Glossary of SWPA Terms

System Terms

ACCESS COVER

A removable device to provide access to a wet well and/or valve box. May include frame, doors, locks, and other accessories.

BEST EFFICIENCY POINT (BEP)

The combination of head and flow at which a given pump operates most efficiently.

BRAKE HORSEPOWER (BHP)

The power delivered to the pump shaft under stated operating conditions of the pump where horsepower is 550 foot/pounds per second, expressed by graph or figured by:
BHP = Q x H x S.G. where:
K x Eff. Q = U.S. GPM
H = Head in Feet
S.G. = 1.0 (for water)
K = 3960
Eff. = Pump Hydraulic Efficiency

CAPACITY

The quantity of liquid that can be contained, or the rate of liquid flow that can be carried.

CAVITATION

The undesirable formation of vapor bubbles within a liquid in a low pressure region of a pump or valve when liquid accelerates at a high velocity, producing an erosion of the surfaces as the bubbles collapse under rising pressure, causing a reduction in efficiency.

CLEAR WATER

Treated, filtered water; the discharge from a water treatment plant.

CLOSE-COUPLED

A pump directly connected to its power unit without any reduction gearing or shafting.

CYCLE TIME

The total time period from when the pump turns On to when it turns Off.

DISCHARGE

The flow or rate of flow from a pump or pumping system.

DISCHARGE DIAMETER

(See Pump Discharge Size).

DISCHARGE PIPE

The pipe that exits the wet well or valve box.

DRY WELL

A dry compartment in a pumping station, near or below pumping level, where the pumps are located.

DUPLEX

A pumping station containing two pumps.

DYNAMIC HEAD

The head (or pressure) against which a pump works.

EDDIES

Circular movements occurring in flowing water, caused by currents set up in the water by obstructions.

EFFLUENT

Wastewater or other liquid, partially or completely treated, flowing out of a septic tank or treatment unit.

FLOOD-PRONE

An area subject to frequent flooding.

FORCE MAIN

A pressure pipe joining the pump discharge at a water or wastewater pumping station with a point of gravity flow.

FREE BOARD

The vertical distance between the normal maximum level of liquid in a tank and the top of the tank.

FRICTION LOSS

The head loss of liquid flowing in a piping system as the result of the disturbances set up by the contact between the moving liquid and the system components. It is a function of pipe diameter, length, surface roughness, and flow rate.

GALLONS PER MINUTE (GPM)

The volume delivered at the pump discharge flange expressed in gallons per minute (GPM). Expressed on the X axis of a pump curve.

GRINDER PUMPS

Specialized submersible pumps which mechanically disintegrate sewage.

GROUNDWATER

Subsurface water occupying the saturation zone. In a strict sense, the term applies only to water below the water table.

GUIDE RAIL SYSTEM

A device which allows the pump-motor unit to be installed in or removed from the wet well, without disconnecting any piping and without requiring personnel to enter the wet well.

H20 WHEEL LOADING

Refers to the type of construction used in the fabrication of access doors or covers for wet wells or valve boxes that must withstand vehicular traffic. Rating is 16,000 lbs. per sq. ft. live load.

HEAD

The height of the free surface of fluid above any point in a hydraulic system; a measure of the pressure or force exerted by the fluid.

HYDRAULIC GRADIENT

The slope of the hydraulic grade line, the rate of change of pressure head; the ratio of the loss in the sum of the pressure head and position head to the flow distance.

IMPELLER

A rotating set of vanes designed to impel rotation of a mass of fluid.

IMPELLER DIAMETER

The concentric outside diameter as measured radially of the pump impeller.

INFILTRATION

The quantity of ground or near-surface water that leaks into a pipe or wet well through joints, porous walls, or breaks.

INFLOW

The extraneous flow which enters a sanitary sewer from sources other than infiltration.

INTAKE

The flow or rate of flow into a pump or pump station.

LAG PUMP

A succeeding or backup pump in a pump system. Control systems usually alternate pump operation.

LEAD PUMP

The first pump to start in a pump cycle.

LIFT STATION

A system that includes pumps, tanks, appurtenant piping, valves, and other mechanical and electrical equipment for pumping water or wastewater. Also see pumping station.

LIQUID LEVEL CONTROLS

In-station devices which start or stop the pump(s) in response to the liquid level within the well. Connected to a control panel.

