Active Chilled Beam Technology

Presented by:

Matt Green

Active Chilled Beam Technology

Section I: Introduction to ACB Technology– Types of Chilled Beams– ACB Technology Advantages– How ACB’s Work– How ACB Systems Compare to Other Systems– Common Applications of ACB Technology– Misapplications of ACB Technology

Section II: ACB System Design Considerations – DOAS/Airside System Design– Chilled Water System Design– Heating with ACB’s– Controlling ACB Systems– Condensation Prevention

Agenda

Section I: Introduction to ACB Technology

Types of Chilled Beams


Types of Chilled Beams – Active Chilled Beams

• Cooling and Heating

• Fresh air supplied through beams

• Very low acoustic signatures

• Very high energy efficiency

• Very high levels of occupant thermal comfort

ACB Technology Advantages

• Energy conservation

• Reduced space consumption

• Reduced maintenance costs

• Increased comfort levels



How ACB’s Work

A) Primary air duct connection (.3-1.2 in. w.c.)B) Primary air plenumC) Secondary air (room air)D) Unit mounted coil (2-pipe or 4-pipe configuration)

E) Mixed air (Induction ratio range 3:1 – 6:1)F) Discharge air (Cooling: 63-66ºF / Heating 75-85ºF)G) Adjustable mounting brackets


How ACB Systems Compare to Other Systems - VAV

Equipment VAV ACB

DOAS/AHU and Fans $285,000 $185,000

Ductwork $260,000 $195,000

Chiller $150,000 $150,000

Copper Piping $55,000 $315,000

Active Chilled Beams $0 $110,000

VAV Units $75,000 $0

Sound Dampers $20,000 $5,000

Temperature Controls $105,000 $130,000

Registers and Diffusers $110,000 $40,000

Total $1,060,000 $1,130,000

Building Sq Footage 50,000 50,000

Cost/Sq Ft. $21 $23

• First costs for ACB are typically higher than VAV:

– 5-10% higher

– Copper pipe largest cost ‘penalty’ for ACB systems

– PEX piping, good alternative, save cost on branch piping insulation

– DOAS/AHU & duct costs are lower in ACB systems

• ACB first costs are trending closer to VAV

• Operating costs are significantly lower for ACB systems

– No Maintenance

– Significant energy savings• Reduction in AHU horsepower

• Increased chiller EER


How ACB Systems Compare to Other Systems - FCU

Equipment FCU ACB

DOAS and Fans $185,000 $185,000

Ductwork $170,000 $195,000

Chiller $150,000 $150,000

Copper Piping $420,000 $315,000

Active Chilled Beams $0 $110,000

Fan Coil Units $185,000 $0

Sound Dampers $5,000 $5,000

Temperature Controls $115,000 $130,000

Total $1,230,000 $1,090,000

Building Sq Footage 50,000 50,000

Cost/Sq Ft. $25 $22

• First costs for ACB are typically lower than FCU:

– 5-10% lower

– Savings on equipment and piping favor ACB systems

• Operating costs are significantly lower for ACB systems

– Fan energy savings

– No maintenance

– Significant energy savings

– Chiller EER


How ACB Systems Compare to Other Systems – Energy Efficiency

Figure from: Centre For Building Science News, Lawrence Berkeley Laboratory, “Hydronic Radiant Cooling Systems”, Fall 1994.* Figure does not include additional fan energy associated with developing pressure for active chilled beam operation.

Flow Cross Section Ratio 1:550

¾“ diameter Water Pipe

The energy that 1 ft3 of water removes requires 3,400 ft3 of air!

18“ x 18“Air Duct


How ACB Systems Compare to Other Systems – Energy Efficiency

Chiller Nominal Tonnage LWT Output Tons kWi EER

250 45 257 319.4 9.6

210 55 257 296.2 10.4

190 60 250 276.1 10.8

Operating cost of the chilled water system can significantly be lower for ACB systems due to the ability to use higher leaving chilled water temperatures

– Improved chiller EER at higher leaving water temperatures

– Allows for downsizing the nominal tonnage of the chiller while maintaining similar output tonnage


Common Applications of ACB Technology

• High sensible cooling load applications

– Heat driven laboratories, offices, etc.

