Active Chilled Beam
System Design & Layout
Salt Lake City, UT ASHRAE Chapter December 2013
Nick Searle
Contents
• Active Chilled Beam Basics
• Design Considerations
• Air System Design & Humidity Control
• Water System Design
• Heating with Active Beams
• Controls
Fan Energy Use in Buildings
“Energy Consumption Characteristics of Commercial Building HVAC Systems” publication prepared for U.S. Department of Energy
0 0.5 1 1.5 2 2.5 3 3.5 4 4.5
Central VAV Central CAV Packaged CAV
D e s ig n L o a d K W /S F Chiller/Compressor Supply & Return Fans Chilled Water Pump Condenser Water Pump Cooling Tower Fan Condenser Fan 0 1 2 3 4 5 6 7
Central VAV Central CAV Packaged CAV
E n e rg y U s e K W h /S F
Water = Efficient Transport
¾” diameter water pipe 10” 1 Ton of Cooling requires 550 CFM of air or 4 GPM of waterActive Chilled Beams
1980 1990 2000 2010
Chilled Ceilings Passive Chilled Beams Active Chilled Beams
• Higher space loads
• Higher occupant densities • Combined ventilation/cooling
preferred
• Integration into fiber tile ceilings required
Active Chilled Beam 0 Operation Principle
Suspended ceiling Primary air plenum
Primary air nozzles
Heat exchanger
1 Part Primary Air
Heat Removal Ratio
70% of sensible heat removed by chilled beam
water coil Airflow
requirement reduced by 70%
Active Chilled Beams 0 System Highlights
• Very high cooling capacity
‒ Up to 100 BTUH/FT2 floor space
‒ Up to 1500 BTUH per LF
• Integrated cooling, ventilation and heating
‒ All services in the ceiling cavity
• Suitable for integration into all ceiling types
Active Chilled Beams 0 System Highlights
• Significant space savings
‒ Smaller ductwork saves space in shafts, plant rooms and ceiling
• Can be installed tight up against the slab
‒ Reduced floor to floor heights
‒ Reduced construction costs on new buildings
• Low noise levels • Low maintenance
Energy Savings 0 Compared to VAV
Source Technology Application % Saving*
US Dept. of Energy Report (4/2001) Beams/Radiant Ceilings General 25A30
ASHRAE 2010 Technology Awards Passive Chilled Beams Call Center 41
ACEE Emerging Technologies Report (2009) Active Chilled Beams General 20
ASHRAE Journal 2007 Active Chilled Beams Laboratory 57
SmithGroup Active Chilled Beams Offices 24
*Compared to VAV
“Energy Consumption Characteristics of Commercial Building HVAC Systems” publication prepared for U.S. Department of Energy
9 ’A 1 0 ” 1 2 ’A 0 ”
Space Savings
Space Savings
8 ’A 0 ” 9 ’A 1 0 ”E x p o s e d C h ill e d B e a m s 6 F lo o rs A ll A ir H V A C S y s te m 5 F lo o rs
Space Savings
ACTIVE CHILLED BEAM DESIGN
CONSIDERATIONS
Building Suitability
Building Characteristics that favor Active Chilled Beams
• Zones with moderateAhigh sensible load densities
‒ Where primary airflows would be significantly higher than needed for ventilation
‒ Sensible Heat Ratio’s (SHR) of 0.8 and above
• Buildings most affected by space constraints
‒ Hi – rises, existing buildings with induction systems
• Zones where the acoustical environment is a key design criterion
• Laboratories where sensible loads are driving airflows as opposed to air change rates
Building Suitability
Characteristics that less favor Active Chilled Beams
• Buildings with operable windows or “leaky” construction
‒ Beams with drain pans could be considered ‒ Building pressurization control should be used
• Zones with relatively low sensible load densities
• Zones with relatively low sensible heat ratios and low ventilation air requirements
• Zones with high filtration requirements for the reA circulated room air
SHR’s for Typical Spaces
SHR Range
Auditoriums, Theaters 0.65 - 0.75
Apartments 0.8 - 0.95
Banks, Court Houses, Municipal Buildings 0.75 - 0.9
Churches 0.65 - 0.75
Dining Halls 0.65 - 0.8
Computer Rooms 0.8 - 0.95
Cocktail Lounges, Bars, Taverns, Clubhouses, Nightclubs 0.65 - 0.8
