Guest comfort is one of the defining factors in the hospitality industry.
Whether guests are arriving after a long journey, attending a conference or staying overnight, the room environment plays a significant role in their overall experience. Temperature stability, quiet operation and intuitive room controls are no longer considered luxuries—they are expected as standard.
When a major international hotel in Coventry began evaluating the replacement of its existing guest room Fan Coil Unit controls, the project was deliberately approached as a proof-of-concept.
Rather than immediately upgrading every room, a dedicated "Test Room" was created where a new control strategy could be installed, commissioned and evaluated under real operating conditions before any wider rollout was considered.
Working alongside Univent Systems Ltd, iACS supplied, commissioned and later refined a complete Siemens Climatix control solution for a modern 4-pipe Fan Coil Unit.
The project demonstrated not only the performance of the hardware but also the value of ongoing software refinement, commissioning expertise and post-installation support, ensuring the final system met the comfort expectations expected within a premium hotel environment.
What This Project Covered
This project demonstrates how iACS delivered:
- 4-pipe Fan Coil Unit controls
- Siemens Climatix controller programming
- Custom FCU application software
- Process Bus integration
- Guest room interface configuration
- Controller commissioning
- Heating and cooling valve optimisation
- Post-installation software refinement
- Live operational testing
- Hospitality HVAC commissioning
Table of Contents
- Project Overview
- Why Hotel Guest Room Comfort Matters
- The Fan Coil Unit Configuration
- Why a 4-Pipe FCU Was Selected
- The Siemens Climatix Control Solution
- The Importance of Process Bus Communication
- Custom SAPRO Application Software
- Commissioning the Test Room
- Refining the Software After Live Operation
- Why Proof-of-Concept Projects Matter
- Commissioning Beyond Day One
- The Project Outcome
- Why This Project Matters
- Before and After the Project
- Key Capabilities Demonstrated
- Looking for Intelligent FCU Controls?
1. Project Overview
Sector
Hospitality & Leisure
Application
Hotel guest room climate control.
Direct Customer
Univent Systems Ltd
End User
DoubleTree by Hilton Coventry
Project
Guest Room Test Room Upgrade
Project Timeline
- Order placed: February 2026
- Initial commissioning: April 2026
- Software refinement: July 2026
iACS Scope
- Siemens Climatix controller supply
- Controller configuration
- Custom SAPRO application software
- Process Bus configuration
- Guest room interface integration
- On-site commissioning
- Software refinement
- Final optimisation
Control Platform
- Siemens Climatix POL424.50 Controller
- POL895.51 / POL871 HMI
- QMXx.P34 Room Unit
Project Status
Successfully commissioned and software optimised.
2. Why Hotel Guest Room Comfort Matters
Unlike many commercial HVAC applications, hotel bedrooms are occupied by different guests every day.
Each guest has different expectations regarding:
- Room temperature
- Heating response
- Cooling response
- Noise levels
- User interface
- Comfort
The HVAC control strategy therefore needs to be both intelligent and intuitive.
A system that responds too slowly can make the room uncomfortable.
A system that reacts too aggressively may overshoot the required temperature.
Similarly, heating and cooling must work together without creating instability or unnecessary energy consumption.
For premium hotels, achieving this balance is essential.
3. The Fan Coil Unit Configuration
The project centred around a 4-pipe Fan Coil Unit installed within a dedicated test room.
Unlike simpler 2-pipe systems, a 4-pipe FCU contains:
- Independent heating coil
- Independent cooling coil
- Heating control valve
- Cooling control valve
- Fan speed control
- Room temperature sensing
This arrangement allows the system to provide heating or cooling whenever required without seasonal changeover.
It also offers much greater flexibility for maintaining consistent comfort throughout the year.
The upgraded room was intended to demonstrate this capability before a possible wider deployment across additional hotel rooms.
4. Why a 4-Pipe Fan Coil Unit Was Selected
A hotel environment rarely experiences identical conditions in every room.
Rooms facing different elevations, varying occupancy levels and changing solar gains often require different heating and cooling demands simultaneously.
A 4-pipe Fan Coil Unit allows each room to respond independently.
Benefits include:
- Faster room temperature recovery
- Simultaneous heating and cooling availability
- Improved guest comfort
- Greater seasonal flexibility
- Better energy management
- More accurate temperature control
However, achieving these benefits depends heavily on the quality of the control strategy.
5.
The Siemens Climatix Control Solution
To support the project, iACS supplied a complete Siemens Climatix control package specifically configured for 4-pipe Fan Coil Unit applications.
The solution included:
- Siemens Climatix POL424.50 programmable controller
- POL895.51 engineering interface
- POL871 HMI
- QMXx.P34 room controller
- Process Bus communications
- Custom SAPRO application software
Rather than supplying only hardware, iACS delivered a complete programmed solution ready for commissioning and optimisation.
6. The Importance of Process Bus Communication
One of the key aspects of the project was the use of Siemens Process Bus communication.
Rather than relying solely on traditional hardwired room controls, the Process Bus allowed the room unit and controller to exchange operational information digitally.
