Project Spotlight: Bespoke AHU Control Optimisation for Aerospace Manufacturing

What This Project Covered

This project demonstrates how iACS delivered:

• Specialist AHU controls troubleshooting
• On-site commissioning support
• Temperature and humidity control optimisation
• Dehumidification P.I.D. loop tuning
• Supply-air control strategy development
• DX cooling cascade reconfiguration
• Electric reheat performance testing
• Live mechanical capacity verification
• Multi-contractor technical coordination
• Application-specific control for precision manufacturing

Table of Contents

1. Project Overview
2. Why Environmental Stability Matters
3. The AHU and Control Requirements
4. The Challenge
5. Understanding the Dehumidification Sequence
6. The iACS Investigation
7. Changing from Return-Air to Supply-Air Control
8. Tuning the Dehumidification P.I.D. Loop
9. Reconfiguring the Cooling Cascade
10. Proving the Mechanical Capacity
11. Coordinating Cooling and Electric Reheat
12. The Result
13. Why This Project Matters
14. Capabilities Demonstrated
15. Looking for Specialist AHU Controls Support?

1. Project Overview

Sector

Aerospace Manufacturing

Application

Precision manufacturing and process-control environment

End User

A leading global aerospace manufacturer.

Direct Customer

Specialist Air Handling Unit manufacturer.

Project Location

Lancashire, United Kingdom

iACS Scope

• Control strategy review
• Technical troubleshooting
• Site attendance
• P.I.D. loop tuning
• DX cooling optimisation
• Dehumidification strategy adjustment
• Live capacity testing
• Final performance verification
  
  

Required Environmental Conditions

• Temperature setpoint: 20°C
• Relative humidity setpoint: 50% rH
  
  

AHU Control Solution

iACS iSMART control panel.

Project Status

Completed and optimised. The troubleshooting and optimisation activities took place during 2026, with final performance confirmation received in July.

2. Why Environmental Stability Matters in Aerospace Manufacturing

HVAC systems serving manufacturing environments must often meet requirements far beyond those of ordinary comfort cooling.

In a commercial office, a small temporary temperature variation may cause minor discomfort. In a precision production environment, the same variation may affect:

• Manufacturing consistency
• Material behaviour
• Product quality
• Process repeatability
• Production schedules
• Quality assurance requirements

The dedicated production area in this project required stable temperature and humidity control throughout the year.

The AHU therefore needed to respond effectively to:

• Changing outdoor temperatures
• High external humidity
• Variable internal heat gains
• Cooling demand
• Dehumidification demand
• Reheating requirements
• Production-related load changes

Maintaining 20°C and 50% rH required the cooling, heating, humidification and heat recovery functions to operate as one coordinated system rather than as independent components.

3. The AHU and Control Requirements

The production space was served by a packaged Air Handling Unit containing several stages of environmental control.

The system included:

• Twin DX condensing units
• DX cooling and dehumidification
• Electric heater battery
• Heat recovery
• Steam humidification
• Temperature and humidity sensing
• Dehumidification P.I.D. control
• Cooling cascade logic

The DX system used Mitsubishi equipment and was designed to provide the cooling capacity required for both sensible temperature reduction and moisture removal.

A Condair steam humidifier provided humidity control when additional moisture was required, while the electric heater battery provided trimming and reheating after dehumidification.

The AHU was controlled by an iACS iSMART panel with application-specific cooling and dehumidification software.

4. The Challenge

During a period of summer weather, the outdoor temperature reached approximately 28°C.

Under these conditions, the production room temperature increased to approximately 24°C, moving the area outside its required environmental tolerance.

The site team also experienced several interconnected issues:

• The control system remained in dehumidification mode for extended periods.
• The DX cooling coil reduced the air temperature to remove moisture.
• The electric heater then attempted to reheat the heavily cooled air.
• Temperature recovery was slower than required.
• Return-air temperature control reacted too slowly to changing internal loads.
• Humidifier faults had also been reported.
• The apparent interaction between heating and cooling created concern that the AHU lacked sufficient capacity.

