Variable temperature chiller coils

A chiller coil system for an asymmetric gas turbine filter house (10) includes a plurality of chiller coil modules (22) arranged in a substantially vertical array, each chiller coil module provided with a cooled fluid inlet pipe (42-52) and a fluid outlet pipe (54,64). Each outlet pipe (54-64) is connected to a common return pipe (39) and at least some of the inlet pipes (42,52) are connected to the common return pipe (39). A mixing control valve (74,76,82,84) is provided for controlling an amount of cooling fluid in the common return pipe (39) to be added to at least some of the inlet pipes (42-52).