Modular PAU Units

Outdoor air enters through a suitably located intake with louvers, screens and dampers. Intake placement should limit exposure to exhaust outlets, traffic emissions and rain. Local temperature and humidity conditions establish the load that downstream treatment sections must handle.

Pre-filters capture larger particles, while fine filters provide additional particle removal. Higher-efficiency stages are selected where the application requires them. Filter area, sealing and pressure drop matter: poorly installed or blocked filters can compromise both fresh-air filtration and airflow delivery.

A chilled-water or DX cooling coil reduces air temperature. When the coil surface is below the incoming air's dew point, moisture condenses and drains away. Coil selection must account for sensible cooling and latent cooling load, particularly during humid outdoor conditions.

Heating is included where the climate or process requires it. Reheat can raise the temperature of already dehumidified air to the required supply condition. Reheat lowers relative humidity by increasing temperature; the cooling or dehumidification stage performs the moisture removal.

The fan moves air through the treatment sections and distribution network. Its duty must provide the required airflow against the combined resistance of internal components and external ductwork. Fan selection should consider the expected increase in filter resistance during service.

Treated air travels through insulated ducts to occupied spaces or approved HVAC connection points. Where supply connects with FCUs or other terminal equipment, inlet conditions, pressure and control coordination must suit that equipment. Airflow balancing helps each zone receive its intended ventilation quantity.

Temperature, humidity and differential-pressure sensors provide operating feedback. Controls can coordinate cooling valves, compatible DX equipment, dampers and fan speed. DDC or BMS integration supports schedules, alarms and performance monitoring when the selected controllers and communication interfaces are compatible.

The frame supports the assembly, while casing panels contain the air stream. Rigidity, insulation and sealed joints influence leakage, heat gain and noise. Access provisions should allow inspection without damaging panels or repeatedly disturbing permanent connections.

The intake section connects outdoor air to the unit. Isolation dampers support shutdown, while motorized dampers can regulate airflow under the approved control sequence. Damper size, leakage characteristics and actuator access should match the ventilation duty.

Filter sections may accommodate pre-filters, fine filters, bag filters or specified HEPA stages. Selection depends on particle-removal requirements and available fan pressure. Secure mounting, sealed frames, accessible replacement space and differential-pressure monitoring help sustain the intended filtration performance.

Chilled-water coils transfer heat to circulating water; DX coils use refrigerant evaporation. Coil rows, circuiting, tube and fin materials, face velocity and air-side pressure drop affect performance. Selection must demonstrate the required leaving-air condition and manageable condensate carryover.

Electric heaters, hot-water coils or compatible recovered-heat arrangements can provide heating or reheat. The chosen method should suit the available utilities and operating cost targets. Electric heating requires coordinated airflow proving, overtemperature protection and electrical capacity.

Fan arrangements can include housed centrifugal fans or plug fans with direct-drive or belt-driven motors. EC fans and VFD-compatible motors provide speed-control options where suitable. Selection should consider the actual operating point, efficiency, service access and vibration isolation.

The drain pan collects moisture removed at the cooling coil. Suitable materials, effective slope and accessible outlets help prevent standing water. Drain traps must match the pressure at the drain connection, with cleaning access and a route that allows reliable condensate discharge.

A wheel, plate heat exchanger, heat pipe or run-around coil can recover energy where compatible air streams and site arrangements permit. Selection should consider recoverable energy, added pressure drop, maintenance and possible contaminant transfer. Sensitive applications require particular care over exhaust-stream suitability.

Some processes need moisture added during dry conditions; others require deeper dehumidification than a standard cooling coil can provide. Humidifier type, absorption distance, water quality and drainage need review. Low dew-point duties may require a specialist dehumidification arrangement.

Acoustic attenuators can reduce sound travelling through the air path. Their selection should balance noise reduction against pressure drop, space and cleanability. Offices, hotels and other noise-sensitive areas benefit from considering both duct-borne sound and noise radiated through the casing.

