Use of Operational Data for diagnosing symptoms and

optimizing HVAC operation at Zero cost

Presented by: Hemant Mehta, P.E.

March 30, 2010

HVAC SYSTEM

HVAC

WATER/STEAM AIR

HEATING COOLING

MEDIUM

USES

Components of HVAC

• 3 components• Generation• Distribution• Utilization

• This presentation deals with how to optimize all components of HVAC system at zero cost.

Do you know your annual costs per square foot?

• You cannot manage without measurement.

• What is your annual fuel and power cost per square feet?

• If you have A research campus in North East, your annual cost for fuel and power should not be more than 6/square foot

• For a commercial property the cost should be less than $4/square foot

Do you know your annual costs per square feet?

• Actual annual costs of a research center (2009)• Gas $3,390,916 • Electric $4,086,465• Total Charges $7,477,381 • Gross Square Feet 1,491,418

• Cost/SQFT $5.014 • Cost / MMBTU $11.193

Let your fingers do the savings

• Electrical and cooling costs are around 75% to 80% of your annual costs.

• If heating cost is more than benchmark of say 20% to 25% then something is wrong

Cooling: 35% - 40%

Heating: 20% - 25%

Electric: 35% - 40%

• Once you know your cost per square foot, try to subdivide these costs for heating, cooling and power

We are all in energy business

Please tell me what is wrong with the next slide

Case: Air flow through AHU

How energy is wasted??OAT: 45

Temp Set: 56

Actual

Temp: 58

Cooling Valve: 42% open to cool air to set temp.

Valve leak, Pre heat temp: 59

Mixed Air Temp: 54

Overheating of air

Read your logs -Temperatures

• What is your short temperature difference?

• The chillers installed during the past 10 years are designed for less than 2 degree difference between refrigerant temperature and water temperatures.

• More than 2 degree differential indicates inefficiencies.

– Possible causes… Inadequate refrigerant Foul tubes Inadequate flow

Evaporator approach

• The temperature difference between the leaving chilled water and the refrigerant temperature

• Nominal: 2 deg F• Questionable: 4 deg F• Bad: 6 deg F or higher

Condenser approach

• The temperature difference between the leaving cooling water and liquid refrigerant.

• Nominal: 2-3 deg F• Questionable: 4-5 deg F• Bad: 6 deg F or higher

Refrigerant Charge & Approach

• Approach increases when the unit is either overcharged or undercharged.

Typical Operating Log

Evaporator approach: 47 – 34 = 13ºF. (>>2ºF)

Chilled Water Delta T: 49 – 47 = 2ºF.

• Inefficient evaporator

Typical Operating Log

Evaporator approach: 42 – 41 = 1ºF. (<2ºF)

Condenser approach: 92.2 – 82.1 = 10.1ºF.

• Efficient Evaporator

• Inefficient Condenser

Read your logs

• What is your condenser water temperature and flow?• The chillers are designed for 85 degree temperature for

peak load.• Many chiller plants are designed for 2 gpm/ton - Trane

Recommendations• Peak load happens for only 200 hours a year. Additional cooling tower capacity is available for use.• Lower condenser water temperatures and/or higher flow will improve efficiency and reduce operating costs.

Chiller Performance at varying ECWT

0.4

0.6

0.8

1

1.2

1.4

1.6

85 83 81 79 77 75 73 71 69 67 65

Entering Condenser Water Temperature, deg F

kW/T

on

100%

90%

80%

70%

60%

50%

40%

30%

20%

Load %

Read your logs

• What is your chilled water delta T?• Poor chilled water Delta T reduces chiller operating

capacity and forces operation of additional equipment.

• Use of additional equipment further reduces operating efficiencies.

• You may not be able to improve the delta T overnight

• However, you can always increase the flow through chiller to compensate for low delta T and increase the chillers operating capacity.

• Always try to operate chillers at 70% or higher loading

Lost Chiller Capacity Due to Poor ΔT

5°C (41°F)

No Flow Through Decoupler

55.5°F

5°C (41°F)

13°C (55.5°F)

150 L/sec (2,400 gpm)

150 L/sec (2,400 gpm)

150 L/sec (2,400 gpm)

150 L/sec (2,400 gpm)

Chiller sees a ΔT of 8°C (14.5°F) at a flow of 150 L/sec (2,400 gpm)The chiller capacity is therefore 5,000 kW (1,450 tons)

Ideal Design Conditions

Lost Chiller Capacity Due to Poor ΔT

5°C (41°F)

9°C (48.25°F)

5°C (41°F)

13°C (55.5°F)

75 L/sec (1,200 gpm)

150 L/sec (2,400 gpm)

75 L/sec (1,200 gpm)

150 L/sec (2,400 gpm)

Chiller sees a ΔT of 4°C (7.25°F) at a flow of 150 L/sec (2,400 gpm)The chiller capacity is therefore 2,500 kW (725 tons)

