Borehole Pump Control Box
What a borehole control box does, how single-phase and three-phase boxes differ, the signs of failure, what you can safely check yourself and what must go to a registered electrician.
Last reviewed . Prices are indicative, from published prices, checked on 2 October 2026. They are not quotes.
Part of the borehole pumps guide.
Do not open the box to find the fault
A control box carries mains voltage. Looking at it from the outside is fine. Opening it, testing it or rewiring it is a job for a registered electrician. We do not publish a wiring diagram or a colour-code table on this page, for a reason explained below.
What a borehole pump control box does
A single-phase three-wire submersible motor cannot start by itself. Franklin Electric's manual says it needs a control box, which contains starting capacitors, a starting relay, overload protectors and, in some sizes, running capacitors. When power is applied, the start and main windings are both energised. As the motor speeds up, the relay opens and drops the starting circuit, and the motor carries on running on the main winding or on the main winding plus the run capacitor.
The box and the motor are one assembly. Franklin warns that running a motor without a control box, or with an incorrect one, can result in motor failure. A South African supplier makes the same point: a box from a different kW rating will fit the wires but carry the wrong capacitors, and the motor will run hot and fail. For example, one local range lists a 35 microfarad capacitor and 6 A for its 0.75 kW box, 45 microfarad and 10 A for its 1.1 kW box, and 50 microfarad and 14 A for its 1.5 kW box. Match kW and voltage exactly.
Single-phase and three-phase boxes in outline
This is an overview, not an installation guide. Which one you have depends on your supply and your motor.
Single-phase (domestic, 230 V)
- A surface box holding the start capacitor and a starting relay, with a run capacitor in some sizes and overload protection in some models.
- Only three-wire single-phase motors need it. It must match the motor's kW and voltage.
- Standard boxes switch manually. Protected versions add overload, voltage and dry-run protection (see below).
Three-phase (400 V and above)
- No capacitor box. The motor is switched by a starter or panel with a contactor and overload relay.
- Franklin says the overload relay must trip in under 10 seconds at 5 times rated current, trip at 120 percent, protect against single phasing and be temperature compensated.
- Protection units can watch under and overload, under and over voltage, current unbalance, an overheated motor and phase reversal.
- Direction of rotation matters: low delivery from a new three-phase pump may mean it is running backward. Reversing it means swapping two leads with the power off, which is electrician work.
Signs a control box is failing
These are possibilities, not a diagnosis. The box, the motor, the pump, the supply and the water system all produce similar symptoms. Franklin's manual cautions that capacitor and relay tests are indicative, not conclusive: a capacitor can test good and still have lost capacity.
| What you notice | What it can point to | What to do |
|---|---|---|
| The pump hums but does not start, or keeps trying | A failed start capacitor or starting relay, or a pump jammed by sand. Franklin Electric notes that a bound pump draws 3 to 6 times normal current until the overload trips. | Switch it off at the DB board. Repeated attempts and rapid cycling can damage the motor. Call a registered electrician. |
| Burnt smell, a swollen capacitor, scorch marks | A component has failed or overheated. These are the visual signs repair guides list for a failed control box. | Switch off at the DB board and do not open the box. A registered electrician should replace the part. |
| The breaker or the box overload keeps tripping | Low supply voltage, a box overheating in the sun, a defective box, a damaged motor or cable, or a worn pump or motor. That is Franklin's fault list for this symptom. | Reset the breaker once. If it trips again, leave it off and call an electrician. |
| The pump starts and stops again and again | Usually the water side: a waterlogged pressure tank, a stuck check valve, a pressure switch fault or a leak. Excessive cycling wears relays and capacitors. | Look for leaks, and ask your pump installer to check the tank air charge. Franklin gives a limit of 100 starts a day for single-phase motors from 0.75 to 4 kW. |
| It runs and runs, or delivers little water | Often not the box at all: a low water level in the borehole, a leak, a worn pump, a blocked intake or a stuck check valve. A box malfunction is also on Franklin's list. | If the borehole may be drawn down, switch off and rest it. Ask your pump installer to check. |
| Nothing happens at all | A tripped breaker, a pressure switch fault, supply voltage outside about 10 percent of the motor rating, loose or corroded connections, or a failed box or motor. | Check the DB board. Everything else needs a registered electrician, because testing needs live voltage. |
What you can check, and what needs a registered electrician
Safe for an owner (look, do not open)
- Look at the DB board. If the breaker has tripped, switch the pump off, reset once, and leave it off if it trips again.
- Look at the control box from the outside. Note a burnt smell, a swollen capacitor, scorching, water or insects inside, or damaged cable. Look only: do not open it.
