7/15/2002PP.AFD.09 1 of 43 Yaskawa Electric America Variable Frequency Drives In HVAC Applications

7/15/2002PP.AFD.09 2 of 43 Energy Savings Methods Energy Savings Methods Variable Frequency Drive Basics What is an Variable Frequency drive? How do variable frequency drives saves energy? Variable Frequency Drive Applications in Buildings Where are the opportunities for applying drives and energy efficient motors? Estimating Savings How do you protect yourself from overly optimistic payback calculations?

7/15/2002PP.AFD.09 3 of 43 Variable Frequency Drive Basics Control Speed Control Torque

7/15/2002PP.AFD.09 4 of 43 Variable Frequency Drive Basics Frequency Controls Motor Speed Speed adjusts as required by the fan or pump application Speed (RPM) % Frequency (Hz)

7/15/2002PP.AFD.09 5 of 43 Variable Frequency Drives Save Energy Affinity Laws Volume 1 / Volume 2 = RPM 1 / RPM 2 Pressure 1 / Pressure 2 = (RPM 1 / RPM 2 ) 2 HP 1 / HP 2 = (RPM 1 / RPM 2 ) 3 Example Reduces speed 25% CFM reduced by 25% Horsepower reduced by 57%

7/15/2002PP.AFD.09 6 of 43 Drive Applications in Buildings Fan Control Pump Control Cooling Tower Control

7/15/2002PP.AFD.09 7 of 43 Drive Applications in Buildings Why Apply Variable Frequency Drives to Fans Comparison of Fan Controls Cost Comparison of Fan Controls Installation

7/15/2002PP.AFD.09 8 of 43 Why Apply Variable Frequency Drives to Fans? Significant Energy Savings: 20% to 50% Low Maintenance: No mechanical linkages or controls to wear out Reduces Noise Level: Slower speed = less noise Reduces Inrush Current: Reduces demand charge

7/15/2002PP.AFD.09 9 of 43 Comparison of Fan Controls Controlling Air Volume - System Overview

7/15/2002PP.AFD of 43 Comparison of Fan Controls Outlet Dampers Inlet Guide Vanes Variable Frequency Drives

7/15/2002PP.AFD of 43 Comparison of Fan Controls Metal plates positioned in the air stream on the outlet side of fan Air volume controlled by opening or closing the damper Fan operates at a constant speed Outlet Dampers Volume (%)

7/15/2002PP.AFD of 43 Comparison of Fan Controls Adjustable vanes positioned in the fan inlet Air volume controlled by altering the vane position Fan operates at a constant speed Inlet Guide Vanes Volume (%)

7/15/2002PP.AFD of 43 Comparison of Fan Controls Variable frequency drive operates the fan motor Adjusts speed to meet volume needs Energy is not waste since motor operates only at required speed Variable Frequency Drives Volume (%)

7/15/2002PP.AFD of 43 Comparison of Fan Controls Input Power Comparison Outlet Dampers Inlet Guide Vanes Variable Frequency Drives

7/15/2002PP.AFD of 43 Cost Comparison of Fan Controls 100,000 sq. ft. building with 4000 hours annual operation. (Two 30 HP supply fan motors) Based on EPRI procedures for estimating energy savings from the application of a drive KWH

7/15/2002PP.AFD of 43 Drive Installation Apply only to systems that vary air flow (Variable Volume System) Lock existing controls in open position Use existing controls to operate Pneumatic control with pressure to electrical transducer Static pressure or temperature transducer Building Automation System Install sensor as far away as possible

7/15/2002PP.AFD of 43 Problems Heat – 120 F (40 C ) maximum Moisture - 90% relative humidity, non-condensing Cold - 14 F (-10 C) Solution Locate indoor Locate in return air stream of rooftop unit Drive Installation Packaged Rooftop Applications

7/15/2002PP.AFD of 43 Drive Installation VDC, mA signal System faults (i.e. fire and freeze state) Serial Communication Operation Tips Drive and BAS both have accel/decel rates Supply fan can effect return fan Reset static pressure control point Building Automation System

7/15/2002PP.AFD of 43 Drive Installation Set Point Effect Minimize static pressure set point to maximize savings The impact of the set point on savings is greater, the lower the system modulates If possible, reset static pressure set point as volume (and friction losses) decrease

7/15/2002PP.AFD of 43 Drive Installation Volume % Static Pressure A D C B Set Point Modulation Curve Lost Saving Opportunity Fan Law Curve Set Point Effect

7/15/2002PP.AFD of 43 Drive Installation Rules Isolate load side conductors (drive to motor) in a dedicated metal conduit Do not run control wiring in the same conduit as the line or load side conductors Do not rely on the metal conduit as a ground, run a separate ground to the drive Protected environment

7/15/2002PP.AFD of 43 Pump Control Why Apply Variable Frequency Drives to Pumps Comparison of Pump Controls Cost Comparison of Pump Controls Installation