Case 1: Mixing Through Decoupler Line

75 L/sec (1,200 gpm)

at5°C (41°F)

Lost Chiller Capacity Due to Poor ΔT

5°C (41°F)

No Flow Through Decoupler

5°C (41°F)

150 L/sec (2,400 gpm)

150 L/sec (2,400 gpm)

150 L/sec (2,400 gpm)

150 L/sec (2,400 gpm)

Case 2: Poor Building Return Temperature

Chiller sees a ΔT of 4°C (7.25°F) at a flow of 150 L/sec (2,400 gpm)The chiller capacity is therefore 2,500 kW (725 tons)

9°C (48.25°F) 9°C (48.25°F)

Small Loss in ΔT Rapidly ReducesChiller Capacity

At a design ΔT of 14.4°F:

Chiller Capacity

0%

20%

40%

60%

80%

100%

78.51011.51314.5

Delta T, deg F

Chi

ller c

apac

ity

How do you improve delta T?• Controlling the chilled water flow through the

chillers

• Use of new control technology at AHUs.

Control Logic

• Master Control Maintain HX water supply temperature or steam

pressure by modulating HTHW water control valve.

• Sub Master Control Maintain HTHW return temperature and float HX

water supply temperature or steam pressure. The amount of float depends on requirements at users. i.e. animal room vs. class room vs. office space.

Control ModificationExisting control: Maintain water supply temperature from heat exchanger

Additional control: Maintain HTHW return temperature

eg: 180 - 185ºFControllerMaintain Range

• Applied revolutionary control logic

New York Presbyterian Hospital

Log Data ~ 20F T

PA State Capitol Complex – CHW ΔT

Field Implemented Improve CHW Operation: Wyeth Bio-TEch• Original design for 1 primary pump per chiller

• Actual operation: standby pump operating at all times

• Operating more pumps increases the flow through the chillers decreasing delta T and chiller performance.

• Flow reduction by 1/3 increased delta T and chiller efficiency.

• The increased efficiency allows the chiller to consume less energy and the increased capacity allows less chillers to run saving more energy.

Field Implemented Improve CHW Operation: Wyeth Bio-Tech

Existing Pumps “ON”

Existing Pump “OFF”

Valves “CLOSED”

Pump “OFF” After Modification

Valves “OPEN” After Modification

Valve “OPEN”

Chiller 3 used during peakChiller 3 completely shut down, Chiller 1 efficiency increased, Chiller 2 operating hours decreased after modification

What is the cost for this modification?? Nothing

What is the annual savings after modification??$190,000

Read your logs

• What is your chilled water pump pressure drop?

Balancing is the biggest crime in a dynamic hydronic system

Benchmark Pressure Drop

Chiller Plant: 45 ft.

Distribution: 50-80 ft.

Building: 45-55 ft.

– Total pumping head during peak load should not be more than 180 feet to 200 feet.

– Higher pressure drop than bench mark indicates additional resistance

Plant B

21 psi (Suction)

120 psi (Discharge)

Biotech Firm – Action Taken

Plant B• Found a bottleneck in the

system.

Biotech Firm – Action Taken

AMGEN From ClientLocation HP Voltage Kw Description Hours per Year KwH per Year Price per KwH Power Factor Annual

Savings

B29100 480 74.6 B29 P-01 8760 653,496 0.12 0.85 $ 92,258 100 480 74.6 B29 P-02 8760 653,496 0.12 0.85 $ 92,258 100 480 74.6 B29 P-03 8760 653,496 0.12 0.85 $ 92,258

B2540 480 29.84 B25 P-01 8760 261,398 0.12 0.85 $ 36,903 40 480 29.84 B25 P-02 8760 261,398 0.12 0.85 $ 36,903 40 480 29.84 B25 P-03 8760 130,699 0.12 0.85 $ 18,452

B30150 480 111.9 B30 P-5251 8760 980,244 0.12 0.835 $ 140,873 150 480 111.9 B30 P-5252 8760 980,244 0.12 0.835 $ 140,873 150 480 111.9 B30 P-5253 8760 490,122 0.12 0.835 $ 70,437

