A war of words has broken out between two groups from the HEVAC manufacturers’ association’s over the claims of a study comparing the relative performance of chilled beams and fan coils.
HEVAC’s Fan Coil Group said the recent Energy Study commissioned by the Chilled Beam and Ceiling Association (see story above ) has failed to use identical design criteria, leading to unfair comparisons of associated technology.
In a statement the Fan Coil Group said: “(The Group) welcomes the opportunity that the publication of the CBCA’s Technical Fact Sheet 2 has provided, to enter into the debate of the advantages that Fan Coils Systems provide over Passive and Active Chilled Beam. Whilst the report claims to be a fair comparison, the CBCA have failed to use identical design criteria which, unfortunately, causes an unfair comparison to be drawn.”
The Fan Coil Group Unit feels there are a number of inconsistencies within the report which it intends to discuss with the CBCA in the coming weeks.
It is also the intention of the Fan Coil Unit Group to issue its own paper defining all of the advantages that a Fan Coil System can offer the whole supply chain within an office building / refurbishment program.”
The Fan Coil Group has identified what it believes are a number of discrepancies, among which are as follows
• The CBCA has used 6 deg C flow, 12 deg C return temperatures for the fan coil system and 14 deg C flow, 17 deg C return temperatures for active and passive chilled beams, making the system comparison very biased towards chilled beams, when in fact to produce a fair comparison 14 deg C flow, 17 deg C return temperatures could have been used for all three systems.
• The running cost calculations have included the AHU supplying air temperature of 18 deg C for the chilled beam systems, but 14 deg C for the Fan Coil system, again compromising the fairness of the system comparison.
• The specific fan power of an AHU supplying fresh air to a chilled beam will be higher than supplying to a Fan Coil System, given the Chilled Beam Systems higher pressure drops
• The cost of 13p/kWh is typical for domestic properties, but the average cost for medium size commercial premises is 8.6p/kWh (DECC’s Quarterly Energy Prices – June 2013), which significantly diminishes the difference in running cost between systems.
• Whilst the report assumes the same fixed Specific Fan Power Factor an AHU supplying a Chilled Beam System would not, in fact, have a fixed SFP