The control package can include temperature and RH sensors, pressure monitoring, airflow measurement, actuators and a control panel. Fan-speed control and BMS connectivity depend on the selected equipment. Defined operating sequences and alarm settings make readings useful for daily operation and troubleshooting.

Single-skin construction uses one casing layer, with insulation arrangements depending on the design. Double-skin panels enclose insulation between inner and outer skins. A double skin modular PAU can offer a protected internal surface and improved thermal or acoustic performance when its complete casing design supports those requirements.

Panel thickness, insulation material and density should be considered together with thermal conductivity, moisture resistance and fire requirements. Thickness alone does not establish casing performance. Select an assembly that limits unwanted heat transfer, protects insulation and supports the application's acoustic and condensation-control needs.

Galvanized steel, pre-coated galvanized steel, aluminium and stainless steel are potential material choices across different equipment designs. Selection depends on structural duty, corrosion exposure, hygiene and cleaning methods. Internal and external materials may differ and should be clearly identified in the specification.

A thermal break interrupts conductive paths through frames or panel connections. This can reduce thermal bridging and the risk of cold external surfaces attracting condensation. Performance still depends on the full casing assembly, air temperatures and surrounding humidity; thermal breaks alone cannot guarantee condensation-free operation.

Hinged doors or removable panels should provide practical access to filters, coils, fans and drains. Gaskets maintain sealing after service. Inspection windows and internal lighting may be specified where useful, with sufficient space outside the unit for opening doors and withdrawing components.

Indoor units need protection appropriate to plant-room conditions. Outdoor units require weather-resistant panels, joints and roof details, suitable corrosion protection and electrical enclosures selected for exposure. Support, drainage, anchoring and safe maintenance access are also part of an outdoor installation.

A chilled water modular PAU uses a cooling coil connected to the central chilled-water system. Coil performance depends on water temperatures, flow and entering-air conditions. This arrangement can suit buildings with an existing chiller plant and adequate capacity for the added fresh-air load.

A DX modular PAU uses a refrigerant cooling coil connected to compatible condensing equipment. Selection should verify fresh-air duty, operating range, capacity modulation and humidity performance. VRF refrigerant integration requires specifically approved equipment and controls; it is not a universal DX connection option.

Horizontal sections are arranged along the plant-room floor, allowing a clear treatment sequence and side access. Confirm the overall length, component withdrawal space and duct connections early. A suitable base and lifting route are essential for practical installation.

A vertical modular PAU can reduce floor footprint by arranging the airflow path vertically. Available height, structural support, drain routing and access to elevated components must be checked. A smaller footprint is useful only when servicing remains practical.

Stacked arrangements can place approved sections or supply and extract paths above one another. They may help where floor space is limited, but require suitable support and access at each level. Internal airflow transitions and maintenance routes should be reviewed before approval.

An indoor unit is installed within a plant room or protected service area. Equipment selection should account for room temperature, humidity, drainage and nearby occupied spaces. Keep delivery routes, ventilation around service areas and component access clear throughout the layout.

Outdoor or roof-mounted units need construction suitable for weather exposure. Roof loading, anchoring, corrosion exposure, rain protection and maintenance access influence the installation. Outdoor air intake and discharge locations should also be coordinated with other building services.

In a draw-through arrangement, the fan is downstream of the cooling coil; in a blow-through arrangement, it is upstream. Fan position affects coil airflow, casing pressures, drainage and where fan heat enters the air stream. Select the arrangement against the required final supply conditions and equipment layout.

Pre-filters capture larger particles before they reach coils and downstream filters. This helps protect treatment components and can extend the service life of finer filtration stages. The selected filter should match the intake environment and be accessible for routine inspection.

Fine filters target smaller airborne particles according to their documented classification. They can support indoor air quality in commercial and industrial buildings. Media type, filter area and dust-loading performance should be assessed alongside the required removal efficiency.

HEPA filtration may be specified for particular healthcare, pharmaceutical or cleanroom duties. Its location, housing seals and testing requirements must match the application. A HEPA stage in the PAU alone does not establish cleanroom classification or satisfy every healthcare ventilation requirement.

