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YK-OHPCBOverhead Passive Chilled Beam
York® Overhead Passive Chilled Beam (OHPCB) systems are designed to achieve effective cooling with a minimal energy cost. Utilizing chilled water as a basis of operation, these units are suitable for a wide variety of air-conditioning applications where reduced operating costs are a priority. These systems provide full cooling, heating, ventilation and humidity control – all with silent operation and minimal maintenance requirements.
Concept
Application Considerations
Product Features
Dimensions
Performance Data
Selection Example
Guide Specifications
3
4
5
6
7–10
11–12
13
Chiller
PassiveChilled Beams
Central Air Handling Unit
Primary Conditioned Air forVentilation & Humidity Control
+-
TemperedWaterCircuit
Po
P1
Po P1<
Ceiling
Detail
Fins
Density
Tem
pera
ture
PassiveChilledBeam
Overhead Passive Chilled Beam
3
CONCEPTThe principle of the Overhead Passive Chilled Beam system is to use terminal chilled water heat exchangers in the ceiling to offset the room sensible cooling loads. The ventilation and humidity control requirements are satisfied using separate primary conditioned air supplied by a central air handling unit.
FIGURE 1: Overhead Passive Chilled Beam System
FIGURE 2: Passive Chilled Beam Natural Convection
Cooling from the YK-OHPCB is achieved by natural convection. The air surrounding the heat exchanger is cooled as it comes into contact with the exchanger; as air temperature is reduced the density of the air increases, resulting in a downward air flow pattern. This happens without the need for any external energy to move the air, resulting in large energy savings which is the primary benefit of the system.
Since the separate primary air system is required only for ventilation and humidity control, the amount of air can be reduced substantially verses conventional air systems. The primary air can often be reduced to the minimum amount required for ventilation, allowing the use of 100% fresh air without the need for air recirculation. This provides further energy savings as well as excellent indoor air quality.
The primary air system is designed to maintain room humidity level above the dew point temperature of the YK-OHPCB,so that the heat exchanger operates without condensation. This avoids many of the maintenance and health concerns associated with other terminal heat exchangers, such as fan coil systems that require condensate removal systems and are susceptible to algae growth and other forms of contamination, as well as blocked drains and leaks.
To avoid the possibility of condensation on the YK-OHPCB, the primary air should be pretreated in a central air han-dling unit so that it can maintain the room dew point temperature approximately 1–3°F (1–2°C) below the entering chilled water temperature (EWT is typically 57°F [14°C]). Additionally, the building ventilation system should be con-trolled to maintain a small amount of positive pressure in the building, ensuring that any air infiltration is exiting the building. For instance, if a window is left open air flow should be out of the building, preventing loss of control of the in-ternal humidity level. For further protection, condensation sensors can be installed on the entering chilled water piping for each operating zone. These sensors will close the chilled water supply or reset the chilled water temperature to a higher level if they detect that the dew point of the air surrounding the chilled water piping is approaching saturation.
YK-OHPCB
4
FLOOR SLAB
PERIMETERRETURN AIR
PERIMETER WALL
Return AirTo provide an air path for the room air to return into the ceiling void and back to the chilled beam it is normal to install perforated ceiling panels or to leave a gap around the perimeter of the false ceiling. This avoids obstructions to the return air flow which can reduce the cooling capacity of the YK-OHPCB.
FIGURE 4: Air Path for Return Air
FIGURE 5: Free Space Above the Chilled Beam
FLOOR SLAB
FALSE CEILING
CHILLED BEAM SKIRT
B
H1
H
Chilled Beam SkirtThe performance of the passive chilled beam enhanced by the provision of a skirt below the heat exchanger. This im-proves the natural convection of the air through the unit. Different skirt heights are available to match the requirement of cooling performance and available ceiling void height.
Free Space Above the Chilled BeamIt is necessary to ensure adequate free space between the top of the chilled beam and the floor slab above to ensure good airflow into the unit. This is distance H1 in the diagram below.
Where there is free air flow to both sides of the unit, H1 should not be less than 25% of the unit width B. If the chilled beam is located adjacent to a wall, within a distance of B or less, then H1 should not be less than 50% of B.
Free Area Below the Chilled BeamYK-OHPCB passive chilled beams can be supplied with or without an air diffuser. We offer as an option a perforated diffuser with a free area designed to match the required unit performance. Other configurations including linear, metal mesh and egg crate diffusers can be supplied.
APPLICATION CONSIDERATIONSAir DistributionBecause the YK-OHPCB operates using natural convec-tion, cooled air flows downwards from the unit. It is there-fore important to locate units carefully in order to avoid down drafts above the room occupants. Units are best placed above unoccupied areas and are typically installed adjacent to perimeter walls or corridor walls.
