Chillers | Archive Titles

Table 1: Relative efficiency of chiller installations
Building size (m²)	3000	7700	11 500
Chiller size (kW)	400	1000	1500
Relative efficiency (cop)
Air-cooled screw	2·8	2·8	3·0
Air-cooled reciprocating	3·3	3·3	3·3
Water-cooled scroll	3·5	3·5	3·5
Water-cooled reciprocating	3	3	3
Water-cooled screw*	4 – 5	4 – 5	4 – 5
Water-cooled centrifugal*	6 – 7	6 – 7	6 – 7
* It should be noted that the cop for water-cooled screw and centrifugal chillers will increase significantly under part load operation.

Table 2: Typical air conditioning systems compressor refrigerants
Type of compressor	Type of refrigerant
Reciprocating and scroll	R134a/R22/R407c
Screw	R134a/R410a/R22/R407c
Centrifugal	R134a

Table 3: Indicative costs of alternative chiller installations
Building size (m²)	3000	7700	11 500
Chiller size (kw)	400	1000	1500
Capital cost (£)
Air-cooled screw	49 000	100 000	144 000
Air-cooled reciprocating	43 000	83 000	114 000
Water-cooled reciprocating
Chiller	32 000	58 000	78 000
Condensing system	50 000	85 000	110 000
Total (£)	82 000	143 000	188 000
Water-cooled centrifugal
Chiller	n/a	78 000	102 000
Condensing system	n/a	85 000	110 000
Total (£)	n/a	163 000	212 000
Water-cooled screw
Chiller	46 000	80 000	108 000
Condensing system	50 000	85 000	110 000
Total (£)	96 000	165 000	218 000
Costs are current in 4th quarter 1999 and based on a central London office development. The rates are for the supply and installation of the chiller plant and include allowances for builders’ work. Allowances for trade discounts, preliminaries and testing and commissioning are excluded. No allowance is made for professional fees or VAT. Operating costs are not included.