7/15/2002PP.AFD of 43 Why Apply Variable Frequency Drives to Pumps? Significant Energy Savings Savings depends on static head of system Soft Start Reduces water hammers Less stress on seals Noise Reduction: Slower speed = less noise

7/15/2002PP.AFD of 43 Comparison of Pump Controls Throttling System Bypass Valve Variable Frequency Drive

7/15/2002PP.AFD of 43 Comparison of Pump Controls Control valves, like output dampers on fans, add resistance to a system Pumping pressure increases as volume decreases Pump runs at a constant speed Throttling System

7/15/2002PP.AFD of 43 Comparison of Pump Controls The same amount of water is pumped regardless of the need for cooling Pump speed is constant Bypass valve modulates in response to pressure changes to maintain constant pressure on pump Bypass Valve

7/15/2002PP.AFD of 43 Comparison of Pump Controls Can be controlled to maintain pressure or flow Energy saving is substantial at reduced speeds Throttling valve not needed Bypass set at minimum for chiller protection Variable Frequency Drive

7/15/2002PP.AFD of 43 Comparison of Pump Controls Throttling vs. Variable Frequency Drive

7/15/2002PP.AFD of 43 Comparison of Pump Controls Input Power Comparison

7/15/2002PP.AFD of 43 Cost Comparison of Pump Controls 100,000 sq. ft. building operated 4000 hours per year. (One 50 HP pump) Based on EPRI procedures for calculating energy savings from the application of a drive KWH

7/15/2002PP.AFD of 43 Installation Opening throttling valve Set minimum speed on drive to assure flow Locate sensor as far away as possible Minimum position on bypass valve Protect the chiller Increase pump savings Connecting to Building Automation System VDC, mA signal Safety faults (i.e. fire and freeze state) Programming concerns (Accel and decel) Serial communication

7/15/2002PP.AFD of 43 Cooling Tower Control Why Apply Variable Frequency Drives to Cooling Towers Comparison of Cooling Tower Control Cost Comparison Installation

7/15/2002PP.AFD of 43 Why Apply Variable Frequency Drives to Cooling Towers? Savings Electrical consumption and demand Water consumption Better control of return temperature, increases chiller efficiency Reduces noise, slower speed = less noise Reduces maintenance Soft starting reduces mechanical stress to gear box and belts Less water = longer lasting media

7/15/2002PP.AFD of 43 Control Comparison of Cooling Towers Single tower control On/Off Two speed motor Two fan cooling tower with two speed motors

7/15/2002PP.AFD of 43 Control Comparison of Cooling Towers Single Tower On/Off Control vs. Variable Frequency Drives On/Off Control 80 Wet Bulb Temp Condenser Water Temp Variable Frequency Drive 60

7/15/2002PP.AFD of 43 Control Comparison of Cooling Towers Single Tower On/Off Control vs. Variable Frequency Drives 80 Wet Bulb Temp Condenser Water Temp Variable Frequency Drive Low Speed High Speed 60

7/15/2002PP.AFD of 43 Control Comparison of Cooling Towers Two - Two Speed vs. Variable Frequency Drives Wet Bulb Temp Condenser Water Temp 82 Variable Frequency Drive Low High Low High

7/15/2002PP.AFD of 43 Cost Comparison of Cooling Tower Controls Comparisons are not simple Every building’s operation costs are different Operation costs are dictated by weather and building utilization Savings comparisons should include increases to the chiller efficiency

7/15/2002PP.AFD of 43 Drive Installation Control return water temperature or refrigerant head pressure Location concerns Consider motor replacement On/off and two speed duty cycling strain motor insulation BAS system Condenser water reset increases savings up to 20% of chiller consumption as condenser water approaches 65 F

7/15/2002PP.AFD of 43 Estimating Savings Methods and required information Reviewing the results Combining energy efficient motors and drives Energy Savings Predictor Program (ESP)

7/15/2002PP.AFD of 43 Methods and Required Information Hand Calculations Rule of thumb for approximate figures Motor HP, type of control, hours of operation Simplified Prediction Programs Energy Savings Predictor (ESP) Voltage, building operation profile Simulation Programs Blast, DOEII, and Trace Weather data, detailed building description, building utilization profile, equipment specifics

7/15/2002PP.AFD of 43 Reviewing the Results Simplified prediction programs Correct operating profile Assuming a large number of operating hours at low flow will bias results Basics for calculations Strictly fan laws or empirical data Consideration of your system limits Static pressure setting effects Static head pressure/minimize pump speed

7/15/2002PP.AFD of 43 Energy Savings Predictor (ESP) Conservative Uses EPRI developed building profile Uses empirical results from EPRI Economic calculations Simple payback Internal rate of return Simple personal computer program

7/15/2002PP.AFD of 43 Energy Efficient Motors and Drives Always consider motor replacement when adding a drive Added savings Older motor may have insulation breakdown Payback of combination may be better than the drive only and is better than motor only