The challenge was not simply to increase cooling demand. The complete relationship between temperature control, humidity control, DX capacity and electric reheating had to be understood.

The investigation needed to determine whether the limitation was caused by the mechanical equipment or by how the control strategy responded to changing conditions.

5. Understanding the Dehumidification Sequence  

Dehumidification requires a different control process from ordinary cooling.

To remove moisture from the air, the cooling coil must reduce the air temperature below its dew point. Water then condenses on the coil and drains away.

This produces air that is:

• Colder than the normal supply-air requirement
• Lower in moisture content
• In need of reheating before entering the occupied or production space

The typical sequence is therefore:

1. Detect high humidity.
2. Increase DX cooling demand.
3. Cool the air below its dew point.
4. Remove moisture at the cooling coil.
5. Reheat the air to the required supply temperature.
6. Continue until the humidity returns to an acceptable level.

The cooling coil and electric heater may therefore operate simultaneously during dehumidification. This is a deliberate process rather than evidence that the two systems are incorrectly fighting one another.

The critical requirement is that the controls coordinate both outputs accurately enough to remove moisture without losing control of the room temperature.

6. The iACS Investigation

An iACS commissioning engineer attended site to work alongside the AHU manufacturer, facilities management team and mechanical contractor.

The investigation followed a structured process:

• Review the live controller values
• Confirm the active operating mode
• Check temperature and humidity setpoints
• Observe cooling demand
• Observe heater demand
• Verify the mechanical cooling capacity
• Review P.I.D. loop response
• Examine the cooling cascade
• Confirm the location of the regulating sensor
• Test the DX and electric heater stages independently

The analysis established that the mechanical plant was capable of providing the required cooling and reheating.

The primary issue was the speed and structure of the control response.

Because the system regulated temperature from the return-air sensor, it waited for changes within the production area to travel through the return-air path before correcting the supply conditions. In a space with rapidly changing thermal loads, this introduced too much delay.

The first major change was to move the primary temperature-regulation reference from the return-air sensor to the supply-air sensor.

Why Return-Air Control Was Too Slow

Return-air control reflects the average condition of the space, but it includes several unavoidable delays:

• Conditioned air must leave the AHU.
• It must travel through the ductwork.
• It must enter and mix within the production area.
• The room conditions must change.
• Air must return through the extract system.
• The return sensor must detect that change.
• The controller must then respond.

This can be appropriate for many comfort applications, but it was too slow for this sensitive production environment.

Why Supply-Air Control Improved the Response

Supply-air regulation allowed the controller to respond directly to the air leaving the AHU.

This enabled the control system to:

• Detect changes immediately
• Correct the delivered-air temperature sooner
• Reduce thermal lag
• Stabilise the space more quickly
• Coordinate cooling and reheating more accurately
• Respond more effectively to changing production loads

The return-air sensor remained valuable for monitoring the overall room condition, while the supply-air sensor became the faster regulating reference.

This application-specific adjustment was a key factor in restoring stable environmental control.

8. Tuning the Dehumidification P.I.D. Loop

The dehumidification P.I.D. loop was then adjusted to make the humidity-control strategy more responsive.

P.I.D. control continuously calculates how much output is required by considering:

• The difference between the measured value and the setpoint
• How long the error has existed
• How quickly the value is changing

A loop that responds too slowly may allow humidity to drift significantly before sufficient cooling is requested. A loop that is too aggressive may cause unstable operation or repeated overshooting.

For this project, the dehumidification settings were revised to provide a faster response.

The changes included:

• Tightening the humidity differential to 10% rH
• Reducing the integral time to 200 seconds
• Shortening the overall dehumidification response
• Increasing the speed at which the controller corrected sustained humidity deviation

These adjustments allowed the system to respond more decisively when the production area moved away from its humidity target.

9. Reconfiguring the Cooling Cascade

The original cooling cascade divided the cooling demand between heat recovery and DX cooling.