This provided:
- Reliable room temperature measurement
- Stable communications
- Simplified installation
- Improved diagnostics
- Greater configuration flexibility
Correct commissioning of the Process Bus was essential to ensure accurate room control and responsive operation.
7. Custom SAPRO Application Software
The controller was loaded with bespoke SAPRO software specifically configured for the application.
Rather than using a generic program, the application was developed around the requirements of a 4-pipe Fan Coil Unit.
The software managed:
- Heating demand
- Cooling demand
- Independent valve modulation
- Temperature control
- Process Bus communication
- Guest interface behaviour
- Controller parameters
The software was loaded via SD card before commissioning began.
8.
Commissioning the Test Room
Following installation by Univent Systems Ltd, iACS attended site to complete the commissioning process.
Activities included:
- Controller configuration
- Process Bus calibration
- Heating valve verification
- Cooling valve verification
- Room sensor validation
- HMI configuration
- Functional testing
- Operational checks
Particular attention was given to ensuring that the independent heating and cooling stages operated correctly and that the room controller accurately reflected the room conditions.
The initial commissioning was successfully completed during April 2026.
9.
Refining the Software After Live Operation
One of the most valuable aspects of this project was that commissioning did not mark the end of iACS's involvement.
After a period of live operation, the hotel requested refinements to improve how the Fan Coil Unit responded to guest interaction and environmental changes.
Rather than leaving the customer to navigate the specialist Siemens programming environment, iACS returned to site to refine the application software.
During the follow-up visit, the engineering team:
- Uploaded an updated software package
- Refined the SAPRO application
- Adjusted operating parameters
- Fine-tuned system behaviour
- Verified the updated control strategy
This ensured the system aligned more closely with the hotel's comfort expectations before wider deployment was considered.
10.
Why Proof-of-Concept Projects Matter
Many large refurbishment projects begin with a single demonstration installation.
This allows building owners to:
- Evaluate occupant comfort
- Assess usability
- Review control performance
- Test installation methods
- Validate commissioning procedures
- Refine software before wider deployment
By investing time in the Test Room, the project team reduced the risk associated with upgrading multiple rooms simultaneously.
It also provided an opportunity to optimise the control strategy using feedback gathered from real operation.
11.
Commissioning Beyond Day One
Commissioning is often viewed as the point where a project finishes.
In reality, the best-performing HVAC systems continue to improve after the first day of operation.
This project demonstrates the importance of:
- Live performance evaluation
- Software refinement
- Customer feedback
- Parameter optimisation
- Ongoing engineering support
Rather than simply proving that the system operated correctly, iACS worked with the customer to ensure it performed exactly as intended under real occupancy conditions.
12. The Project Outcome
Following the software update and final optimisation, the upgraded Test Room was successfully commissioned and handed over.
The completed system delivered:
- Stable room temperature control
- Independent heating and cooling management
- Responsive guest operation
- Reliable Process Bus communication
- Optimised Siemens Climatix performance
- Successfully refined application software
The project demonstrated the suitability of the Siemens Climatix platform for advanced 4-pipe Fan Coil Unit applications within premium hotel environments and provided a successful proof-of-concept for potential future upgrades.
13. Before and After the Project
| Initial Requirement | Final iACS Solution |
| Evaluate a new hotel room control strategy | Complete proof-of-concept installation |
| Upgrade an ageing FCU control system | Modern Siemens Climatix platform |
| Improve guest comfort | Optimised heating and cooling control |
| Commission a 4-pipe FCU | Fully configured and tested control strategy |
| Validate Process Bus communication | Successfully calibrated room network |
| Refine operation after occupancy | Bespoke SAPRO software updated and optimised |
14. Why This Project Matters
Large hospitality refurbishment programmes often begin with a single room.
That room becomes the benchmark against which every future installation is measured.
This project highlights the importance of combining quality hardware with experienced commissioning and ongoing software support.
By returning after initial commissioning to refine the software, iACS demonstrated that successful HVAC controls are not simply about supplying products, they are about ensuring the final control strategy delivers the level of comfort expected by the end user.
15. Key Capabilities Demonstrated
Siemens Climatix Programming
Configuration and optimisation of the Siemens POL424.50 controller.
4-Pipe FCU Control
Independent management of heating and cooling coils.
Process Bus Integration
Digital communication between room units and controller.
SAPRO Software Development
Custom application programming tailored to the project.
On-Site Commissioning
Complete commissioning and operational verification.
Post-Installation Optimisation
Software refinement following live operation.
Hospitality HVAC Expertise
Control strategies focused on guest comfort and operational flexibility.
Looking for Intelligent Fan Coil Unit Controls?
Whether you're upgrading hotel guest rooms, refurbishing commercial buildings or implementing a proof-of-concept before a wider rollout, iACS can provide intelligent Fan Coil Unit control solutions tailored to your application.
Our expertise includes:
- Fan Coil Unit controls
- 2-pipe and 4-pipe FCU strategies
- Siemens Climatix programming
- Custom application software
- Commissioning and optimisation
- Process Bus integration
- Post-installation software support
- HVAC troubleshooting and refinement
By combining high-quality hardware with practical engineering expertise, iACS helps ensure your HVAC system delivers the comfort, flexibility and reliability expected from a modern building.