Jails 0.8 - 0.95
Hospital Patient Rooms, Nursing Home, Patient Rooms 0.75 - 0.85
Kitchens 0.6 - 0.7
Libraries, Museums 0.8 - 0.9
Malls, Shopping Centers 0.65 - 0.85
Medical/Dental Centers, Clinics and Offices 0.75 - 0.85 Motel and Hotel Public Areas 0.75 - 0.9
Motel and Hotel Guest Rooms 0.8 - 0.95
Police Stations, Fire Stations, Post Offices 0.75 - 0.9
Precision Manufacturing 0.8 - 0.95
Restaurants 0.65 - 0.8
Residences 0.8 - 0.95
Retail, Department Stores 0.65 - 0.9
Other Shops 0.65 - 0.9
School Classrooms 0.65 - 0.8
Role of the Primary Air
• Ventilate the occupants according to ASHRAE 62A 2004
• Handle all of the latent load in the space
‒ Primary air is only source of latent heat removal
• Create induction through chilled beam
Primary Air Design
• Central AHU sized to handle:
‒ sensible and latent cooling/heating of the ventilation air ‒ portion of the sensible internal cooling/heating loads
AND
‒ all of the internal and infiltration latent loads
• Primary air delivered continuously to the chilled beams
‒ VAV primary air can be considered for the perimeter if the sensible loads are high
• Chilled beam water coils provide additional sensible cooling/heating to control zones
Primary Air Temperature 0 Cooling
55°F or Lower 65°F or Higher
• Reduces or eliminates reheat
• Ideal for labs or hospitals with code required minimum air changes
• More or longer beams
required in some applications • Reduces lengths/quantities of
beams
• Good for office buildings with high perimeter loads
• Often used with VAV in
applications with high sensible loads
Air must be suitably dehumidified whatever
the dry bulb temp is!
Room Neutral Air
• Sensible recovery device (downstream of coil) • Desiccant dehumidification units
Reducing Primary Air Temperature
Active Chilled BeamsPrimary Air Pressure Primary Air Flow Rate Supply Air Flow Rate Supply Air Temp Out (Cooling) Primary Air Sensible Cooling Secondary Air Sensible Cooling Nett Unit Sensible Cooling Chilled Water Flow Rate
Qty Unit TAG Zone Name Unit Model 2 or 4 Pipe Coil Nominal Length (feet) PPA(Inch w.c.) QPA(CFM) QSA
(CFM) tSAout(°F) qPAs(Btuh) qSCAs(Btuh) qs(Btuh) QSCHW
(GPM)
2 ACBA1 1 DADANCO ACB50 2 8 0.7 105 529 59.3 2281 6770 9051 1.3
Room Design Primary Air Secondary Chilled Water Secondary Hot Water Elevation Feet
% Propylene Glycol
Cooling 75°F 50% RH 55°F 80% RH 58°F 110°F 0 0 Heating 70°F 50% RH 55°F 83% RH
Typically 25% + more chilled beams required when using 65°F primary air
Active Chilled Beams Primary Air Pressure Primary Air Flow Rate
Supply Air Flow Rate Supply Air Temp Out (Cooling) Primary Air Sensible Cooling Secondary Air Sensible Cooling Nett Unit Sensible Cooling Chilled Water Flow Rate Water Pressure Drop Qty Unit TAG Zone Name Unit Model 2 or 4 Pipe Coil
Nominal Length
(feet)
PPA(Inch
w.c.) QPA(CFM) QSA(CFM) tSAout(°F) qPAs(Btuh) qSCAs(Btuh) qs(Btuh)
QSCHW (GPM) SCHW pressure drop (Feet w.c.)
3 ACBA1 1 DADANCO ACB50 2 8 0.5 70 359 59.4 760 5325 6085 1.1 7.9
Room Design Primary Air Secondary Chilled Water Secondary Hot Water Elevation Feet % Propylene Glycol % Ethylene Gylcol
Cooling 75°F 53% RH 65°F 70% RH 58°F 70°F 0 0 0 Heating 70°F 50% RH 107°F 83% RH
Latent Load Calculation
• The amount of cooling required to remove the moisture from the air
Q
L= 0.68 x q x ∆w
gror QL = 4,840 x q x ∆ w
lbWhere A
QL= latent heat (Btuh)
q = air volume flow (cfm)
∆ wgr = humidity ratio difference (grains water/lb dry air)
Dehumidification Air for 1 Person 0 200BTUH
0 5 10 15 20 25 30 35 40 45 44 45 46 47 48 49 50 51 52 P ri m a ry a ir f lo w ( C F M )Primary air dew point (°F)
55% RH 52% RH 50% RH 30% less air Room Design Condition
Supply Water Temperature Safety Margin
Climatic Ceilings by “Energie”
Passive Chilled Beams + 1°F Active Chilled Beams A 2.9 °F Do not design below room dew point!
