Condensation Control Experiences in an historic Building with Movable Sash

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_at_psu.edu
Web http//doas-radiant.psu.edu
2
What are your first thoughts when you consider
ceiling radiant cooling panels?

Capacity
3
Requirement for Ceiling Radiant Cooling Panel
Application
4
Site for the condensation control experiences
1900s Engineering Units
5
3 of 12 36 X 96single glazed movable sash
serving the 40 x 80 lab
6
The Space as seen from inside
7
System Schematic
8
Size and extent of the major components in the
system
9
Condensate 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.

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 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.

11
Students 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
The data
OA DPT
Windows opened
CHWT exceeds room DPT after 22 min
CHWT to panels
Room DPT
13
Extreme Condensation, after 8.5 hr. on a chilled
panel intentionally held 14oF below the space DPT
Isothermal
Fin
14
Control response
Valve begins to modulate again to maintain CHWT
at the space DPT
Windows opened
Valve responds
Valve closed
15
No Condensation on the panel after the test
16
Very Slight Condensation on the chilled water
supply pipe to the panel
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
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

19
QUESTIONS
20
Oh, 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 lt50
  ceiling need be in panels
• VAV reality check
• 1 cfm/ft2 at 55F can do about 20 Btu/hr-ft2.

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 dimensioncost savings in
  construction
• And OP cost is reduced by 30 to 40 percent
  compared to VAV.

22
Finally,

• Terror resistance.
• The system would look schematically look like