The strategy operated approximately as follows:

• 0–40% demand assigned to heat recovery
• 40–100% demand assigned to the DX cooling coil

Although this approach can improve efficiency in suitable operating conditions, it restricted how quickly the system could access the full DX cooling capacity during demanding summer and dehumidification conditions.

iACS reconfigured the cascade to provide:

• 0–100% direct authority over the DX cooling stage

This meant the controller no longer had to progress through the earlier part of the cascade before requesting meaningful mechanical cooling.

The revised strategy made the full DX capacity immediately available when temperature or dehumidification demand required it.

This was particularly important during high outdoor temperatures, when the system needed to react quickly to both sensible and latent cooling loads.

10. Proving the Mechanical Capacity

Before recommending mechanical alterations, the iACS engineer carried out live testing to confirm whether the existing equipment had enough capacity.

The DX cooling demand was manually forced to 100%.

During this test, the supply-air temperature reduced to approximately:

6.7°C

This confirmed that the DX system could provide substantial cooling and was capable of lowering the air temperature sufficiently for effective dehumidification.

The electric reheater was then forced to 100% demand.

The system successfully increased the air temperature from the low-temperature dehumidification condition to approximately:

20.8°C

This demonstrated that:

• The DX cooling system had sufficient capacity.
• The electric heater could recover the supply temperature.
• Both mechanical stages were operational.
• The fundamental limitation was not undersized plant.
• The performance issue could be resolved through control optimisation.

By proving the available capacity, iACS helped avoid unnecessary mechanical upgrades and the associated cost, disruption and delay.

11. Coordinating Cooling and Electric Reheat

One of the most important lessons from this project was that simultaneous cooling and heating does not always indicate energy waste or incorrect operation.

During dehumidification, both stages serve different purposes:

• The DX coil removes moisture.
• The electric heater restores the required supply temperature.

The original sequence created the appearance that the electric heater was opposing the cooling coil. In practice, the issue was that the control loops and cascade did not respond quickly enough to the production area's changing load.

Following optimisation, the sequence became more coordinated:

1. Humidity rises above the required tolerance.
2. DX cooling increases quickly.
3. Air is cooled below its dew point.
4. Moisture is removed.
5. The electric reheater trims the air back toward the supply setpoint.
6. Supply-air regulation responds immediately.
7. Room temperature and humidity stabilise.

The optimisation allowed the AHU to complete the dehumidification process while continuing to protect the required space temperature.

12. Managing the Humidifier

The AHU also incorporated a Condair steam humidifier for periods when the relative humidity fell below the required setpoint.

During the wider troubleshooting period, humidifier faults had been reported. These were considered alongside the overall humidity-control investigation to ensure the system could manage both sides of the humidity requirement:

• Dehumidification when humidity was too high
• Humidification when humidity was too low

This is especially important in year-round precision environments because the AHU must maintain stability across significantly different seasonal conditions.

A complete humidity strategy must therefore coordinate:

• Humidity sensor readings
• Steam humidifier demand
• DX dehumidification
• Electric reheat
• Temperature control
• Safety and alarm conditions

13. Working Collaboratively Across the Project Team

The technical work had to be coordinated across several stakeholders, including:

• The AHU manufacturer
• The facilities management provider
• The mechanical contractor
• The end user's production team
• iACS controls engineering

The site was a sensitive production environment, meaning troubleshooting had to be completed without unnecessarily disrupting manufacturing operations.

Rather than assigning blame to any single component or contractor, the project team used live data and functional testing to understand how the complete system behaved.

This collaborative approach allowed iACS to:

• Prove the mechanical capacity
• Identify control-response delays
• Agree practical software changes
• Test each stage independently
• Verify the revised sequence
• Avoid unnecessary plant modifications
• Restore the required production environment

14. The Result

Following the changes, the AHU achieved immediate and sustained improvement.

