Hi all,
I'm running a borehole pump in a 20-year-old well, primarily used for irrigation during the warmer months (not livestock). Over the past year, we've drawn around 1000 m³ through the system at about 16 GPM (60 LPM). The pump is a 230 V, 6A absorption-type, drawing around 1242 W at a 0.9 power factor, so roughly 1 kW of mechanical power delivered. The well has never run dry in two decades, and the surrounding geology is sandy yellow subsoil (formerly extracted as building sand).
The original 7A thermal overload breaker began tripping recently, so I replaced it with an 8A unit, which also now trips—but under specific conditions:
When the new pump was installed, it delivered twice the flow rate of the old unit and initially drew a large quantity of sand, which likely caused internal wear (scoring, possible bearing degradation). I now clean the Netafim 2" filter monthly or every 300 m³, and sand ingress is now minimal.
My Assessment:
I’m evaluating the Schneider LS9D09 electronic thermal overload unit, along with an appropriate contactor. That route involves time and cost—around half the price of a replacement pump, plus rewiring.
Before I go down that road—surely I’m not the first to run into this? Are there established best practices for protecting borehole pumps in outdoor (hot, sealed) installations? Any advice on more robust overload protection, thermal compensation, or cooling strategies that still preserve IP67 would be appreciated.
I'm running a borehole pump in a 20-year-old well, primarily used for irrigation during the warmer months (not livestock). Over the past year, we've drawn around 1000 m³ through the system at about 16 GPM (60 LPM). The pump is a 230 V, 6A absorption-type, drawing around 1242 W at a 0.9 power factor, so roughly 1 kW of mechanical power delivered. The well has never run dry in two decades, and the surrounding geology is sandy yellow subsoil (formerly extracted as building sand).
Issue:
The original 7A thermal overload breaker began tripping recently, so I replaced it with an 8A unit, which also now trips—but under specific conditions:
- If the pump is restarted too quickly (e.g. after only a minute of downtime), the overload trips—even at night when ambient temperatures are around 20 °C / 68 °F.
- During daytime operation, after ~1 hour of continuous running, it trips again—presumably due to elevated enclosure temperatures (likely 40 °C / 105 °F or higher).
- The control equipment is mounted outdoors in a metal IP67-rated enclosure, in direct sun. The box contains:
- 2x liquid level relays (one always active)
- Contactor
- Isolator
- Motor control unit (capacitor + thermal overload relay)
- The enclosure is fully sealed (no ventilation, to maintain IP67 rating).
- Power is supplied via armoured cable connected to a plug socket, allowing me to use a plug-in power meter (limited sample rate).
- Recorded power draw:
- Startup: ~1260 W
- Normal operation: ~1190–1242 W
- Control gear accounts for ~7 W of this.
Background:
When the new pump was installed, it delivered twice the flow rate of the old unit and initially drew a large quantity of sand, which likely caused internal wear (scoring, possible bearing degradation). I now clean the Netafim 2" filter monthly or every 300 m³, and sand ingress is now minimal.
My Assessment:
- The pump likely suffered accelerated wear early on, so it may be working slightly harder, but not excessively—based on current power draw.
- The thermal overload trips are most likely caused by high enclosure temperatures, especially considering the overload is located inside a sealed, sunlit box.
- The current protection is a basic thermal relay, not compensating for ambient heat.
Options I'm Considering:
I’m evaluating the Schneider LS9D09 electronic thermal overload unit, along with an appropriate contactor. That route involves time and cost—around half the price of a replacement pump, plus rewiring.
My Question:
Before I go down that road—surely I’m not the first to run into this? Are there established best practices for protecting borehole pumps in outdoor (hot, sealed) installations? Any advice on more robust overload protection, thermal compensation, or cooling strategies that still preserve IP67 would be appreciated.