Condensation – Radiant Panel Test
Condensation after 8.5 hours on a chilled surface
intentionally held 7.8°F colder than the space DPT. Not one droplet fell under these
conditions
Chilled Ceilings in Parallel with Dedicated Outdoor Air Systems: Addressing the Concerns of Condensation, Capacity, and Cost Stanley A. Mumma, Ph.D., P.E.
• Building was designed for 80 BTUH/ft2 perimeter load
• Actual load in building use was 40 BTUH/ft2
Parameter Proposed in design Actual observed load
Area (Sq.ft) 200 200
Sensible Load (Btuh) 16,000 8,000
Latent Load (Btuh) 400 400
Minimum Outside Air (CFM) 40 40
Quantity of ACB’s 2 2
• Chilled beams selected for double actual required primary air to achieve overestimated load
• Primary air providing 65% of the total sensible cooling of the actual load
2 x beams at 115 CFM
• Therefore if load drops to 65% no waterside cooling will occur
• If load drops below 65% space will overcool unless reheat is used
• Assumptions on building materials performance
• Equipment loads that never eventuate
• Use of generic performance data
• Use of safety factors
• Lack of familiarity with load calculation software
Exclude loads:A
Outside air load
Plenum gain
Fan motor gain
Duct losses
Location Sensible Zone Load
North 25A30 Btuh/Sq.ft
East 35A45 Btuh/Sq.ft
South 30A40 Btuh/Sq.ft
West 40A50 Btuh/Sq.ft
Interior 15A20 Btuh/Sq.ft
If loads exceed these values review closely
CHW System Design Options
• Secondary loop
‒ Tap into district CHW loop
‒ Heat exchanger into return – no GPM demand ‒ Can increase main plant efficiency
• Dedicated chiller & DX
‒ Dehumidification by DX AHU
‒ Significantly increased COP A 11+
• Twin chillers
‒ One for AHU’s – 6 COP
Mixing Valve
S T
Secondary chilled water supply to beams Secondary chilled water return Supply temperature monitor Primary chilled water supply Primary chilled water return SCHW Pump 45°F 58°F 64°F T Primary chilled water return
Secondary Loop
S
T
Secondary chilled water supply to beams Secondary chilled water return Supply temperature monitor Primary chilled water supply Primary chilled water return Heat Exchanger SCHW Pump 54°F 45°F 58°F 64°F T
Dedicated Chiller
T
To chilled beam zones
Bypass Valve Chilled water pump Dedicated chiller 11+ COP Cooling Tower Geothermal Loop Geothermal Heat Pump 64°F 58°F
District Chilled Water Loops
• No demand in district loop GPM • Increases main chiller plant COP
Tap into return pipe with heat exchanger and secondary loop
Reverse Return Pipe Design
S
Advantages of 20Pipe Beams Versus 40Pipe
• Higher coil performance
‒ 4 pipe performance is compromised ‒ 75% Cooling (12 pipes)
‒ 25% Heating (4 pipes)
• Fewer or shorter beams
• Lower hot water temperatures
‒ 90°F for 2 pipe ‒ 130°F for 4 pipe
Boiler Efficiency 0 Lower Hot Water Temp
• Hot water typically 90A130°F• Reduce boiler energy consumption by maximizing efficiency of a
condensing boiler through very low return water temperatures
• Use of water to water heat pumps
(KN boiler efficiency chart courtesy of Hydrotherm)
20Pipe Beams and Terminal Heating
S S T Terminal Heating Coil 2APipe Active Chilled Beams Chilled Water SupplyChilled Water Return Hot Water Supply
Airside Control
