sections are arranged side by side. They suit AHU rooms with more floor length but limited height and are the most common commercial air handling unit configuration.

A vertical air handler stacks sections one above the other, saving floor space. This compact air handler design is ideal where the AHU room is small but ceiling height is available.

A chilled water air handler uses chilled water from a central chiller plant, making it a true water coil air handler. Chilled water floor mounted air handling units are the preferred choice for large buildings, malls, hospitals, and airports because of their flexibility, efficiency, and capacity range.

A DX air handling unit uses refrigerant directly in its coil and works with an outdoor condensing unit, so the condenser and air handler operate as a matched pair. When comparing chilled water AHU vs DX AHU, DX units suit medium-sized projects where a chiller plant is not feasible, while chilled water AHUs are better for large, multi-zone buildings.

A treated fresh air unit, also called a fresh air handling unit (FAHU), handles 100% outdoor air. It filters, cools, and dehumidifies fresh air before supplying it to the building or to other AHUs and FCUs. In the AHU vs FAHU comparison, a standard AHU mainly conditions return air, while a FAHU is dedicated to treating AHU fresh air.

Recirculation AHUs primarily condition return air with a controlled amount of fresh air. They are energy efficient and widely used in offices, retail, and hospitality spaces.

Hygienic AHUs feature smooth internal surfaces, stainless steel components, cleanable construction, and HEPA filtration. They are used in hospitals, operation theatres, pharmaceutical plants, food processing units, and cleanrooms.

Heat recovery AHUs and energy recovery AHUs use a thermal wheel or plate heat exchanger to recover energy from exhaust air and pre-cool incoming fresh air, significantly lowering cooling load.

Outdoor AHUs have weatherproof casings, rain hoods, and protective roofs. They are installed on terraces or open areas when there is no space for an indoor air handling unit room.

AHU CFM is calculated from the sensible heat load of the space and the desired supply air temperature difference. Room volume, occupancy, and application also influence the required AHU airflow and air volume.

The cooling capacity in tonnes of refrigeration (TR) depends on sensible and latent loads, fresh air load, and design conditions. Compress India carries out detailed heat load calculations to select the right coil capacity for your building.

Some applications, such as hospitals, operation theatres, and cleanrooms, specify minimum air changes per hour (ACH). In these cases, airflow is selected to meet the required ACH as well as the cooling load.

AHU external static pressure (ESP) is the resistance offered by ducts, diffusers, dampers, and fittings outside the unit. Accurate AHU static pressure calculation ensures the fan delivers the design airflow. Long duct runs and HEPA terminals often require a high static pressure floor mounted AHU.

Coil face velocity is typically kept within recommended limits to avoid water carryover, excess pressure drop, and noise. Proper face velocity improves dehumidification and coil life.

25 mm panels suit many comfort cooling applications, while 50 mm panels provide better insulation, lower heat gain, and improved acoustic performance for demanding and energy-sensitive projects.

PUF (polyurethane foam) insulation offers excellent thermal performance at lower thickness. Rockwool insulation offers superior fire resistance and acoustic performance. The choice depends on fire safety requirements, noise needs, and budget.

Thermal break profiles separate the inner and outer frame, preventing heat bridging and external condensation. They are recommended for hygienic AHUs and for humid climates like Mumbai.

A well-built double skin AHU has low casing air leakage, ensuring that filtered and cooled air reaches the space rather than leaking out. Good sealing improves efficiency, hygiene, and airflow accuracy.

• G4: Pre-filter for coarse dust and larger particles.
• F7: Fine filter for commercial buildings and offices.
• F9: High-grade fine filter AHU stage for hospitals and sensitive areas.
• HEPA: Very high-efficiency filtration for operation theatres, ICUs, cleanrooms, and pharma areas.

Offices and malls typically use G4 + F7 filtration. Hospitals use G4 + F9, with HEPA filters for critical areas. Pharma plants and cleanrooms use multi-stage filtration with terminal HEPA filters to meet cleanroom classification requirements.

UV-C lamps installed near the cooling coil and drain pan help control mould and bacterial growth, keep coils cleaner, and support better indoor air quality.

