Title: Condensation Control Experiences in an historic Building with Movable Sash
1Condensation 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_at_psu.edu
Web http//doas-radiant.psu.edu
2What are your first thoughts when you consider
ceiling radiant cooling panels?
Capacity
3Requirement for Ceiling Radiant Cooling Panel
Application
4Site for the condensation control experiences
1900s Engineering Units
53 of 12 36 X 96single glazed movable sash
serving the 40 x 80 lab
6The Space as seen from inside
7System Schematic
8Size and extent of the major components in the
system
9Condensate control method
- Maintain the panel inlet water temperature above
the space DPT - Condensate sensor is hard wired into the power
supply of the panel spring return control valve.
10Field 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 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.
11Students 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.
12The data
OA DPT
Windows opened
CHWT exceeds room DPT after 22 min
CHWT to panels
Room DPT
13Extreme Condensation, after 8.5 hr. on a chilled
panel intentionally held 14oF below the space DPT
Isothermal
Fin
14Control response
Valve begins to modulate again to maintain CHWT
at the space DPT
Windows opened
Valve responds
Valve closed
15No Condensation on the panel after the test
16Very Slight Condensation on the chilled water
supply pipe to the panel
17What 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.
18Conclusion
- 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
19QUESTIONS
20Oh, about capacity concerns
- Rules 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. - Whats 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 ceiling need be in panels
- VAV reality check
- 1 cfm/ft2 at 55F can do about 20 Btu/hr-ft2.
21First 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 dimensioncost savings in
construction - And OP cost is reduced by 30 to 40 percent
compared to VAV.
22Finally,
- Terror resistance.
- The system would look schematically look like