Charlie Bigham’s,

The Customer

Charlie Bigham’s, a well-known producer of high-end quality ready-meals began supplying some of the UK’s biggest supermarkets in 1996.

The Brief

Now a household name, Charlie Bighams expanded their food production facilities with the opening of a new London ‘kitchen’ and the redevelopment of Dulcote Quarry (Project West). Dulcote is now home to their new 6,500m2 award-winning ‘Food Production Campus’.

The Solution

The design, installation and commissioning of a high-quality and sophisticated ‘HFC free’ refrigeration system that will deliver substantial energy cost savings to the client. The new refrigeration plant consists of:

New Central Ammonia System and Glycol Cooling Central System

  • Low temperature over-circulated pumped ammonia fed through 5 spiral freezers equating to 805 kW at -20oC
  • Frequency regulated screw compressor and a fixed speed regulated screw compressor – both with Unisab III controllers and oil cooling via ammonia thermosyphon
  • Frequency regulated reciprocating compressor with Unisab III controller
  • Future connection allowance for Phase II compressor installation
  • An evaporative condenser installed for Phase I. A second condenser will be installed at 608 kw for rejected heat from Phase II loading.
  • Future HeatPac 104S Heat Pump Unit – Delivering over 500kW of hot water at 60oC, which is used to pre-heat the hot well to the boiler feed and also a means of defrosting the spiral coils
  • Primary and secondary hot water loop with one 10m3 non-pressurised buffer vessel
  • 6 MW surge vessel with variable speed duty standby ammonia liquid pumps
  • 4000kg high pressure receiver for the system charge removed from the low side of the system
  • All nodes on the compressors have been designed with UPS back-up to aid in reducing spikes in network communications

Glycol Air Coolers and  Process Cooling & AHU Circuits

For some of the high bay stores, ‘Aspiration type’ air coolers were chosen due to their better air distribution design compared with the standard dual discharge models, which have opposing air direction.

  • Dairy Store – Two dual discharge air coolers at +2°C room temperature
  • Veg Prep – Two dual discharge air coolers at +4°C room temperature
  • Dairy Store – Two dual discharge air coolers at +2°C room temperature
  • Finished Goods Area – Four draw though air coolers at +2°C room temperature
  • Finished Goods Area – Dual discharge air cooler at +2oC room temperature
  • Switch room – Air cooler drive system for rejected heat 25 kW (Qcooling) glycol air cooler maintaining a room temperature of 20oC -25oC, using rejected heat for the drive systems in the refrigeration switch room
  • Dispatch Picking Room – Four 25kW, 4.0C room temperature draw through air coolers in conjunction with valve station and one dual discharge air cooler.
  • Tempering Room – Two draw through air coolers at 10 kW each with a cooling capacity of +4oC Air. Included with each is a glycol valve station, defrost power pack and re-heater induction heater – thyristor controlled.
  • Packing Hall – A injection loop for a 123 kW AHU with circulation pump and valves
  • Preparation Area – A injection loop for a 145 kW AHU with circulation pump and valves
  • Heroic Space – A injection loop for a 97 kW AHU with circulation pump and valves
  • Client’s Sauce Produce – Two process cooling tumble chill circuits

Other benefits to the above cooler selection include:

  • Completely cleanable specification
  • Hinged tray arrangement for cleaning – JDI standard
  • All casing is thicker and more ridged and formed pieces to reduce the number of fixing and potential vibration
  • Hygiene certified product
  • ISO 14001 certified
  • Euro vent certified product
  • Air separated tray, which prevents condensate in the tray
  • 7mm fin spacing with quality Delta T
  • Operating pressure designed to a maximum 6-bar fluid condition
  • Fans are low noise design around 59 dBA at 3 metres free field
  • Fan guard selections have stainless construction
  • All drain points exist from the side of the tray as opposed to the bottom of the tray and have been installed in stainless thin wall dairy tube as opposed to plastic, with correct rodding points and cleaning ports.

Cold Store Refrigeration (-18oC) CO2

  • Two 12 kw -20oC ceiling mounted R744 (CO2) DX evaporators complete with electric defrost heaters. CO2 evaporation temperature at -28oC
  • Special design with extra accessories including:
  • Insulated inlet hood in galvanised steel
  • Shut up socks
  • 300mm stubs in stainless steel 304
  • Copper stubs (PED compliant)
  • Two CO2 direct expansion compression packages with a cooling capacity of 14.4 kW, an evaporating temperature of -35oC and condensing temperature of -3oC. The pressure rating of the system is designed to 54bar MOP based on sub critical design utilising secondary DTX Coolflow medium (Glycol).

The supply of a reliance unit maintains the standing pressure of the CO2, should the factory glycol system at low loads have insufficient load to maintain the standing pressure of the unit.

Glycol Process Pumps

  • Two end suction cold glycol pumps – each pump sized to flow rate 93.39 m3/hr (accounted for Phase II 30% additional load). Both pumps are frequency regulated based on the required differential loop pressure and a configuration of duty/ standby arrangement. 

Glycol PHX

  • Two plate heat exchangers with a cooling capacity of 381 kW at -15oC + 20% over surface evaporating pressure to deliver -7oC secondary DTX fluid to the forced cooled air coolers.
  • Pressurisation unit and expansion vessel

NCG Air Purger

  • Multipoint air purger

Electrical Works

  • Control panels serving all refrigeration equipment
  • One remote station control panel for evaporators control and local interface
  • Field wire to all refrigeration equipment
  • Automation system (designed by JDI Controls) for common controls, evaporators control and data acquisition
  • Communication link between each of the stations
  • Anybus Communicators – Used as a protocol convertor gateway that connects the plant to Ethernet for better functionality and sequence control across the factory.

Technical Specifications

Maximum ambient temperature (peak)

+31°C dry bulb

 Design dry bulb temperature


Design wet bulb temperature


Power supply required

415V / 3 Phase / 50 Hz

Design condensing temperature


Design duty of the HT system

1569.5 kW, instantaneous

Phase I duty

1109.35 kW, instantaneous

Phase II duty

519.48 kW, instantaneous

Design evaporating temperature

-15.°C, 2K loss allowance

Circulation rate Pumped NH3 [frequency regulated]

4n1, 13.38m3/hr flow rate

Circulation rate minimum

4n1, 1.92 m3/hr flow rate

Design duty of HT Glycol

821 kW, system instantaneous

Design glycol flow temperature


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