NET POSITIVE SUCTION HEAD (NPSH)

The net positive suction head is the total suction head in feet of liquid absolute determined at the suction nozzle and the referred datum less the vapor pressure of the liquid in feet absolute.

NET POSITIVE SUCTION HEAD AVAILABLE (NPSHA)

The absolute pressure of the liquid at the inlet of the pump.

NET POSITIVE SUCTION HEAD REQUIRED (NPSHR)

Based on the need of a specific pump. Remains unchanged for a given head, flow, rotational speed, and impeller diameter; changes with wear, liquids, and temperature.

NON-CLOG

A pump designed to pass solids of a specific size. For example, a submersible pump with a 4-in. discharge may be capable of passing 3-in. spherical solids.

PEAK FACTOR

A variable multiplier used with average flow to determine required pump capacity for wastewater lift stations or potable water booster stations. Variation is determined by the size and type of facility.

PEAK FLOW

Maximum flow.

PUMP CASING

See Volute.

PUMP DISCHARGE SIZE

The inside diameter of the discharge port of the pump as measured at the integrally cast discharge flange to the pump casing (volute).

PUMP HYDRAULIC EFFICIENCY

Expressed as a percentage of liquid horsepower to brake horsepower over the recommended operating range of the indicated impeller size(s).

PUMP RELEASE SYSTEM

See Guide Rail System.

PUMPING STATION

Discharges into a pressurized force main (See Lift Station).

RAW WATER

Untreated water; usually the water entering the first treatment unit of a water treatment plant.

RPM

Revolutions per minute of the motor/pump rotating assembly.

SANITARY WASTEWATER

Wastewater discharging from the sanitary conveniences of dwellings, including apartment houses, hotels, office buildings, industrial plants, or institutions.

SCUM

Floating matter which rises to the surface of a liquid and forms a layer or film.

SEALING FLANGE

The connection between the pump discharge and force main when used with guide rail systems.

SEDIMENTATION

The process of subsidence and deposition of suspended matter carried by water, wastewater, or other liquids, by gravity. It is usually accomplished by reducing the velocity of the liquid below the point at which it can transport the suspended material.

SEPTIC TANK

An underground vessel for treating wastewater (most often from a single dwelling or building) by a combination of settling and anaerobic digestion. Effluent is usually disposed of by leaching. Contents (also called septage) is pumped out periodically and hauled to a treatment facility for disposal.

SEWAGE

Household or commercial wastewater that contains human waste. Distinguished from industrial wastewater.

SIMPLEX

A pumping station containing one pump.

SIPHON

The potential for atmospheric pressure to force a liquid through an inverted "U"-shaped tube from one point to another lower point over the barrier created by the inverted "U".

SLUDGE

The accumulated solids which separate from liquids, such as water or wastewater, during processing.

SOLIDS-HANDLING

The capability of a pump to pass solids of a specific size, such as 3-in. spherical solids.

SPECIFIC SPEED

An index number used to classify rotational pumps into three basic categories related to their vane and hydraulic configurations. NS = RPM x GPM H3/4 The pump types are radial flow, mixed flow and axial flow.
Ns = 500 to 4,500 as radial flow
Ns = 4,500 to 10,000 as mixed flow
Ns = 10,000 to 15,000 as axial flow

SPHERE SIZE

The maximum physical diameter of a non-deformable sphere that can pass through the pump without obstruction or interference of any kind from volute entry port to discharge port.

STATIC ELEVATION (STATIC HEAD)

The vertical distance between the level of the source of supply and the high point in the force main or the level of the discharge to the atmosphere.

STORM WATER

Surface water from rain, snow, or melting ice which runs out from the surface of a drainage area. It is normally collected in sewers separate from the sanitary sewers, and receives minimal, if any treatment, prior to discharge to a receiving water. When collected in a combined sewer system, the resulting mixture of sanitary sewage and storm water is called combined wastewater.

SUBMERGENCE

The depth of fluid above the center line of the volute on a vertical submersible pump. Requirements will vary depending on the nature of the fluid and the hydraulic configuration of the sump.

SUBMERSIBLE PUMPS

Submersible wastewater pumps are vertical, close-coupled, extra-heavy duty pump-motor units which are designed to operate under the liquid they are pumping. They are solids handling, usually have a 3-in. or larger discharge, and are also called submersible sewage pumps. Also see Grinder Pumps.

