Technical
position of the VAV valve for fan energy savings , and is particularly effective at managing highly variable latent loads .
Care must be exercised to monitor the return air CO2 levels to ensure that the space is not underventilated . Additionally , a dewpoint sensor on the chilled water supply line is necessary to give priority control of the ventilation air in the event that the latent load exceeded the limits of the dehumidification effect offered via the primary air supply .
Night setback , chilled water , hot water , and primary air reset are all effective strategies in mitigating operational costs . These should be considered a fundamental aspect of building control , given their relatively low cost-to-benefit ratio .
ARTICLE NOTES
• For additional information on dedicated outdoor air systems , see http :// doasradiant . psu . edu /.
• † Class I and II areas as defined by CSA Standard Z317.2 , Table 1 , Ver . 01 , 2001 .
• Primary air volume = 4,000 cfm ( 1887 L / s ) at 2.4 in . w . c . ( 600 Pa ) increased to 3.0 in . w . c . ( 750 Pa ). Total sensible capacity increase provided by active chilled beam = 50 %. Increase in fan bhp = 14.1 %. 15 in . SISW AFPF , 9-blade , Arr . 3 ., CLII . § Acoustic sound pressure levels determined using selection program data from Twa Panel Systems , Inc . ( MAC Beam software Ver . 11 ).
MAINTENANCE In a properly designed ACB project , the coil surfaces will not condense . The fins of the unit mounted coils will remain dry , and will not become tacky . Although not true for every space , maintenance vacuuming can be as infrequent as once every three to five years . Additionally , since the fin surfaces of an ACB are relatively well gapped , dust and dirt particles tend not to bridge the fin surfaces . ACBs equipped with rubber nozzles may need to be replaced as a result of dry rot within their service life . Maintenance is nearly a nonissue with active chilled beams and can be used to address a variety of challenging applications .
SUMMARY Although they are not the solution for every space within commercial and institutional buildings , the strengths of active chilled beams are becoming a more useful tool to handle challenging spaces in today ’ s high performance buildings . The difficulty of meeting comfort requirements with a mechanical system that is exceedingly transparent is becoming easier thanks to the growing popularity of decoupled ventilation systems and active chilled beams .
REFERENCES 1 . Rumsey , P . 2007 . “ Chilled beams in labs : eliminating reheat and saving energy on a budget .” ASHRAE Journal 49 ( 1 ): 18 – 25 .
2 . Feustel , H . 1994 . “ Hydronic radiant cooling systems .” Center for Building Science News . Berkeley , Calif .: Lawrence Berkeley National Laboratory
3 . Butler , D ., et al . 2007 . Chilled Beam Application Guidebook , second ed . Belguim : REHVA .
4 . Zboril , V ., et al . “ Air flow distribution in rooms with chilled beams .” Proceedings of Roomvent 2007 .
ABOUT THE AUTHORS Darren Alexander , P . Eng ., is a partner and technical director for Twa Panel Systems in Nisku , AB Canada , a member of Technical Commitee 5.3 ’ s subcommittee for chilled beams , and a corresponding member of TC 6.5 , Radiant and Convective Space heating and Cooling , as well as a contributing member to the AHRI committee for establishing chilled beam testing standards . Mike O ’ Rourke is a past chairman of TC 6.5 , and president of Radiant Advantage in Highlands Ranch , Colo . RACA
QUOTE OF THE MONTH
“ Always think outside the box and embrace opportunities that appear , wherever they might be .” — Lakshmi Mittal .
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RACA Journal I April 2022 www . hvacronline . co . za