Grundfos SQFlex Helical Rotor Solar Pump

The SQFlex system is a reliable water supply system based on renewable energy sources, such as solar and wind energy, and incorporates an SQF submersible pump. Very flexible as to its energy supply and performance, the SQFlex system can be combined and adapted to any need according to the conditions of the installation site. Being designed for continuous as well as intermittent operation, it is suitable for water supply in remote locations.

The SQF pump range comprises two pump technologies: the helical rotor pump (3 in) for high heads and small flow rates, and the centrifugal pump (3 in and 4 in) for low heads and large flow rates. This listing covers: Helical rotor pump (3 in) for high heads and small flow rates. All pump types are in stainless steel AISI 304.

The motor is developed specifically for the SQFlex system and designed according to the permanent-magnet principle with a built-in electronic unit. The MSF 3 motor range comprises four maximum power input (P1) ratings — 300 W, 900 W, 1400 W and 2500 W — with a speed range of 500-3600 rpm or 3000-10700 rpm depending on motor size, power input and load. The motor has three internal limitations: maximum power input (P1), maximum current of 8.4 A or 12 A, and maximum speed. The pump delivers its maximum performance when one of those limitations is reached.

In terms of power supply the motor is flexible: it can be supplied with either DC or AC voltage — 30-300 VDC (100-300 VDC for the 2500 W motor) or 1 x 90-240 V, 50/60 Hz. The SQFlex system can also be powered by batteries with a 30-300 VDC supply and a maximum current of 8.4 A; DC operation is limited to the highest possible power at that voltage — for example, 48 VDC gives a limiting maximum power of 403 W.

• Dry-running protection — a water level electrode on the motor cable, 12 to 24 in above the pump depending on pump type, measures contact resistance to the motor sleeve through the water. When the water level falls below the electrode the pump stops, and it restarts automatically five minutes after the level is back above it.
• Maximum Power Point Tracking (MPPT) — the built-in microprocessor continuously optimizes the pump duty point to the input power available. MPPT is available for pumps connected to DC supply.
• Wide voltage range — operates at any voltage from 30-300 VDC (100-300 VDC for 2500 W) or 90-240 VAC, which makes installation and sizing easy.
• High efficiency — the MSF 3 is a permanent-magnet motor with higher efficiency across the power range than a conventional asynchronous motor, helped by a segmented stator, and with high locked-rotor torque even at low power supply.
• Over- and undervoltage protection — the pump stops if the voltage falls outside the permissible range and restarts automatically when it returns. No extra protection relay is needed. The motor is protected against supply transients to EN/IEC 61000-4-5 (6 kV); in areas with high lightning intensity use external lightning protection.
• Overload protection — above the upper load limit the motor compensates by reducing speed; below minimum speed it stops, stays stopped for 30 seconds and restarts automatically. No extra motor protection is required.
• Overtemperature protection — a temperature sensor in the electronic unit stops the motor above 185 °F and restarts it once the temperature drops to 165 °F.
• Reliability — carbon / ceramic bearings, excellent starting capabilities and the protection functions above.
• Simple installation and service — low weight, no motor starter or starter box, and a modular pump and motor design. The cable and the end cover with socket are fitted with screws so they can be replaced.

Salt content. Resistance of the stainless steel to chloride, for a pumped liquid of pH 5 to 9:

Electrical connection. The MSF motor is connected to the power supply on two wires plus protective earth. As the integrated electronic unit handles both DC and AC supply voltages, it makes no difference how the wires + and - or N and L are connected.

Panel voltage and output. The SQFlex pump is most efficient at 120 V and above, up to a maximum of 300 V. To maximize pump performance, connect panels to obtain at least 120 V. Grundfos states the following loss in gallons per day against panel output voltage for systems of the same wattage:

Solar panel wiring. In series, voltages add and amperage stays the same: four 70 V, 1.43 A, 100 W panels in series give 280 V at 1.43 A. In parallel, amperages add and voltage stays the same: the same four panels give 70 V at 5.72 A. In a series / parallel circuit, two series pairs wired in parallel give 140 V at 2.86 A. Panel wattage always adds — 400 W in every case.

Drop cable sizing. Grundfos gives the maximum cable length as L = (ΔP x q x Vmp squared) / (Wp x 0.00162) ft, where ΔP is the power loss in %, q is the cross section of the submersible drop cable in square inches, Vmp is the maximum power voltage in V and Wp is the array watt peak. Use the sizing tool at Grundfos Product Center for exact losses.

Starting sequence. The starting sequence has three steps: charging the capacitor, positioning of the rotor, and start. During start-up the motor makes small rotations to bring the rotor into the correct starting position; these rotations also ensure there is water in the pump and that the pump parts are lubricated. Current consumption is uneven during start-up and constant once the motor has started. After the pump has started it takes a while to fill the riser pipe — at moderate energy supply and high head, up to one hour.

Helical rotor pumps. With sufficient energy the pump will normally be running within one minute. If the motor does not start within 15 minutes the pump rotor may be stuck due to dryness, which can happen when a pump has been in storage for some time: dismantle the pump and loosen the rotor, or add water to the pump rotor / stator assembly. If sufficient energy is not available the starting sequence is repeated.

Under normal operating conditions the pumps and the controls are maintenance-free. Maintenance is confined to the solar modules: clean them when they are dirty using only clean water without soap and a soft brush or cloth, with no sand or abrasive particles in the water; keep grass and trees from casting a shadow on them; and tighten screws and nuts on the support structure if they have loosened. Before specific troubleshooting, check that the modules are intact and unshaded, the cables, pipes and hoses are intact, the water level is at least 3 ft above the pump and the dry running sensor is under water. Troubleshoot solar systems in the middle of an unclouded day. A solar array is live whenever there is daylight: isolate every DC and AC source before working on the pump, the cable or the controls.

• Villages, schools, hospitals and single-family houses
• Farms — livestock watering and irrigation
• Game reserves — watering applications
• Conservation areas — pumping of surface water
• Floating pump installations for pumping water from ponds and lakes

Type key. In 6 SQF-2: 6 is the rated flow in GPM at 3000 rpm, SQF is the type range and -2 is the number of stages.

Order by part number. 3 SQF-2 — 95027332 · 3 SQF-3 — 95027333 · 6 SQF-2 — 95027334 · 6 SQF-3 — 96834840 · 11 SQF-2 — 95027335.

System components. A complete system also needs a switch box or control unit, the solar array and support structure, submersible drop cable, cable clips, straining wire and wire clamps, and riser pipe. Level switch, zinc anodes and Grundfos motor-shaft grease (96037562) are available on request. We supply the pump, controls and DC protection; email us the site details and we will put the package together.