Offices, hospitals, production facilities and controlled environments have different filtration needs. General particle filters do not remove every gas or odour; those duties may require separate treatment media. Select stages against the actual contaminants and approved application requirements.

Filters create resistance that generally rises as dust accumulates. Differential-pressure monitoring helps identify when service is needed. A constant-airflow fan may consume more power as resistance increases, while an unregulated fan can deliver less air. Replacement limits should follow the selected filter and operating requirements.

Use location-specific dry-bulb and wet-bulb conditions, with humidity data consistent with the design basis. The hottest condition may differ from the most demanding dehumidification condition. Evaluate seasonal and part-load operation where they influence the required treatment performance.

Define supply-air temperature and moisture content, using dew point or humidity ratio where appropriate. Relative humidity must be interpreted with temperature. The selected supply condition should account for the room's moisture load, ventilation quantity and contribution from other cooling equipment.

Sensible load relates to reducing air temperature; latent load relates to removing moisture. Outdoor air can carry a substantial latent load even when its temperature is moderate. Evaluate both loads to avoid selecting a unit that cools adequately but leaves the building too humid.

Apparatus dew point represents the effective coil-surface condition used in assessing cooling and dehumidification. Leaving-air performance also depends on airflow, contact with the coil and cooling-medium conditions. Confirm the selected coil's predicted duty rather than judging performance by row count alone.

Moisture condensed at the coil must leave the unit through a properly designed drain pan and drain connection. Poor drainage can cause overflow, wet insulation and hygiene problems. Coil face velocity and pan coverage should also limit moisture carryover into downstream sections.

Where dehumidification produces air colder than the required supply temperature, reheat can adjust the final condition. Heating does not remove additional moisture. Evaluate recovered heat and other suitable sources against capital cost, energy use and the approved operating sequence.

Individual treatment sections create an application-specific air path. This lets the design combine only the required functions and arrange approved shipping splits. It is particularly useful for complex ventilation duties and buildings with limited equipment access.

Successive filter stages can protect components and deliver the specified particle-removal performance. Correct seals and pressure monitoring help maintain that performance in use. Higher-filtration applications benefit when the fan and service arrangements are designed around the complete filter package.

Equipment can be selected with a cooling source suited to the project. Water-based coils connect with an appropriate chilled-water plant, while DX coils require compatible refrigerant equipment. This flexibility helps new-build and retrofit projects use suitable existing infrastructure.

A fan selected for the required pressure can deliver air through extensive ducts and treatment sections. This supports buildings with long distribution routes or demanding filtration. The required duty should be calculated carefully, because unnecessary pressure increases fan power and noise.

Efficient fan and motor combinations reduce losses at the selected operating point. VFD-compatible motors and EC fans can provide controlled speed adjustment. Buildings with changing ventilation demand can benefit when control settings maintain the required airflow and pressure relationships.

Insulated casing can limit unwanted heat transfer and reduce radiated noise. Performance depends on the panel assembly, frame and seals. This is especially relevant where cold treated air passes through humid plant rooms or equipment sits near occupied areas.

Compatible controls can coordinate sensors, dampers, cooling and fan speed while reporting operating status to the BMS. Defined alarms and trend data help operators identify deviations. Multi-zone commercial buildings and facilities teams benefit from visibility into fresh-air system performance.

Accessible filters, coil faces, drain pans and fan assemblies make routine servicing more practical. Door layout and component withdrawal space should be planned together. Buildings requiring regular maintenance benefit from access that reduces dismantling and supports thorough inspection.

Casing, drain-pan and coil materials can be specified for the environment and cleaning requirements. Suitable corrosion resistance and cleanable surfaces support equipment life and hygiene. Coastal locations, healthcare areas and industrial processes may require closer material review.

Some modular platforms permit approved changes to sections or components. Adaptability depends on dimensional compatibility, structural limits and available fan or coil capacity. It can support planned future upgrades when expansion provisions are assessed during initial selection.

