PUMP STATIONELECTRICAL DESIGN40 Years Lessons LearnedMaynard Wayne Robertson, PE, CEMmwrobertson@vaughnmelton.commwrdcr@comcast.netTAUD Technology Conference Gatlinburg, TN March 13, 2013

Pump Station Design Requirements

• Tennessee Dept. Environment & Conservation

• Environmental Protection Agency

• NFPA- 70- National Electrical Code

• Tennessee Fire Marshall- Electrical Inspections

• OSHA/TOSHA

TDEC Requirements

• General Design Requirements for Sewerage Works

• Key Chapters for Pump Stations; 1, 2, 14

• Chapter 2. Section 2.5 Pump Stations

• Alarm System and totalizers on All stations

• 2.6.3 All wet well wiring to be Class l, Division l, per NEC

• 2.7.3 PS Capacity Greater Than - 1.0 MGDRequires Flow MetersRequires Back Up Power System

TDEC Requirements

• Chapter 2.6.1.6 Requires to comply with All OSHA Rules. Work place safety.

• Chapter 2.7- Operability/ Reliability Do you need generator/backup power? Essentially EPA requirements.

• Reliability Class 1, Class 2, Class 3.

TDEC

• 2.5 Septicity Controls. I guess something that smells BAD. Do not make it smell worse. Setting controls for minimum time in wet well.

• Auto Pump Out (Timed pump start after low level contact made, low cost to reduce odor )

• Electric Power Systems Chapter 1.3.11.5

• www.tn.gov/envionment/wpc/publications• Design Criteria for Sewerage Works

National Electrical Code

• Latest Version NEC-2011

• Next Version NEC-2014

• Code revised on Three Year Cycle

• Version adopted in Tennessee NEC-2008

NFPA CHAPTER 70

• National Electric Code / 70E work place safety

• NEC 2008 Used Statewide*Exceptions In Some Cities NEC-2011

• 70E Work Place General Safety Requirements

• Installation Of Equipment

• Protection Of Electrical Equipment

NEC-2008Organization

• Chapters: One thru NineArticles Tables Appendix

• Chapters: One Thru FourBasic Wiring Requirements. Apply to all Wiring Installations.

• Chapters: Five thru NineSpecial Conditions

NEC Chapters• Chapter 1 – General• Chapter 2 – Wiring and Protection• Chapter 3- Wiring Methods and Materials• Chapter 4 – Equipment for General Use

• Chapter 5 – Special Occupancies• Chapter 6 – Special Equipment• Chapter 7 – Special Conditions

• Chapter 8 – Communications Systems(Stands alone)• Chapter 9 – Tables• Annex A thru H ; Informational Only

Key NEC Articles for Sewer Pump Stations

Articles: 200, 215, 220, 240, 250, 310, 312, Table 310.16, 400, 430, 445, 500 & 700.

Note: Entire Code Applies Always!!

Tennessee State Fire Marshall

• Requires Electrical Inspection of all New and Modified Electrical Installations.

• Require Use of Listed Equipment- UL, etc.

• Current Enforcement NEC -2008

• Authority Having Jurisdiction

EPA

• EPA-430-99-74-001Operability and Reliability

• Class 1 Standby Power nearly always required

• Class 2 Standby Power maybe Required

• Class 3 Normally not Required

Service Terms

• Service

• Service Entrance

• Metering

• Service Disconnect

• Service TypeOverheadUnderground

• Single or Three Phase• Available fault Current

NEC Voltage

• Low Voltage = Less Than 600 Volts

• Single Phase120/240 VoltsMotors 5 HP or Less( 7.5 & 10.0 are manufactured)

• Three Phase120/240 Volt Delta Connected120/208 Volt Wye Connected277/480 Volt Wye connected

Electrical Service Entrance• Capacity for both pumps to operate• Service disconnect rated for service entrance and capacity to

allow second motor to start without tripping• Service Equipment( Main Breaker and panel boards, etc.)

rated for available fault current• Fault Currents can be high at PS as result of large transformer

and short wire runs• Standard Interrupting capacity: 10,000, 22,000, 65,000amps• Grounding and Bonding• Adequate work space in front of electrical equipment• For outdoor locations shield panels from sun and heat

Wiring Methods

• NEC Article 250 Grounding and Bonding• Table 250.122 Size of Equipment Ground

Conductor• Grounded Conductor• Ground Wire• Lightning protection• Table 310.16 /Table 310.15B(2)a, more than 3

conductors in raceway/conduit • Conductors Rated at 75C• Conductors Rated for Wet Location

Control Panels

• Correct NEMA Enclosure ( 3R, 4X, etc. )• Ventilation/Cooling• Drains• Labeled (UL, CSA)• Alarms• Control Transformer (Reduce line Noise)• Instrumentation (Runtime, Volts, Amps,

Calibration)

Motor Starters

• Manual• Across the Line starters( NEMA SIZE 0, 1, 2, etc.)• Part winding• Auto transformer• Soft Start• VFD (6 pulse more noise and 12 pulse less

noise)• VFD noise may interfere with controls/SCADA

PHASE CONVERSION

• Single Phase Power to 3 Phase Power

• Phase Conversion Using VFD

• Size VFD Based On Single Phase Load Plus 15% 20Hp, 3P, 230V, FLA=54 Amp Based on single phase = 100 Amp Use 120 Amp VFD

Common WWPS Problems• Corrosion, Corrosion, Corrosion!!!!• Electrical Junction Boxes in Wet Wells• Excessive Pumps starts/ Short run time• Unlisted Electrical Equipment (Inspector Rejects)• FAILURE TO DERATE CONDUCTORS in Conduit. (more than

three)• Lack of Phase Loss Protection• Phase to Phase Voltage/excessive voltage difference.• Poor Electrical Grounding• No Isolation of sewer gas from control Panels thru use of

junction boxes with double conduit seals. Complete failure less than 1 year.

• Circuit Breakers too small, Result excessive heat in Panel.

Common WWPS Problems• NO Conduit Seals, Sewer Gas direct line to control Panel.

• Pump Rotation

• Wrong NEMA Class Enclosures

• Low Equipment Electrical withstand Ratings.

• VFD noise on Control circuits

• No GFIC Receptacles

• Generators/ transfer switches improperly wired/ Phase Reversed.

Checklist/Records

• Always use startup Checklist• Voltage, Line to Line, Line to Ground, Phase to

Phase• Amperes• Discharge Head• Pumping Rate• Photos• Nameplate Data• Terminals Tight

WWPS Life Cycle Cost

• Initial Cost• Installation• Commissioning Cost•Maintenance and Repairs Cost• ENERGY COST 90 PERCENT OF TOTAL• High Efficiency Motors• High Efficiency Pumps

Generators

•Correctly Sized to start second pump with all loads energized •Portable /Permanent• Transfer switches/ Manual or

automatic• Fuels/ Diesel, Natural Gas, Propane,

Gasoline.• Long Term maintenance cost

PUMP STATIONELECTRICAL DESIGN40 Years Lessons LearnedMaynard Wayne Robertson, PE, CEMmwrobertson@vaughnmelton.commwrdcr@comcast.netTAUD Technology Conference Gatlinburg, TN March 13, 2013