1. 1 Condensation Control Experiences in an “historic” Building with Movable Sash ASHRAE Anaheim Seminar 53, 1/28/04 Stanley A. Mumma, Ph.D., P.E. Professor, Architectural Engineering Penn State University email: sam11@psu.edu Web: http://doas-radiant.psu.edu

2. 2 What are your first thoughts when you consider ceiling radiant cooling panels? $ Capacity

3. 3 Requirement for Ceiling Radiant Cooling Panel Application 20-70% less OA, DOAS Unit W/ Energy Recovery Cool/Dry Supply Parallel Sensible Cooling System High Induction Diffuser Building With Sensible and Latent cooling decoupled

4. 4 Site for the condensation control experiences: 1900’s Engineering Units

5. 5 3 of 12 36” X 96”single glazed movable sash serving the 40’ x 80’ lab

6. 6 The Space as seen from inside

7. 7 System Schematic

8. 8 Size and extent of the major components in the system Radiant panels8 @ 2’ x 40’—640 ft 2: <4 ton Chiller2 @ 5 ton each High Induction diffusers8 @ 2’ x2’—150 scfm each Air handling unit with EW, MSOperated at 1200 scfm Extensive instrumentationT, flow—air & water, RH, CO 2 DDC ControlsBACnet, web accessible PumpsTwo circuits at 22 gpm.

9. 9 Condensate control method 1. 1.Maintain the panel inlet water temperature above the space DPT 2. 2.Condensate sensor is hard wired into the power supply of the panel spring return control valve.

10. 10 Field experience, student co-op? The lab is used by a new (but just one) group of students per year Near the beginning of the semester, I will address them on the system—and make just a few points. Leave the doors or windows open and radiant cooling will be lost—not recommended Piling things on top of the panels will cause the cooling to be reduced—not recommended Slicing the exterior duct insulation not a good idea, condensate may drip on you and your work.

11. 11 Student’s response? They never opened the windows or propped the doors open. The condensation control was unchallenged An instantaneous open door and window tests on a hot humid summer day thus ensued.

12. 12 The data: Windows opened OA DPT Room DPT CHWT to panels CHWT exceeds room DPT after 22 min 2.5F

13. 13 Extreme Condensation, after 8.5 hr. on a chilled panel intentionally held 14 o F below the space DPT IsothermalFin

14. 14 Control response: Windows opened Valve responds Valve closed Valve begins to modulate again to maintain CHWT at the space DPT

15. 15 No Condensation on the panel after the test:

16. 16 Very Slight Condensation on the chilled water supply pipe to the panel

17. 17 What about the controls cost in a large movable sash building with many zones Panel capacity control: CV, VT or VV, CT Our building used ~CV, VT A large multi zone building would likely use VV, CT to each zone What 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.

18. 18 Conclusion: In 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. The passive fail safe sensor has yet to be activated under automatic control— consequently no condensation problems

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20. 20 Oh, about capacity concerns Rules of thumb: 400 ft 2 /ton, or 30 Btu/hr-ft 2 Panel capacity, 20-30 Btu/hr-ft 2 Conclusion, entire ceiling and perhaps some of the wall must be covered with panels. What’s 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 panels VAV reality check: 1 cfm/ft 2 at 55F can do about 20 Btu/hr-ft 2.

21. 21 First cost must be higher? Reductions 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 dimension—cost savings in construction And OP cost is reduced by 30 to 40 percent compared to VAV.

22. 22 Finally, Terror resistance. The system would look schematically look like: Outdoor air unit with TER OA Space 3, DOAS in parallel w/ CRCP Radiant Panel