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NEBBinar: Retro-Commissioning for Comfort and Energy Efficiency

August 21, 2013

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Moderator

Jim Huber, NEBB Vice President and President of Complete Commissioning Jim Huber is the President of Complete Commissioning. He has over 29 years of industry experience, is a Certified Energy Manager, and has extensive experience with BACNET, LON, MODBUS, and other building automation protocols and communication networks. He has programming, tuning, and testing experience with multiple systems and applications, as well as building systems commissioning, sound and vibration measurement, and testing and balancing.

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Speaker

Dave McFarlane, Principal Project Director, Atkins Dave McFarlane is a principal project director in the asset management practice and head of the Retro-Commissioning group for Atkins, one of the world’s leading engineering, design, and project management consultancies. Prior to joining Atkins, Dave was the president of Technical Commissioning, Inc. (Fort Myers, FL) and McFarlane, Inc. (Grand Forks, ND). He was a member of NEBB’s Commissioning Committee; he chaired the committee in 2003-2004 and rejoined in 2011. Dave serves as an instructor for NEBB’s courses in Commissioning and Retro-Commissioning. He speaks at conferences nationwide, and has written numerous articles for a variety of industry publications.

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What is Retro-Commissioning

Case study: Grand Forks ND County Office

Question and Answers

Agenda

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Retro-Commissioning

A systematic, documented process that identifies and implements low cost

operational and maintenance improvements which improve building

efficiency and allows the building to meet the current design requirements

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Retro-Commissioning

•Ensure that the building meets the Current Facility Requirements (CFR)

•Reduce energy usage

•Improve comfort

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What is Retro-Commissioning

Case study: Grand Forks ND County Office

Question and Answers

Agenda

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Grand Forks County Office Retro-Commissioning

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Grand Forks Country Office

• Seven story - 140,000 square feet

• Five floors office space w/conference rooms

• Meeting rooms on sixth floor

• Mechanical room on the 7th floor

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Interior/exterior walls and conference rooms Floors 1-5

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Interior/exterior walls and conference rooms

Floor 6

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Interior offices

Perimeter offices

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County Commissioners Chambers

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Perimeter link

Meeting room

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Establish baseline

• Review the past 2-3 years energy bills

• Convert to MM BTU ft2/year

• Energy intensity is ~ 151,000 BTU/ft2/yr

Session 21 Energy Savings

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Natural Gas

-

2,000

4,000

6,000

8,000

10,000

12,000

14,000

16,000

1 2 3 4 5 6 7 8 9 10 11 12

PremodificationGas Use

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Electrical Usage KWH

80,000

130,000

180,000

230,000

280,000

330,000

1 2 3 4 5 6 7 8 9 10 11 12

PremodificationKWH

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Electrical Demand KW

0

100

200

300

400

500

600

700

800

1 2 3 4 5 6 7 8 9 10 11 12

PremodificationKW

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Compare baseline to typical

• For North Dakota typical energy intensity: 93,000 BTU/ft2/yr

• County office energy intensity: ~ 151,000 BTU/ft2/yr

• Projected savings achievable through retro-commissioning: $45,000 annually

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Discovery phase

•Determine what is wrong

•Review documents, plans and specs

•Interview maintenance staff

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Plans and specs showed

4 VAV air handlers

4 boilers

VAV boxes with 2-way valves

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Session 21 Energy Savings

AHU Quadrants

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HW pumps and fans with VFD’s Pump and fan VFD’s

Plans and specs showed

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Discovery and maintenance staff perspectives

•Building had electric baseboard supplement heat

•Too many occupant complaints about temperature controls

•Lack of understanding of Building Management System (BMS)

•Systems in overridden and in manual control

•BMS system not used to potential

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Light shelves

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Heating pumps

100%

VFD 60 Hz

Leaking reheat valves

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Site investigations • Fresh air dampers open on night set back

• Control sequence cooled building

• Building in occupied mode

• Occupied air flow: meeting/conference rooms

• Space stats not controlling within 1oF

• Occupants had full thermostat control

• Mixed air control set at a constant 55 F o

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Site investigations

• Equal occupied and unoccupied heating variable air volume (VAV) set points

• Min/max heating VAV set points are the same

• Equal unoccupied interior and exterior zones air flow

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Site investigations

Heat from dimmer switch

Boilers reset to 120 during summer months

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Site investigation

• Electric baseboard on whenever OA below 50 F

• Duct static pressure sensor set at 2” pressure

• Most VAV boxes call for reheat

• Most VAV boxes damper position 50-75% in summer

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Site investigations

• Outdoor CO2 is 370 PPM. Indoor CO2 is 425 PPM

• Chiller energized at 50 F OAT

• Many VAV min / max set points had been occupant complaint adjusted

• Room registers read between .5 and 4.0 CFM / Ft2

• Building positive, then negative

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RA fan and SA fan not tracking

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Analysis phase

• Computer modeling

• Determine if we can predict the current energy usage before changes are made

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Corrective action items

• Recalculate new air flows based on the actual people, lights, equipment, glass walls and roof loads.

