Condensation Control Experiences in a Building with Movable Sash.ppt

Condensation Control Experiences in an“historic”Building with Movable SashWhat are your first thoughts when you consider ceiling radiant cooling panels?Requirement for Ceiling Radiant Cooling Panel Application20-70%less OA,DOAS Unit W/Energy RecoveryCool/Dry SupplyParallel Sensible Cooling SystemHigh Induction DiffuserBuilding With Sensible and Latent cooling decoupledSite for the condensation control experiences:1900s Engineering Units3 of 12 36”X 96”single glazed movable sash serving the 40 x 80 labThe Space as seen from insideSystem SchematicSize and extent of the major components in the systemRadiant panels8 2 x 40640 ft2:4 tonChiller2 5 ton eachHigh Induction diffusers8 2 x2150 scfm eachAir handling unit with EW,MSOperated at 1200 scfmExtensive instrumentationT,flowair&water,RH,CO2DDC ControlsBACnet,web accessiblePumpsTwo circuits at 22 gpm.Condensate control method1.Maintain the panel inlet water temperature above the space DPT 2.Condensate sensor is hard wired into the power supply of the panel spring return control valve.Field experience,student co-op?nThe lab is used by a new(but just one)group of students per yearnNear the beginning of the semester,I will address them on the systemand make just a few points.Leave the doors or windows open and radiant cooling will be lostnot recommended Piling things on top of the panels will cause the cooling to be reducednot recommended Slicing the exterior duct insulation not a good idea,condensate may drip on you and your work.Students response?nThey never opened the windows or propped the doors open.The condensation control was unchallengednAn instantaneous open door and window tests on a hot humid summer day thus ensued.The data:Windows openedOA DPTRoom DPTCHWT to panelsCHWT exceeds room DPT after 22 min2.5FExtreme Condensation,after 8.5 hr.on a chilled panel intentionally held 14oF below the space DPTIsothermalFin Control response:Windows openedValve respondsValve closedValve begins to modulate again to maintain CHWT at the space DPTNo Condensation on the panel after the test:Very Slight Condensation on the chilled water supply pipe to the panelWhat about the controls cost in a large movable sash building with many zones nPanel capacity control:CV,VT or VV,CTnOur building used CV,VTnA large multi zone building would likely use VV,CT to each zonenWhat happens then in large building if the windows go open?Monitor the window position If OA DPT exceeds space design close the modulating control valve.Conclusion:nIn the historic building with a large area of movable sash,condensation control was achieved easily,even when the space DPT was suddenly elevated by opening all of the doors and windows.The test was repeated many times,with the same outcome.nThe passive fail safe sensor has yet to be activated under automatic control consequently no condensation problems Oh,about capacity concernsnRules of thumb:400 ft2/ton,or 30 Btu/hr-ft2 Panel capacity,20-30 Btu/hr-ft2 Conclusion,entire ceiling and perhaps some of the wall must be covered with panels.nWhats the problem here?A large percentage of the design chiller load is OA DOAS can take part of the space sensible and 100%of the space latent load Generally for low density occupancy spaces 50%ceiling need be in panelsnVAV reality check:1 cfm/ft2 at 55F can do about 20 Btu/hr-ft2.First cost must be higher?nReductions in first cost with DOAS/radiant Large reduction in chiller size,and associated cooling towers,pumps etc.Ductwork is significantly reduced and VAV boxes eliminated.AHU is much smaller.More rentable space.Floor to floor dimensioncost savings in constructionnAnd OP cost is reduced by 30 to 40 percent compared to VAV.Finally,nTerror resistance.The system would look schematically look like:Outdoor air unit with TEROASpace 3,DOAS in parallel w/CRCPRadiant Panel