- Look at where it sits. If it is in direct sun or a damp pit, tell your electrician, because that shortens capacitor life and causes unnecessary overload trips.
- Walk the water side: look for leaks at the tank, taps and pipes, and listen for rapid cycling. A waterlogged tank or a leak makes a pump start too often.
- Write down the pump and motor make, the kW, the voltage, the box label and when each fault happened. Give it to the electrician.
- Find your Certificate of Compliance for the installation, and ask any electrician for their registration details.
Registered electrician only
- Opening the box. Franklin Electric's own tests on a live single-phase box say the power must be on and that you must not touch live parts.
- Measuring voltage or current, and testing or replacing capacitors, relays or the whole box.
- Any change to wiring, earthing or the supply cable.
- Fitting surge arresters, dry-run or voltage protection.
- Three-phase starters and panels, including checking the direction of rotation.
- Anything that adds to or alters the electrical installation.
The law: registered person and Certificate of Compliance
The Electrical Installation Regulations, 2009 (under the Occupational Health and Safety Act) set the rules. This is a plain-language summary of the regulations as published, not legal advice.
- The user of an electrical installation is responsible for its safety, safe use and maintenance (regulation 2).
- The user must have a valid Certificate of Compliance for the installation (regulation 7(1)), with a narrow exception for some installations that predate October 1992 (regulation 7(3)). Where an addition or alteration is made, a Certificate of Compliance is needed for at least the addition or alteration (regulation 7(4)).
- Only a registered person may issue a Certificate of Compliance (regulation 9(1)). A registered person is registered as an electrical tester for single phase, an installation electrician or a master installation electrician (regulation 1).
- A registered person must exercise general control over all electrical installation work, and no person may allow such work without that control (regulation 5(4)).
- Anyone who does installation work as an electrical contractor must be registered as one (regulation 6(1)), and anyone who undertakes the work must make sure a valid Certificate of Compliance is issued for it (regulation 9(4)).
In practice: ask for the electrician's registration details, get the Certificate of Compliance, and ask whether a like-for-like control box swap needs a new certificate on your installation. That last question is for the registered person to answer, not for this page. A supplier's installation guide also says to confirm the installation against SANS 10142-1 and to have a qualified electrician do it.
Why there is no wiring diagram on this page
Searches for a borehole pump control box wiring diagram are common, and we understand why. We do not publish one, because wiring depends on the make, the kW, the capacitor and relay type, and the motor leads. A diagram for a different box, even at a different kW, can connect a motor wrongly and destroy it, and it can be dangerous to the person doing the work. Even the colours on a motor cable are not a safe guide: Franklin includes a procedure for technicians to identify leads when the colours are unknown or mixed.
Use the diagram printed on, or supplied with, your own box, or the manual from the maker of your motor and box. Franklin Electric publishes its diagrams in its own AIM manual, and that covers Franklin equipment only. Then have a registered electrician do the work. Give them the box label, the pump and motor make, the kW and the voltage.
Surge and dry-run protection
A basic box starts the pump. It does not protect it from lightning, from running dry or from a bad supply. These protections cost far less than a new pump, and each needs an electrician to fit.
Surge and lightning
A Borehole Water Association article says lightning can induce tens to hundreds of thousands of volts in underground cables, far more than a 230 V motor or a controller can take. It recommends arrestors at the control box and in a weatherproof box near the borehole, earthed to the motor shell or metal rising main rather than a ground rod, and checked after thunderstorms.
Franklin agrees: use properly rated arrestors on every submersible installation, earthed to the motor frame or to a metal drop pipe or casing that reaches below the pumping level. It says a ground rod gives little or no protection for the motor.
Dry running
A pump supplier lists three ways to protect against dry running: an intelligent control box, a level probe or a float switch. Franklin makes load-sensing devices that shut the motor off if the load drops below a preset level for 4 seconds, and a microprocessor unit that monitors for dry well, waterlogged tank, high and low voltage, and mud or sand clogging.
Protection is not a licence to over-pump. The same supplier says to size the pump below the tested yield and set it at least 3 m below the pumping water level. See the yield testing guide.
Overload, voltage and heat
Overload and voltage protection come with the protected boxes described in the price table. Franklin says control boxes should never be mounted in direct sunlight, that heat shortens capacitor life and causes needless tripping, and that a damp well pit speeds corrosion. A box with a voltage relay must stay upright. If yours sits in the sun or a damp pit, ask your electrician about moving or shielding it.
Solar pumps use a controller, not a capacitor box
A DC solar borehole pump runs from the panels through a controller. One South African supplier describes an MPPT controller with no inverter and no batteries, storing water in a tank instead. Ask the supplier before you substitute a different one. Read the solar borehole pumps guide for sizing and prices.