• Use ASHRAE 98% design

• Use actual people loading for fresh air

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Analysis phase

• Actual operating data

• Total fan air flow

• Actual fan static pressures

• Actual fan amperage readings

• System type, fan wheel type and fan speed

• Actual run times

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Analysis phase

• Actual data

• Average Min / Max set points

• Occupied / unoccupied set points

• VAV occupied unoccupied set points

• Fan type and fan speed

• Run times

• Actual fresh air CFM

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Analysis phase

• Actual operating data

• Total fan discharge temp

• Hot water temps

• Chilled water temps

• Space temp

• Type of fin tube heat and fin tube parameters

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Analysis phase: actual space data

• Actual people, light load, equipment load

• Actual occupied times

• Actual space temperatures

• Actual glass area and parameters

• Actual roof area, wall area and parameters

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Analysis phase: actual utility cost data • Gas cost per therm

• KWH cost

• KW demand cost

• Auxiliary fuel costs

• Local degree days / bin temperatures

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Analysis phase

• DOE 2 or Super DOE

• Crunch the numbers and compare

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Natural Gas

-

2,000

4,000

6,000

8,000

10,000

12,000

14,000

16,000

1 3 5 7 9 11

Projected Gas Use

PremodificationGas Use

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-

30,000

60,000

90,000

120,000

150,000

Annual Natural Gas Summary

PremodificationProjected

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Electrical Demand KW

0

100

200

300

400

500

600

700

800

1 2 3 4 5 6 7 8 9 10 11 12

Projected KW

PremodificationKW

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-1,0002,0003,0004,0005,0006,0007,0008,000

Annual Electrical KW Demand Summary

PremodificationProjected

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Electrical Usage KWH

80,000

130,000

180,000

230,000

280,000

330,000

1 3 5 7 9 11

ProjectedKWH

Premodification KWH

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0

500,000

1,000,000

1,500,000

2,000,000

2,500,000

Annual Electrical KWH Summary

PremodificationProjected

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Office Energy Intensity

• Current Intensity is ~ 151,000 BTU/ft2/yr

• Area Average ~ 93,000 BTU/ft2/yr

• Computer modeling ~ 85,000 BTU/ft2/yr

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Session 21 Energy Savings

Corrective action items

•Make the corrections needed to obtain the results outlined in the modeling.

•Rebalance air and water flows to new ASHRAE 98% requirements

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Repair leaky valves

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Eliminate restrictive duct

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Corrective action items

• Adjust throttling range and dead band on all VAV thermostats and AHU Controllers

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Improper Control - Too tight

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Improper Control - Too Loose

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Proper Control

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Adjust occupied/unoccupied sequence

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Fixes and corrective actions

• Rezone for interior exterior zones

• Set VAV box up with different occupied/unoccupied min/max

• Set conference room VAV box to standby

• Unoccupied interior VAV set to zero air flow

• Set 6th floor conference room VAV’s to standby mode

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Fixes and corrective actions

• Lock thermostats between 68 and 75F

• Reset discharge temperature on cooling

• Reset hot water 140 to 180F

• De-energize electric fin tube above 30 F

• De-energize the fin tube in the unoccupied mode

• Rotate the fin tube usage off for 1 of 5 minutes

• Shut boiler off at 40F unoccupied

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Acceptance phase

• Energy Procedures • Winter temps-- 70-74 F • Summer temps– 73-77 F • No space heaters

• Monitor usage for one year

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Grand Forks County Office Retro-Cx Results

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Yearly energy usage per square foot Pre-modification 151,000 BTU/FT²

Typical 93,000 BTU/FT²

Modeling 85,000 BTU/FT²

Actual: 76,000 BTU/FT²

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Results 2002-2012

Gas 29.8 % $417,200

KW-hr 45.9 % $642,600

Demand 26.3 % $368,200

Total 100 % $1,400,000

Energy levels have stayed at projected levels for the past eleven years

\

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Three years after RCx

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Question and Answers

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Contact information

Jim Huber, NEBB Vice President and President of Complete Commissioning Tel: +1.301.877.2260 Email: JHuber@completecx.com Dave McFarlane, Atkins Tel: +1.239.791.8771 Ext. 460-1021 Email: Dave.McFarlane@atkinsglobal.com

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