FIGURE 3: Recommended Placement of Chilled Beam
Overhead Passive Chilled Beam
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PRODUCT FEATURESConfiguration OptionsYK-OHPCB passive chilled beams are available in a variety of configurations to match the meet the specific needs of different projects: • Nominal unit heights of 5", 8" & 12" (120mm, 200mm & 300mm) – including the chilled beam skirt – to match various performance and available space needs. • With or without outlet diffusers. Available diffuser configurations include: - Perforated (standard) - Linear - Metal Mesh - Egg Crate
Variable Sizes & CapacitiesThe YK-OHPCB is available in different widths – nominally 12" & 24" (300mm & 600mm) as standard to match with most ceiling systems. Multiple lengths are available in increments of 12" (300mm), from 48"–120"(1200mm–3000-mm). Customized widths & lengths can be made available to match particular project requirements.
Simple MountingUnits can be easily suspended from the overhead concrete slab, using threaded rod or hanging wire support systems to match acoustical fiber board or plaster ceilings. Units can also be installed without false ceilings.
ControlsThe cooling capacity of the YK-OHPCB is controlled using a chilled water control valve connected with a room ther-mostat. It is also recommended to install condensation sensors on the supply chilled water piping to each zone, to close the chilled water supply or increase its temperature in the event that the surrounding air dew point temperature approaches the temperature of the chilled water inlet pipe.
Silent OperationAir movement though the YK-OHPCB is based solely on natural convection. The unit is therefore completely silent during operation.
Hygienic OperationThe cooling coil in the unit operates dry. As a result, there is no need for condensate drain pans in the unit and con-densate drain piping. This eliminates health risks associated with algae growth in drain pans, as well as smells and problems that can arise from stagnant condensate in drain pans and drain pipes.
Ventilation Humidity & Air Quality ControlVentilation, humidity and air quality control is provided as part of the primary air supplied by a central air handling unit (AHU). The AHU ensures that incoming air is dehumidified to control room humidity for comfort conditions and to eliminate the possibility of condensation on the chilled beam coils. The AHU should also include high efficiency air filters to control room air quality and will normally use 100% fresh air, eliminating the need for air recirculation.
Low MaintenanceYK-OHPCB series passive chilled beams include no fans / motors, air filters, condensate pans, drains, or any other moving parts. As a result, maintenance is limited to cleaning the exposed metal surfaces and removing dust from the coil every 2–5 years, depending on the cleanliness of the supply air.
L
D
W
H
DIMENSIONS
6
YK-OHPCB
UNIT SIZE 48"(1200mm)
60"(1500mm)
72"(1800mm)
96"(2400mm)
120"(3000mm)
L 47-3/4"(1194mm)
59-3/4"(1494mm)
71-3/4"(1794mm)
95-3/4"(2394mm)
119-3/4"(2994mm)
W 11-3/4" | 23-3/4"(295mm | 595mm)
H 5" | 8" | 12"(120mm | 200mm | 300mm)
D 1/2"Ø(12mm)
H = 10”H = 12”
H = 8”
H = 6”
ROOM MINUS MEAN WATER TEMPERATURE (°F)
12” WIDE
CO
OLI
NG
CA
PAC
ITY
(Btu
h/ft)
10 11 12 13 14 15 16 17 18 190
50
100
150
200
250
300
350
400
H = 10”H = 12”
H = 8”
H = 6”
ROOM MINUS MEAN WATER TEMPERATURE (°F)
14” WIDE
CO
OLI
NG
CA
PAC
ITY
(Btu
h/ft)
10 11 12 13 14 15 16 17 18 190
50
100
150
200
250
300
350
400
450
H = 10”H = 12”
H = 8”
H = 6”
ROOM MINUS MEAN WATER TEMPERATURE (°F)
16” WIDE
CO
OLI
NG
CA
PAC
ITY
(Btu
h/ft)
10 11 12 13 14 15 16 17 18 190
50100
150200
250300
350400
450500
PERFORMANCE DATACooling CapacitiesThe cooling capacities of passive chilled beams are rated on a Btu/h(watt)-per-length basis, and vary according to the difference between the room temperature and the mean of the entering and leaving chilled water temperatures. Typically the chilled water supply temperature is 56–57°F (13–14°C) and the leaving water temperature 59–60°F (15–16°C), giving a mean temperature of 57.5–58.5°F (14°C). The cooling capacity also varies according to the height of the unit and its skirt (dimension H). Unit capacities are shown in FIGURES 6–10.
