Abstract:
An electrical control system for energy efficient pump stations providing for continuous operation of a single primary pump with a second pump functioning as the support pump and a third pump acting as the standby/emergency pump. All pumps are of equal horsepower and horsepower selection is determined by the system curve to select the lowest, most efficient horsepower necessary to discharge water at the highest inflow rate while not allowing the water level to drop below the submerged pump level during continuous running of the primary pump. A timer having an indicator arm rotates one full revolution every thirty days changing the pump sequence to reduce wear and tear on individual pumps. Each pump functions as the primary, secondary and backup/emergency pump for the same number of hours during the monthly cycle. Adding control circuits enables one or more pumps to be added when necessary.

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     The invention of this Control System is unique as it is designed to control the operation of the pumps as presented in the Energy Saving Green Waste Water Pump Station Design concept (patent pending application Ser. No. 13/335,908). 
     BACKGROUND OF THE INVENTION 
     Pumping stations in sewage collection systems, also called lift stations, are normally designed to handle raw sewage that is fed from underground gravity pipelines (pipes that are laid at an angle so that a liquid can flow in one direction under gravity). Sewage is fed into and stored in an underground pit, commonly known as a wet well. The well is equipped with electrical instrumentation to detect the level of sewage present. When the sewage level rises to a predetermined point, a pump will be started to lift the sewage upward through a pressurized pipe system called a sewer force main from where the sewage is discharged into a gravity manhole. From here the cycle starts all over again until the sewage reaches its point of destination—usually a treatment plant. By this method, pumping stations are used to move waste to higher elevations. In the case of high sewage flows into the well (for example during peak flow periods and wet weather) additional pumps will be used. If this is insufficient, or in the case of failure of the pumping station, a backup in the sewer system can occur, leading to a sanitary sewer overflow and the discharge of raw sewage into the environment. 
     Sewage pumping stations are typically designed so that one pump or one set of pumps will handle normal peak flow conditions. Redundancy is built into the system so that in the event that any one pump is out of service, the remaining pump or pumps will handle the designed flow. In these days there are a lot of electronic controllers in the market designed specially for this application. The storage volume of the wet well between the ‘pump on’ and ‘pump off’ settings is designed to minimize pump starts and stops, but not enough to enable the pump to run continuously. 
     Traditional sewage pump stations incorporate both a wet well and a dry well. More modern sewage pumping stations do not require a dry well or pump house and usually comprise only a wet well. In this configuration, submersible sewage pumps with closely coupled electric motors are mounted within the wet well itself, submerged within the sewage. Due to the much reduced health and safety concerns, and smaller footprint and visibility, submersible pump sewage pumping stations have almost completely superseded traditional drywell sewage pumping stations. 
     Control panels provide the electrical power required to operate submersible pumps in lift stations. The traditional waste water pump station design requires five float switches including two sets of starts and stops for the primary pump (Pump-A) and the second pump (Pump-B) with the fifth float switch controlling the emergency alarm. Start switches for Pump-A and Pump-B are located at the wet well mid-elevation and are about six inches apart from each other. The lower start switch turns on Pump-A and the higher start switch turns on Pump-B. Both stop switches of Pump-A and Pump-B are located about six inches lower than the top of the motor and stop both pumps at the same time. A logic controller handles typical float switch and pump failures and can continue to operate the lift station on only one functioning float switch. 