• Constant volume air
‒ Reduces cost
‒ Maintains constant control of humidity ‒ Guarantees minimum fresh air delivery
• Monitor room dew point
‒ Use small quantity of high quality sensors ‒ Do not use RH sensors
‒ Locate sensors in room not in ceiling
• Reduce primary moisture content to control room RH
Waterside Control
• Variable water flow
‒ Pressure independent control
• Two position valves or modulating valves
• 6Away valves can be used on 4 pipe into 2 pipe chilled beams
• Reschedule or shut off SCHW only if primary moisture content cannot reduced
Waterside Control Sequence
71 72 73 74 75 76 R o o m T e m p e ra tu re ( °F ) Time D e a d Z o n e D e a d Z o n e SCHW ON SCHW OFF SCHW ON SCHW OFF HW ONTypical Start Up Control Sequence
• Dry out cycle before engaging SCHW pumps
• Setback primary air humidity ratio
• ONLY initiate pumps when room dew point is within design limits
Condensation and Dew Point Sensors
Drip sensor
Condensation sensor Dew point sensor
ACTIVE BEAM SYSTEM DESIGN
COST CONTROL
First Cost Control
• Many projects still designed with far to many beams
‒ Caused by confusing selection software or low performance beams
• 4Apipe system designs are costly
‒ 2Apipe system with terminal heating or 6Away valves reduce cost
• Mechanical contractors unfamiliar with system
PEX Piping Significantly Reduces Costs
• 70% reduced pipe material cost
‒ $0.60 v’s $1.95 per linear foot
• Reduced labor, much faster installation
‒ No torches or soldering, no glue
• Longevity – 50 year life expectancy
‒ No corrosion
• Dampens water rushing noise and water hammer noise • Does not require insulation
• Plenum rated systems available
Active Chilled Beam
Selection & Layout
ACB Selection & Layout Tips
• Select beams for minimum possible primary air
• 0.4 – 0.7” w.c. typical airside beam ∆P
• Be aware of airside/waterside cooling ratio
‒ Maximize waterside cooling
• Chilled beams throw more air than VAV diffusers
‒ Be wary of air velocities
ACB Selection & Layout Tips
• Careful positioning near walls & columns
‒ Can interfere with beam if too close
• Chilled beams positioned closer than 6’ centers may not cool correctly
‒ Minimum 2 x tile spacing rule of thumb
• Use manufacturers selection software
Tips to Minimize Primary Air Flow
• Be wary of overrating cooling loads • Use low temperature primary air
‒ 45 – 48°F is possible but beam must be internally insulated
• Locate beams along perimeter to increase output
‒ Use a higher on coil temperature when beams are positioned along perimeter
‒ This additional capacity is often overlooked
DOAS with Booster Fans
A + A + Outdoor Air DEDICATED OUTDOOR AIR UNITA A
FAN BOOSTERS
Return Air Return Air
ACTIVE CHILLED BEAM ZONES ACTIVE CHILLED BEAM ZONES
LAYOUT EXAMPLE
@ OFFICE BUILDING @
Building With Exterior Cellular Offices
