Course # W 51 HVAC Motor Control Solutions

Presenter: John Polites - Automation Engineer

Wednesday, May 3rd - 9:00 AM – 10:00 AM

State College Room

Topics of Discussion:– Motor Load & Starting Methods – Motor Control for HVAC Applications– Energy Savings with Variable Frequency Drives– Introduction to PF400 HVAC Drive

AC MOTOR LOADS

– Constant Torque

– Variable Torque

– Constant Horsepower

AC Motor Load Types

Constant Torque Motor Loads

Variable Torque Motor Loads

• Typical of Centrifugal Pumps and Fans• Pumps: Hot Water, Chilled Water, Condenser

Water, Distribution• Fans: Supply, Return, Relief, Exhaust, Cooling

Tower Fans• Torque and Horsepower Drops As Square of Speed

Reduction; • Excellent Potential for Energy Savings with a VFD versus a

throttling Valves, Dampers or Inlet Vanes

Variable Torque Application Types

Two Pump Types:

• Positive Displacement Pumps

• Move fluid chamber to cause fluid to flow

• Constant Torque Load Profile

• Centrifugal Pumps

• Move fluid by rotation of an impeller

• Variable Torque Load Profile

• Hydronic Pumps: Hot Water, Chilled Water, Condenser Water &

Distribution

HVAC Pump Types

Components of the Pump System

• Pump• Motor• Coupling• Base Plate• Piping• Valves• Inlet Source

– Above Pump– Below Pump

• Discharge Static Head

Pump Type and Applications

HVAC Systems

• The purpose of an HVAC (heating, ventilating, and air-conditioning) system is to provide and maintain environmental conditions within an area called the "conditioned space."

• The commercial system selected for a particular application should endeavor to provide the optimum environment for employee comfort and productivity, process function, and good indoor air quality with energy efficiency and cost-savings

HVAC Systems

• Air Handling Systems– Air Handling Units (AHU), Rooftop Units (RTU), Makeup Air Units

(MUA), Exhaust Fans (EF), Variable Air Volume Boxes (VAV),,fan unit (FU)

• Hydronic Systems– Chilled Water (CHW) – [Chillers and Pumping Packages]– Condenser Water (CW) – [Cooling Towers]– Hot Water (HW) - [Boilers and Pumping Packages]

• Building Automation System (BAS)– HVAC Controls, Direct Digital Controls (DDC), Energy Management

System (EMS), Facility Management System (FMS)

Types of HVAC Systems

HVAC Motor Control (Starters or VFDs)

Typical Commercial HVAC Systems

Supply fan will be controlled by PF400

Controllers measure Static Pressure and send speed signals to both VFD’s

VAV boxes located in each

room distribute conditioned airReturn fan will be controlled by PF400

Traditional Variable Air Volume (VAV) Air Handling Unit

These motors are controlled by a Variable Frequency Drive

Variable Frequency drives Replace the wasteful Check valve system

Chilled Water Pumping System

Valves replaced when drives are used

Motors controlled by VFD’s in new applications

Condenser Water Pump System

NC

NETWORK CONTROLLER

TYPICALLY MOUNTEDIN NETWORK CLOSET

ETHERNETFIELD BUS

BAS SERVER

BAS OWS

BAS PRINTER

BUILDINGLOCAL AREA

NETWORK

ASC APPLICATION SPECIFIC CONTROLLER(HOT WATER SYSTEM)

ASC

ASC

ASC

ASC

APPLICATION SPECIFIC CONTROLLER(CHILLED WATER SYSTEM)

APPLICATION SPECIFIC CONTROLLER(AIR HANDLING UNITS)

APPLICATION SPECIFIC CONTROLLER(ROOFTOP UNITS)

APPLICATION SPECIFIC CONTROLLER(VARIABLE VOLUME BOXES)

Building Automation Systems (BAS)

> Controllers Send Output Commands to VFDs and Motor Starters: Start/Stop Control & Speed Commands

> Run/Fault Commands Sends Status Commands for Starter Device to Controllers.

