PUMP STATION
ELECTRICAL
DESIGN
40 Years Lessons Learned
Maynard Wayne Robertson, PE, CEM
mwrobertson@vaughnmelton.com
mwrdcr@comcast.net
TAUD 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 MGD
Requires Flow Meters
Requires 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-2008
Organization
• Chapters: One thru Nine
Articles
Tables
Appendix
• Chapters: One Thru Four
Basic Wiring Requirements.
Apply to all Wiring Installations.
• Chapters: Five thru Nine
Special 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-430-99-74-001
Operability 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 Type
Overhead
Underground
• Single or Three Phase
• Available fault Current
NEC Voltage
• Low Voltage = Less Than 600 Volts
• Single Phase
120/240 Volts
Motors 5 HP or Less( 7.5 & 10.0 are manufactured)
• Three Phase
120/240 Volt Delta Connected
120/208 Volt Wye Connected
277/480 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
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•
•
•
•
•
•
•
•
•
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 STATION
ELECTRICAL
DESIGN
40 Years Lessons Learned
Maynard Wayne Robertson, PE, CEM
mwrobertson@vaughnmelton.com
mwrdcr@comcast.net
TAUD Technology Conference
Gatlinburg, TN March 13, 2013