UK: The HEVAC Association’s fan coil manufacturers’ group is to publish its own paper on the advantages of fan coil systems in response to last week’s comparison report by rival chilled beam manufacturers.
Manufacturers within Association’s Fan Coil Group Unit feels there are several other inconsistencies within the Chilled Beam and Ceiling Association’s (CBCA) Technical Fact Sheet 2 which, it says, it intends to discuss with the CBCA in the coming weeks.
Following the Cooling Post’s report on the controversial report which one manufacturer described last week as “biased”, the Fan Coil Group’s official response repeats accusations that the CBCA have failed to use identical design criteria, so creating an unfair comparison.
The CBCA announcement repeats concerns over differences in flow temperatures used for comparison. A 6ºC flow, 12ºC return temperature was used for the fan coil system and 14ºC flow, 17ºC return temperatures for active and passive chilled beams. A fair comparison would have been to use 14ºC flow and 17ºC return for all three systems, say the fan coil manufacturers.
The Fan Coil Group also complains of what it sees as an unfair comparison in the running cost calculations for the AHU supplying air temperature of 18ºC for the chilled beam systems, but 14ºC for the fan coil system.
It also says the higher pressure drops with chilled beams requires a higher specific fan power than a fan coil system. A typical specific fan power level for a fan coil at design conditions, it points out, is 0.2W/l/s, which means on average it will be 0.15W/l/s
Running cost comparisons used in the CBCA report are also disputed: “The cost of 13p/kWh is typical for domestic properties, but the average cost for medium size commercial premises is 8.6p/kWh, which significantly diminishes the difference in running cost between systems.”
The report’s use of a fixed specific fan power factor for an AHU supplying a chilled beam system is also challenged, the fan coil manufacturers saying that this would not be the case.
Finally, there is concern that the report does not take into account the option to vary fresh air and ventilation rates based on occupancy demand which is available with fan coil systems.