SUMP

See Wet Well.

SYSTEM HEAD CURVE

A graph showing the relationship of static head and friction head at various flow rates through a given piping system.

TOPOGRAPHY STUDY

A study that relates to the shape of the land surface and to the characteristics of the underlying soil and rocks.

TOTAL DYNAMIC HEAD (TDH)

The difference between the elevation corresponding to the pressure at the discharge flange of a pump and the elevation corresponding to the vacuum or pressure at the suction inlet of the pump, corrected to the same datum plane, plus the velocity head at the discharge flange on the pump, minus the velocity head at the suction inlet of the pump. The value or quantity used to express the energy content of the liquid per unit height. Expressed on the Y axis of a pump curve.

TRIPLEX

A pumping station containing three pumps.

VALVE BOX

A metallic or concrete box or vault containing valving, to allow access for service and maintenance without having to enter the wet well.

VAPOR PRESSURE

That portion of pressure above atmospheric pressure that is required to maintain a liquid state for a given fluid at a specified temperature.

VELOCITY

The speed at which a liquid is moving. Usually measured in feet per second.

VOLUTE

The casing of a centrifugal pump made in the form of a spiral or volute as an aid to the partial conversion of the velocity energy into pressure head as the water leaves the impeller.

VORTEX (VORTICES)

A revolving mass of water in which the streamlines are concentric circles and in which the total head of each streamline is the same.

WASTEWATER

The spent or used water of a community or industry which contains dissolved and suspended matter.

WATER HAMMER

A series of shocks within a piping system when the flow of liquid is stopped suddenly, with a sound like hammer blows.

WET WELL

A tank or pit which receives drainage, stores it temporarily, and from which the discharge is pumped.

Valve Terms

AIR BINDING

The phenomenon in a pipeline or tank when excess air pockets produce sufficient headloss to stop flow.

AIR VALVE

Generic name used to describe a family of valves used to control the release and admittance of air to a wastewater pipeline or liquid handling system. Common types include air release, air/vacuum, and combination.

CHECK VALVE

A unidirectional valve which is opened by the fluid in one direction and which closes automatically to prevent flow in the reverse direction. Cv — A flow coefficient for valves that is equal to the number of gallons per minute that will pass through the valve with a 1 PSI pressure drop.

ECCENTRIC ACTION

A design feature of some plug valves where the seat centerline is offset from the valve centerline so that as the valve opens, the closure member lifts off of the seat.

FLOW CHARACTERISTICS

A measure of the ability of a valve to control flow as it moves from full open to full closed. Common characteristics include quick opening, linear, and equal percentage.

FLOW RATE

The volume or mass of a liquid that passes through a cross section of conduit in a given time. Often expressed in gallons per day (GPD) (or cubic meters per day) or gallons per minute (GPM) or liters per minute (LPM).

HEAD LOSS

The energy (or pressure) reduction in a pumped liquid due to dynamic losses, such as friction, in a piping system, or due to a change in elevation of the liquid, also see friction loss.

ISOLATION VALVE

A valve used to isolate part of a pipeline, a process, or a piece of equipment.

PUMP CONTROL VALVE

A quarter-tum, power-actuated valve such as a ball or plug a valve used with long force mains. The valve is electrically wired with the pump panel to control the changes in velocity in the system over several minutes to prevent surges.

SHUT-OFF VALVE

A bi-directional valve that when closed prevents flow in either direction.

SURGE

Transient pressure waves or pressure surges in a forcemain resulting from rapid changes in fluid velocity. When audible, referred to as a water hammer.

Electrical Terms

ALARM LIGHT

A light which is used to attract attention when a problem occurs in the system.

ALTERNATING CURRENT (AC)

A current which reverses in regularly recurring intervals of time and which has alternative positive and negative values, and occurring a specified number of times per second. The number is expressed in cycles per second or Hertz (Hz).

ALTERNATOR

A relay device designed for alternating the run cycle or duplexing action of two or more motors automatically. An alternator is a solid state unit with an output relay, and is used in the automatic control circuit to the motor starters to rotate the duty cycle of each motor.

AMBIENT TEMPERATURE

Temperature of the surroundings in which the equipment is used or operated.