The revised control strategy successfully maintained:

• 20°C temperature
• 50% relative humidity

The system was witnessed controlling effectively from the supply-air sensor, with the cooling and reheat stages responding correctly during dehumidification.

Subsequent monitoring by the facilities team confirmed that the return-air temperature remained at approximately 20.8°C, even while the external temperature was around 28°C.

The facilities team described the result as a significant improvement in environmental performance.

Most importantly, the required production conditions were restored without replacing the existing AHU, increasing the heater capacity or making disruptive mechanical modifications.

15. Before and After the Control Optimisation

16. Why This Project Matters

This project demonstrates the difference between supplying HVAC equipment and delivering a complete control solution.

Even correctly selected mechanical equipment can underperform when the software is not fully aligned with:

• The building's thermal behaviour
• The process requirements
• The sensor locations
• The rate at which loads change
• The interaction between temperature and humidity
• The available heating and cooling stages

Control strategies that perform effectively in a typical comfort application may need to be adapted for a precision manufacturing environment.

By combining detailed diagnostics, live capacity testing and application-specific software changes, iACS was able to release the performance already available within the installed equipment.

The intervention avoided unnecessary capital expenditure while securing the environmental conditions required for production.

17. Key Capabilities Demonstrated

Bespoke AHU Controls Engineering

The control strategy was adapted to match the unique operational requirements of the production area.

Advanced P.I.D. Loop Tuning

The humidity-control loop was adjusted to provide a more responsive and stable dehumidification sequence.

DX Cooling Cascade Optimisation

The cooling strategy was reconfigured to provide immediate access to the full available DX capacity.

Critical-Environment Temperature Control

Supply-air regulation was used to reduce thermal lag and improve the response to changing process loads.

Live Mechanical Capacity Testing

Cooling and reheating stages were tested independently to prove that the installed mechanical equipment was capable of meeting the requirement.

Complex System Troubleshooting

The investigation considered the interaction between cooling, reheating, humidification, dehumidification, heat recovery and sensor response.

Multi-Contractor Coordination

iACS worked collaboratively with the AHU manufacturer, facilities team and mechanical contractor to deliver a practical resolution.

18. The Value of Specialist Commissioning

Commissioning is not simply a final check that equipment switches on.

For complex AHUs, specialist commissioning should verify:

• Whether sensors are positioned appropriately
• Whether P.I.D. loops respond at the correct speed
• Whether control stages cascade correctly
• Whether mechanical capacity is fully accessible
• Whether heating and cooling work together as intended
• Whether humidity control affects temperature stability
• Whether the system performs under realistic load conditions

This project demonstrates how detailed commissioning can identify performance improvements that may not be visible during initial installation or basic functional testing.

19. Supporting Critical Manufacturing Environments

Aerospace is only one example of an industry where stable environmental control is essential.

The same engineering principles can support:

• Pharmaceutical manufacturing
• Electronics production
• Laboratories
• Cleanrooms
• Food manufacturing
• Healthcare environments
• Specialist printing processes
• Research facilities
• Precision engineering
• Battery manufacturing

Wherever production quality depends on stable temperature and humidity, the AHU control strategy must be designed around the process rather than relying solely on standard comfort-control logic.

Looking for Specialist AHU Controls Support?

Whether your Air Handling Unit is struggling to maintain temperature, experiencing unstable humidity, remaining in dehumidification or failing to respond quickly enough to changing loads, iACS can help.

Our engineering team provides:

• AHU control-strategy reviews
• P.I.D. loop tuning
• Temperature and humidity optimisation
• DX cooling integration
• Dehumidification control
• Humidifier integration
• On-site troubleshooting
• Commissioning support
• Retrofit controls
• Remote diagnostics

From standard commercial ventilation to highly sensitive manufacturing environments, we combine intelligent controls with practical site engineering to ensure your AHU performs as intended.

Speak with the iACS team today to discuss how our specialist AHU controls and commissioning services can improve environmental stability, reduce unnecessary mechanical alterations and safeguard your critical processes.