auditing commercial refrigeration - kw engineering · auditing commercial refrigeration what to...

Auditing Commercial Refrigeration What to Look for?

Steve Rottmayer P.E.

© 2013 kW Engineering, Inc.

Q: Why is this sector important? A: Grocery has the highest energy intensity

Grocery stores and food service have

higher end use intensities (kWh/sf)

than any other common

commercial building type.

- 10 20 30 40 50 60

Grocery

Food Service

Health Care

Other

Office

Public Order and Safety

Retail

Lodging

Public Assembly

Education

Service

Warehouse

Religious Worship

Energy Use Intensity (kWh/sf)

Commercial Building Stock Energy Use


Source: 2003 Commercial Building Energy Consumption Survey (CBECS),

U.S. DOE, www.eia.doe.gov/emeu/cbecs/.

Refrigeration End Use in Grocery Stores

• Refrigeration is largest end use by far in grocery stores

• Typical use is over 50% of store’s total


Source: 2006 Commercial Building Survey Report, Pacific Gas &Electric.

Vapor Compression Cycle


Fuller Moore, Environmental Control Systems, McGraw Hill Inc., 1993, pg 220.

www.dataaire.com

Efficient Refrigeration Guiding Principles 1. Minimize loads from

infiltration, defrost, lighting and motors

2. Maintain lowest possible head pressure

3. Maintain highest possible suction temps and maximize compressor efficiency


www.copeland-corp.com

low pressure

in

high pressure

out

Avoid lowest common denominator operation.

Use the capabilities of your system & controls!

Principle 1 – Minimize Loads • Strip Curtains • Glass Doors and Night Covers • Door Gaskets and Auto Closers • Case Loading • Insulate Suction Lines


• Evaporator Fan Controllers • High Efficiency Evaporator Fan Motors • Anti-sweat Heater Controls • Defrost Controls • Case-lighting Controls • High Efficiency Case Lighting

Refrigerated Case Airflow


Improper Case Loading


SOURCE: PROPER PRODUCT LOADING IN DISPLAY CASES IMPACTS FOOD SAFETY AND ENERGY EFFICIENCY, Southern California Edison Refrigeration Technology and Test Center, Energy Efficiency Division

Night Covers • Helps reduce infiltration &

radiation heat losses when store is closed

• Made with durable materials

• Helps maintain product temperatures

• Savings require that employees use them!


SOURCE: Market Group Ventures Inc. 1-800-519-1222 www.econofrost.com

http://www.econofrost.com/�

Night Covers: Savings & Benefits


SOURCE: Effects Of The Low Emissivity Shields On Performance And Power Use Of A Refrigerated Display Case, Southern California Edison Refrigeration Technology and Test Center, Energy Efficiency Division, Aug 8, 1997

Overall Compressor Savings were about 9% of daily use or 36% of load when covers were used.

Check defrost time clocks! • Don’t defrost more often than necessary • Don’t defrost during the peak energy use

periods – 12 to 6pm


Example of Over-Defrosting • Customer was defrosting – 4 times/day for 70

minutes each • Freezer temperature hit 50°F • Reset to 4 times/day for 15 minutes each • Energy Savings = 79% or $820/year


Anti-sweat Heater Controls • Electric resistance

heaters in the doors of freezer cases that use heat to prevent fogging of case door windows

• Often run continuously

• 10 to 20 kW is typical


Anti-sweat Control – Costs & Savings • Simple paybacks are in the range of

6 months to 3 years • Savings depend on climate, with dry areas

having greater opportunity for savings than humid areas.

• Typical anti-sweat cycling savings can range from 20% to 80% of the anti-sweat heater load plus associated refrigeration system savings

• May have significant peak kW savings if the summer peak is not humid. Throughout most of the western U.S. the electrical system peak is not usually coincident with humid weather.


Case-lighting Controls • Cases are typically

illuminated continuously • In most stores these lights

are on one or two electrical panels

• Adding controls to turn off the case lights at night is very cost effective. It not only reduces the amount of energy the lights consume, but also reduces the amount of heat that is added to the cases by the lights.


Case-lighting Controls – Costs & Savings • Typical savings are 25% of the

case lighting load • Plus refrigeration load • May amount to 5% to 7% of

the overall refrigeration load at the store

• Typically 70,000 kWh • No associated peak demand

savings with case lighting controls.