AMMETER

Meter for measuring the current in an electrical circuit, displayed in amperes.

AMPERE

The unit of electric current flow. One ampere will flow when one volt is applied across a resistance of one ohm.

AUDIBLE ALARM

Horn, siren, bell, or buzzer which is used to attract the attention of the operator when a problem occurs in the system.

AUXILIARY CONTACTS

Contacts of a switching device in addition to the main current contacts that operate with the movement of the latter. They can be normally open (NO) or normally closed (NC) and change state when operated.

CAPACITOR

A device which introduces capacitance into an electrical circuit. The capacitor, when connected in an alternating current circuit, causes the current to lead the voltage in time phase. The peak of the current wave is reached ahead of the peak of the voltage wave. This is the result of the successive storage and discharge of electric energy.

CIRCUIT BREAKER

A mechanical switching device capable of making, carrying, and breaking currents under normal conditions. Also making, carrying for a specific time, and automatically breaking currents under specified abnormal circuit conditions, such as those of short circuit. Circuit breakers have an ampere trip rating for normal overload protection and a maximum magnetic ampere interrupting capacity (AIC) for short circuit protection.

COMMERCIAL POWER

The term applied to power furnished by an electric power utility.

CONDENSATION HEATER

A device that warms the air within an enclosure and prevents condensation of moisture during shut-down periods. Also known as a space heater.

CONDUCTOR

A wire, cable or bus bar designed for the passage of electrical current.

CONTACTOR

An electro-mechanical device that is operated by an electric coil and allows automatic or remote operation to repeatedly establish or interrupt an electrical power circuit. A contactor provides no overload protection as required for motor loads, sometimes called a power relay.

CONTACTS

Devices for making and breaking electrical circuits, which are a part of all electrical switching devices.

CURRENT

The amount of electricity measured in amperes which is flowing in a circuit.

CYCLE

A given length of time (See Alternating Current). In the U.S., electric current is 60 cycle (60 Hz).

CYCLE TIMER

A timer that repeatedly opens and closes contacts according to preset time cycles. Also known as a repeat cycle timer.

DELTA CONNECTION

A common three phase connection shaped schematically like the Greek Delta. The end of one phase is connected to the beginning of the next phase, or vice versa.

DESIGN LETTER

A letter that is shown on the motor nameplate indicating NEMA's classification of that motor. Classification encompasses characteristics such as full-voltage starting, locked rotor torque, breakdown torque, and others that determine
electrical type.

DISCONNECTING MEANS (DISCONNECT)

A device or group of devices, or other means whereby all the ungrounded conductors of a circuit can be disconnected simultaneously from their source of supply.

ELAPSED TIME METER

An instrument used to record the amount of time each pump runs. One elapsed time meter is used per pump.

ELECTRIC UTILITIES

All enterprises engaged in the production and/or distribution of electricity for use by the public.

EMERGENCY POWER (ALTERNATE SOURCE OF POWER)

An independent reserve source of electric power which, upon failure or outage of the normal power source, provides stand-by electric power.

ENCLOSURE

The cabinet or specially designed box in which electrical controls and apparatus are housed. It is required by the National Electrical Code (NEC) to protect persons from live electrical parts and limit access to authorized personnel. It also provides mechanical and environmental protection. An enclosure should be designed to provide the required protection and sized to provide good, safe wire access and replacement of components. It can be manufactured of steel, galvanized or stainless steel, aluminum, or suitable non-metallic materials.

EXPLOSION-PROOF MOTOR

A motor in a special enclosure. The purpose of the enclosure is twofold: 1) If an explosive vapor (gas) should explode inside the motor, the frame of the motor will not be affected. 2) The enclosure is so constructed that no such explosion will ignite vapors outside the motor.

FACTORY MUTUAL (FM)

Independent U.S. agency associated with the insurance industry which tests for safety.

FREQUENCY

The number of complete cycles of an alternating voltage or current per unit of time and usually expressed in cycles per second or Hertz (Hz).

FULL LOAD AMPS (FULL LOAD CURRENT)

The current flowing through a line terminal of a winding when rated voltage is applied at rated frequency with rated horsepower.

FULL LOAD CURRENT

The greatest current that a motor or other device is designed to carry under specific conditions; any additional is an overload.

