A control box for a borehole pump sits above ground, often on a pole or a wall near the hole, and does two jobs: it starts the pump and it protects it. Inside are the parts that get a single phase motor turning, the switches that stop it when the water runs out or the voltage goes wrong, and often surge protection against lightning. This page explains what the parts and wires do in plain terms. It is not a wiring guide: the box and its connections are mains electrical work for a qualified electrician.
2 wire and 3 wire pumps
Single phase borehole pumps come in two kinds. A 2 wire pump has its start gear built into the motor, so the cable carries two conductors plus an earth, and the box above ground only has to switch and protect it. A 3 wire pump keeps its start gear above ground: the cable carries three conductors plus an earth, and the control box holds the capacitor and the relay that start and run the motor. That is why a 3 wire pump will not run without its box, and why the box must match the pump's motor size. Three phase pumps, common on farms, need a starter and phase protection instead.
What is inside the box
- Capacitor: helps a single phase motor start and run. A failed one makes the pump hum and not start, or trip. See pump spares.
- Relay or starter: switches the motor and, on 3 wire pumps, the start circuit.
- Overload: trips the motor if it draws too much current.
- Dry run protection: stops the pump when the water runs out, by sensing the current, a probe in the hole or a level switch.
- Voltage protection: cuts out on under or over voltage, useful where the supply is weak or surges after load-shedding.
- Surge and lightning protection: worth having in Highveld storm areas.
Timers, floats and variable speed drives
Many boxes also decide when the pump runs. A float switch in the tank starts the pump when the level drops and stops it when the tank is full, so a water tank on a stand fills without anyone watching. A timer limits pumping to set hours, useful on a low yield borehole that needs time to recover. A variable speed drive (VSD) runs the pump at the speed the demand needs, which gives steady pressure at the taps and a soft start that is easier on the motor and pipe. VSDs suit bigger pumps and booster systems.
Why an electrician wires it
A control box connects mains power to a motor sitting in water, through a cable that may run a long way down a hole. A wrong connection can burn out the motor, leave the protection doing nothing, or make the pipe and borehole head dangerous to touch. Fixed electrical installations should be done by a qualified electrician, and a registered electrician issues a Certificate of Compliance: ask for one. The electrician works from the maker's diagram for your equipment. See borehole pump installation for the full set.
What to put in your request
- Pump motor size in kW
- 2 wire, 3 wire or three phase
- Protection wanted: dry run, voltage, surge
- Float switch or timer to fill a tank
- Whether you need an electrician to fit it
Pump Control Boxes for homes, farms and businesses
- Homeowners: a box with dry run and surge protection for a garden borehole pump
- Smallholdings and plots: a float switch and control box so the pump fills the tank on its own
- Farms: three phase panels with phase failure protection on irrigation boreholes
- Complexes, estates and body corporates: a VSD panel giving steady pressure from a communal borehole
- Offices, shops, hotels and lodges: a lodge borehole box with a timer to rest a low yield hole
- Factories, plants and depots: pump panels with overloads and alarms for process water
- Mines and quarries: starter panels and protection for site water and dewatering pumps
- Municipalities, schools and clinics: village borehole panels with lightning protection and lockable doors
- Contractors and drillers: an electrician fitting control boxes on a borehole install contract
Frequently asked questions
Do you supply or wire control boxes yourselves?
Can you send me a wiring diagram for my pump?
Why does my control box keep tripping?
Does a 2 wire pump need a control box?
Pump Control Boxes by province and city
- Johannesburg
- Pretoria
- Centurion
- Midrand
- Sandton
- Randburg
- Roodepoort
- Krugersdorp
- Randfontein
- Germiston
- Boksburg
- Benoni
- Kempton Park
- Alberton
- Vanderbijlpark
- Vereeniging
- Durban
- Pinetown
- Pietermaritzburg
- Richards Bay
- Newcastle
- Ladysmith
- Gqeberha (Port Elizabeth)
- East London
- Kariega (Uitenhage)
- Mthatha
- Cape Town
- Bellville
- Paarl
- Stellenbosch
- George
- Worcester
- eMalahleni (Witbank)
- Middelburg
- Secunda
- Mbombela (Nelspruit)
- Rustenburg
- Brits
- Klerksdorp
- Potchefstroom
- Mahikeng
- Polokwane
- Tzaneen
- Kimberley
- Upington
- Bloemfontein
- Welkom
- Sasolburg