Your solar pump is running, but the tank is filling too slowly or the irrigation pressure is lower than expected. That does not automatically mean the inverter is too small or faulty. Water delivery depends on the available solar power, the pump and motor, the water source and the pipe system working together.
This guide helps you organise the observations that distinguish normal solar variation from a change that needs technical assessment. It is a starting point for understanding low output, rather than instructions for changing electrical connections or protection settings.
First Define What “Not Enough Water” Means
Low flow, low pressure and insufficient daily water volume are different problems. A pump may deliver adequate flow into an open tank but struggle to meet an irrigation pressure requirement. It may also perform well around midday while falling short of the daily volume needed.
Record the actual result where measurement is available: flow, delivery pressure, tank-level change or water volume over a defined period. Compare it with the original design requirement under similar conditions. A visual impression of the outlet alone can be misleading.
Separate a New Problem From an Original Sizing Problem
Ask whether the system previously delivered the required water. A recent decline suggests checking what changed: weather, shading, water levels, pipework, demand or equipment condition. A system that has never met the requirement may need its original sizing and configuration reviewed.
Record when the problem began and whether it is constant or tied to a time of day. Include any maintenance, replacement equipment or new irrigation zones. This context is often more useful than requesting a larger inverter immediately.
Sunlight Changes the Available Pumping Power
In direct solar pumping, available power varies through the day and with weather. A compatible controller adjusts operation within its configured limits. Morning or late-afternoon output may therefore differ from output during stronger sunlight.
Maximum power point tracking (MPPT) helps use the power available from the PV array. It cannot create power that the array is not producing. Clouds, shading, contamination and seasonal conditions can affect performance.
Panel wattage is a rated value under specified conditions, not a promise of continuous site output. Compare daily delivery and representative seasonal conditions, rather than judging the system from one short observation.
A Running Motor Does Not Guarantee the Required Flow
A centrifugal pump must develop enough head to move water through the system. Head includes the lift, required delivery pressure and losses through pipes, fittings and other equipment.
At a lower operating speed, a pump may not develop enough head for meaningful delivery against a particular system requirement. The display can show operation while little water reaches the destination. The pump curve and permitted speed range are important to the assessment.
A solar inverter controls the compatible motor. It does not change the pump’s hydraulic design or guarantee that the selected pump suits the required flow and head.
Borehole Water Levels Can Change the Duty
The water level measured while a borehole is resting is different from the level during pumping. Drawdown can increase the lift the pump must overcome. Seasonal changes may also alter the available water and operating conditions.
If delivery declines during a pumping period, include available water-level and yield information in the assessment. That pattern can have several causes; it does not prove that the inverter has failed.
The sustainable borehole yield must be considered alongside demand. Increasing electrical capacity cannot make the source supply unlimited water, and dry-run protection must not be bypassed to extend operation.
Pipework and Demand May Have Changed
A longer delivery route, added filters, more fittings or a higher destination can alter the system requirement. Leaks, restrictions and changes in valve position can also affect what reaches the user.
Opening additional irrigation zones increases the demand on the arrangement. Water storage and irrigation pressure are separate needs: filling a tank successfully does not establish that the same pump will operate all sprinklers at their required pressure.
Share the pipe layout and recent changes with the responsible team. Inspections and maintenance must follow the site’s safe procedures; this guide is not an instruction to dismantle pressurised equipment.
Use the Inverter Display as Evidence
Where readings are available on the normal operator display, record operating frequency, status and the exact fault or warning code. Include the time, weather conditions and observed water delivery.
A fault code reports a condition according to the exact model’s documentation. It does not automatically identify a failed component. An undervoltage indication, for example, needs assessment in the context of the actual supply and installation.
Do not clear the history before recording it or change parameters simply to suppress a warning. Motor data, limits and protection functions need verification by the responsible technician.
PV Matching Requires More Than Counting Panels
The array must suit the inverter’s voltage and current requirements as well as the power demand. Module ratings, series and parallel arrangements, temperature effects and the controller’s operating limits all matter.
Adding panels without reviewing the design can create an incompatible arrangement. A bigger inverter does not automatically use the existing array effectively or solve a hydraulic problem.
Ask a qualified installer to assess the PV arrangement, electrical measurements and connections. PV DC circuits can remain energised in daylight; customers should not open equipment or disconnect live connectors to investigate output.
Patterns That Help Organise the Enquiry
| Observation | Useful information to collect |
|---|---|
| Low output mainly early or late in the day | Time, weather, operating frequency and delivery during stronger sunlight |
| Low output throughout a clear day | Original duty, pump curve, PV specification, display readings and recent changes |
| Output falls after running for a while | Timing, borehole water-level information, fault history and operating conditions |
| Tank fills, but irrigation pressure is insufficient | Required zone flow and pressure, number of active zones and the storage/booster arrangement |
| Frequent stops or warnings | Exact code, equipment model, when it occurs and available technician findings |
These patterns guide the next questions. They are not confirmed diagnoses.
Example: Demand Has Increased Since Installation
A farm originally used its solar pump to fill a storage tank. Later, additional irrigation zones were connected and expected to run together. The pump may still perform its original task while failing to meet the new combined flow and pressure requirement.
The useful review compares daily water demand, irrigation pressure, source capacity and the pump’s operating range. Possible changes depend on that assessment; a replacement inverter alone should not be promised as the answer.
A Relevant Solar Inverter Example
Softcore Group Industrial Solutions lists solar pump inverters, including the VEICHI SI23 range. The exact model must match the motor, PV arrangement and control requirements. Replacing a controller should follow confirmation of the requirement.
What to Share for an Assessment
- Complete inverter, pump and motor codes, with label photographs
- Whether the system ever met the required output
- Required daily volume, flow and pressure where specified
- Observed delivery, operating times and weather conditions
- Exact displayed warnings and normal operating readings
- PV module details and existing installation documents
- Borehole yield and pumping water-level information where available
- Recent changes to demand, pipework or equipment
For a product enquiry, contact Softcore Group Industrial Solutions at info@softcoregroup.co.za. System diagnosis, hydraulic sizing and electrical assessment should be handled by the responsible technical team before replacement equipment is selected.
Technical Resources
Visit our Technical Resources & Manuals page to find or request documentation for the exact listed model.
Technical Note: This article provides general information, not a confirmed fault diagnosis. Do not bypass protection, alter electrical connections or raise operating limits without qualified assessment. Installation, programming and commissioning are included only where expressly quoted.
Related Articles
- How to Size a Solar Pump System for a Borehole
- Solar Pump Inverters: MPPT and DC Input Ranges
- Solar Irrigation for Farms
Featured photograph: Süleyman Şahan / Pexels. Illustrative irrigation image; the photograph does not establish the system’s power source.