FUSE

An over-current protective device which consists of a conductor that melts and breaks when current exceeds rated value beyond a predetermined time.

GENERAL PURPOSE RELAY

A relay that is adaptable to a wide variety of applications as opposed to a relay designed for a specific purpose or specific application

GENERATOR

A machine for converting mechanical energy into electrical energy or power.

GENERATOR RECEPTACLE

A contact device installed for the connection of a plug and flexible cord to supply emergency power from a portable generator or other alternate source of power. Receptacles are rated in voltage, amps, number of wires, and if they are male or female.

GROUND

A connection, either intentional or accidental, between an electric circuit and the earth or some conducting body serving in place of the earth.

GROUND FAULT INTERRUPTION (GFI)

A unit or combination of units which provides protection against ground fault currents below the trip levels of the breakers of a circuit. The system must be carefully designed and installed to sense low magnitude insulation breakdowns and other faults that cause a fault ground current path. The GFI system must be capable of sensing the ground fault current and disconnecting the faulted circuit from the source voltage.

GROUNDED NEUTRAL

The common neutral conductor of an electrical system which is intentionally connected to ground to provide a current carrying path for the line to neutral load devices.

GROUNDING CONDUCTOR

The conductor that is used to establish a ground and that connects equipment, a device, a wiring system, or another conductor (usually the neutral conductor) with the grounding electrode.

HAND-OFF-AUTOMATIC (HOA)

Selector switch determining the mode of system operation. H is the hand mode only. 0 is system Off. A is automatic operation.

HAZARDOUS LOCATIONS

Those areas as defined in the NEC where a potential for explosion and fire exist because of flammable gasses, vapors, or finely pulverized dusts in the atmosphere, or because of the presence of easily ignitable fibers or flyings.

HERTZ (Hz)

A unit of frequency equal to one cycle per second.

HIGH POTENTIAL TEST

A test which consists of the application of a voltage higher than the rated voltage between windings and frame, or between two or more windings, for the purpose of determining the adequacy of insulating materials and spacing against breakdown under normal conditions. It is not the test of the conductor insulation of any one winding.

HORSEPOWER

A method of rating motors whereby values are determined by factors including rotational speed and torque producing capability as well as other factors.

IN-RUSH CURRENT

Starting Amps.

INTERLOCK

Interrelates with other controllers. An auxiliary contact. A device connected in such a way that the motion of one part is held back by another part.

INTRINSICALLY SAFE

A term used to define a level of safety associated with the electrical controls used in some lift stations. Intrinsically safe equipment and wiring is incapable of releasing sufficient electrical or thermal energy under normal or abnormal conditions to cause ignition of a hazardous atmospheric mixture — without the need for explosion-proof enclosures in the hazardous area. Any associated devices must be outside the hazardous area with an approved seal-off fitting used as an isolating barrier.

KILOWATT (KW)

A unit of measure of electrical power. One kilowatt equals 1000 watts. Used where larger units of electrical power are measured.

LIGHTING ARRESTOR

(See surge arrestor).

LOCKED ROTOR CURRENT

Amount of electrical energy in amps required to start a motor from a stopped position, which can be 3 to 8 times higher than the normal running amps of the motor.

LOCKOUT

A mechanical device which may be set to prevent the operation of a pushbutton or other device.

MANUAL TRANSFER SWITCH

A switch designed so that it will disconnect the load from one power source and reconnect it to another source while at no time allowing both sources to be connected to the load simultaneously.

MEGGER OR MEGOHMETER

A high resistance range ohmeter utilizing a power source for measuring insulation resistance.

MEGOHM

A unit of resistance equal to one million ohms.

MOTOR CIRCUIT PROTECTOR

A molded case disconnect switch specifically designed for motor circuits. It has a trip unit that operates on the magnetic principle only, sensing current in each of the three poles with an adjustable trip point. It provides short circuit protection, required by the National Electrical Code (NEC). It differs from a standard breaker in that it does not have a thermal overload unit.

MOTOR EFFICIENCY

A measure of how effectively a motor converts electrical energy into mechanical energy. Motor efficiency is never 100 percent. It is a variable that depends on a given motor's performance. Tabulated at 100, 75 and 50 percent load, it is the ratio of power output to power input.

