Building Operator

Certification – Level I

A Partnership of the CUNY Institute for Urban Systems

Building Performance Lab, the CUNY School of Professional

Studies, and the New York State Energy Research & Development

Authority

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Building Operator Certification Level I (BOCI)

Building Systems: Electrical

CUNY School of Professional Studies

CUNY Building Performance Lab

The BOC

Motors: Lesson 4

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Lesson 3 Review

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Motors

Lesson Objectives

Be able to

Apply principles of motor construction and operation to improve efficiency and life of motors

Inventory motors with detailed characteristics from nameplate data

Calculate motor load factors and energy consumption

Describe the benefits of efficiently-running motors and a motor maintenance program

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Agenda for Session

Importance of Motors and their energy implications (30 min) Basics of Motor Construction, Operation and Maintenance (90 min) Understanding Motor Sizing, Loading and Calculating Motor Energy Usage (60 min)

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Motors are among the biggest energy users in a facility. They consume 30- 35% of the electricity used in commercial and institutional facilities in the U.S.

Because motors are one of a facilities biggest energy users, their efficient operation can greatly influence the energy budget. It is important to understand how motors work, how they draw power and the factors that influence how much power they consume. A motor performs more efficiently when properly maintained.

Motors are used for everything that has motion, as well as part of processes, like the HVAC system for compressors and fans.

Consider: Where are there motors in your facility?

Motors and Energy Use

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Energy Efficient Motors

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Energy Efficient Motors, Continued When you buy a car, you may make an effort to select a car with high efficiency to save on the cost of gas. You should do this to a much greater extent for the purchase of a motor. The cost of gas is a relatively small part of the cost of ownership of a car. 15,000 miles/yr / 25 GPM = 600 gal/yr x $4/gal = $2400/yr This is 10% of the cost of the car $24,000 A motor can use 10 times the “cost of the motor” in the cost of electricity over its life time. Savings = $4600 Cost = $460 What kind of motor selection strategy do these figures suggest?

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Motor Efficiency

Motor Efficiency is a measure of the Work Output to the Energy Input

Eff = Output / Input

83 - 88% “Standard”

>90% Premium, 94% for larger motors

(larger motors built to higher efficiency range)

Manufacturers must test and publish their motor efficiencies – available in catalogs, spec sheets and on unit nameplates

Baseline efficiencies are required by federal law (see next slide)

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Motor Efficiency

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Benefits of Energy Efficient Motors

• Reduced heat load on building air conditioning system • Lower operating expenses

• Environmental benefits – Reduction in Greenhouse Gas

emissions

• Reduced current on customer's distribution system

• Utility rebates and tax credits may be available to change and maintain high efficiency motors

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Standard vs. Energy Efficient Motors

Std Efficiency Motors, Average Efficiency Replace with EPAct Motors

% Eff. At 75% load Annual Energy Use (kWh), cost

Purchase Price (35% disc)

% Eff. at 75% load

Annual Energy Use (kWh), cost

Annual Saving kWh, cost

Payback Period

HP

5 84.00% 26,644 $233 88.2% 25,374 1,270 2.44

$1,998 $1,903 $95 10 86.75% 51,653 $375 90% 49,773 1,919 2.6

$3,874 $3,730 $144 15 87.55% 76,771 $562 91% 73,780 2,991 2.5

$5,758 $5,534 $224 20 89.30% 100,206 $666 92.6% 96,626 3,579 2.48

$7,515 $7,247 $268 25 89.90% 124,457 $800 93.10% 119,952 4,505 2.36

$9,334 $8,996 $338 50 91.60% 244,211 $1,617 93.9% 238,027 6,185 3.48

$18,316 $17,852 $464

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BREAK

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Basic Principle of Electric Motors How it works: • Motor with a permanently

magnetized stator

• Electricity applied to the rotor creates a strong magnetic field in rotor

• Force in the rotor will rotate the rotor

Applications: • Used in small equipment

• Preferred for tools for easier adjustment of motor speed

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Basic Principle of Electric Motors, cont’d

Video 1: How an Electric Motor Works 5a 4:45 min www.ehow.com/video_4951184_electric-motor-work_.html

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There are many different kinds of motors, that work on same principles but components configured differently.

The AC single-phase and three-phase induction motors are the most common.

DC powered motors less common

Typical Electric Motor Construction

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AC Induction Motor Stator

High production of heat from electric current. Heat must be removed or windings will fail prematurely.

The stationary “windings” where electro-magnetic field is induced. Windings are wiring wrapped around a metal core.