     Efforts to improve energy efficiency of pump stations and to reduce maintenance costs of the pumps have been made over the years. The continual rise of energy costs to power the pumps has strained municipal and state budgets at a time when revenues have fallen. Infrastructure maintenance competes for tax dollars and is often put off as budget cutting is forced. The most highly touted improvement was the introduction of variable speed pumps in pump station design. The variable speed pumps were proven to reduce energy costs in other applications. However, in studies done by Dr. Thomas Walski, P. E comparing variable speed pumping to constant speed pumps in systems for the relatively flat system head curves in water distribution systems (Walski, 2001, 2005, 2111; Walski, Bowdler and Wu, 2005), Dr. Walski found in each case, “when a pump is selected to correctly match the system, the constant speed pump has a lower energy cost than the variable speed pump whether the storage is on the discharge side as in elevated water storage or on the suction side as in a wet well at a sewage pumping station”. So when are variable speed pumps more efficient? Dr. Walski states, “Variable speed pumping becomes more attractive in distribution systems that have no discharge side pumping and hence the pumps cannot be turned off. Instead, they must be run continuously.” Since variable speed pumps are not more efficient in waste water pump stations and maintenance costs for variable speed pumps can be significantly higher than those for constant speed pumps plus the initial purchase cost of variable speed pumps is known to be higher than constant speed pumps, there is a need for a new method to reduce energy and maintenance costs without significant costs of retrofitting existing pump stations. 
     BRIEF SUMMARY OF INVENTION 
     The invention of this control system is designed to control the operation of the submerged pumps as presented in the Energy Saving Green Waste Water Pump Station Design concept (patent pending application Ser. No. 13/335,908). The pumps will be of minimum horsepower with a single pump running constantly after initial power up of the pump station. There are three or more submerged pumps run by this control system with the constant run pump functioning as the primary pump, a second pump having the role of the support pump and the third pump (in a three pump station) functioning as the standby/emergency pump. This invention includes a timer that controls the rotation of the pumps in their roles as primary, secondary and standby/emergency pumps. The timer control provides for each pump to function in each role equally each month so that wear and tear is reduced on the pumps. The detailed description section discusses the configuration of pump stations with three, four or more pumps. The control system to run the Energy Saving Green Waste Water Pump Station Design pump station has been invented so that energy and maintenance costs for running pump stations can be significantly reduced, greenhouse gasses associated with excessive energy usage in inefficient current pump station methods can be reduced, reduction of dependence on foreign oil can be achieved through efficiency and so that American jobs can be created through retrofitting current stations with this invention. 
    
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING 
         FIG. 1  is a schematic view of a control circuit suitable for a single submerged pump. 
         FIG. 2  is a schematic view of the electrical diagram for the power circuit and the control circuit for three submerged pumps further providing for continuous operation of a single pump, the support of a second pump and the operation of a standby/emergency pump. The figure includes the timer that controls the primary, secondary and standby/emergency pump running sequence. 
         FIG. 3  provides a side view (View  1 ) and a top view (View  2 ) of a Green Three Pump Lift Station compatible for use with the Green Waste Water Pump Station Control System. The placement of the submerged pumps and the start and stop switches are identified. 
     
    
    
     DETAILED DESCRIPTION OF INVENTION 
     This invention is the control method for green lift stations with three or more submerged pumps whereby the primary pump runs continuously. The specific embodiment shown in  FIG. 2  relates to the control panel that operates a pump station under the Energy Saving Green Waste Water Pump Station Design concept (patent pending application Ser. No. 13/335,908). Further the embodiment shown in  FIG. 3  relates to the float switch levels of a three pump lift station. The number of pumps in a lift station can be increased and the sequence of operation of this invention can be adapted to accommodate additional pumps as will be explained herein. 
     For better understanding of the control system in the Energy Saving Green Waste Water Pump Station Design, it is beneficial to first explain the operation of control of a submerged pump.  FIG. 1  provides the electrical diagram operation of a submerged pump. In  FIG. 1 , there are two electrical circuits that are powered from two separate power sources. These are the pump&#39;s power circuit  110  and the pump&#39;s control circuit  123 . 
     The pump&#39;s power circuit  110  is powered by three phase 480 volts or three phase 208 volts of electric power where the distribution panel  111  sends the current to the pump through the power circuit breaker  112  proceeding to the contactor  113 . If the contactor  113  is closed by control, the power goes to the motor starter  114  causing the motor  115  to run. 
     The pump&#39;s control circuit  123  is powered by single phase 120 volts of electric power. The 120 volt current goes through the stop-switch  116 , start-switch  117 , overload relay  118  and energizes the actuator  119  of the contactor  113 . The power circuit  110  and the control circuit  123  interact with each other only in the contactor  113 . The total coordinated function of several elements in the power circuit  110  and the control circuit  123  will insure the safe operation of the pump. 
