John Miller's 25-year-old well pump in rural Nevada was showing classic well pump failure signs: longer run times, pressure drops, strange noises. With a 400 ft deep well, he knew a well pump replacement couldn't wait.
Instead of sticking with another traditional 240V water pump, John decided to go solar. But the new pump ran on 192V—not the 240V his old system used. Could he reuse his existing well wire? This case study tells the story.
Why John Chose a Solar Well Pump?
From Traditional Pump to Solar
As John began planning his transition from a traditional grid-powered system to a solar water pumping solution, several important concerns emerged. The biggest question was whether his existing submersible well pump wire could be reused for the new setup, especially given the depth of his 400 ft well.
Another critical consideration was voltage drop, which becomes a major issue in deep well applications. Over long cable runs in rural installations, voltage loss can reduce pump efficiency and affect startup performance. John needed to ensure the new solar system could operate reliably without excessive power loss through the existing wiring.
That’s when he turned to the Flowatt pump specifications. The unit operates on 192 Vdc (140–400 Vdc) for solar input and 220 Vac (110–240 Vac, 47–63 Hz) for generator backup. This wide voltage range gave John confidence that even with voltage drop over 400 ft, the system would remain stable above the minimum operating threshold. The flexible design allowed him to move forward without replacing his existing infrastructure.
how to calculate voltage drop?
To determine whether his existing submersible pump wire could handle the new Flowatt 192v DC pump, John had to calculate voltage drop. Here's how he did it.
Step 1: Find the pump's current draw.
The Flowatt 192V DC submersible well pump has a Rated Current of 13 Amps at 192 Vdc (see spec sheet). This was the number John needed.
Step 2: Know your wire gauge and length.
John's well is 400 ft deep. Assuming his existing wire was 12 AWG copper (common for 240V pumps of that era), the total wire length is actually 800 ft (down and back).
Step 3: Apply the voltage drop formula.
A basic formula for DC voltage drop is:
Voltage Drop (V) = 2 × Length × Current × Resistance per foot
For 12 AWG copper wire, resistance is about 0.001588 ohms per foot.
John calculated: 2 × 400 ft × 13A × 0.001588 = 16.5 Volts dropped
Step 4: Compare to the pump's tolerance.
The Flowatt mppt solar charge controller accepts 140–400 Vdc. A 16.5V drop from 192V leaves 175.5V—well within the operating range. John's existing wire was acceptable.
Step 5: Consider the generator (AC) mode.
On AC power (220V), the pump draws roughly 1500W / 220V ≈ 6.8A. At this lower current, voltage drop is even less of a concern.
Key takeaway: John learned that reusing his submersible pump wire was safe because the Flowatt pump's wide voltage range (140–400V) tolerated the calculated voltage drop. Always run the numbers before pulling new wire.
A Successful Switch to Solar Pumping
After running the numbers, John felt confident. His existing submersible pump wire was safe, and the Flowatt's wide voltage range gave him peace of mind. He placed his order and completed the installation. Today, his 400 ft well runs on sunshine—with a generator ready for cloudy days. The old 240V pump is gone, and so are the high electric bills. For John, switching to solar wasn't just a well pump replacement. It was an upgrade to energy independence.
