Improving Performance with a Building Tune-Up. Janice Peterson, P.E. LEED AP Market Manager, Building Operations BetterBricks

Transcription

1 Improving Performance with a Building Tune-Up Janice Peterson, P.E. LEED AP Market Manager, Building Operations BetterBricks

2 How much is too much? Most buildings can cut total energy use by 5-30% while fully maintaining or improving both comfort and function Energy/Facilities Connections

3 Better Building Performance Ways to Improve and Maintain Building Performance Da aily Enhanced O&M Expand routine actions and practices Adopt preventative maintenance routines Improve and sustain building performance over time Lock-in gains made through other activities Pe eriodic Building Tune-Up Equipment Replacement Improve systematic problem diagnosis Identify and implement cost-effective operational improvements and equipment fixes Prudent upgrades to building infrastructure to improve efficiency Capture benefits of new technologies Align equipment assets with anticipated tenant needs

4 The Tune-Up Process The steps in a building tune-up are: Assemble the project team Complete basic maintenance Review data Interview occupants and building engineers Conduct the initial on-site inspection Diagnose performance problems Make an action plan

5 BetterBricks.com

6 Common Opportunities: The Top Four

7 Top Four Opportunity Areas for a Building Tune-Up Equipment Scheduling Sensor Error Simultaneous Heating and Cooling Outside Air Usage

8 Equipment Scheduling The easiest way to save equipment energy is to turn it off! Also, longer operating hours : Result in shorter equipment life Increase the frequency of parts replacement Cause the need for more frequent cleaning (chiller bundles, boiler tubes, fan coils, etc.) A good first step is to walk through the building when it is unoccupied.

9 Lighting and Plug Load Scheduling Some things to look for: Does the custodial staff turn off lights after hours as they go through the building? Does a lighting g time clock account for weekends and holidays? Do the lights actually turn off as programmed? Have special event schedules been reprogrammed back to normal? Is there a system in place to make sure computer power saving modes are enabled?

10 HVAC Load Scheduling Do programmed schedules for fans, pumps and other equipment match requirements? (and is the schedule being implemented?) Is optimum start and stop programming being used? If fan-powered boxes or baseboards can operate independently from the air handler, are they yprogrammed to match occupancy? Do the chiller and boiler have lockouts based on outside air temperature? Are the chiller and boiler prevented from operating at the same time? Are DHW circulating pumps scheduled d off?

11 Sensor Error Calibration Critical control sensors should be calibrated at least twice a year Incorrectly placed Failed

12 Sensor Error Critical control sensors include: Mixed air temperature Return air temperature Outside air temperature Supply air temperature Chilled water temperature Hot water temperature Carbon dioxide Sensor Issues in Disguise Loads not met Economizer not working Equipment on when not needed Simultaneous heating and cooling

13 Case Study: County Office Building 141,000 sqft High usage EUI of kbtu/sqft 20% over expected VAV rooftop air handling units 3 water-cooled chillers / hydronic reheat In-house staff with maintenance outsourced

14 Case Study: County Office Systems operating 24/7 to maintain comfort Duct static difficult to maintain at peak Chiller operation all year Boiler operation all year Numerous cold draft complaints Discharge air cannot reach 55 F Full economizer at 81 F ambient Perimeter heating on at 55 F ambient Major finding: 6 F difference in mixed vs. OSA at 100% economizer mode

15 Case Study: County Office Energy Recommendations Calibrate temperature sensors Optimize discharge air reset schedules Implement On/Off scheduling and lockout of chillers and boilers Reinitiate heat recovery chiller operation Modify mixed air control Go back to reset of chilled water supply temp.

16 Case Study: County Offices Tune-Up Results Annual savings of 1.1 Million kwh Annual savings of 30,800 therms Capital cost of $600 Investigation cost of $5, year payback Very happy building owner

17 Simultaneous Heating and Cooling Two examples: Supply air temperature is lower than it needs to be causing more reheat A water control valve is leaking, allowing hot and cold water to mix Equipment capacity is lowered, occupants are uncomfortable, energy use increases and maintenance increases.

18 Outside Air Usage Economizers = Free cooling But: If you have one, it s probably not working! Failed outside air sensor Incorrect thermostat Incorrect control logic Broken linkages Etc.

19 Outside Air Usage Other typical problems with outside air Minimum ventilation rate never adjusted for a change in occupancy Minimum ventilation rate is set by damper positions rather than by measured air flow Damper leaks when closed during unoccupied times CO2 sensor is improperly located

20 Digging Deeper Check out the BetterBricks Symptom Diagnosis Tool BetterBricks.com

21 Symptom Diagnosis Tool Currently list contains 68 symptoms each related to one or more of 11 systems, e.g., chillers, cooling towers or air distribution Symptom points to the possibility of an energy performance problem Symptoms could be observed by building operators or a contractor responsible for operations and maintenance, such as: o Boiler starts and stops frequently o Chiller operates when outside air temperature is low o Equipment operates during unoccupied hours o Exterior doors are hard to open or don't close securely o Mixed-air temperature is near outside-air temperature during heating mode o Return and/or exhaust fan does not shut off with supply fan o Space is too warm or cool o Static pressure in duct varies significantly during occupied hours o Supply-air temperature is high during warm weather o VSD does not vary the discharge-air fan speed

22 Example : MAT near OSAT while system in heating mode If the system is working properly, the Mixed Air Temperature (MAT) should normally be closer to the Return Air Temperature (RAT) (which is warmer) than to the Outside Air Temperature (OSAT). A depressed MAT as described above can force the heating system to expend more energy to reach the required SAT. The heated air available from the return air system is wasted to the outside. RA OSA MA Supply Air

23 Example : Possible problems Type Explanation Explanation Explanation Problem Problem Problem Problem Problem Problem Problem Problem Description System is controlling for humidity Normal condition during periods of low system air flow Normal condition if the system has a high percentage of OSA as part of the design SAT setpoints are overridden Miscalibrated or improperly located MAT sensor. Failed damper or actuator Stratified air in the mixed air plenum Return airpath is restricted by a mechanical or fire damper being closed Return air fan is not on or not operating at expected conditions Building is under negative pressure due to excessive exhaust or stack effect Building is under positive pressure due to failed AHU return fan

24 Example : Diagnostic steps Inspect the dampers and their operators when the condition occurs. Cycle the dampers via the DDC system and make sure they are responding properly and do not bind.

25 Example : Confirming the problem % 90 90% 80 80% 70 70% % 50% 40% Temperature ( F) Damper Position 30 30% 20 20% 10 10% 0 0% 6:00 7:00 8:00 9:00 10:00 11:00 12:00 13:00 14:00 15:00 16:00 17:00 18:00 19:00 20:00 Time MAT SAT OSAT RAT OSA Damper (%)

26 Example : Confirming the solution 100 Normal Operation % 90% 80% 70% Temperature ( F) Damper Positio n % 50% 40% 30% 20% 10% 6:00 7:00 8:00 9:00 10:00 11:00 12:00 13:00 14:00 15:00 16:00 17:00 18:00 19:00 20:00 Time MAT SAT OSAT RAT OSA Damper (%) 0%

27 Example : Chiller operating while OSAT is low Energy is wasted operating the chilled water system when airside economizers can be used for free cooling. This also reduces the life span of all operating equipment. Low loads on chillers can also cause refrigerant slugging within a chiller, which can ruin it, resulting in large repair charges.

28 Questions? BetterBricks Building Operations Program

29 The Goal: A Cycle of Continuous Improvement