• A pressure sensor within an air duct or pipe measures the system pressure

• As the pressure changes an analog signal is sent to the BAS

• The BAS sends a start stop and speed command to variable frequency drives (VFDs) or motor starters

• When valves and dampers close, the pressure rises in the ducts or pipes, which reduces the speed

Basic BAS Systems Control Strategies

• This is a typical view on a building automation computer screen showing the status of various points in an air handling system

Building Automation System Graphic

Motor Starting Methods

• Full Voltage Starting

• Reduced Voltage Starting– Wye - Delta Starters– Autotransformer – Soft Starters

• Variable Frequency Drives

Types of HVAC Motor Starting Methods

SMC-Flex

Full Voltage Starting

• Full Voltage Starting Characteristics– Contacts close immediately supplying full line

voltage to motor.• Advantages:

– Lowest starter cost– Simple starter designs

• Easy to maintain and troubleshoot• Disadvantages:

– Inrush Current• 6-10 times rated running current• Issue when peak demand charges are

enforced by utilities– Initial Torque

• Mechanically hard on system• Reduced life of belts, gears

DisconnectDisconnect

FusesFuses

ContactorContactor

Overload Overload RelayRelay

L1 L2 L3

T1 T2 T3

NEMA Rated

ServiceabilityContacts Replaceable Flexible Overload Selection

Emphasis on:

IEC RatedEmphasis on:ReplacementContacts only replaceable on large sizes onlyConserve panel spaceClass 10 Overload Protection

IEC & NEMA Motor Starters

SMC-Flex

Use SCR’s to ramp voltage supplied to motor over a user defined time period

Advantages:• Reduces inrush current• Reduces starting torque• Reduces mechanical stress on motor & loads

Solid State Soft Starters

Reducing the VoltageReducing the Voltage

Reduces the CurrentReduces the Current

Reduction In Torque!!Reduction In Torque!!

LRT

100%

100%0Percentage of Full Speed

(.5)2 = .25 or 25%

Soft Starter Speed Torque Curve

Manual Starters

• Range Overview– 1HP, 115, 230, 277 VAC – 0.75 HP, 115/230 VDC– 1 or 2 Pole– Thermal Overload

• Ideal for small Fan and Pump Applications

Commercial OEM Products

Adjustable Speed Drives

Solid State AC Variable Frequency = Variable Speed

AC Motor

DC Bus

AC InputFixedFrequency

InverterConverter AC OutputVariableFrequency

Variable Frequency Drives Basics

Benefits• Solid state technology• Wide control options• Small size power units• Good efficiency• Lower cost, smaller motors• Retrofit existing motors• Bypass capability

460

60

Hertz

230

Volts

MaxFrequency

30

Voltage Hertz Motor RPM

0 0 0

115 15 438

230 30 875

345 45 1313

460 60 1750

Base Voltage

Base Frequency V/Hz

460 60 7.67

230 60 3.83

208 60 3.47

• To improve process control though speed and torque control

• To improve system efficiencies• To extend life of equipment by reducing

mechanical stress• To Achieve Energy Savings on Fan and Pump

Applications• To meet the ASHRAE Energy Standards 90.1 -2001

– Variable flow control on fan & pump systems

Why Should I consider using a Variable Frequency Drive (VFD)?

• Integral RS485 Communications• Supports DSI Accessories• Integral LCD Keypad

Optimized for Commercial Fan and Pump Applications

Stand-Alone

• Application Specific Features for Fans and Pumps

• Rated for Variable Torque Loads

Packaged

Allen Bradley PF400 HVAC Drive

• Ratings– 200-240V, 2.2-37 kW (3-50 Hp)– 380-480V, 2.2-100 kW (3-150 Hp)

• 110% Overload for 60 seconds• Enclosure

– IP20 / UL Open• 3-10 HP (240V AC) & 3-20 HP (480V AC)

– IP30 / NEMA 1 / UL Type 1• 3-10 HP (240V AC) & 3-20 HP (480V AC) (with optional kit)• 15-50 HP (240V AC) & 25-150 HP (480V

AC)• Environment

– IP20 rated for 50° C– IP30 rated for 45° C

PF400 Ratings

Main Input Disconnect

3 Contactor Full Feature Bypass with

Disconnect

3 Contactor Basic Bypass with Disconnect

Allen Bradley PF400 HVAC Drives

Standard VFD

• Configurable Keypad with local – remote start/stop and speed controls

• Compatible with Building Automation System Inputs/Outputs (Start/Stop, Speed and Feedback)

• Standard BAS Communications: – RS485, Modbus RTU, Johnson Controls

N2 & Siemens P1• Future Communications:

– Lonworks & Bacnet• Process PI• Inertia Ride Through• Power Loss• Flying Start• S Curve, Accel & Decel profiles• V/Hz Control• Motor Overload protection• Communication interfaces to Building

Automation Systems• Analog & Digital inputs & outputs• Manual Bypass Capabilities• Purge Start Input and Frequency• Fire/Freeze Stat Interlock Inputs

Variable Frequency Drive Control Capabilities

Analog Output Dip Switches

Analog Input Dip Switches

24V DC Source/Sink

Relay Outputs Analog and Discrete Wiring

RS485 Ports

Starting Method

% Voltage at Motor

Terminals

% Motor Starting Current % Line Current % Motor Starting Torque

Lock Rotor

Current

Full Load Current

Lock Rotor Current

Full Load Current

Lock Rotor Current

Full Load Current

Full Voltage 100 100 600 100 600 100 100

Autotrans.            