What a borehole control box costs
Indicative, from published prices on South African supplier sites, checked on 2 October 2026. These are prices for the box as a part. Electrician's labour, call-out and any Certificate of Compliance are extra, and we found no published figure for those that we could rely on.
| Type | What it does | Indicative price | Note |
|---|---|---|---|
| Standard single-phase box, manual switching | Holds the start and run capacitors; starts and runs the motor. | About R190 to R570 | Parts only, for motors up to 2.2 kW. Hurricane-range listings exclude VAT (R190 to R235), two suppliers include it (R330 and R570), and one gives R450 without saying. |
| Box with built-in motor protection | Adds overload protection against over-current. | From about R1,270 | Pumps.co.za, including VAT. |
| Digital protection panel | Electronic monitoring and protection with a fault display. | From about R2,220 | Pumps.co.za, including VAT. |
| Intelligent control box | Dry-run, overload, over- and under-voltage protection, with automatic restart. | From about R3,840 | Pumps.co.za, including VAT. Its 230 V boxes range from R250 to R3,900. |
| Three-phase starters and protectors | Starting and protection for 400 V and 525 V motors. | Priced to specification | No published figure we could rely on. |
Price depends on kW, brand and protection level. A cheaper box saves money until the day a dry run or a lightning strike destroys the pump, which one supplier's guide says protection costs far less than replacing. We do not rank brands.
Before you replace a control box
- Confirm the motor is a single-phase three-wire type and note its kW and voltage. The box must match both.
- Ask whether to fit a protected box. Think about dry running, overload and voltage swings on your supply.
- Ask what the electrician will test, and what will be on the Certificate of Compliance.
- If the box failed more than once, ask why. A waterlogged tank, low voltage or a hot position kill boxes.
Control box questions
What does a borehole pump control box do?
For a three-wire single-phase submersible motor it holds the starting capacitor, the starting relay, overload protection and, in some sizes, a running capacitor. These get the motor turning and then drop out the starting circuit. Without the right box, or with the wrong one, the motor can fail.
Can I use any control box on my pump?
No. The box and the motor work as one assembly. A box rated for a different kW will fit the wires but carry the wrong capacitors, and the motor will run hot and fail. Match the kW and voltage exactly, and ask the maker or supplier if you are unsure.
Can I wire or repair a control box myself?
Do not. Electrical installation work in South Africa has to be under the control of a registered person, and a Certificate of Compliance can only be issued by one. Mistakes can ruin the motor, and Franklin warns of serious or fatal electric shock where equipment is not earthed properly. Look at the box from the outside, then call a registered electrician.
Why does my borehole pump hum but not start?
A failed start capacitor or starting relay, a jammed pump, or low supply voltage can all do this. They look the same from the outside, and even an electrician's capacitor test is only indicative, so the fault needs a registered electrician with the right test gear.
How much does a borehole pump control box cost?
A standard manual single-phase box is listed from about R190 to R570 as a part. Boxes with overload protection, digital protection or dry-run protection run from about R1,270 to R3,840. Labour and any Certificate of Compliance are extra.
Do solar borehole pumps have a control box?
They have a controller instead of a capacitor box. A DC solar pump runs from the panels through a controller (an MPPT controller in the range one supplier describes), with no inverter or batteries. See the solar pumps guide.
Need a pump repaired or a control box replaced?
Switch the pump off, note the symptoms, and ask for a quote. Check that whoever does the electrical work is a registered person and will issue a Certificate of Compliance.
Sources
- Electrical Installation Regulations, 2009 (Government Gazette 31975, 6 March 2009) (registered persons, Certificate of Compliance, user responsibility)
- Franklin Electric AIM manual: 50 Hz submersible motors (what a box contains, fault lists, three-phase protection, surge arrestors, load-sensing devices, box location. Covers Franklin equipment only)
- Pumps.co.za: borehole pump guide (protection tiers and prices, matching box to motor, dry-run protection, solar controller)
- BWA Borehole Water Journal: lightning, the not-so-silent borehole pump killer (John Tonkin, 2016) (surge arrestors and earthing)
- Borehole Pumps South Africa: standard control box 220 V, 0.75 kW (price, capacitor and current rating)
- Borehole Pumps South Africa: standard control box 220 V, 1.1 kW (price, capacitor and current rating)
- Hurricane Pumps: standard control box 220 V, 1.5 kW (price, capacitor and current rating)
- Jordan Group: control box (price)
- ACDC Dynamics: 0.75 kW control box for submersible motor (price including VAT)
- Reverse Osmosis SA: borehole control box for 1.1 kW motor (price including tax)
- Borehole Repair: borehole pump not working (visual signs of a failed control box)