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AC Motors: Single-and Three-Phase

Single Phase power: 120 V, typical for smaller motors, < 5 HP < 1 HP are called “fractional HP”, common on smaller circulation pumps

3-Phase power: 208/240 V and higher • Phases must be in BALANCE (close to equal voltage and

amperage) or overheating and premature failure • Shaft can rotate in wrong direction if leads reversed. Check

rotation after any work!

Motors must have proper power supply at rated voltage. Amperage will vary based on load. Motors can tolerate limited duration under-voltage or over-loading but will eventually over-heat and fail.

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NEMA Nameplate Data Standardization

* type and frame

* Horsepower output.

* Time rating

* Maximum ambient temperature for which motor is designed.

* Insulation system designation.

* RPM at rated load.

* Frequency.

* Number of phases.

* Rated load current: LRA and RLA

* Voltage.

* Code letter for locked rotor kVA. (See MG 1-10.37.)

* Design letter for medium motors. (See MG 1-1.16.)

* NEMA nominal efficiency when required by MG 1- 12.55

* Service factor if other than 1.0.

* For motors equipped with thermal protectors, the words "thermally protected" if the motor provides all the protection described in MG 1-12.52. (See MG 1-1.71 and MG 1-1.72.)

* For motors rated above 1 hp equipped with over-temperature devices or systems, the words OVER TEMP. PROT.-." A type number as described in MG 1- 12.53 inserted in the blank would identify the protection type.

Motor manufacturers have agreed on motor characterization so that data is readily available to know motor equivalencies.

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Generic Nameplate

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Electric Motor Nameplate Data HP - mechanical work produced at the shaft

1 HP = 746 watts

Required Voltage for motor operation, Phases (single or 3-phase)

Rated Amps LRA - Locked Rotor Amps – Motor is not turning RLA – Rated Load Amps – Running at Rated HP

Efficiency 83 - 88% Standard, >90% Premium

Type (torque characteristics in relation to current) Type B - general duty, most common Type B limits inrush of current (Type A does not, which can cause

problems with sizing the starter)

Frame NEMA dimensions for replacement across mfrers (The frame size sets

important mounting dimensions such as foot hole mounting pattern, shaft diameter, and shaft height. NEMA standards do not set some dimensions that can turn out to be important if the motor must fit into a confined space.)

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What Do All Those Things on an AC Motor Nameplate Mean?

Have you ever ordered a motor on power, speed, and enclosure? PO says maybe "5 hp, 1,800 rpm, TEFC." New-motor nameplate says "HP 5, RPM 1748, Enclosure TEFC, Des B, Frame 184T, Amps 7.0, PH 3, HZ 60, Duty Cont, Volts 460, Type P, Amb 40 C, SF 1.15, INS CL F, EFF 82.5, P.F. 80, DE bearing 35BC02JGG30A26, ODE bearing 3OBC02JGG3OA26."

Should you reject the motor because it is not rated at 1,800 rpm? What does all that extra information on the nameplate mean? Do you care? The answers are "maybe," "we'll discuss it in a minute," and "you probably should."

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Electric Motor Nameplate Data (Continued) We are teaching this for 2 reasons:

1. So you understand motors and their ratings

2. You have to get the information off of one nameplate of a motor at your facility. Preferably a large motor

Important: A motor with an efficiency of 84% is “average to low” efficiency. On the low end of the “average scale”

Important: Calculate the amount of power that a motor draws

We know: Power = Volts x Current (Watts= Volts x Amps)

The maximum power a motor can draw = Volts x Maximum Current

What do you need from the Nameplate?

Answer: Rated Voltage and Rated Current

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Motors Starting and Protection

• Current Inrush – short duration high amperage (LRA).

• Safely connect and disconnect motor circuit on control signal

• Need to protect motor from extreme overheating, from any of various sources: • Rotor jammed (alignment, bearings) • Excess load • Load (pump or fan) bound • Shaft bound • Under-voltage

Motor Starter

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Motors Starter Provides start relaying from controls

Power circuit “pulls in” via electromagnetic coil on call from lower voltage control circuit

Regulates starting power inrush larger motors (“soft-start” and solid-

state) Soft start starts a motor gently;

regulates power “rushing” into motor so as not to be abrupt. This reduces motor wear and power usage

Protects against thermal overloads Excessive load conditions Low-voltage conditions (P = A x V) Transients

Motor Starter

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Motor Starters, Continued

3 leads of electricity to a motor

From left to right – symbols:

Lead connection – 3 phases

Contacts of breaker

Contacts of overload device

Temp sensor of overload device

The motor

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Belts: Common Cause of Energy Waste

• Pulley and sheave need to be in good alignment

• Loose belts slip, so power is not delivered to load – wastes energy. • Adjust to

proper tension. • Consider “low-

slip” belts.