Section selection allows the treatment process to match airflow, filtration and moisture-control requirements. This helps avoid an unsuitable fixed arrangement while keeping the design focused on the functions the building actually needs.

Approved shipping sections can pass through access routes that cannot accommodate one large assembled unit. Planning section dimensions, weights and joining methods early can simplify delivery and reduce installation disruption in occupied buildings.

Horizontal, vertical and selected stacked arrangements provide layout choices. Matching the unit to the available plant-room geometry can improve space use, provided access doors, component withdrawal areas and drain arrangements remain practical.

Dedicated access to individual components helps technicians inspect and clean the treatment path. This supports preventive maintenance and timely fault detection, with less need to disturb unrelated sections during routine service.

Suitable filter stages, cleanable construction and moisture control can support demanding indoor-air-quality requirements. The treatment strategy should address the actual contaminant sources and work alongside ventilation distribution, exhaust and housekeeping practices.

Correct coil selection, drainage and coordinated controls help maintain the required fresh-air supply conditions. This can reduce uncontrolled moisture entering occupied spaces and support the wider HVAC system during humid weather.

The PAU can be coordinated with chillers, compatible DX equipment, FCUs, ducts and building controls. Assessing connection conditions and spare capacity supports an upgrade that works with the existing building services.

Where the selected platform permits, individual sections or components may be modified or replaced. Future changes still require engineering review of airflow, pressure, cooling duty, controls and space; modular construction does not make every upgrade interchangeable.

A dedicated PAU filters and conditions ventilation air separately from room cooling equipment. Intake protection, cooling, drainage and supply controls are central to this duty. Coordinate the treated-air quantity and condition with each zone's ventilation and moisture requirements.

Buildings with substantial occupancy or make-up-air demand need equipment sized for a significant outdoor-air load. Coil duty, fan pressure and intake capacity deserve particular attention. Heat recovery may be worth assessing where a suitable exhaust stream is available.

Moisture-sensitive spaces require a defined supply-air dew point and a coordinated room-control strategy. Cooling or specialist dehumidification, reliable drainage and optional reheat are important. Check part-load conditions as well as peak cooling duty.

Facilities with demanding particle-control requirements may need multiple filter stages and verified housing integrity. Include adequate fan pressure and accessible replacement space. Final room performance also depends on terminal filtration, air distribution and the wider contamination-control design.

Treated make-up air can support positive pressure where the approved design calls for it. Supply must be coordinated with extract, transfer air and building leakage. Pressure sensors and airflow controls may be needed; some healthcare or process areas require negative pressure instead.

A PAU can manage ventilation-air treatment while FCUs address the allocated room load. Coil selection and air-delivery connections must suit both systems. Verify the FCUs' remaining sensible and latent duties against the actual PAU supply conditions.

Sectional delivery can help bring equipment through narrow entrances and service corridors. Confirm every section's dimensions and weight against the full route. Site joining space, lifting arrangements and sealed connections are essential to a workable installation.

Modular PAU replacement can address ageing equipment, access constraints or changed fresh-air requirements. Review existing ducts, cooling utilities, drainage, power and controls before selecting the replacement. Plan shutdowns and temporary arrangements around the building's operation.

Some projects require a specific combination of filtration, humidity treatment, heat recovery or acoustic attenuation. Define the required outlet conditions and process restrictions first. The assembled sections must function as one coordinated system with verified pressure and control performance.

Controlled environments can require precise moisture control, cleanable construction and specified filtration. Fresh-air treatment must coordinate with recirculation, terminal filters and room-pressure relationships. Cleanroom classification and process qualification depend on the complete facility system and its validation requirements.

Healthcare ventilation requirements vary by room use and infection-control strategy. Assess outdoor-air quantity, filtration, hygiene and pressure relationships for each area. A general PAU configuration should not be assumed suitable for every clinical, isolation or procedure room.