MOTOR HORSEPOWER RATING

The motor horsepower nameplate rating fully loaded at the ambient temperature.

MOTOR, ELECTRIC

A rotating device which converts electrical power into mechanical power.

NEC

The National Electrical Code (NEC) is the standard of the National Board of Fire Underwriters for electric wiring and apparatus, as recommended by the National Fire Protection Association.

NEC CODE LETTER

Motors with 60 and 50 Hertz ratings shall be marked with a code letter designating the locked-rotor KVA per horsepower on 60 Hertz.

NEMA

National Electrical Manufacturers Association, a non-profit trade association supported by the manufacturers of electrical apparatus and supplies. NEMA promulgates standards to facilitate understanding between the manufacturers and users of electrical products.

NEUTRAL

The point common to all phases of a polyphase circuit, a conductor to that point, or the return conductor in a single phase circuit. The neutral in most systems is grounded at or near the point of service entrance only.

NFPA

National Fire Protection Association. Sponsors and publishes the National Electrical Code (NEC).

NORMALLY OPEN and NORMALLY CLOSED

The terms "Normally Open" and "Normally Closed" when applied to a magnetically operated switching device — such as a contactor or relay, or to the contacts thereof — signify the position taken when the operating magnet is de-energized. These terms pertain to all switches.

OHM

Unit of electrical resistance. One volt will cause a current of one ampere to flow through a resistance of one ohm.

OHMMETER

A device for measuring electrical resistance expressed in ohms.

OVERLOAD PROTECTION

Overload protection is the effect of a device operative on excessive current, but not necessarily on short circuit, to cause and maintain the interruption of current flow to the device being governed. Re-set may be manual or automatic

OVERLOAD RELAY

A relay that responds to electric load and operates at a preset value of overload. The unit senses the current in each line to the motor and is either bimetallic, melting alloy or solid state actuated. It may be of the non-compensated or ambient-compensated type, and of a standard or fast-trip design.

PHASE (THREE PHASE CIRCUIT)

A combination of circuits energized by alternating electromotive forces which differ in phase by one-third of a cycle (120 degrees). In practice, the phases may vary several degrees from the specified angle.

PHASE MONITOR

A device in the control circuit of motors which monitors the three phase voltage and protects against a phase loss (single phasing), under voltage (brown outs), phase reversal (improper phase sequence) and phase imbalance. Most are adjustable to set the nominal voltage and some have a LED indicator to indicate acceptable voltage and phase conditions. The output contacts are used to control the motor starters and provide signaling for telemetering.

PILOT DEVICE

Directs operation of another device:

  • Float switch — A pilot device responding to liquid levels.
  • Limit switch — A pilot device operated in response to a mechanical operation.
  • Pressure switch — A pilot device operated in response to pressure levels.
  • Temperature switch — A pilot device operated in response to temperature values.

All of the above switches cause a contact change of the switch at pre-set or adjustable points.

PILOT LIGHT

A lamp available with various colored lenses designed to operate on a control voltage. They are each turned On and Off to provide the required indication for specific functions or alarm conditions. They are available in various sizes and voltage ratings. They are each designed for a specific bulb style and base configuration and some have an integral transformer to allow the use of low voltage bulbs. Bulbs may be either incandescent or LED types.

POWER FACTOR

The ratio of the true power to the volt-amperes in an alternating current circuit. Power factor is expressed in a percent of unity either lagging for inductive loads or leading for capacitive loads. Resistive loads produce a unity power factor.

PUSHBUTTON

Part of an electrical device, consisting of a button that must be pressed to effect an operation.

RATED VOLTAGE

The voltage of electrical apparatus at which it is designed to operate.

REDUCED VOLTAGE

A starter that is used to furnish reduced voltage for starting an alternating current motor. It includes the necessary switching mechanism. This is the most widely used reduced voltage starter because of its efficiency and flexibility.

RELAY

An electric device that is designed to interpret input conditions in a prescribed manner and, after specified conditions are met, to respond and cause contact operation or similar abrupt changes in associated electric control circuits.

RELAY, ELECTROMAGNETIC

A relay controlled by electromagnetic means, to open and close electric contacts.

RELAY, SOLID STATE

A completely electronic switching device with no moving parts or contacts.

REMOTE CONTROL

Control function initiation or change of electrical device from a remote point.

