Circuit Components for a control unit

[Mecheng]

Hi,

I am designing a control system to power and control a 3phase motor/pump. the hydraulic part is ok but the electrical part I am trying to figure out what circuit componets I reuqire to make it a safe system. (a professional comapny will bild this for me but i wld like to understand the system myself to control the cost)

I assume I need the following:
1. circuit Breaker (RCD)
2. Contactor
3. Relay stack

I wonder how the level switch and pressure switches should be wired in the system. I am trying to look for eqipment in RS and Farnell...

Any block diagrams / pointers would be fantastic.

Regs

[PinkertonD]

I have a single phase 240vac control on my 365' deep well. The off-the-shelf high/low pressure switch costs about 24-bucks, the 50-A contactor I bought surplus for $30. It is 3-ph but I only use one phase contacts and the 240vac activation coil.

This controls the contactor.
http://www.grainger.com/Grainger/SQU...H02?Pid=search