AHU & Chiller Installation

One of Europe’s leading meat processors approached Space Engineering, to provide a ventilation solution, for one of their meat processing facilities in England.

We were tasked with providing conditioned air for two large production areas.  For this task, a Dutch Blower Air Handling Unit was selected, along with an ICS chiller to cool the coils on the AHU.

The AHU and chiller system ventilates two production areas, providing determined conditioned air volumes, temperatures and humidity levels.  Together with the existing coolers mounted in the areas, the system obtains the required room conditions:

• Area A & B Normal Production +5c 50% RH
• Area A & B High Season Production +0c 50% RH
• Area A & B Cleaning +5c 98% RH
• Area A & B Drying +5c 50% RH
• Area A & B Weekends +5c 50% RH

Across the year there are ‘normal’ and ‘high season’ conditions, which require different room condition, and therefore different set points.  During each day of production, there are 3 modes of operation.

• Production (a. normal / b. high season
• Cleaning
• Drying – This results in different settings, as ventilation requirements differ in each mode.  Production mode switches between normal and high season, but cleaning and drying are the same regardless of the season.

There are also separate modes for:

• Weekends and holidays (when there is no production
• Stopped (when ventilation is stopped manually)
• Fire detection

The weatherproofed modular Dutch Blower AHU unit was externally mounted on a roof platform, with weather louvres having vermin mesh backing.  Hinged lockable access doors were installed to allow easy access for maintenance and replacement parts.  All dampers have opposed blades.  On the process part of the unit the fresh air damper is sized for the full air volume (6.111m3/s), with both the return air and fresh air dampers motorised.  During part of the evening for a few hours each day, the unit runs on 100% fresh air.  The fresh air damper will motor fully opened and the return air damper closed.  During this period there is no requirement for dehumidification.

The AHU is essentially split into two parts, with a decadent rotating wheel joining the two areas.  The bottom half is a standard AHU with a fresh air VCD (volume control damper) and return air VCD.  It can switch between recirculation and direct fresh ‘ambient’ air.  Once the air has entered the AHU it goes through filters and passes through the decadent wheel (which turns slowly to capture the moisture from the air passing through).  The air then continues through two cooling coils.  This now chilled air with reduced moisture is transported through the ductwork to the desired areas of supply.

The top section of the AHU is the special part that draws fresh air through the VCD, through filters and across fins, in the heat recovery section, which is used to pre-warm the air.  The air then travels past a gas burner, which heats the air before it passes through the decadent wheel.  This dry’s out the moisture that was captured within the segments of the decadent wheel, with the warm air passing back through the fins, pre-warming the air entering the regeneration section as it exits the regeneration fan and out of the discharge VCD.

The decadent wheel, in the bottom, absorbs the moisture for the air that passes through it.  In the top section the moisture is evaporated by superheating the air that passes through the wheel.

Cooling for the AHU is provided via a glycol system, chilled by the ICS Chiller.  The temperature control for the air flowing through the AHU is regulated by two 3 port valves fitted to either coil on the AHU.  These open to allow chilled glycol through the coil to achieve temperature setpoint, and close (recirculate) the glycol when cooling is not required.  The three point valves are controlled by RDM.

The ICS low temperature chiller has a thermal cooling duty of 200kW, with two independent circuits.  These are run off 4no scroll compressors with four steps of capacity control.

To serve the ventilation system ductwork VCD’s, RDM Controls and Control Systems have been installed on this project, with a PLC and touch screen display, providing temperature and humidity control.  A control panel was installed to serve the RDM control system.

There is also a free cooling function programmed into the RDM which, if enabled in parameters, opens the fresh air damper on AHU fully and closes the AHU damper automatically if the outside ambient temperature is below the desired level.

To achieve the delivery of large air volumes, and continuity to air change rates, a fabric sock system was installed into Area B.  This allows the area to maintain comfortable working conditions without compromising a good distribution of supply.

Space Engineering supplied and installed all of the AHU connecting supply and return ductwork networks.  All branch ducts, diffusers / return air grilles were complimented with manual volume control dampers, opposed blade complete with locking quadrants (unless motorised which were supplied with a drive arm).  Insulated access panels were installed in all ductwork to permit inspection and cleaning.  The supply and return  / extract ductwork was insulated and vapour sealed, to prevent degradation, condensation, and retain duct thermal integrity.

As part of our package of works, structural steelwork was installed to form a new gantry for the chiller and AHU, and steelwork support for the ductwork and new walkways (all the ductwork is accessible walkways).  New metal ties and frames were also installed throughout the roof voids to strengthen the buildings structure and ability to support the new steelwork.

The system is up and running and successfully meeting the expectations of both our client and our engineering team.