RESISTANCE

The non-reactive opposition which a device or material offers to the flow of direct or alternating current. Usually measured in ohms.

RPM

Revolutions per minute of the motor/pump rotating assembly.

SAFETY SWITCH

An enclosed, manually-operated disconnecting switch, which is horsepower and current rated. Disconnects all power lines simultaneously.

SEAL FAILURE ALARM

The sensing and indication of the intrusion of water into the oil-filled seal chamber between the inner and outer shaft seal of a submersible pump.

SELECTOR SWITCH

A multi-position switch which can be set to the desired mode of operation.

SERVICE FACTOR

A safety factor designed and built into some motors which allows the motor, when necessary, to deliver greater than its rated horsepower.

SINGLE PHASE

A circuit that differs in phase by 180 degrees. Single phase circuits have two conductors, one of which may be a neutral, or three conductors, one of which is neutral.

STANDBY POWER SUPPLY

The power supply that is available to furnish electric power when the normal power supply is not available.

STAR CONNECTION

Same as a "Y" or "Wye" connection. This three-phase connection is so called because, schematically, the joint of the "Y" points looks like a star.

STARTER

A device used to control the electrical power to motors and provide overload protection as required by the NEC. The starter can be operated manually, electrically, or by automatic pilot devices. A starter has two basic parts — a contactor for power switching and an overload relay for protection.

STARTING AMPS (LOCKED ROTOR)

The maximum current drawn by the motor during the starting period.

STARTING RELAY

A relay — actuated by current, voltage or the combined effect of current and voltage — which is used to perform a circuit-changing function in the primary winding of single phase induction motor within a pre-determined range of speed as the motor accelerates; and to perform the reverse circuit-changing operation when the motor is disconnected from the supply line. One of the circuit changes that is usually performed is to open or disconnect the auxiliary winding (starting) circuit.

SUBMERSIBLE MOTOR

A motor whose housing and terminal box is so designed that the motor can run underwater — completely submerged at an allowable temperature.

SURGE ARRESTER

A protective device typically connected to the input power for limiting surge voltages on equipment by discharging or bypassing surge current.

SWITCH

A device for making, breaking, or changing connections in a circuit.

TELEMETERING

The transmitting of alarm and control signals to and from remote lift station controls and a central monitoring location.

TERMINAL BLOCK

An insulating base equipped with terminals for connecting wires.

THERMAL OVERLOAD PROTECTOR

Device, either a bimetal element or electric circuit, which protects motor windings from excessive temperature by opening a set of contacts. This device may reach its pre-set trip point as a result of ambient temperature, current, or both. May be automatic or manually set.

THREE PHASE CIRCUIT

A combination of circuits energized by alternating electromotive sources which differ in phase by one third of a cycle — that is, 120 degrees. A three phase circuit may be three wire or four wire with the fourth wire being connected to the neutral point of the circuit which may be grounded.

TIME CLOCK

A device used to schedule electrical On/Off cycling operations. The device may be solid state or electro-mechanical. The cycling operation must be programmed manually. The time clocks may operate in any increments of days, weeks, minutes, or hours.

TIME DELAY RELAY (TDR)

A device with either mechanical or solid state output contacts that performs a timing function upon energization or control signal.

TRANSDUCER

A device to condition and transform an analog signal to a specific variable output electrical signal proportional to the input signal. Typical inputs include variable pressure, level, voltage or current. Some common outputs are 0 to 1mA, 4 to 20 mA, and various mVdc signals. A transducer must be specifically designed to be compatible with the input/output requirements of the total system.

TRANSFORMER

A static electric device consisting of a single winding, or two or more coupled windings, used to transfer power by electromagnetic induction between circuits at the same frequency, usually with changed values of voltage and current.

TVSS (Transient Voltage Surge Surpressor)

A protective device connected to the control voltage for protection of the control equipment from fast acting transient voltages.

VFD

Variable frequency drive.

VOLTAGE (NOMINAL)

A nominal value assigned to a circuit or system for the purpose of conveniently designating its voltage class (as 120/240, 480/240, 600, etc.). The actual voltage at which a circuit operates can vary from the nominal within a range that permits satisfactory operation of equipment.

VOLTMETER

An instrument for measuring voltage.

WATT

A unit of measure of electrical power.

WYE CONNECTION

See Star Connection.