WHAT IS A C.P.C. ?
C.P.C. stands for Constant Pressure Control . Its principal function is to maintain a constant pressure (hence its name) in a water supply system.
Some of the other functions it accomplishes are :
Soft start and soft stop of the main pump motor which reduces water hammer
Increased energy savings
WHAT IS A C.P.C. MADE UP FROM ?
PLEASE NOTE:
The connections between components are for illustrative purposes only
They are as follows
1- The Transistor Inverter - This device allows us to change the frequency of the incoming power supply . ( 1 or 3 phase ) This changed frequency, ranging from O.5 HZ to 60 HZ, is applied to the main pump motor thereby giving it an RPM range from 30 to 3600 RPM.
2 - P.L.C. - programmable Logic Controller This is nothing more than a standard computer without keyboard or screen. The P.L.C. contains a program that controls all the functions of the C.P.C.
3- Pressure Transmitter - The P.L.C. needs to know what pressure the system is presently at. This is the job of the Pressure Transmitter it converts the water pressure into a electrical signal which varies as the water pressure varies . This electrical signal is then fed into the P.L.C.
4- Pressure switch - The pressure switch is only used when the first auxiliary pump is switched to " HAND ". Its main purpose is to maintain a water supply in the event of main pump failure.
5- Main Pump - This pump is the one that is connected to the Transistor Inverter this is why it should always be a three phase motor.
6- Auxiliary Pump - This pump is to supplement the main pump due to overloading . It is sized usually smaller than the main pump.
Eg: 5 HP main + 3 HP aux
7.5 HF main + 5 HP aux
10 HP main + 7.5 HP aux
The magnetic for the auxiliary pump is controlled in the auto position by the P.L.C. and in the hand position by the Pressure switch. Our C.P.C. will support up to three auxiliary pumps .
7- Pressure gauge
8- Control switch - This switch allows the P.L.C. to go ahead and control the system.
9- H-0-A or " hand off auto '' switch - This switch selects between auto or manual mode for each of the auxiliary pumps. Each pump has its own switch.
10- Magnetics + Overload blocks - These handle the flow of current for each pump and also protects the motors from overloads.
11- Disconnect - Completely disconnects all power from the C.P.C.
12- Analog Digital section of P.L.C - Converts the analog signal from the pressure transmitter into a digital signal for the P.L.C. It also converts the digital speed signal from the P.L.C into an analog signal for the Transistor inverter.
13- Pressure Tank - Of nominal size its only use is to smooth out any pressure fluctuations and supply some drawdown on start up.
14- Water Fault Light "BLUE" - This light does not actually indicate a fault of any sort it only indicates that the pressure is out of the setpoint range.
15- Electric Fault Light "RED" - This light will indicate a fault with the inverter.
16- Run Lights "GREEN" - These lights will indicate which pumps are running .