     The power circuit  110  elements include the distribution panel  111 , the power circuit breaker  112 , the contactor  113 , the starter  114  and the motor  115 . The distribution panel  111  is a load center which receives power from the utility network. The power supply to the distribution panel  111 , in most cases, is three phase 480 volts or three phase 208 volts. In small lift stations, the power could be single phase 240 volts. The power circuit breaker  112  is part of the distribution panel  111  and serves two purposes. First, it acts as a manual make and break of the pump&#39;s power circuit  110 . Second, it serves as a safety device to protect the pump motor from burning up due to motor  115  overload. The contactor  113  is an automatic make and break of the pump&#39;s power circuit  110 . The interaction of control with the power circuit  110  is through the actuator  119 . The starter  114  reduces rushing current and protects the motor  115  from burning. The rushing current of a motor due to the absence of electro-magnetic force within the motor is six to seven times that of the rated full load current. The motor  115  usually is a sealed three phase motor. 
     The control circuit  123  elements include a 120 volt power supply usually coming from a three phase panel of 208 volts/120 volts or single phase of 240 volts/120 volts; a 20 amp control circuit breaker  124  which makes and breaks power to the control circuit  123 ; a stop switch  116  that acts as a motor  115  protective device by ensuring the motor  115  remains fully submerged; a start switch  117  whereby closing it&#39;s primary float switch and auxiliary contactor  125  by way of the auxiliary relay  120  the pump starts to run and continues to run until the water level drops down to the stop switch  116  at which time the pump stops; an overload relay  118  that normally is a closed relay, is thermal and when the motor  115  becomes hot due to overload, the relay  118  will break the control circuit  123  and stop the motor  115  by way of the actuator  119 . When the motor  115  cools down, the relay  118 , having a bimetal element, will connect the circuit. The actuator  119  coordinates the function of all elements in the control circuit  123  on the power circuit  110 . It is the means of interaction of control on the power circuit  110 . Light indicators  121  &amp;  122  are also elements of the control circuit  123 . When the pump is stopped, the red light indicator  121  will turn on. The green light indicator  122  will turn on when the pump is running. 
     Having an understanding of the operation control of a submerged pump, discussion now proceeds to the components of the Green Waste Water Pump Station Control System.  FIG. 2  illustrates the components of the Green Waste Water Pump Station Control System. This control system is an expansion of the diagrams and processes explained in  FIG. 1  for one submerged pump and it has been developed to insure that the operation of a lift station functions in accordance with the Energy Saving Green Waste Water Pump Station Design concept (patent pending application Ser. No. 13/335,908). This system works as a result of the cooperation and coordination of several collective elements, each having special functions. Some of the elements will have a single function while others may have multiple functions. 
     The power circuits  222   a ,  222   b  and  222   c  as shown in  FIG. 2  provide electric power to pumps  226   a ,  226   b  and  226   c    FIG. 2 . The power source for power circuits  222   a ,  222   b  and  222   c  is three phase 480 volt or three phase 208 volt power supplied from the power utility. The distribution panel  111   FIG. 1  (not shown in  FIG. 2 ) is a load center having an enclosure, bus bar and circuit breakers. The power circuit breakers  112   FIG. 1  (not shown in  FIG. 2 ) are devices providing a manual means to safely connect or disconnect the power circuits  222   a ,  222   b  and  222   c  even under load, in other words, when the pump rated current is passing through its power circuit. Circuit breakers  112   FIG. 1  (not shown in  FIG. 2 ) for power circuits  222   a ,  222   b  and  222   c  also are safety devices and will interrupt the power to the pumps  226   a ,  226   b  and  226   c  when the current is larger than 115% of the motor rated amps. Most manufacturers provide 15% as the overload safety factor for one hour of motor operation. When the power circuit breaker  112  acts as the safety device, a timely response to protect the motor is dependant on the magnitude of the overload. Slowing action or thermal overload at a rate of 45% to 500% of the pump rated current determines the timing for the breaker  112  to act which may be 30 seconds to a few minutes. The acting device is a bi-metal element and acts by elevation of temperature. When there is a very large overload, the magnetic overload of the breaker  112  interrupts the current instantaneously, on the order of a fraction of a second. The action is by magnetic force generated by a coil which is in series with the circuit  222   a ,  222   b  and  222   c  and 100% of the current passing through it. 