80 % tap 80 80 480 64 480 64 115

65 % tap 65 65 390 42 390 42 76

50 % tap 50 50 300 25 300 25 45

Part Winding 100 65 390 65 390 45 81

Star - Delta 100 33 198 33 198 33 60

Solid State 0-100 0-100 0-600 0-100 0-600 0-100 0-180

Variable Frequency

Drive0-100 0-100 0-200 0-100 0-200 0-100 0-180

Motor Characteristics with Different Starting Methods

HVAC Motor Control Price Comparison

Motor HP VFD Soft Starters NEMA Combination Starters

IEC Combination Starters

5 $ 900 $ 1,100 $ 780 $ 620

10 $ 1,000 $ 1,200 $ 813 $ 697

20 $ 1,600 $ 1,600 $ 1,195 $ 902

40 $ 2,700 $ 2,400 $ 1,959 $ 1,466

50 $ 3,400 $ 2,800 $ 1,975 $ 1,513

Standard Features:

•480 VAC, 3-Phase

•NEMA 1 Enclosure

• Input Disconnect Switch

•Motor Thermal Overload Protection

ENERGY SAVINGS WITH VFDs

Centrifugal Pump Energy SavingsThere are two methods used to accomplish the continuously varying flow:

• One method is throttling which changes the system curve by use of control or throttling valve.

• The other method is to vary the speed of the pump which modifies the pump curve.

• Building Automation System controls the pump starter or VFD and control valve based on HVAC sequence of operation.

Typical Pump Curves

Pump Curves Throttled with Control Valves

Pump Curves Controlled by a VFD

Energy Savings with VFD’s

(GPM Proportional Brake HP-Torque)

Centrifugal Pump Energy Savings

Many air handling systems require operation at a wide variety of points. There are several methods used to modulate or vary the flow (or CFM) of a system to achieve the optimum points. These include:

• Cycling – As done in home heating systems. This produces erratic airflow and is unacceptable for commercial or industrial uses.

• Outlet Dampers – Control louvers or dampers are installed at the outlet of the fan. To control airflow, they are turned to restrict the outlet, which reduces the airflow.

• Variable Inlet Vanes – by modifying the physical characteristics of the air inlet, the fans operating curve is modified which changes the airflow.

• Variable Frequency Drives – By changing the actual fan speed, the performance of the fan changes producing a different airflow.

Typical Fan Curves

Fan Energy Savings

Building Automation System controls the fan starter, control dampers and air system sensors based on HVAC sequence of operation.

Fan Curves with Outlet Dampers Fan Curves with Variable Inlet Vanes Fan Curves with VFD

Fan Energy Savings

Sample Fan Energy Savings Report

• Energy Savings Software– (www.sydist.com)

• Energy Savings Report– VFD Specs– Energy Savings Calculations– Energy Savings Summary

VFD Energy Savings Software Tools

Schaedler Yesco Distribution

HVAC Market

Plan & Spec Market– New Construction, Additions and Renovations– Track projects online through Harrisburg Builders Exchange– Mechanical plans/spec takeoffs for motor control that’s

furnished by the HVAC contractor– Application coordination with mechanical equipment specs,

building automation system sequences of operations and electrical power system plans

Retrofit Market– Provided electrical energy solutions/products to Design/Build

and Energy Service Teams i.e.: Variable Frequency Drives and Lighting Retrofit Solutions

– VFD Fan or Pump Energy Savings Reports www.sydist.com– VFD Replacement Program

Schaedler Yesco Distribution - HVAC Market

• Local Central PA Support with (5) Staffed Motor Control Specialist

• Product Guide Specifications & Submittal Packages

• Certified VFD Startup – VFD Checklist and Reports

• Onsite Training

• Available Spare Parts

• 24/7 Emergency Service

• Online Allen-Bradley Drives Technical Support– www.ab.com/support/abdrives

Motor Control Support

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