Differential pressure gauges or sensors across each filter indicate when filters are clogged. This allows timely replacement, maintains airflow, and prevents unnecessary energy consumption.

Forward curved fans are compact and suitable for lower static pressure applications. Backward curved fans offer higher efficiency and are better suited to higher static pressure systems and large airflow.

Plug fans are direct-driven fans without a scroll housing, offering compact installation, easier cleaning, and good efficiency. An EC fan AHU uses electronically commutated motors with built-in speed control, delivering excellent part-load efficiency and low noise.

Belt-driven fans allow speed adjustment through pulleys but need regular belt tensioning and replacement. Direct-drive fans eliminate belt losses and maintenance, improving reliability and efficiency.

A VFD air handling unit uses a variable frequency drive to vary fan speed according to demand. This reduces energy consumption, allows precise airflow control, and extends motor life.

High-efficiency IE3 and IE4 motors reduce electrical losses and operating costs, especially for AHUs that run long hours every day.

EC fans and VFDs match fan speed to actual load, cutting fan energy significantly during part-load operation.

Heat recovery wheels transfer energy between exhaust air and incoming fresh air, reducing the load on the chiller and cooling coil.

Selecting coils and filters with lower pressure drop reduces the fan power needed to move the same airflow.

CO₂ sensors adjust fresh air quantity based on actual occupancy. This avoids over-ventilation during low occupancy and saves cooling energy.

Two-way valves and pressure independent control valves (PICV) regulate chilled water flow through the coil according to load, improving temperature control and reducing pumping energy.

Sensors in the supply and return air paths provide accurate AHU temperature control and AHU humidity control, which is critical in hospitals, labs, and pharma areas.

Motorized damper actuators control fresh air, return air, and exhaust air automatically based on schedules, CO₂ levels, or economizer logic.

Differential pressure switches provide filter clog alarms and fan status indication, helping maintenance teams act before problems affect comfort.

Floor mounted AHUs with BMS integration can be monitored and controlled centrally through BACnet or Modbus protocols. AHU building automation enables scheduling, trend logging, alarm management, and energy optimisation.

Floor mounted AHUs handle very high airflow, making them ideal for malls, auditoriums, airports, and large offices.

Multi-stage filtration, UV-C options, and fresh air control deliver superior indoor air quality compared to decentralised systems.

AHUs provide controlled fresh air and effective dehumidification, which is especially important in humid coastal cities like Mumbai.

Since the fan and motor are located in a separate air handler room, occupied spaces stay quiet and free from equipment noise.

Floor level installation makes filter changes, coil cleaning, and motor servicing easier and safer than working at ceiling height.

With double skin construction and proper maintenance, a quality AHU unit can serve reliably for many years.

Floor mounted AHUs need an air handling unit room with sufficient space and service clearances. This must be planned early in building design.

An AHU does not produce cooling by itself. It requires a chiller plant or DX condensing unit.

Air distribution through ducts requires ceiling space, proper design, and insulation.

The initial investment is higher than packaged units, but it is offset by better performance, efficiency, and service life in large buildings.

Compress India helps you plan the AHU room, ducting, and plant capacity in advance, so these limitations are managed from day one.

High footfall areas need large airflow, strong fresh air supply, and reliable cooling. An AHU for a shopping mall or a floor mounted air handling unit for a commercial building delivers all three.

AHUs for office buildings maintain comfort, fresh air, and quiet workspaces, supporting productivity.

AHUs for hospitals provide HEPA filtration, pressure control, humidity control, and required air changes. A properly designed AHU room in a hospital serves operation theatres, ICUs, and isolation rooms with clean, controlled air.

Pharma AHUs and cleanroom AHUs maintain strict temperature, humidity, and particle count requirements for regulated production areas.

AHUs for hotels keep lobbies, restaurants, and banquet halls comfortable even during peak occupancy.

Large public spaces need high-capacity chilled water AHUs with reliable, continuous operation.

Low-noise AHUs with acoustic treatment ensure comfort without disturbing performances or screenings.

An industrial air handler controls temperature, humidity, and hygiene in production and processing environments, making it the right AHU for industrial buildings.

The Zeco air handling unit range is made by an Indian manufacturer known for double skin and hygienic AHUs for commercial, healthcare, and industrial applications.