     Contactors  223   a ,  223   b  and  223   c    FIG. 2  are also elements in the power circuits  222   a ,  222   b  and  222   c , automatically connecting or disconnecting the power to the pumps  226   a ,  226   b  and  226   c . Control circuits a, b &amp; c  FIG. 2  supervise the operation of the pumps  226   a ,  226   b  and  226   c  only through the contactors  223   a ,  223   b  and  223   c . The effect of control on the power circuits  222   a ,  222   b  and  222   c  is by the actuators  224   a + 225   a ,  224   b + 225   b  and  224   c + 225   c    FIG. 2 . Actuators  224   a + 225   a ,  224   b + 225   b  and  224   c + 225   c  automatically connect or disconnect the power circuits  222   a ,  222   b  and  222   c  through the contactors  223   a ,  223   b  and  223   c . The actuators  224   a + 225   a ,  224   b + 225   b  and  224   c + 225   c  have two components. They are the actuator coils  224   a ,  224   b  and  224   c  and the actuator arms  225   a ,  225   b  and  225   c . The actuator arms  225   a ,  225   b  and  225   c  have movable contact parts attached to them. The actuator coils  224   a ,  224   b  and  224   c  provide electromagnetic force when energized by the current from control circuits a, b &amp; c. This magnetic force pulls the actuator arms  225   a ,  225   b  and  225   c  closing the power circuits  222   a ,  222   b  and  222   c . The actuator arms  225   a ,  225   b  and  225   c  are made of pure iron rod. The force of the magnet closes the contacts and in the absence of the magnetic force, the spring action breaks the contacts. The motor starter  114   FIG. 1  (not shown in  FIG. 2 ) reduces the rush in current and prevents the motors  226   a ,  226   b  and  226   c  from overheating at the start. The motors  226   a ,  226   b  and  226   c  are three phase submerged pump motors, fully closed with a mechanical seal. 
     In  FIG. 2 , control circuits a, b and c provide for the safe operation of the lift station. The control circuit system is a combination of several elements. The action of each element occurs at a certain time and the coordination &amp; cooperation of the elements is essential for the successful operation of the lift station. The components are the power source  227 , the timer  228 , the timer contactors  229   a ,  229   b  and  229   c  and the indicator arm  228   i . The power source  227  usually is 120 volts, single phase from a low voltage distribution panel of three phase 208 volts or single phase 240 volts. It is essential that the pumps  226   a ,  226   b  and  226   c  run in sequence with equal running time to insure all three pumps  226   a ,  226   b  and  226   c  experience the same wear and tear. To change over the pump operation automatically, timer contactors  229   a ,  229   b  and  229   c  are added to control circuits a, b and c. The timer contactors  229   a ,  229   b  and  229   c  connect the 120 volts of control power to control circuits a, b and c in sequential manner. The timer  228  is similar to a clock in that the timer  228  face has 30 divisions each representing one day. A single indicator arm  228   i  on the timer  228  rotates clockwise with one full rotation occurring over a 30 day period. If position T 1   FIG. 2  is zero days, then positions T 2   FIGS. 2  and T 3   FIG. 2  will be ten days and twenty days respectively. The timer contactors  229   a ,  229   b  and  229   c  are in series with the control circuits a, b and c and connect or disconnect the 120 volt power source to the control circuits a, b and c when the timer indicator  228   i  is in position T 1  or T 2  or T 3  and energize or de-energize the respective contactor coils  229   a ,  229   b  and  229   c.    