• Sound sensitive applications

– Libraries, hospitals, universities, etc.

• Retrofit applications (CAUTION)

– ACB’s require minimal overhead clearance

• LEED Applications

– Superior energy efficiency, individual temperature control, and innovation


Misapplications of ACB Technology

• Spaces with high ceilings (above 14’)

– Manufacturing, warehouses, etc.

• Spaces with high latent loads

– Indoor pools, gymnasiums, etc.

• Spaces with uncontrolled humidity

– Atriums, vestibules, hallways, etc.

• Spaces with restrictions on recirculated air

– Class I and Class II hospital areas

Section II: ACB System Design Considerations

DOAS/Airside System Design

A DOAS is required for the following:

– Dewpoint control to prevent condensation on the ACB’s

– Provide minimum ventilation requirement (ASHRAE Std. 62)

– Must handle 100% of the OA’s latent and sensible load

– Must handle 100% of the zone’s latent load

– Induce sufficient airflow through ACB’s to satisfy zone sensible load

– Positively pressurize building envelope to prevent infiltration


DOAS/Airside System Design

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There are (2) common DOAS discharge air temperature strategies:

1. Low temperature / low dewpoint strategy (type III desiccant)

– Not always recommended due to risk of overcooling the space and/or requiring reheat. Consider in applications high space latent loads.

2. “Neutral air” strategy – thermally neutral but dry air (68-72ºF db / 50-55% RH)

– Maximizes system efficiency, ACB’s handle ≈100% of space sensible load

– Free reheat should be incorporated into DOAS unit (i.e. “alpha plate”, sensible wheels, wrap around heat pipe, hot gas reheat)

– At summer design conditions, discharge air temperature can be reset colder to satisfy increased loads


Chilled Water System Design

Chiller Nominal Tonnage LWT Output Tons kWi EER

250 45 257 319.4 9.6

210 55 257 296.2 10.4

190 60 250 276.1 10.8

The ACB’s chilled water supply temperature is dependent on the space’s design dewpoint

– Supply water temperature should be at least 2-3ºF above the space’s design dewpoint to prevent condensation.

– Supply water temperature should be as high as possible to take advantage of increased chiller EER and ability to downsize nominal chiller capacity without reduction in output tonnage.

– Utilizing higher supply water temperatures allows for more available hours for water side economizer.

– ACB chilled water system temperature rise is lower (typically 6-8ºF) compared to traditional hydronic systems (typically 10-12ºF). The system designer should pay close attention to ACB coil water pressure drop to avoid excessive pump head.



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DEDICATED CHILLER(S)

– Two independent chilled water loops

– Allows higher supply water temperature for ACB chilled water loop

– Increased chiller EER for ACB water loop

– Ability to downsize nominal chiller capacity without reduction in output capacity for ACB water loop

– Higher first cost due to multiple chillers



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COMMON CHILLER(S) / MIXING VALVE

– One common chilled water loop

– Mixing valve controlled by sensor installed downstream of the discharge of the secondary pump(s)

– Does not allow for higher supply water temperatures

– Decreased chiller EER

– Cannot downsize nominal chiller capacity

– Should only be considered when ACB chilled water load is significantly less than DOAS load



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COMMON CHILLER(S) / HEAT EXCHANGER

– One common chilled water loop

– Modulating control valve controlled by sensor installed in outlet side of the water to water heat exchanger

– Does not allow for higher supply water temperatures

– Decreased chiller EER

– Cannot downsize nominal chiller capacity

– Should only be considered when ACB chilled water load is significantly less than DOAS load; and there is a requirement to isolate primary chilled water loop from the secondary water loop



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TRADITIONAL CHILLER(S) / DECOUPLED DOAS

– DOAS decoupled from chilled water loop






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GEO CHILLER(S) / DECOUPLED DOAS

– DOAS decoupled from chilled water loop




– Can utilize advanced geothermal water to water heat pump technology for exceptional energy efficiency

– Recommended for LEED projects


Heating with ACB’s

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• ACB’s available in 2-pipe in 4-pipe configurations

• Use of ACB’s for heating is dependent on the building envelope

– For internal zone or zones with <300 BTU/ft ACB’s are an excellent option

– For zones between 300-400 BTU/ft, ACB’s can be effective

• Air directed at 75fpm horizontally towards the window

– For zones above 400 BTU/ft, ACB’s are not effective

• Risk of drafts

• Should use finned tube radiation

• For low temperature / low dewpoint primary air systems zone reheat should be incorporated to prevent overcooling the space.