Edgetech AHU solutions come from an Indian air handling specialist offering AHUs and air-side equipment for comfort and process applications.

Blue Star is a well-known Indian HVAC brand offering a wide range of central air conditioning equipment, including air handling units.

Voltas offers air handling units as part of its central air conditioning and HVAC product range.

Daikin AHU and Daikin air handling unit solutions are available for chilled water and DX applications across commercial projects.

Carrier offers air handling units for commercial and industrial HVAC systems as part of its central cooling range.

Trane provides air handling units designed for commercial and institutional buildings.

Other options include VTS air handling units and a number of specialised manufacturers of custom and modular AHUs. Compress India recommends the most suitable brand and model based on performance, budget, delivery timelines, and service support.

Supply airflow, return airflow, and external static pressure are measured and compared with design values.

Entering and leaving air and water temperatures are recorded to verify cooling capacity and dehumidification.

Airflow at each diffuser and branch is measured and balanced so every zone receives its design airflow.

Temperature control, valve operation, damper actuators, alarms, interlocks, and BMS communication are tested before handover.

Filters are cleaned or replaced at defined intervals depending on dust levels and filter pressure drop.

Coil cleaning with suitable chemicals restores heat transfer and airflow and reduces energy consumption.

Regular cleaning and sanitization of the drain pan prevents blockages, odours, and microbial growth.

Belts are tensioned or replaced, bearings are greased, and motor current and insulation are checked to prevent breakdowns.

Dampers and actuators are inspected to ensure smooth movement and correct fresh air control.

• Comprehensive AMC: Covers scheduled maintenance plus the cost of specified spare parts, offering predictable annual costs.
• Non-Comprehensive AMC: Covers scheduled maintenance and service visits, with spare parts charged separately as needed.

Causes: clogged filters, dirty coil, belt slippage, closed dampers, or duct leakage.

Solution: Clean or replace filters, clean the coil, adjust belts, check dampers, and seal ducts.

Causes: low chilled water flow, high water temperature, faulty control valve, or dirty coil.

Solution: Check chilled water supply, valve operation, strainers, and coil condition.

Causes: high coil face velocity, blocked drain, or incorrect trap design.

Solution: Clean the drain, correct the trap height, and check airflow across the coil.

Causes: excess fresh air, oversized unit, or high chilled water temperature.

Solution: Adjust fresh air, review controls, and optimise chilled water temperature or add a TFA unit.

Causes: fan imbalance, worn bearings, loose parts, or failed isolators.

Solution: Balance the fan, replace bearings, tighten components, and repair isolators.

Causes: poor tensioning, misalignment, or lack of lubrication.

Solution: Align pulleys, tension belts correctly, and follow a lubrication schedule, or convert to direct drive.

Causes: stagnant water, dirty coil, or wet insulation.

Solution: Clean and sanitize the coil and drain pan, fix drainage, and consider UV-C lamps.

Replacing belt-driven fans with EC fans reduces energy consumption, eliminates belt maintenance, and lowers noise.

Adding a VFD allows airflow to follow demand and brings quick energy savings.

Corroded or leaking coils can be replaced with new high-efficiency coils to restore cooling performance.

Upgrading to higher filter grades and adding UV-C lamps improves indoor air quality and coil hygiene.

Refurbishment may include new panels, insulation, drain pan, fan, motor, and controls to extend the life of an existing AHU.

AHU unit price is largely driven by airflow (CFM) and cooling capacity (TR). Smaller units for individual zones cost less, while large chilled water AHUs for malls, hospitals, and airports cost more. Higher static pressure requirements also increase the fan and motor size and the overall price.

Panel thickness (25 mm or 50 mm), insulation type (PUF or Rockwool), thermal break profiles, stainless steel components, HEPA filtration, heat recovery wheels, EC fans, and BMS-ready controls all influence the air handler unit cost.

Installation cost includes rigging, plinth work, vibration isolation, chilled water piping, ductwork, insulation, electrical panels, testing, and commissioning. Ducting is often a significant part of the total project cost.

If you are looking for an air handler for sale for a commercial or industrial project, share your building area, application, and drawings with Compress India. Our team will recommend the right unit and provide a transparent quotation.