Belts are most common form of connecting motor shaft to load (pump or fan). Pulley and sheave sizes provide means of setting motor speed.

How do you check alignment? Tension?

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Motors: Common causes of early failure • Bearings (lubrication)

• Shaft Alignment, belts

• Movement and vibration (supports)

• Extended over-load (high amperage)

• Excessive start-stop (load short-cycling)

• poor air flow/blockage (from dirt, dust)

• phase imbalance, low voltage

• loose connections

Biggest enemy is over-heating, that can be from various sources – mechanical and/or electrical

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Discuss: Common causes of early failure and what you see in the field

What kinds of problems do you experience with motors?

What kinds of routine observations, adjustments and maintenance do you perform?

Do you have regularly scheduled maintenance? Maintenance triggered by certain observations? Do you have a maintenance check-list?

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Checklist of Maintenance Practices for Motors

Check for over-loading. Periodically check and record Amps with a multi-meter.

Lubricate. Manufacturers provide recommendations for how and when to lubricate. Noise can indicate binding from misalignment or bearing failure.

Inspect electrical connections at the motor and starter to be sure that they are clean and tight. (Thermograph scan)

Check shaft and belts for alignment, tension.

Provide good ventilation to dissipate heat. Remember: for every 20°F increase in motor operating temperature, motor life is estimated to be halved

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Motor Maintenance Knowledge Check

Check for rated ‘Amps’ – Use a Clamp On Ammeter to check the current to the motor does not exceed the rated ‘Amps’ of the motor.

Ask: What happens to a motor that is blocked with dust or has no air circulation through it?

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Good Checklist – Found at http://www1.eere.energy.gov/femp/pdfs/OM_9.pdf

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Motors Schedule – Manage Your Motors

• Collect motor information to help you understand your facility’s largest energy users (Big Loads) and your Peak Demand

• Collect motor information to help you select the best motors when a replacement is needed ; will help you develop inventory of building motors to speed replacement

• Motor Master – Free software to select the best motors: www.eere.energy.gov

LOAD LOCATION, DESCRIPTION HP V A Ph KW, connected TIME OF OPER KW, on-

peak OPER HRS/YR KWH /YR

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Exercise: Create a Motor Schedule from the following facility description

Rooftop exhaust fans: 5, each with 0.5 HP motor

4 Air Handlers: each with 20 HP fan motor

Boiler with 5 HP burner fan motor and 1.5 HP oil pump motor

Hot Water Circulator: 2 pumps, each 10 HP, alternated

Chilled Water: 2 pumps, each 10 HP, alternated

Condenser Loop: 2 pumps, each 10 HP, lead-lag

Cooling Tower: 3 cells, each fan with 5 HP motor, lead-lag

Water Pressurization: 3-pump station, 1.5 HP (lead) + 2 – 5 HP

Hot Water Re-circulation: 1 – 1.5 HP pump

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MotorMaster (type it into Google and go to page on www.eere.energy.gov) o Free software o Database of 25,000 available electric motors,

efficiencies and prices o User enters current motor inventory and utility rates o MotorMaster recommends replacement units based on

lifecycle savings, added resources at • Link to Motor Payback Calculator (online tool)

Motor Replacement Plan

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BREAK

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Motor Sizing and its Implications

Motors are typically over-sized, for their loads (pumps, fans). Further, Pumps or fans are typically over-sized for their loads. The result is significant motor over-sizing. This has implications for efficiency, power consumption, and possibilities for motor speed reduction.

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Motor Efficiency vs. Load

Motor efficiency drops off at part-loads, but not severely until very light loads Larger motors generally hold their efficiencies better at part loads.

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Load Factor • Indicates how much of Rated Output (HP), the motor is

actually doing to satisfy its load.

• Can be measured by motor “slip” (rpm) or by amperage.

• A motor draws only as much power as it needs to satisfy its load. So, if we use a clamp-on amp meter on a motor rated for 10 amps and the meter reads 7 amps, the motor is running at a 70% load factor.

• Because of this, using Rated Output or Rated Power to calculate motor energy can significantly over-estimate actual usage (and potential savings). It is important to establish Load Factors when assessing large motors. Question for discussion: What happens if a motor is run

without Load?

