AHR Expo - BACnet to the Rescue

8/6/2019 AHR Expo - BACnet to the Rescue

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Presenter comments and opinions may not reflect views and opinions of BACnet International. Presentation is property of BACnet International and cannot be reproduced without permission .

BACnet to

the Rescue! Steve Tom

Director of Technical Information, Automated Logic Corporation



Banner Bank Building

• LEED NC Platinum core & shell

– 1’st Platinum in Boise ID

– 1’st Platinum spec office bldg – 19’th Platinum in the world

• BACnet Controls!

• Modeled energy 50% of 90.1

• 60% less water use

• Cost no more to build

www.BACnetInternational.org



Banner Bank Details

• 11 Story Bldg - 195,000 SF

• $25 Million Construction Cost

– $128/SF – Leases comparable with existing 20 +

year old buildings

• Lighting control with Daylight Harvesting

– 65% less lighting load

• Modeled Energy Use = 41% of conventional bldg



Major HVAC Systems

Geothermal Heat

Efficient AHU

Efficient Chiller

Weather ForecastPrecool

Demand Controlled Ventilation

Underfloor Air Distribution



Problems

• Zones didn’t communicate with AHUs

– AHU’s manually adjusted

• AHU’s didn’t communicate with supply – Chillers & Geothermal ran in stand-alone mode

• Everything set to meet “worst case” needs

• Energy use significantly over budget

• Occupant complaints about comfort



What Went Wrong?

•

Contract dispute over integration – Specified how equipment should operate – not how

equipment should work together as a system

– Multiple vendors: Who should do integration?

– Specs did not include enough detail on commissioning

• Primary controls contractor left project!



Now What?

• New contractor hired for integration

– Associated with different vendor’s control products – Only accepted job because it was BACnet

• Surveyed building to find problems

– Reviewed plans, specs, as-builts, and actual construction

• Studied LEED Requirements

• Built a plan to Integrate Equipment into Systems



Integration Strategies

• Trim and Respond – AHU provides, say, 60˚ air at start-up

• Zones request cooler air if above cooling setpoint

– AHU Responds by dropping temp, say, 0.5˚

• No request for 5 min? Raise temp, say 0.5˚

– Chiller adjusts temp based on requests from AHUs

– Adjust hot water supply temp similarly

– Also works with VAV Static Pressure Reset




• Morning Start-Up

– Stand-alone: AHU starts, say, 2 hrs before occupancy – Integrated: Zones tell AHU when to start

• Based on model of how fast system can heat or cool zones

• Zones “learn” heating and cooling capacity over time

• Net Result: wait until last minute to turn on AHU

– Mild weather: turn on just before occupancy

– Very hot or very cold: turn on early

• Optimum Stop

– Turn chiller off early & “coast” on cold water in system.

Max Cool

Max Heat

Zone Temp




• Night Purge with Morning Precool – Read weather forecast into control system

• BACnet Web services can bring in weather forecast

– Superventilate with cool OA during start-up

• Forecast above 70˚: Cool building to 70˚



– Requires coordination between AHU and Zones



Results

• Integrated approx. 3,000 BACnet Points in 4 Months

– BACnet Discovery made this possible

• Geothermal use dropped 45%• Electrical consumption dropped 6-9%

– Includes 5 data centers, high-density tech offices

• Operating expense $1.12/SF

– Comparable local buildings $1.30 to $1.50/SF

• Occupant compliments replaced complaints

– One of highest occupancy & retention rate in area

– Occupancy grew from 90% to 99%



Results (Con’t)



Results (Con’t)



Results (Con’t)



Lessons Learned

• BACnet Works “As Advertised”

– Multiple vendors devices integrated

into one system – Able to switch primary controls contractor

• BACnet is “Necessary but not Sufficient”

– Makes integration possible, doesn’t guarantee success

– Need to specify what will be integrated & by whom• Need point lists, sequences of operations, etc.

• ASHRAE Guideline 13 & CtrlSpecBuilder can help



• Need to specify how system performs

– Go beyond stand-alone equipment sequences

– How do zones affect AHU’s, chillers, etc. – Optimize overall system performance

• Controls and contractors are not commodities

– Have different strengths and weaknesses

– Pick best combination for your project

Lessons Learned (con’t)



Most Important Result

• Owner happy with building

– Success depends on having someone

who’s willing to say “I want to see thisoperate the way it’s supposed to” insteadof “I want to get paid and move on to thenext job.”

– Would definitely use BACnet on another

project. “That’s the standard for allsystems going foreword. Openstandards are critical to making thingswork.”



BACnet to the Rescue!

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AHR Expo - BACnet to the Rescue

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