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 MEDIUM HEATING COOLING 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 • Once you know your cost per square foot, try to subdivide these costs for heating, cooling and power • 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 Heating: 20% - 25% Cooling: 35% - 40% Electric: 35% - 40%
We are all in energy business Please tell me what is wrong with the next slide
How energy is wasted?? OAT: 45 Temp Set: 56 Actual Temp: 58 Mixed Air Temp: 54 Valve leak, Pre heat temp: 59 Overheating of air Cooling Valve: 42% open to cool air to set temp.
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 • Inefficient evaporator Evaporator approach: 47 – 34 = 13ºF. (>>2ºF) Chilled Water Delta T: 49 – 47 = 2ºF.
Typical Operating Log • Efficient Evaporator Evaporator approach: 42 – 41 = 1ºF. (<2ºF) Condenser approach: 92.2 – 82.1 = 10.1ºF. • 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. 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 Ideal Design Conditions 150 L/sec (2,400 gpm) 150 L/sec (2,400 gpm) 13°C (55.5°F) 55.5°F No Flow Through Decoupler 5°C (41°F) 5°C (41°F) 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)
Lost Chiller Capacity Due to Poor ΔT Case 1: Mixing Through Decoupler Line 75 L/sec (1,200 gpm) 150 L/sec (2,400 gpm) 9°C (48.25°F) 13°C (55.5°F) 75 L/sec (1,200 gpm) at 5°C (41°F) 5°C (41°F) 5°C (41°F) 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)
Lost Chiller Capacity Due to Poor ΔT Case 2: Poor Building Return Temperature 150 L/sec (2,400 gpm) 150 L/sec (2,400 gpm) 9°C (48.25°F) 9°C (48.25°F) No Flow Through Decoupler 5°C (41°F) 5°C (41°F) 150 L/sec (2,400 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)
Small Loss in ΔT Rapidly ReducesChiller Capacity At a design ΔT of 14.4°F:
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 Modification Existing control: Maintain water supply temperature from heat exchanger Additional control: Maintain HTHW return temperature Maintain Range Controller eg: 180 - 185ºF
~ 20F T New York Presbyterian Hospital • Applied revolutionary control logic Log Data
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 Chiller 3 used during peak Chiller 3 completely shut down, Chiller 1 efficiency increased, Chiller 2 operating hours decreased after modification Valve “OPEN” Valves “CLOSED” Valves “OPEN” After Modification Existing Pumps “ON” • What is the cost for this modification?? Nothing • What is the annual savings after modification??$190,000 Pump “OFF” After Modification Existing Pump “OFF”
Read your logs • What is your chilled water pump pressure drop? Benchmark Pressure Drop Chiller Plant: 45 ft. Building: 45-55 ft. Distribution: 50-80 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 Balancing is the biggest crime in a dynamic hydronic system
Biotech Firm – Action Taken Plant B 120 psi (Discharge) 21 psi (Suction)
Biotech Firm – Action Taken • Plant B • Found a bottleneck in the system.
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.
Zero Cost: $176,000 a year savings From: Paul Schwabacher [mailto:email@example.com] Sent: Monday, July 15, 2002 4:39 PM To: firstname.lastname@example.org; Santo Saglimbeni; email@example.com; Michael Shallo; Joseph R. Castellano Subject: 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.
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 firstname.lastname@example.org www.wmgroupeng.com