Office buildings need ventilation suited to occupancy and operating hours. Fresh-air filtration, moisture control and efficient fan operation support comfort. Integration with FCUs, AHUs or VRF-served spaces should preserve the required outdoor-air delivery to each zone.

Offices and occupied support areas can benefit from centralized fresh-air treatment. Operating schedules, internal occupancy and moisture requirements influence selection. Ventilation for these areas should be coordinated with, and assessed separately from, the data centre's technical equipment-cooling design.

Guest rooms, meeting spaces and public areas can have different ventilation schedules and humidity loads. Quiet fans, acoustic treatment and stable moisture control are useful. Coordinate treated fresh air with bathroom, kitchen and other extract systems.

Retail ventilation demand can vary with occupancy and trading hours. Fan control and suitable cooling capacity help manage changing conditions. Entrances, tenant exhaust and long distribution routes should be considered when determining fresh-air quantity and building-pressure strategy.

Manufacturing facilities may need conditioned make-up air to replace process exhaust and support occupied areas. Specify filtration and materials for the actual environment. General ventilation equipment does not replace dedicated capture or treatment for hazardous process emissions.

Production spaces may require moisture control, hygienic surfaces and suitable filtration to support product and process conditions. Cleaning practices, zoning and exhaust arrangements influence selection. Preventing unwanted condensate and allowing access for inspection are important design priorities.

Classrooms, lecture spaces and shared areas need ventilation matched to occupancy. Accessible filters, reliable fresh-air delivery and operating schedules support daily use. Demand-based control may be appropriate where the approved design permits modulation of ventilation quantity.

Large public facilities can require substantial outdoor-air capacity across multiple zones. Robust filtration, coordinated fan control and practical service access are important. Intake exposure, operating hours and changing passenger occupancy should be included in the design basis.

Determine outdoor-air quantity from occupancy, space use, process needs and the applicable ventilation design. State the required flow in CFM or CMH and identify zone distribution. Floor area alone is insufficient for reliable modular PAU sizing.

Provide project-location dry-bulb and wet-bulb conditions or equivalent moisture data. Consider the conditions that govern dehumidification, not only peak temperature. This is particularly important for coastal and monsoon-exposed locations where outdoor moisture loads can be substantial.

Define the required discharge temperature and moisture condition. Confirm whether these apply at the coil outlet, unit outlet or room inlet. Fan heat and duct heat gain can alter supply temperature, so the selection basis should identify the relevant measurement point.

Calculate the temperature-reduction and moisture-removal duties at the required airflow. Check the PAU's contribution to room loads and the remaining terminal-unit duty. A total cooling-capacity figure without stated air conditions does not demonstrate humidity performance.

Calculate the resistance of ducts, fittings, grilles and other components outside the unit's agreed boundary. Internal filters, coils and dampers must also be included in overall fan selection, separately from external resistance. Clearly defined boundaries prevent omissions and double counting.

Select filter performance for outdoor-air quality, occupied-space needs and any process requirement. Check housing integrity, clean and final pressure drop, and replacement access. Higher efficiency should be coordinated with fan capacity and the full air-quality strategy.

For chilled-water integration, verify available temperatures, flow and plant capacity. For DX systems, verify compatible condensing equipment, operating range and control interfaces. Review these utilities before approving a replacement or adding fresh-air duty to an existing system.

Choose the fan against airflow and total required pressure at a suitable operating point. Review power, efficiency, speed-control capability and acoustic data. Service requirements for belts, bearings or direct-drive assemblies should fit the site's maintenance arrangements.

Check the complete delivery route, including doors, corridors, lifts and lifting locations. Compare these with each shipping section's dimensions and weight. The final layout must also accommodate access doors, filter replacement, coil removal and safe maintenance work.

Confirm the installation environment before specifying casing and electrical protection. Outdoor units need suitable weatherproofing and support; indoor units still require condensation control and accessible drainage. Local corrosion exposure can influence material and finish selection.

