Solar Pump Installation & Commissioning: A Field Guide

Most solar pump problems reported as faults are installation problems. The four that account for the majority are an array string outside the controller's MPPT voltage window, undersized or badly spliced cable, a pump set at the wrong depth relative to the dynamic water level, and dry-run protection that was never properly configured. None is a component failure, and all four are cheaper to prevent than to diagnose from 80 metres down a borehole.

This guide covers installation and commissioning for a solar pumping system: what to check before you start, how to get the array and the wiring right, how to lower a submersible safely, and a structured first-start procedure. Sizing is a separate exercise — see the step-by-step sizing guide — and borehole-specific selection is covered in the deep-well selection guide. Follow the manufacturer's manual and local electrical regulations where they differ from any general guidance here; a solar array in the hundreds of volts is a serious electrical installation.

Before anything is unpacked

A short pre-installation check prevents most return trips.

• Verify the pump against the site data. Confirm the borehole's measured inner diameter against the pump's stated outer diameter, and the intended setting depth against the pump's maximum immersion rating. In the Aquasolar range that is 150 m for the deep-well series and 20 m for the high-flow open-well models.
• Confirm the duty. Check the model's rated head against the total dynamic head from the survey, and the rated flow against the well's sustainable yield. If flow exceeds yield, fix the design now, not after the first dry-run trip.
• Check the water data. Sand content and pH decide whether the pump you have is the right material specification — impeller pumps in this range are rated to ≤0.05% sand, screw pumps to ≤0.25%, with a liquid temperature range of 0–40 °C and pH 5–9.
• Inventory and inspect. Pump, controller, motor cable, splice kit, safety rope, rising main, array modules, mounting frame, earthing/grounding materials, level probe or float. Check the cable insulation for transit damage over its whole length.
• Measure motor insulation resistance before installation, and record the reading. That single number, taken again after installation, tells you whether damage happened during lowering.

Siting and mounting the array

Orientation and tilt. Face the array towards the equator — south in the northern hemisphere, north in the southern. Tilt is conventionally set at roughly the site latitude, which in low and mid latitudes usually lands in a 10–30° range. Keep a minimum tilt of about 10–15° even near the equator so that rain helps wash the glass rather than pooling dust.

Shading is disproportionate. Because modules in a string carry the same current, shade on one module drags down the whole string. Survey the site for shade across the whole day and the whole year — the winter sun is much lower, so a tree or building that clears the array in June may shade it in December.

Structure and access. Mount high enough and strongly enough to survive local wind loads and livestock. Leave room to walk around the array for cleaning, and consider a fence where animals or theft are a risk. Do not mount modules where the tank, mast or a taller neighbouring row will shade them.

Keep the controller out of the weather. In this range the submersible motor is rated IP68 but the controller is IP66 — mount it in shade, ventilated, above flood level, and out of direct rain. Note that controllers up to 750 W are integrated into the pump assembly while units from 1,100 W upwards use an external controller box that needs its own protected mounting.

Array wiring: the MPPT voltage window

This is the step most often got wrong, and it is worth understanding rather than copying.

Modules in series add voltage and keep current the same. Modules in parallel add current and keep voltage the same. The controller needs the array's operating voltage to sit inside its MPPT tracking window, and the array's open-circuit voltage to stay under the controller's maximum input rating.

• Too few modules in series and the array voltage never reaches the window: the pump either does not start or runs slowly all day, and the array looks "too small" when it is only miswired.
• Too many in series and open-circuit voltage can exceed the controller's limit, which risks damage.

Two effects catch people out. Open-circuit voltage rises as cells get colder, so the worst case for over-voltage is a cold, bright morning, not a hot afternoon — check the string against Voc at the lowest expected temperature. And operating voltage falls as cells heat up, which is part of why arrays are oversized relative to pump power in the first place.

The practical rule: use the module string configuration on the pump's datasheet. Every model in this catalogue publishes a nominal system voltage and a recommended array — for example 3 × 300 Wp on a 600 W, 72 V pump, or 10 × 300 Wp on a 2,200 W, 280 V pump — and system voltages across the range run from 12 V up to 385 V. If you must substitute a different module wattage, keep the series count and voltage behaviour equivalent rather than just matching total watts.

Also observe polarity and use the controller's own PV input terminals. These controllers include reverse-connection protection, but protection is a safety net, not a wiring method.

Cable, splices and earthing

Cable size is part of the hydraulics. Voltage dropped in cable is head the pump cannot produce. The published guidance for this range is 2.5–4 mm² copper by model, sized for approximately a 50 m run, stepping up one cross-section per additional ~50 m of drop. Count the full circuit: array to controller, and controller to motor.

Splices must be immersion-rated. A submerged joint needs a proper heat-shrink or resin splice kit, made up cleanly and in the dry. Insulation tape and generic connectors fail — sometimes months later, always expensively.

Support the cable. Clip it to the rising main at intervals so it cannot chafe against the casing as the column moves, and leave no tension on the cable itself.

Earthing and surge. Bond the array frame and the controller to earth as required by local regulation. Long cable runs to an exposed array in a lightning-prone region are the standard case for surge protection on the PV input — a modest cost against a destroyed controller.