Overhead Passive Chilled Beam
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FIGURE 6
FIGURE 7
FIGURE 8
YK-OHPCB
H = 10”H = 12”
H = 8”
H = 6”
ROOM MINUS MEAN WATER TEMPERATURE (°F)
20” WIDE
CO
OLI
NG
CA
PAC
ITY
(Btu
h/ft)
10 11 12 13 14 15 16 17 18 190
100
200
300
400
500
600
700
H = 10”H = 12”
H = 8”
H = 6”
ROOM MINUS MEAN WATER TEMPERATURE (°F)
24” WIDE
CO
OLI
NG
CA
PAC
ITY
(Btu
h/ft)
10 11 12 13 14 15 16 17 18 190
100
200
300
400
500
600
700
800
8
FIGURE 9
FIGURE 10
NOTE: Performance is based on chilled water flow rate of 0.5 gpm (0.03 l/s), outlet diffuser free area of 50% and minimum distance between the top of the chilled beam and any air flow obstruction above is 50% of the passive chilled beam width.
WATER FLOW (GPM)
WATER FLOW CAPACITY FACTOR
CA
PAC
ITY
FAC
TOR
0.0 0.5 1.0 1.5 2.0 2.5 3.00.70
0.75
0.80
0.85
0.90
0.95
1.00
1.05
FREE AREA CORRECTION FACTOR30% 0.7840% 0.8850% 1.00
100% 1.06
PERFORMANCE DATACooling Capacity Correction FactorsCooling capacity is affected by the following factors, which need to be taken into account when determining overall cooling capacity:
• The distance between the top of the unit and the floor slab above (dimension H1). Where there is free air flow to both sides of the unit H1 should not be less than 25% of the unit width B. If the chilled beam is located adjacent to a wall within a distance of B or less then H1 should not be less than 50% of B.
Overhead Passive Chilled Beam
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• Chilled water flow rate. The capacities in FIGURES 6 & 7 are based on a chilled water flow rate of 0.5 gpm (0.03 l/s). For other flow rates the capacities should be multiplied by the cor- rection factors from FIGURE 11.
• The free area of any diffuser or screen below the heat exchanger. Capacity correction factors are detailed in TABLE 1.
FIGURE 11
TABLE 1
YK-OHPCB
WATER FLOW (GPM)
WATER PRESSURE DROP: 12” / 14” WIDE(DOUBLE WATER CIRCUIT)
WA
TER
PR
ESSU
RE
DR
OP
(FT.
H2O
)
0.0 0.5 1.0 1.5 2.0 2.5 3.00
2
4
6
8
10
4 FEET
6 FEET
8 FEET
10 FEET
WATER FLOW (GPM)
WATER PRESSURE DROP: 16” / 20” WIDE(DOUBLE WATER CIRCUIT)
WA
TER
PR
ESSU
RE
DR
OP
(FT.
H2O
)
0.0 0.5 1.0 1.5 2.0 2.5 3.00
2
4 FEET
6 FEET
8 FEET
10 FEET
4
6
8
10
WATER FLOW (GPM)
WATER PRESSURE DROP: 24” WIDE(DOUBLE WATER CIRCUIT)
WA
TER
PR
ESSU
RE
DR
OP
(FT.
H2O
)
0.0 0.5 1.0 1.5 2.0 2.5 3.00
4 FEET
6 FEET
8 FEET
10 FEET
2
4
6
8
10
12
14
16
10
Chilled Water Pressure DropThe chilled water pressure drop can be determined from FIGURES 12–14 below.
FIGURE 12
FIGURE 14
FIGURE 13
Overhead Passive Chilled Beam
11
SELECTION EXAMPLESpecified DataOffice (LxWxH):Acoustical Ceiling:Occupants:ASHRAE 62-2010 Minimum Ventilation:Indoor Design Condition:Chilled Water Supply Temperature:Chilled Water Return Temperature:Required Room Sensible Cooling:
Calculation / SelectionTroomTmean Water TemperatureTroom – Tmean Water TemperatureChilled Water Temperature Rise
1. Quantify ventilation requirements according to ASHRAE 62-2010:
• QOZ = RP PZ + RA AZ
• QOZ = (5 cfm/person)(2 people) + (0.06 cfm/ft2)(150ft2) = 19cfm
2. Determine required dew point of supply air in order to remove the latent load from the space:
• Load/Person = 250 Btu/h sensible & 155 Btu/h latent
• 2 People = qL = 310 Btu/h
• qL = 0.68 (cfm) ΔW
• ΔW = = = 24 gr/lb
Space design condition = 75°F, 50% RH. At this state the humidity ratio = 65 gr/lb.