Define acceptable sound conditions for the plant room and served spaces. Assess fan sound, duct transmission, casing radiation and structure-borne vibration. Acoustic treatment should be incorporated without overlooking its effect on pressure drop and installation dimensions.

Prepare an operating sequence and required BMS point list. Identify which parameters must be measured, controlled, alarmed or trended. Confirm controller interfaces and responsibility for integration so that equipment, control-panel and building-system scopes align.

Consider inspection frequency, replacement-filter availability, component access and operating interruptions. Where an AMC is required, define preventive visits, performance checks, reporting and corrective-work scope. Planning serviceability during selection can reduce avoidable maintenance effort later.

Need help selecting a modular primary air handling unit? Send your airflow requirement, supply-air targets and site layout for an engineering discussion.

Both arrangements can perform the same fresh-air treatment duty when correctly selected. The main differences relate to construction, configuration and installation practicality.

A PAU is an air-handling assembly selected for primary or dedicated outdoor-air duty. AHU is a broader equipment term; an AHU can also be designed for 100% outdoor air. The distinction is the specified function, not an automatic difference in quality or capacity.

PAU, TFA and FAHU terminology often overlaps. A TFA unit generally describes treated fresh-air equipment, while FAHU describes a fresh air handling unit. These names alone do not establish size, dehumidification performance or modular construction.

A fan and motor selected near an efficient operating point can reduce power for the required air delivery. Lower losses also reduce heat added to the air stream. Appropriate sizing supports lower operating cost without sacrificing ventilation performance.

VFD or EC control can adjust fan speed to the approved airflow demand. Where ventilation quantity may decrease, both fan power and outdoor-air treatment load can fall. Savings depend on the control strategy; minimum ventilation, humidity and pressure requirements must remain satisfied.

Selecting suitable filter area and media can reduce fan resistance while preserving required particle-removal performance. This directly affects fan power and filter operating cost. It does not directly reduce the outdoor-air cooling load, but can lower the fan heat that cooling equipment must handle.

Coil sizing should balance heat transfer, moisture removal and resistance. Excessive pressure drop increases fan power, while inadequate coil duty can compromise humidity control. Evaluate coil performance and fan energy together to support efficient operation at the required supply condition.

Insulation limits unwanted heat gain or loss, while effective sealing helps deliver the intended treated airflow. These influence cooling demand and wasted treatment energy. Casing leakage may also increase the airflow needed to achieve the required delivery, affecting fan power and operating cost.

Suitable recovery equipment can reduce outdoor-air heating or cooling demand; moisture-transfer devices may also reduce latent duty. Added air resistance, pumps and drives consume energy. Assess the net benefit across climate, operating hours, exhaust quality and maintenance needs before selecting recovery.

Where the ventilation design permits, occupancy or other demand signals can adjust outdoor-air delivery. Appropriate modulation can reduce fan power and the amount of air requiring treatment. Control limits must maintain required ventilation, moisture management and pressure relationships throughout operation.

Schedules, setpoints and operating trends can reveal unnecessary running, excessive fan pressure or simultaneous cooling and reheat. Correcting these issues can reduce fan and thermal energy. Useful optimization requires reliable sensors, defined control limits and review of actual building needs.

Dirty filters increase resistance; fouled coils can reduce heat transfer and raise pressure drop. Maintenance helps preserve airflow, cooling and moisture-removal performance. At constant airflow, cleaner components can reduce fan demand; in unregulated systems, servicing can restore airflow lost through blockage.

Verify the delivery route and lifting plan against each section's dimensions, weight and approved lifting points. Inspect delivered sections for transport damage. Protect coils, filter frames, panel joints and controls during movement and temporary storage.

Join sections in the approved sequence on a level support. Fit the specified joint seals and fasteners, checking alignment of the internal air path. Poorly sealed connections can cause leakage or allow untreated air to enter downstream of filters.

Supports should distribute operating loads without distorting the casing. Select vibration isolators for the equipment weight and operating characteristics. Where flexible duct or pipe connections are used, coordinate them with the isolation design so rigid connections do not bypass it.