     The operation of the timer contactors  229   a ,  229   b  and  229   c  begins with the indicator arm  228   i  at position T 1  or zero days. The coil of contactor  229   a  will energize thereby connecting control circuit a to the 120 volt power source while the two other circuits b and c have no power and are disabled. Under this condition, Pump-A  226   a  runs as the primary pump. Pump-B  226   b , on circuit a, runs as the secondary pump and Pump-C  226   c , on circuit c which is energized by the closing of the overflow switch  232   a  so that the overflow circuit  234   a  brings power to circuit c, is the standby/emergency pump that will run under emergency conditions. Contactor  229   a  remains energized for a period of ten days until the indicator arm  228   i  reaches point T 2 . At this time, contactor  229   b  is energized so that current now powers control circuit b. Pump-B  226   b  has now become the primary pump. Pump-C  226   c , on circuit b, becomes the secondary pump and Pump-A  226   a , on circuit a powered by overflow circuit  234   b  when overflow switch  232   b  is connected, becomes the standby pump for emergency operation. Pump-B  226   b  runs continuously for ten days as the primary pump until the indicator arm  228   i  reaches point T 3  thereby energizing control circuit c. Pump-C  226   c , on circuit c, begins operation as the primary pump. Pump-A  226   a , on circuit c, operates as the secondary pump and Pump-B  226   b , on circuit b powered by overflow circuit  234   c  when overflow switch  232   c  is connected, becomes the standby pump for emergency operation. After continuous operation of Pump-C  226   c  as the primary pump for ten days, the indicator arm  228   i  reaches point T 1  and the above cycle repeats every thirty days. 
     The following discussion applies to elements in the  FIG. 2 . In order to simplify the reading, whenever references are to drawing elements that apply to “a” “b” and “c” in general, only the numerical reference will be given. For instance, references for float switches  230   a ,  230   b  and  230   c ,  231   a ,  231   b  and  231   c  and  232   a ,  232   b  and  232   c  will simply be identified as  230 ,  231  and  232 . Float switches  230 ,  231  and  232  are water level control devices that are stationary at desired elevations. Their effect on control is by connecting or disconnecting the power to the control circuits a or b or c. The connecting and disconnecting action of the float switches  230 ,  231  and  232  is mechanical and is accomplished by the forces of floater buoyant force or floater gravity force. There are two kinds of float switches, break (stop switch)  230  and make (start switch)  231  and  232 . Stop switches  230  break the 120 volt power to the actuator coil  224  stopping the motor  226 . When a pump motor  226  is running, discharging the water causes the water level to drop down to an elevation slightly below the stop switch  230  level. At this point, the stop float is out of the water and the weight of the stop floater will break the control circuit a or b or c followed by the power circuit  222  stopping the pump  226 . The stop switch  230  works by stop float weight (a stop float is similar to the typical start float  235  identified in  FIG. 2 ). The start switches  231  and  232  act when the water level rises slightly higher than the floater level. The net force of buoyancy minus weight will close control circuit a, b or c, depending on the position of the timer indicator arm  228   i , and energize the actuator  224 . The actuator  224  closes the motor contactor  223  and establishes 480 volts of power in the pump&#39;s power circuit  222 . The pump  226  starts and begins discharging water out of the well  300   FIG. 3  causing the water level to drop down. As soon as the water level drops down a few inches below the level at which the stop switch  231  floater is fully elevated, the stop switch  231  floater is out of the water and its weight will pull down the start switch  231  interrupting the power to the actuator  224  thereby stopping the pump  226 . In situations where the water level repeatedly moves a few inches up and then a few inches down, the motor  226  starts and stops frequently, the contactor  231  almost shatters and the motor  226  will burn. For the pump  226  to continuously run until being stopped by the action of the stop switch  230 , the continuity of the current through the start switch  231  should be maintained. The auxiliary relay  233  sustains the current to the actuator  224  by its coil  120   FIG. 1  being energized by the initial action of the start switch  231  and its own auxiliary contactor  125   FIG. 1 . 