• Inexpensive to implement - $2000 to $8,000 per store

• Simple paybacks 0.2 to 2 yrs


Case lighting alternatives

• Number of manufacturers now coming out with LED products

• Save lighting and cooling energy • Dimmable • Long lifetimes


www.gelcore.com

Case Study – LEDs w/ Occ Sensors


Source: LED Freezer Case Lighting Systems, Dave Bisbee, CEM, SMUD, July 25, 2008.

Monitored Results - LEDs and Occupancy Sensors


Source: LED Freezer Case Lighting Systems, Dave Bisbee, CEM, SMUD, July 25, 2008.

Energy Efficiency – Principle 2 Principle 2 • Clean Condensing Coils • Verify Set-points and Sensor Calibration • Evaporative Pre-cooling • Minimize Head Pressure • Floating Head Pressure Controls • Heat Reclaim


Presenter

Presentation Notes

Why are we here? “Packaged units represent cooling for 49% of commercial buildings space” Esource

Typical Air-cooled Control Strategies 1. Interlock with compressor

(simplest – self contained) 2. Fixed pressure

(e.g. dead band around setpoint) 3. Linear reset, e.g.

4. Floating head pressure


OAT Number of Fans

67 1

72 2

77 3

82 4

Typical Condenser Fan Controls: Evaporative • Indirectly sets

system head pressure

• Two-speed fans are typical

• Set manually with pressure switches or temperature controls (sump temp or dew point)


Low-cost EEM’s: Minimize Head Pressure • Keep condensers clean and clear

from obstructions • Verify setpoints of controllers &

check for successive fan operation • Verify sensor calibration • Make sure VFD’s are not bypassed

and are unloading when they should


Floating Head Pressure Controls • Head pressure is allowed

to “float” to a lower level • Control the fans to

maintain a fixed approach at the condenser: – Low temp systems:

target ΔT of 8°F to 12°F – Medium temp:

target ΔT of 10°F to 15°F.

• Trade off condenser fan energy for compressor energy savings


Floating Head Pressure - Costs & Savings • Savings range from 3% to

10% of refrigeration system use

• Savings vary depending on – previous condenser fan

control strategy – heat reclaim – sub-cooling – condenser capacity

• If condensers are undersized for refrigeration loads, savings may be minimal

• Paybacks 1 to 4 years


Source: P Cuneo, Source for HVAC and Refrigeration.

Energy Efficiency – Principle 3 Principle 3 • Check Refrigerant Lines • Maximize Suction Pressure • Floating Suction Pressure Controls • Mechanical sub-cooling • Multiplex systems conversion • High Efficiency Compressors • Variable Frequency Drives on Compressors


Presenter

Presentation Notes


Typical Suction Controls • Suction pressure sets

temp that system can serve

• Fixed pressure setpoint – compressor cycles on when suction pressure rises

• Manual setting • Used for staging in

parallel systems • Can be set lower than

necessary by techs and forgotten


Check refrigerant level and recharge


If the sight glass is clear there is a full charge.

If the system needs service, hire a professional.

If the sight glass has bubbles or foam during normal operation (not startup), call a technician

If the indicator turns pink, you have moisture in the refrigerant

Check refrigerant lines for icing


call service company if ice is present.

Suction Pressure Commissioning • Pressure switches at the

compressors are often old and difficult to set precisely

• Often the pressure setpoints are unnecessarily low to avoid complaints

• Set suction setpoints as high as possible to meet the needs of the circuit


Post Avg Suction 16 psig

Post Avg SST -22°

Pre Avg Suction 8 psig

Pre Avg SST -35°

Suction Pressure Cost & Savings • Savings in the range of 1%

to 5% of the total refrigeration system energy

• Savings are approximately 2% gain in efficiency for each 1°F rise in suction temperature

• Demand impacts are relatively small but they exist - about 1% to 2% of total refrigeration system demand © 2013 kW Engineering, Inc.

General Replacement Guide: CFC to an HCFC CFC or HCFC to an HFC

2011


References and Resources • Compressor performance at

www.emersonclimate.com • Benchmark at:

poet.lbl.gov/cal-arch • Summary of measures and tools

www.focusonenergy.com/Business/Commercial-Business/Grocery

• www.refrigeration-engineer.com Good discussions on diagnostics © 2013 kW Engineering, Inc.

Presenter

Presentation Notes


http://www.emersonclimate.com/�

http://poet.lbl.gov/cal-arch�

http://www.focusonenergy.com/Business/Commercial-Business/Grocery�

http://www.focusonenergy.com/Business/Commercial-Business/Grocery�

http://www.refrigeration-engineer.com/�

Thanks! Any Questions?


auditing commercial refrigeration - kw engineering · auditing commercial refrigeration what to...

Documents