Connect ducts with suitable transitions, sealing and independent support. Avoid abrupt changes that disturb airflow near fans or coils. Insulate treated-air ducts where required and provide balancing and measurement access appropriate to the distribution layout.

Coordinate coil supply and return connections with the approved piping arrangement. Provide specified isolation, control, straining, venting and balancing provisions. Flush and test the system, then confirm coil water flow and temperatures against the equipment selection.

Refrigerant piping must suit the selected coil, condensing equipment and refrigerant. Confirm approved pipe sizes, routing, length limits and control connections. Installation, pressure testing, evacuation and charging should follow the specific equipment instructions and project requirements.

Provide sufficient space for the required trap, a suitable drain gradient and cleaning access. Trap dimensions depend on pressure at the outlet. Verify that condensate discharges during fan operation and that the drainage arrangement prevents unwanted air or contaminated-water entry.

Confirm electrical supply against the selected motor, heaters, drives and control panel. Coordinate cable sizing, isolation, protection and earthing with the approved design. Check phase sequence where applicable and complete electrical inspections before starting the equipment.

Install sensor and actuator wiring according to the control schematic. Coordinate signal types, power supplies and cable segregation to reduce interference. Check instrument positions and point identification before testing the complete operating sequence.

Confirm the communication interface, point list and integration responsibility before commissioning. Test status, alarms, measured values and permitted commands. Local equipment protection should remain effective during communication failure and under remote control.

Keep access routes and component withdrawal spaces clear after ducting, pipes and cables are installed. Verify that doors can open fully and filters can be removed. The final layout should allow coil, drain and fan servicing throughout the equipment's operating life.

Contact Compress India for modular PAU installation services, replacement planning or integration with your existing HVAC system.

Measure total airflow using an appropriate calibrated method and check distribution to the served zones. Compare readings with the approved schedule. Fan-speed indication alone does not confirm actual ventilation delivery.

Measure pressure at defined locations and compare the results with the selection basis. Distinguish external resistance from internal component losses. Unexpected pressure readings can indicate blocked filters, duct restrictions, damper issues or measurement-boundary differences.

Record entering and leaving air conditions together with airflow and cooling-medium conditions. For chilled-water coils, include water temperatures and flow where measurable. Evaluate DX operation against its approved duty and equipment-specific commissioning requirements.

Check supply temperature at the specified acceptance point under stable operation. Account for fan heat, reheat and downstream duct gains. Verify that control action maintains the required condition rather than relying on a single favourable reading.

Measure temperature and humidity together and establish the corresponding moisture condition. Compare supply-air dew point or humidity ratio with the design requirement. Room RH alone does not isolate PAU performance from infiltration or internal moisture sources.

Record the initial pressure drop across each fitted filter stage at the tested airflow. Check filter identity, seating and bypass seals. Set pressure alarms and service limits according to the selected filters and approved operating requirements.

Verify rotation, speed, mounting and operating current. Inspect belts and alignment where fitted, and check fan or motor bearings as applicable. Compare operation with the selected fan duty and motor limits.

Record relevant voltage, phase currents and power readings at the operating condition. Check protection settings and load balance where applicable. Include heaters, drives and auxiliary equipment when assessing the full unit load.

Assess equipment vibration, isolator performance and unusual operating sound. Review fan balance, mounting and nearby structural transmission if readings are unacceptable. Acoustic verification should use the measurement conditions agreed for the project.

Confirm effective pan drainage and trap operation with the fan running. Check for pooling, leaks, overflow and moisture carryover. Drainage performance should be demonstrated before the system is handed over for routine operation.

Compare installed sensors with suitable reference instruments and check controller scaling. Confirm that sensor positions represent the air conditions being controlled. Record any adjustment so later readings can be compared with the commissioning baseline.

Test start-up, shutdown, cooling, reheat, dampers and fan control against the approved sequence. Include applicable airflow proving, heater protection and fault responses. Check how the system behaves under part-load operation and relevant simulated failures.

