Lessons Learned OnLessons Learned On New Technologies:New Technologies:  Chilled BeamsChilled BeamsTerry Autry – The RMH Group, Inc.Juan Moreno – EMC Engineers, Inc. – Eaton’s Electrical Services & SystemsKen Urbanek – MKK Consulting Engineers, Inc.

Where’s the beam?Where s the beam?

What is it really?What is it really?• A Fin on Tube Hydronic to Air Heat Exchanger System• Works just like a hydronic coil except with alternate construction details, dimensions and air moving system.

• There are different types including passive and active beams• There are different types including passive and active beams.

Passive Chilled BeamOverviewPassive Chilled Beam Overview

Passive Chilled BeamOverviewPassive Chilled Beam Overview

Passive Chilled BeamOverviewPassive Chilled Beam Overview• Like a duct hydronic coil, but with some differences.

• Construction Details:  low fin per inch to reduce pressure drop

• Dimensions:  4 to 20” wide, 3’ to 10’ long

• Alternate Air Moving System:  Passive through convection –NO forced air system.

Passive Chilled Beam Applications• Cooling Applications Only!• Supplemental Ventilation System Still Required For:

• Outside Ventilation Airildi h idifi i ( hi l )• Building Dehumidification (more on this later)

• As Such – Limited Application, Typically for supplemental coolingg

• Has Been Used to Supplement Under Floor Air Distribution (UFAD) and Displacement Ventilation (DV)• Convective Airflows Can Disturb/Change UFAD & DV Performance

• Supplement Active Chilled BeamsSupplement Active Chilled Beams

Passive Chilled BeamDesignPassive Chilled Beam Design• Must Avoid Operation Below Dew Point!

• Higher chilled water temp, 59ºF to 65ºF• Dehumidify ventilation air!L Δ b & C il i• Low ΔT between Room & Coil requires large surface area and high water flow rate.  This is a lot of copper.

• Capacity Rules of Thumb:• ~150 Btuh/sqft for passive chilled beam• For Comparison: ~20 25 Btuh/sqft• For Comparison:   20‐25 Btuh/sqft(100% coverage) for radiant ceiling panels

h/ f f• For Comparison:  ~750 Btuh/sqft for active chilled beam

Passive Chilled Beam Special Considerations• Passive = Air Distribution Is Limited At BEST!

• Locate near heat load source to assist natural convection.

• Passive = Think Wide Open!  All air is naturally flowing, do not restrict the airflow path.   Make sure the Architect doesn’t push you in a corner.

• If grouping with baseboard heat use common zones!• If grouping with baseboard heat, use common zones!

• One More Time Passive Chilled Beams, especially, do not have condensate pans/drains.  Watch our for dew point!

Active Chilled BeamOverviewActive Chilled Beam Overview• What is an Active Chilled Beam?

• Induction Device• 0.5” w.c. average pressure drop• Can induce 2 to 5 times the amount of primary air suppliedCan induce 2 to 5 times the amount of primary air supplied• Includes a hot and/or cold water coil• Distributes air in room the same way as a linear diffuser

Active Chilled Beam Applications

• Ideal • Spaces with high sensible heat ratios (SHR)• When total outside air flow is 35% max., above minimum required ventilation air flowrequired ventilation air flow

• Not as ideal• Spaces with lower SHRs require more than 35% additional primary air flow than the minimum required ventilation air flowprimary air flow than the minimum required ventilation air flow rate to keep space dew point below chilled beam coil temperature

• CFM= Q /0 68 (W W )• CFM= Qlatent/0.68 (Wspace‐Wprimary Air)• At sea level• W=grains of moisture per lb of dry air

Active Chilled BeamDesignActive Chilled Beam Design• Classroom Psychrometric Chart

Active Chilled BeamDesignActive Chilled Beam Design• There’s No Free Lunch!!

• Myth: Total heat rejection is less• Reality: Heat rejection is the same for a VAV or chilled beam system assuming the same envelopsystem assuming the same envelop

• ACB Manufacturer Salesman Pitch: “I can do the same load with less beams than the other guy”

• Reality: Very little variance in capacities as long as the THROWS• Reality: Very little variance in capacities as long as the THROWS and PRESSURE DROPS remain the SAME

• Assumption: The manufacturer selected the beam, it must meet my required capacitiesmy required capacities

• Reality: No!! Check selections based on thermodynamic principles

Active Chilled Beam Special Considerations• Keep It Simple!!

• Four Pipe vs. Two Pipe• Separate Hydronic Systems for AHUs and ACBs vs Single, shared hydronic systemshydronic systems

• Condensation Strap‐On Sensors vs. RH or Dew Point Sensors• Combination of Diffusers and ACBs in Space vs ACBs OnlyC t L b S t S t C t L b S• Computer Labs on Separate System vs Computer Labs on Same Central System

• Have in Mind…• There is no air‐side economizer!!• Follow air balance methodology per manufacturer’s requirements gy p q

Active Chilled Beam Installation and Operation• The Good

• No electrical power required• Space requirements are very  similar to slot diffusers• No special training for installers is required• Water conveyed in piping is normally between 58 deg F and 105 deg F, no insulation required

• The Not So Good• Heavier than slot diffusers, weight is  between 70 and 180 pounds

• Support system needs to be more robust than supports required for slot diffusers

• Waterside temperature delta is low: 4 to 6 deg F requiring larger diameter piping than standard terminal coilsB l i i f f i h!!!• Balancing is an act of faith!!!

Chilled Beams Temperature ControlChilled Beams Temperature Control

2‐Pipe Cooling/Heating ACB2 Pipe Cooling/Heating ACB

Avoid the Indoor Rain Forest!Avoid the Indoor Rain Forest!

Control of Secondary Water Temperature Is Critical

AHU Chilled Beam

EconomicsEconomicsFirst Cost Comparison

VAV ACBVAV ACBAHU Large Small

Ductwork Large Small

Duct Risers Large Small

Ceiling Space Large Small

Piping Small LargePiping Small Large

Control Medium Large

EconomicsEconomics

Chilled Beams 15 25%more initial cost ∼15‐25% more initial cost than typical VAV system

∼12‐15 year simple packback compared to typical VAV systemsystem 

Operational ComparisonOperational Comparison

VAV ACBVAV ACBFan Energy High Low

Pump Energy Low High

Maintenance High Low

Occupant Comfort Low High

Noise High LowNoise High Low

Risk of Condensation Low High

Thank you!Thank you!