     To explain the operation of the standby/emergency pump start switch  232   a , the operation of the system where Pump-A is the primary pump, Pump-B is the secondary pump and Pump-C is the standby/emergency pump will be given. This occurs when the timer indicator arm  228   i  is in position T 1  so that control circuit a is energized. When the water level in the wet well  300  is elevated above the standby/emergency pump  226   c  start switch  231   c  level, the operation of the standby/emergency pump  226   c  becomes essential. Responding to this emergency condition, the start switch  231   c  closes the emergency control circuit c but control circuit c still has no power to command the operation of the standby/emergency pump  226   c . Further elevation of the water will close the overflow switch  232   a  energizing control circuit c through control circuit a so that Pump-C, functioning as the standby/emergency pump  226   c , begins operation. 
     A pump station operating under the Energy Saving Green Waste Water Pump Station Design concept (patent pending application Ser. No. 13/335,908) operates differently than those operating under traditional pump station designs. Pump stations designed under the traditional method have two or more pumps that turn on and off as determined by water levels. One pump is the lead pump and the other is the lag pump so that they do not start simultaneously. However, the two pumps do in fact run together and stop at the same time. In contrast, the Energy Saving Green Waste Water Pump Station has a minimum of three pumps  226   a ,  226   b  and  226   c . The location of the indicator arm  228   i  on the timer  228  determines which control circuit a, b or c is energized. When control circuit a is energized, Pump-A  226   a , is continuously running as the primary pump  226   a . The second pump, Pump-B  226   b , supports the primary Pump-A  226   a  when the water level rises to the start switch level  231   b  (located on circuit a) and backup/emergency Pump-C  226   c  runs if one of the first two pumps fails or when extreme water inflow conditions like tropical storms require additional pumping capacity. The case for four or more pumps will be explained later. The primary pump, Pump-A  226   a , initially turns on when power is turned on to the pump station by manually turning on the power at the distribution panel  111  via the power circuit breaker  112 . This occurs when a newly constructed pump station or one retrofitted under the Energy Saving Green Waste Water Pump Station Design begins operation. It also occurs after pump station maintenance requiring the powering down of the station has taken place. 
     The operation of a full cycle sequence of the Energy Saving Green Waste Water Pump Station will be explained here.  FIG. 3  (View  1 ) shows the location of the start, stop and overflow control switches in the three pump Energy Saving Green Waste Water Pump Station Design.  FIG. 3  (View  2 ) shows the top view of the pumps in a three station. Under the condition where the timer indicator  228   i    FIG. 2  is in position T 1   FIG. 2  so that circuit a  FIG. 2  is the energized circuit, well water rising a few inches beyond the fully submerged pump elevation point  310  results in the buoyant force of the floater connected to stop switch  311  closing the stop switch  311  of primary Pump-A  307 . When the water rises to the elevation of the start switch  312  of the primary Pump-A  307 , the floater connected to start switch  312  closes the starter switch  312  of primary Pump-A  307  and primary Pump-A  307  starts to run. Primary Pump-A  307  continues to run until the dropping of the water level causes the Primary Pump-A stop switch  311  to break the 120 volts of control circuit a and primary Pump-A  307  will stop. Primary pumps run continuously under the Energy Saving Green Waste Water Pump Station Design and pump horsepower is predetermined with one pump continuous operation and energy conservation the primary focus. However, the primary pump stop switch is required so that if, for any reason the water level in the station drops below full pump submersion elevation  310 , the pump will stop in order to protect the pump from overheating. Lowering the elevation of stop switch  311  for the purpose of increasing well capacity is limited to the submersion depth  310  of the pumps  304 ,  307  and  308 . As long as the inflow rate is smaller or equal to the pump discharge, only Pump-A  307  will operate as the primary pump. When the inflow rate is larger than the discharge of Pump-A  307 , the water level will rise to the elevation of stop switch  313  of Pump-B  304 . This will result in the floater, attached to stop switch  313  of secondary pump Pump-B  304 , closing the circuit so that the control power reaches to the line side of start switch  314 . When the water level rises to the point that it reaches start switch  314  of Pump-B  304 , Pump-B  304  will start to run as the secondary pump. If, due to unusually extreme conditions such as a major storm or the break of a water main, the inflow rate is larger than the discharge of Pump-A  307  plus that of Pump-B  304 , then the water level will rise and close the stop switch  315  of standby/emergency Pump-C  308 , and further up will close the start switch  316  of Pump-C  308 . Since the timer contactor  229   c    FIG. 2  in control circuit c  FIG. 2  is off, Pump-C  308  will not start. When the water level rises another six inches, the overflow switch  317  connects the 120 volts of power from circuit a  FIG. 2  to control circuit c  FIG. 2  through standby/emergency Pump-C  308  overflow circuit  234   a    FIG. 2  and the standby/emergency Pump-C  308  will start to run as the emergency pump. The overflow switch  317  also triggers an emergency alarm that is audible, turns on an external warning light and transmits a signal via cell phone or other communication device to the waste water plant operators. Under this condition, all three pumps are operating until lowering the water level disconnects the stop switch  315  of Pump-C  308  resulting in resuming normal operations with primary Pump-A  307  and secondary Pump-B  304  running. 