Confirm point mapping, engineering units, alarm transmission and permitted remote commands. Test communication-loss behaviour and trend recording where included. Handover should clearly identify the operating setpoints and responsibilities for future changes.

Inspect filter condition, seals and pressure drop. Replace filters when their specified service limits or application requirements call for it; there is no universal replacement interval. Wash only filters designed for cleaning, and avoid reusing damaged or unsuitable media.

Inspect coil faces for dust, fouling and damaged fins. Use cleaning methods compatible with the coil materials and coatings. Keeping the air path clean helps preserve heat transfer, moisture removal and manageable air-side resistance.

Clean pans, outlets and traps, checking for standing water and blocked discharge. Confirm trap seals and drainage during operation. Regular attention helps prevent overflow, wet insulation and contamination within the unit.

Check impeller cleanliness, balance, fasteners and free movement. Deposits or damage can change airflow and vibration. Investigate unusual sound or reduced delivery before adjusting fan speed to compensate for an unidentified fault.

Review motor mounting, connections, operating current and signs of overheating. Inspect bearings and cooling provisions according to the motor design. Lubrication or other servicing should follow the equipment instructions rather than a general schedule applied to every motor.

Inspect belts for wear, tension and pulley alignment. Incorrect tension can reduce drive performance or overload bearings. Use the specified belt type and replacement method, then verify fan speed and operation after adjustment.

Compare vibration with the commissioning baseline and investigate changes. Fan imbalance, worn bearings, loose fasteners or damaged isolators may be involved. Trending helps identify deterioration before it produces wider equipment or structural problems.

Check casing joints, panel condition, door latches and seals. Air leakage can waste treated air or bypass filtration. Repair damaged gaskets and insulation, paying attention to corrosion, moisture ingress and condensation marks.

Verify temperature, humidity and pressure sensors at intervals suited to their duty. Incorrect readings can drive unnecessary cooling, reheat or fan operation. Check both the instrument and controller scaling when investigating a control problem.

Review filter and other monitored pressure readings against airflow and service history. Check that sensing tubes are clear and connected correctly. A changed pressure reading should be investigated in context rather than assumed to indicate filter blockage alone.

Recheck airflow, supply conditions, drainage and electrical readings against the baseline. This can identify gradual performance loss that routine visual inspection misses. Include operating trends where available to evaluate both peak and part-load conditions.

For low airflow, high humidity, condensate leakage, unusual noise or high power consumption, request modular PAU troubleshooting services. A structured diagnosis helps establish whether cleaning, control adjustment, repair, retrofitting or replacement is appropriate.

Ask about a modular PAU annual maintenance contract with a defined visit schedule, inspection scope and service records.

Check the selection against approved outdoor conditions, airflow, leaving-air targets, cooling load and pressure. Review filtration and utility compatibility together with the fan and coil calculations. Resolve differences between consultant schedules and actual site conditions before final equipment approval.

Confirm casing, insulation, coil, fan, motor, filter and damper details against approved submittals. Review component suitability for corrosion exposure, cleaning and operating conditions. Control-panel and instrumentation quality also influence the reliability of the completed system.

Compress India's role is HVAC engineering, site integration, installation, commissioning and service. Where equipment supply is included in the agreed scope, the project quotation should identify the selected OEM or supplier, equipment specification and warranty responsibility. Manufacturing origin is established through the equipment documentation and approved submittals.

Inspect dimensions, section alignment, casing seals, coil condition, fan mounting and filter installation. Verify electrical and control-panel work against approved drawings. Record and resolve defects before performance testing rather than allowing them to become operating problems.

Handover records should include tested airflow, pressure, air conditions, electrical readings and relevant control checks. State the conditions, instruments and acceptance basis used during testing. These records provide a useful reference for future servicing and performance investigation.

Identify the requirements applicable to the selected equipment, building use and project location in the approved specification. Filtration classification, casing performance, electrical requirements and any specialist hygiene obligations should be documented as relevant. Certification claims must be supported by the specific equipment's valid documentation.