Lowering a submersible pump

• Fit the safety rope. A stainless or polypropylene rope rated well above the assembly's wet weight, secured at the well head, is the cheapest insurance in the whole installation. Published pump weights in this range run from about 4.3 kg for a 2″ screw to 42 kg for the largest 6″ unit, before the rising main and water column.
• Assemble and lower in a controlled way. Support the weight on the rising main, never on the cable. Use a tripod or gantry for heavier assemblies. Keep the cable and rope paying out together, clipped as you go.
• Set the depth deliberately. The pump must sit below the lowest expected dynamic water level with a margin for seasonal decline, and above the well screen and bottom sediment so it does not draw in sand. Take the figures from the pumping test and driller's log; record the final setting depth in the handover documents.
• Do not exceed maximum immersion. 150 m for the deep-well series here; 20 m for high-flow open-well models.
• Fit a non-return valve in the rising main per the manufacturer's instructions, and a well cap or sanitary seal to keep surface contamination out.
• Re-measure insulation resistance after lowering and before energising. A drop against your pre-installation reading means cable or splice damage — find it now, while the pump is still retrievable cheaply.

Dry-run and level protection

Dry running is what actually kills submersible motors, and the protection has to be configured, not merely present. Controllers in this range publish protection against overload, over-current, under-load, under-voltage, reverse connection, over-temperature and dry running, plus soft start.

• Dry-run / low-water protection stops the pump when the water level falls to the intake. Confirm it is enabled and, where the controller offers a sensitivity or restart-delay setting, that the delay is long enough for the well to recover rather than short enough to cycle repeatedly.
• Tank-full control. A float switch or level probe that stops the pump when the tank is full prevents both overflow waste and pointless running. Many controllers accept this input directly — wire it during installation, not as an afterthought.
• Repeated dry-run trips are a design signal, not a nuisance. They mean the pump's flow exceeds the well's sustainable yield. The fix is a lower flow over a longer day into more storage, not disabling the protection.

Commissioning: a first-start sequence

Work through this in order and record the readings. The controller's LED display shows voltage, current, power, speed and error codes, which is all the instrumentation the procedure needs.

Two commissioning notes. Judge output against the irradiance you actually have — a pump commissioned at 09:00 under haze will not produce its rated flow, and that is not a fault. And if drawdown keeps falling for the whole hour of step 9, the pump is outrunning the well; resolve it before handover.

Fault-finding the usual field problems

The pattern to notice is that "the pump is faulty" is rarely the first explanation. Cable, array configuration, setting depth and well yield account for most of the table, and all four are recorded during a proper commissioning — which is exactly why the records matter.

Maintenance that actually pays

• Clean the modules on a schedule suited to local dust. Soiling is the cheapest lost output to recover.
• Check the array structure and wiring for wind damage, chafing and rodent damage at least annually.
• Watch the numbers, not just the water. A gradual fall in flow at a comparable irradiance is the early warning of wear, scale or a developing electrical problem.
• Re-check the water level across seasons, especially in the first year, and confirm the setting depth is still appropriate.
• Keep the commissioning record with the system. When something does go wrong years later, the original readings turn guesswork into diagnosis.

Next step

Browse the full pump range and each series' published protections, ratings and cable guidance, check your duty point with the free sizing calculator, or send us your borehole and site details and our engineers will confirm the configuration before you order.

FAQ

How many solar panels does a solar pump need, and how should they be wired?

Total array power is normally about 1.3–1.5 times the pump's rated power, but the wiring configuration matters just as much as the total. The string must deliver a voltage inside the controller's MPPT window and keep open-circuit voltage under the controller's maximum, so follow the module string configuration published on the pump's datasheet. Remember that open-circuit voltage rises in cold conditions, so check the worst case against a cold bright morning rather than a hot afternoon.

At what depth should a submersible solar pump be installed?

Below the lowest expected dynamic (pumping) water level with a margin for seasonal decline, and above the well screen and bottom sediment so it does not draw sand. Take the figures from the borehole's pumping test and the driller's log rather than from a rule of thumb, and stay within the pump's maximum immersion rating — 150 m for the deep-well series in this range and 20 m for high-flow open-well models. Record the final setting depth in the handover documents.

Why is my solar pump not producing full flow?

Check the causes in order of likelihood: voltage drop from undersized cable, an array string outside the MPPT window, shading or soiled modules, and total head that was underestimated because pipe friction or outlet pressure was left out of the calculation. Undersized pipework and partially blocked filters or emitters are also common. Judge output against the irradiance you actually have at the time of testing — reduced flow under haze or early morning sun is expected, not a fault.

What causes a solar pump to keep tripping on dry run?

Almost always a pump whose flow exceeds the borehole's sustainable yield, so the water level is drawn down to the intake. Setting the pump too shallow and seasonal water-table decline are the other frequent causes, and a restart delay that is shorter than the well's recovery time turns one trip into constant cycling. The correct fix is a lower flow pumped over a longer day into larger storage — never disabling the protection, which is what saves the motor.

Do I need to earth a solar water pump installation?

Yes — bond the array frame and the controller to earth in accordance with local electrical regulations, which is a requirement rather than an optional extra on an installation running at up to several hundred volts DC. Where the array is exposed and the region is prone to lightning, surge protection on the PV input is strongly advisable, as it is a small cost against a destroyed controller. Have the electrical work done by a qualified installer.

Can I install a solar pump myself?

The mechanical work on a small surface or shallow-well system is within reach of a competent person following the manual, but two parts warrant professional involvement: the electrical installation, because array voltages in this range run up to 385 V DC, and lowering a deep-well pump, where a dropped assembly is expensive to recover and the splice and cable work must be immersion-rated. Whoever does the work, complete the commissioning sequence and record the readings — that record is what makes later diagnosis possible.