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Quantification of Motor Energy Performance

• This section deals with calculating: • Load Factor • HP to KW • KWs/KWHs • Savings resulting from reduced operation • Determining load, if you have other info

• A most useful conversion factor is

>1 HP = 746 watts = .746 KW

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MOTOR CALCULATION FORMULAE 1 HP = .746 KW Motor KW = [rated HP x .746 x Load Factor] / motor Efficiency Motor Load Factor (%)

“Slip Method” LF (%) = [(Synchronous speed – Tested Speed) / (Synch Speed – Rated Speed)] x 100

(synchronous speeds, 1800 4-pole, 3600 2-pole)

“Amperage Method”

LF (%) = Tested amperage / Rated amperage

Motor KW from Amperage and Voltage Measurement (use if HP is not available) KW = [V x A x Power Factor / 1,000 (single-phase) KW = [V x A x Power Factor x 1.73 / 1,000 (three-phase)

Assume Power Factor = .80 if no other information is available

Motor Energy Consumption KWH= Motor KW x Operating Hours

Herzog simplified formula: Motor KW = HP x .55

load factor = .6 Efficiency = .8

.55 = (.746 x .6) / .8

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Quantification - Motors Example of Savings from reduction of operating hours

> Assume 170 days per year, 100 heating-days per year

Motors: 20 HP fan motor, 62% load factor, 84% efficiency Shut-down for 2 hours per day (1 hp = 0.55 kW)

Energy Saved = Rate of Use x Reduction of Hours of Use Energy Saved = kilo-Watts x Reduction of Hours of Use

= [ 20 HP x .55 ] x 2 x 170 = 3,740 KWH

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There are 3 basic steps to solve this problem: Convert HP to kW Energy = kW x hours = kW-hrs Find the savings in kW-hrs

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Load Factor and Motor Size Reduction

Low load factor indicates that motor can probably be down-sized. Reducing HP yields equivalent energy savings. Be careful that the load is not variable.

Conduct a load study to determine if a motor can be down-sized. The load study should include the driven-device (fan, pump) loading as well. It may also be possible to “trim” the pump impeller, reducing flow and motor load.

Re-sizing should be part of any planned approach to change-out of motors for higher efficiency.

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Motor Size Reduction vs Speed Control

Slowing down a driven-device and its motor is another way to address over-sizing.

Look for throttled pumps or fans as for speed control. • If continuously throttled, belt-driven equipment can be slowed down

by changing the pulleys and sheaves. • If the load varies, then control speed by application of Variable

Frequency Drive (VFD), a solid-state control addition.

Energy reduction is a cubic function of speed reduction, so energy saving potential is very large.

• VFD and the calculation of their energy savings is considered as a BOC Level-2 topic.

• But see the handy chart in Herzog, page XX

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SUGGESTION FOR PROJECT #4

Identify one or more significant motors in your facility.

Develop a plan to measure key operating characteristics and calculate (baseline) energy usage.

Identify a strategy for improving motor energy performance (simply changing to higher efficiency models without confirming sizing and operating hours is not sufficient)

Calculate the savings associated with the changes you identify.

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Closing: Some Guidelines for efficient motor operations in HVAC systems. From: FEMP 9.10.5 • Turn off unneeded motors

• Reduce motor system usage • Reducing load in building

• For example, reducing solar load on a building will reduce the amount of time the air handler motors would need to operate

• Efficiency of mechanical systems affects run-time of motors. For example, • Check ventilation systems for excessive air

• Repair duct leaks • Re-sheave fan if air is excessive

• Improve compressed air systems • Locate and repair compressed air leaks

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FEMP 9.10.5 - Guidelines for efficient Motor operations (cont’d) • Sizing motors is important – Do not assume an existing

motor is properly sized for its load, especially when replacing motors. • Identify actual motor loading. There are several ways to

estimate actual motor loading -See MotorMaster software (MotorMaster www.eere.energy.gov)

• Downsize motors, if possible Many motors operate most efficiently at 75% to 85% of full load rating. Under-sizing or over-sizing reduces efficiency.

• Replace motors with an energy-efficient version

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Lessons to Take Home to Your Facility

• Even a seemingly modest (small) increase in motor efficiency can lead to measurable (often large) reductions in energy use and costs.

• Overheating is the largest contributing factor for premature motor failure – make every effort to ensure your motors do not overheat.

• Are my motor maintenance practices up to snuff? Should I be adding procedures?

• Do I have or should I consider creating a motor schedule for my facility?

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Next Week

No readings Project 1 Due Exam #1