– Typically a reheat coil is installed in the zone’s primary air ductwork

– Alternate option is to utilize a 4-pipe ACB design


Controlling ACB Systems

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• Chilled water flow control

– Each zone’s flow is controlled by a single thermostat and a single control valve

– 2-position zone valves (i.e. on/off control) are typically used

– Manual isolation valves should be installed

Zone ControlsZone Manifold


Controlling ACB Systems

• Primary air flow control can be balanced with the following:

– Manual balancing damper (i.e. iris type) are used on constant primary airflow systems

– VAV boxes are used on variable primary airflow systems

• Should be considered in zones with highly variable latent loads.

• Demand control ventilation can also be integrated into a VAV control strategy

• Occupancy sensors can be integrated into a VAV control strategy. When zone is unoccupied, VAV box closes.


Condensation Prevention

• Dewpoint control should be primary consideration in the condensation prevention control strategy

• Additional control strategies include:

– The DOAS system should be cycled during unoccupied mode to maintain setback temperature and dewpoint set points. In addition, a “dry out” cycle should be implemented after long periods of unoccupied mode operation (i.e. weekends)

– Dewpoint sensors can be used to detect then disable the ACB system when a condition where condensation could occur is present. Alternately, moisture sensors on water piping can be used.

– Window switches can be used to disable the ACB system when a window is opened and ambient conditions will result in condensation

Section II: Summary

Benefits of ACB Technology• Energy conservation

– 40-70% less primary air, compared to all air systems

– 75-100% of the space sensible cooling delivered by water

– Significant reduction in fan energy

– Increased EER of chiller

• Reduced space consumption

– Smaller overall mechanical footprint, reduced duct work size

– Increase of space ceiling height

• Reduced maintenance costs

– No moving parts

– No filters at the beam required, beams vacuumed every 5-10 years

• Increased comfort levels

– Excellent air distribution,

– Secondary air temperature close to room temp.

– Lowe noise level, beam systems typically operate with around 10 dB(A) less noise than traditional VAV systems

Section III: References

Dadanco Frequently Asked Questions. Retrieved from: http://www.activechilledbeam.com/chilled_beam_questions.asp

Darren Alexander and Mike O’Rourke. Design Considerations for Active Chilled Beams (ASHRAE Journal, 2008, September).

Geoffrey P. McMahon. Chilled Beams: The Science of Lab Cooling. Retrieved from: http://www.aeieng.com/downloads/articles/ES%20Jan%20%2009%20Chilled%20Beams.pdf

Maija Virta, David Butler, Jonas Graslund, Jaap Hogeling, Erik Lund Kristiansen, Mika Reinikainen, and Gunnar Svensson. REHVA – Chilled Beam Application Guidebook (Federation of European Heating and Air-Conditioning Associations, 2004).

Peter Rumsey and John Weale. Chilled Beams in Labs: Eliminating Reheating & Saving Energy on a Budget (ASHRAE Journal, 2007, September)

Trox Chilled Beam Design Guide. Retrieved from: http://www.trox.us/usa/service/download_center/structure/technical_documents/air_water_systems/usa_products/leaflets/Chilled_Beam_Design_Guide.pdf

Section III: Summary

THANK YOU

Questions?

Primary ContactMatt Green, Sales Engineer

Office: 630-693-0926Cell: 630-730-4917Fax: 630-693-0931

[email protected]

Secondary ContactJordan Stiebel, Inside Sales Engineer

Office: 630-693-5876Fax: 630-693-0931

[email protected]

www.thermosystemsinc.com

Education

Active Chilled Beam Technology