B38 30 480 22.38 B38-08-P1 8760 98,024 0.12 0.85 $ 13,839 30 480 22.38 B38-08-P2 8760 98,024 0.12 0.85 $ 13,839

B27 20 480 14.92 B27-01 8760 130,699 0.12 0.85 $ 18,452 20 480 14.92 B27-02 8760 130,699 0.12 0.85 $ 18,452

B14 50 480 37.3 B14-CW-P0001 8760 326,748 0.12 0.83 $ 47,241 50 480 37.3 B14-CW-P0002 8760 326,748 0.12 0.83 $ 47,241

B15 60 480 44.76 B15 -P001 8760 392,098 0.12 0.85 $ 55,355 60 480 44.76 B15 -P002 8760 392,098 0.12 0.85 $ 55,355

B33 7.5 480 5.60 B33 -P01 8760 49,012 0.12 0.83 $ 7,086 7.5 480 5.60 B33 -P02 8760 49,012 0.12 0.83 $ 7,086

B3240 480 29.84 B32-P001 8760 261,398 0.12 0.902 $ 34,776 40 480 29.84 B32-P002 8760 261,398 0.12 0.902 $ 34,776 40 480 29.84 B32-P003 8760 261,398 0.12 0.902 $ 34,776

Total 1,325 7,841,952 $ 1,109,488

Boilers

• Stack Temperature− Stack temperature for boilers should commonly lie in

range of 300 – 350 ºF− A high stack temperature may suggest the building up of

soot or scale inhibiting the heat transfer or the rupture in a refractory baffle wall.

From: Paul Schwabacher [mailto:pschwaba@nyp.org]Sent: Monday, July 15, 2002 4:39 PMTo: hmehta@wmgroupeng.com; Santo Saglimbeni; martray@nyp.org; MichaelShallo; Joseph R. CastellanoSubject: Re: Economizer is working.

Thanks everyone, this is great news. 3.2% improvement x $5.5 million annual gas expense will save $176,000 a year. Not bad for closing a damper.

Ray: Please keep damper manually closed at all times and monitor flue gas temperature. We should only be using boilers that have functioning economizer -- other boilers should be for stand-by only.

Mehta: is there any risk of sulfur or acid condensing when burning gas?Joe & Mike: Please track list of energy conservation measures completed and planned w/estimated savings.

Zero Cost: $176,000 a year savings

HVAC – Case Study

• Steam trap survey along with a regularly scheduled testing schedule during 2007 retro-cx

• Location: The Vanguard Chelsea

• High Rise Residential Building survey of only common area steam traps in the basement resulted in annual energy savings of approx.$11,000 with payback period of 4 months.

HVAC – Case Study

• During 2007 Retro-cx• Location: The Vanguard

Chelsea• Installing variable

frequency drive on cooling tower that was previously a constant speed fan resulted in annual savings of $22,000 with a payback period of 6 months

HVAC – Case Study

• Resetting domestic hot water set point from 135 F to 120 F

• Location: The Vanguard Chelsea

• Results: Annual Energy Cost Savings of $10,000 with no implementation cost, done by in-house staff.

HVAC Practical Examples

• Installation of Carbon Monoxide Sensor for operation of indoor garage exhaust

• Location: Dish Network Satellite office

• Results: Annual Energy Savings of $2,500 and payback period of 1 months

HVAC – Case Study

• Replacing faulty sensor on rooftop unit that was preventing unit from operating economizer mode during 2009 retro-cx – outside air dampers were fully open all the time.

• Location: Fordham University

• Results: Annual Energy Cost Savings of $37,600 with payback period of 1 month

HVAC – Case Study

• Conversion of dual duct air system to variable air volume system, per air handler, during 2009 retro-cx

• Location: Fordham University

• Results: Annual Energy Cost Savings of $20,000 to $80,000 with average paypack period of 4 ½ years

HVAC – Case Study

• Installation of demand control ventilation system on air handlers

• Location: Fordham University

• Results: Annual Energy Cost Savings of $135,000 with average payback payback of 4 ½ years

HVAC – Case Study

• Increasing chilled water set point from 42 F to 45 F to match chilled water coil design inlet temperatures on air handlers

• Location: Fordham University

• Results: Annual Energy Cost Savings of $9,000 with no implementation cost, done by in-house staff

HVAC – Case Study

• Replacing chilled water valves that were leaking by – in two campus buildings during retro-cx 2009

• Location: Fordham University

• Results: Annual Energy Cost Savings of $41,000 with paypack period of 2 months

HVAC – Case Study

• Temperature calibration of faulty thermostat on fan coil units

• Location: Fordham University

• Results: Annual Energy Cost Savings of $11,500 with paypack period of 2 ½ months

HVAC – Case Study

• Implementation of outside air / hot water reset schedule on existing building management system

• Location: Fordham University

• Results: Annual Energy Cost Savings of $92,000 with payback period of 3 months

Summary

• You as a facility manager are too busy to take care the needs of your bean counters

• You must empower your plant operators.• It is not difficult to change their culture by teaching.• This will only make them proud of their work.• Hire an expert if you have to.• Teach them to read what they record on logs.• As engineers we can really make a difference• Go bust energy and make our planet better for our

kids

Thank You

Hemant Mehta, P.E.President

WMGroup Engineers, P.C.(646) 827-6400

hmehta@wmgroupeng.comwww.wmgroupeng.com