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Table 1: Redundancy and N + 1
System descriptionNumber and capacity of modulesTotal installed capacityRedundant installed capacity
1 module1 x 1000 kVA1000 kVAZero
1 + 1, (ie N =1)2 x 1000 kVA2000 kVA1000 kVA
2 + 1, (ie N = 2)3 x 500 kVA1500 kVA500 kVA
3 + 1, (ie N = 3)4 x 350 kVA1400 kVA400 kVA
4 + 1, (ie N = 4)5 x 250 kVA1250 kVA250 kVA
etc.   
Table 2: Cost summary
Element Range within analysis Cost model
 Max £/m2 Min £/m2 £/m2 %
Environmental control systems 1200 640 940 27
Ventilation systems 190 150 160 5
Electrical installations 2200 1500 1905 55
Protective installations 250 200 227 6·5
Communications installations 200 150 155 4·5
Special installations100 50 80 2
Total 4140 2690 3467 100
PROJECT DETAILS
Cost datum Third quarter 2004
Location Central London
Gross office internal floor area 35000 m2
Data centre net area 1000 m2
Procurement route Competitively tendered lump sum with contractor’s design responsibility
DESIGN CRITERIA
External design temperatures
Winter – 4°C (saturated)
Summer 28°C db, 19°C wb
Internal design temperature
Offices 22°C +/- 2°C
Fresh air ventilation 15 litres/s/person
COST BREAKDOWN
ENVIRONMENTAL CONTROL
Chilled water plant for enhanced cooling to data centre, serving 1000 W/m2 with redundancy to N + 1 standard: 1000 m2 at £425/m2£425/m2
Chilled water distribution within data centre to free-standing cooling units with associated water softening plant, condensate, humidification and insulation. 1000 m2 at £515/m2£515/m2
Environmental control total£940/m2
VENTILATION SYSTEM
Supply and extract ventilation, including dedicated gas extract system. Low level distribution, including floor grilles: 1000 m2 at £160/m2 
Ventilation system total £160/m2
ELECTRICAL INSTALLATION
Mains distribution with single incoming hv, N + 1 transformers, distribution busbars and cables. 1000 m2 at £140/m2£140/m2
Standby generators with redundancy to N + 1 standard, controls, fuel storage, exhaust flues. 2250 kVA at £190/kVA.£427/m2
UPS back-up system, 10 minute batteries with 10 year life, input/output switchboard. (2 + 1) 600 kVA at £215/kVA£387/m2
Critical mains distribution and lv switchboards, pdus, transfer switches for dual-fed equipment. 1000 m2 at £730/m2£730/m2
Cabinet supplies, dual armoured cable fed via BS 4343 outlets. 600 supplies at £230 each.£138/m2
Lighting, suspended luminaires, wiring and controls. 1000 m2 at £48/m2£48/m2
Data cable containment, underfloor cable basket. 1000 m2 at £35/m2£35/m2
Electrical installations total £1905/m2
PROTECTIVE INSTALLATIONS
Gaseous extinguishing system using inert gas. 1000 m2 at £192/m2£192/m2
Leak detection, underfloor adjacent to cooling plant and pipework. 250 m at £80/m£20/m2
Earthing and bonding 1000 m2 at £15/m2£15/m2
Protective installations total £227/m2
COMMUNICATIONS INSTALLATIONS
Analogue addressable fire detection and alarm system providing Category L1 cover plus interface with gaseous system. 1000 m2 at £30/m2£30/m2
Extra for very early smoke detection, aspirating system sensing above and below raised floor. 1000 m2 at £50/m2£50/m2
Security, cctv, intruder detection and access control, linked to main system (based on 20 cameras and four access points) 1000 m2 at £75/m2.£75/m2
Communications installations total £155/m2
SPECIAL INSTALLATIONS
Building energy management system, controls and monitoring, interfaced to main building management system.  
1000 m2 at £80/m2£80/m2
Special installations total£80/m2
TOTAL COST OF DATA CENTRE SERVICES£3467/m2
EXCLUSIONS
Inflation beyond third quarter 2004
General builders’ work
Specialist builders’ work such as floor strengthening, blast protection, screening for electromagnetic interference
Fit-out works beyond the data centre boundaries
External works such as enhanced hv supply or dual hv feeds
Main contractor’s overheads, profit and attendance
Main contract preliminaries
Professional and prescribed fees
Contingencies and design reserve
Tax allowances
VAT