3. Using a recommended supply air dew point of 50°F and a humidity ratio of 53 gr/lb will provide the supply air required to condition the latent load of the space:
• cfm = = = 38 cfm
The cfm required to condition the latent load exceeds the required ventilation. Use larger of the two.
4. Determine sensible cooling provided by the supply air to the space:
• qS = 1.085 (cfm) (ΔT)
• Use supply air temperature of 55°F db
• qS = 1.085 (38) (75-55) = 824.6 Btu/h
5. Determine sensible cooling for passive chilled beam:
• 2730 Btu/h - 495 Btu/h = 2235 Btu/h
10' x 15' x 9' = 150 ft2 Area24" x 24"2(2 people x 5 cfm) + (0.06 cfm/ft2) x 150 ft2 = 19 cfm75°F db / 50% RH | Room Dew Point 55°F57°F | Room Dew Point 55+2°F61°F2730 Btu/h (People + equipment, lights & envelope sensible loads)
75°F(57 + 61°F) / 2 = 59°F75 - 59°F = 17°F61 - 57°F = 4°F
qL–
0.68 (cfm)
qL–
0.68 ΔW
310 Btu/h–0.68 (19 cfm)
310 Btu/h–0.68 (65-53)
YK-OHPCB
12
6. Determine water flow rate:
• qS = 500 gpm ΔT
• = 1.10 gpm
7. The following is output needed/length for each length of passive chilled beam:
Using FIGURES 6 & 7 for capacity and FIGURE 8 for water flows greater than 0.5 gpm yields the following:
The following passive chilled beams will meet the requirements for the space:
2235–500 (60-56)
WIDTH HEIGHTFIGURE 6CAPACITY(Btu/h/ft)
CORRECTIONFACTOR
CORRECTEDCAPACITY(Btu/h/ft)
12"
5" 87 1.25 109
8" 114 1.25 142.5
10" 130 1.25 162.5
24"
5" 175 1.25 218.75
8" 220 1.25 275
10" 245 1.25 306
NOMINAL SIZE BTU/H/FT4' 477
6' 318
8' 238
10' 191
WIDTH HEIGHT LENGTH
TOTALSENSIBLECAPACITY
(Btu/h)
PRESSUREDROP
(ft. w.g.)MODEL NUMBER
24" 5" 10' 2187 4.2 YK-OHPCB-10-24-5
24" 8" 8' 2200 3.4 YK-OHPCB-8-24-8
Overhead Passive Chilled Beam
13
GUIDE SPECIFICATIONSYork YK-OHPCB series passive chilled beam systems shall be used to compensate for heat loads in a building and shall maintain the thermal comfort of the occupied areas within the required comfort parameters.
Functional DescriptionThe system shall comprise York YK-OHPCB series passive chilled beams installed in the ceiling to provide cooling required to offset the sensible cooling loads of the occupied area.
Ventilation and humidity control of the occupied space shall be handled by a separate primary air system using air supplied from a central air handling unit. The central air handling unit shall supply primary air at reduced humidity levels to ensure room dew point is maintained at least 1–3°F (1–2°C) below the temperature of the chilled water sup-plied to the passive chilled beams.
Construction and Performance● Each passive chilled beam shall comprise an air-to-water heat exchanger, body and skirt to enhance heat transfer. The beams shall be nominally 24" (600mm) wide to match the projects ceiling grid and shall have an overall length of 72" (1800mm).
● The heat exchanger shall be constructed from seamless copper tube with aluminum fins with a fin spacing of 3 Fpi. Each heat exchanger shall be suitable for operation with a water pressure of 250 psi and shall be factory leak tested at 300 psi pressure.
● The body and skirt of the passive chilled beams shall be manufactured from electro galvanized steel with a thickness of at least 22 ga. (0.8mm).
● The passive chilled beams shall be provided with optional perforated air diffusers that have a free area of at least 50% installed below the passive chilled beams. The diffusers shall be manufactured from electro galvanized steel with a thickness of at least 22 ga. (0.8mm) and finished with RAL9010 30% gloss polyester powder paint.
● The passive chilled beams shall be tested and rated in accordance with Standard EN14518.
InstallationThe passive chilled beam assembly shall be suitable for suspension from the floor slab above the ceiling usingthreaded rod or a steel wire hanging system attached to the passive chilled beams using factory supplied hanging brackets.
©2014 Johnson Controls | The performance specifications are nominal and conform to acceptable industry standards. For applications at conditions beyond these specifications, consult the local Johnson Controls office. Johnson Controls, Inc. shall not be liable for damages resulting from missapplication or misuse of its products.
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