Office 1 35 BTUH/ft2 12’ 12’ Office 2 35 BTUH/ft2 Office 3 50 BTUH/ft2 Office 5 30 BTUH/ft2 Office 6 30 BTUH/ft2 TOTAL AREA 2,520 FT2 Office 7 30 BTUH/ft2 Office 4 30 BTUH/ft2 Occupants: Area: Ventilation: Cooling: Latent load: Heating Load: 1 144 ft2 15 CFM 7200 BTUH 288 BTUH 3000 BTUH Occupants: Area: Ventilation: Cooling: Latent load: Heating Load: 1 144 ft2 15 CFM 5040 BTUH 288 BTUH 2500 BTUH Occupants: Area: Ventilation: Cooling: Latent load: Heating Load: 1 144 ft2 15 CFM 5040 BTUH 288 BTUH 2500 BTUH Occupants: Area: Ventilation: Cooling: Latent load: Heating Load: 1 144 ft2 15 CFM 4320 BTUH 288 BTUH 2100 BTUH Occupants: Area: Ventilation: Cooling: Latent load: Heating Load: 1 144 ft2 15 CFM 4320 BTUH 288 BTUH 2100 BTUH Occupants: Area: Ventilation: Cooling: Latent load: Heating Load: 1 144 ft2 15 CFM 4320 BTUH 288 BTUH 2100 BTUH Occupants: Area: Ventilation: Cooling: Latent load: Heating Load: 1 144 ft2 15 CFM 4320 BTUH 288 BTUH 2100 BTUH Occupants: Area: Ventilation: Cooling: Latent load: Heating Load: 15 1,512 ft2 170 CFM 30,240 BTUH 3024 BTUH 0 BTUH Office 8 20 BTUH/ft2ACB Design Parameters
• Room Conditions:
‒ 75°F db/53% RH ‒ 70°F db winter
• Primary Air Conditions:
‒ 55°F db/51.6 wb (48.7 DP) – Summer & Winter
• Chilled Water
‒ 57°F versus a 56.5°F room dewpoint (53% RH)
• Warm Water
ACB Layout
12’ 12’ Office 5 Office 6 TOTAL AREA 2,520 FT2 Office 7 Office 4 DOAS Max. O/A 485 CFM S/A R/A VAV V A V A C B A1 A C B A2 ACBA3 A C B A8 b A C B A8 a A C B A8 f A C B A8 eACBA4 ACBA5 ACBA6 ACBA7
PRIM. AIR Min. 15 CFM Max. 35 CFM PRIM. AIR Min. 15 CFM Max. 35 CFM PRIM. AIR Min. 15 CFM Max. 45 CFM PRIM. AIR Min. 15 CFM Max. 25 CFM PRIM. AIR Min. 15 CFM Max. 25 CFM PRIM. AIR Min. 15 CFM Max. 25 CFM PRIM. AIR Min. 15 CFM Max. 25 CFM
PRIM. AIR 270 CFM Min. 105 CFM
Max. 215 CFM Max. 270 CFM Office 1 35 BTU’sAHR/FT2 Office 2 35 BTU’sAHR/FT2 Office 3 50 BTU’sAHR/FT2 30 BTU’sA HR/FT2 30 BTU’sA HR/FT2 30 BTU’sA HR/FT2 30 BTU’sA HR/FT2 Internal Offices 20 BTU’sAHR/FT2 A C B A8 d A C B A8 c Min. 170 CFM Min. O/A 275 CFM
Beam Layout Notes
• 1Away beam in the perimeter offices
‒ Captures solar load, increases beam output ‒ Higher onAcoil temperature
‒ Free’s up ceiling space for lighting ‒ Works well for heating
• Interior office
‒ 2Away throw beams
‒ Check velocity between colliding airstreams ‒ Minimum of 1 beam per 300 ft2
10Way Perimeter Beam
• Increased on coil temp • Increased cooling output • Less primary air required
VAV Reheat Design Parameters
• Room Conditions:
‒ 75°F db/50% RH ‒ 70°F db winter
• Primary Air Conditions:
‒ 55°F db/55 wb – Summer & Winter
• Chilled Water
‒ 45°F
• Hot Water
VAV Layout
Office 1 35 BTU’sAHR/FT2 12’ 12’ Office 2 35 BTU’sAHR/FT2 Office 350 BTU’sAHR/FT2 Office 5 Office 6
TOTAL AREA 2,520 FT2 Office 7 Office 4 AHU O/A 275 CFM S/A R/A VAV 7 V A V IO MAX 232 CFM MIN 63 CFM MAX 232 CFM MIN 63 CFM MIN 63 CFM MAX 332 CFM MAX 199 CFM MIN 50 CFM MAX 199 CFM MAX 199 CFM MAX 199 CFM MIN 50 CFM MIN 50 CFM MIN 50 CFM MIN 304 CFM MAX 1,394 CFM VAV 6 VAV 5 VAV 4 V A V 2 V A V 1 Internal Offices 20 BTU’sAHR/FT2 30 BTU’sA HR/FT2 30 BTU’sA HR/FT2 30 BTU’sA HR/FT2 30 BTU’sA HR/FT2 E/A 275 CFM Max. 2986 CFM Min. 693 CFM
VAV ACB+DOAS
• Total Air System Size
‒ 565 CFM
• Airflow @ Max Turndown
‒ 275 CFM
• Max. Airflow
‒ 0.22 CFM/FT2
• Min. Average Airflow
‒ 0.11 CFM CFM/FT2
• Airflow @ 60% Load
‒ 0.11 CFM FT2
• Total Air System Size
‒ 2986 CFM
• Airflow @ Max Turndown
‒ 693 CFM
• Max. Airflow
‒ 1.18 CFM/FT2
• Min. Average Airflow
‒ 0.27 CFM CFM/FT2
• Airflow @ 60% Load
‒ 0.71 CFM FT2