     After 10 days, the timer contactor  228   i    FIG. 2  connects the 120 volts of power to control circuit b  FIG. 2 . The components on control circuit b will function exactly as those identified above for circuit a. Connecting power to circuit b results in Pump-B  304  assuming the role as the primary continuous run pump, Pump-C  308  becomes the secondary pump and Pump-A  307  functions as the standby/emergency pump. After another 10 days, the timer contactor  228   i  connects the 120 volts of power to control circuit c. The components on control circuit c will function exactly as those identified above for circuits a &amp; b. Connecting power to circuit c results in Pump-C  308  assuming the role as the primary continuous run pump, Pump-A  307  becomes the secondary pump and Pump-B  304  functions as the standby/emergency pump. The above full cycle will be repeated by the indicator arm  228   i  returning to position T 1 . 
     The Energy Saving Green Waste Water Pump Station Design also applies to lift stations having four or more pumps. Lift stations that regularly experience drastic changes in inflow rates often warrant the addition of one or more pumps to the three pump design. A 24 hour inflow profile revealing significant differences between the maximum and minimum inflows is the first step in identifying the four or more pump design station candidate. If the ratio of maximum to minimum of inflow is equal to or greater than three, the design of the well with four pumps is more feasible. 
     The Energy Saving Green Waste Water Pump Station Design controlled by this control system invention saves energy by employing three or more pumps with the lowest effective horsepower possible. Each pump is identical so that the sequencing process of rotating the pumps every ten days can be accomplished. This rotation of pumps extends useful life of the pumps and reduces maintenance costs. Increasing the horsepower of the three pumps instead of adding one or more pumps of equal horsepower increases energy costs. More importantly, the continuous run of the higher horsepower primary pump may result in the discharge rate exceeding that of the inflow thereby lowering the water below the fully submerged pump elevation resulting in frequent start and stops of the primary pump. This condition wears on or damages the running pump. An Energy Saving Green Waste Water Pump Station Design controlled by this invention for four pumps employs a fourth pump as the standby/emergency pump having one quarter of the total wet well horsepower versus one third of the horsepower installed in the three pump station. 
     Large re-pump stations also warrant additional pumps. In re-pump stations, the storage capacity has very little or no effect on water level regulation because of the large volume of inflow. It is essential that the pump capacity be large enough to respond to these inflows. For this reason, re-pump stations should be designed with a minimum of four pumps in such a way that three pumps are capable of discharging the inflow under worst case scenarios with the fourth pump functioning as the standby/emergency pump. 
     The Green Waste Water Pump Station Control System diagram for a four pump lift station operating under the Energy Saving Green Waste Water Pump Station Design concept is similar to that in  FIG. 2  with three pumps. An additional circuit would be added for the fourth pump so that Pump-A runs as the primary pump, Pump-B runs as the secondary pump, Pump-C runs as the tertiary pump and Pump-D is the standby/emergency pump. The face of the timer  228   FIG. 2  will have four contactors positioned at 90 degrees off each other and the automatic change over of pumps occurs every seven and a half days.