Submersible pump cable: flat, round, two and three wire

Flat against round, and why both exist

Submersible pump cable is a 600-volt assembly of two or three insulated conductors with a ground, made specifically to hang in a well alongside a drop pipe. The flat form is moulded into a ribbon so it can be taped to the pipe without building a lump that catches on the casing. The round form is twisted and jacketed, used where the run is in open water or where the well is large enough that a ribbon is awkward.

Both are built with a tough outer jacket, usually PVC or a nylon-reinforced PVC, because the cable is dragged over a casing lip and then sits in water for decades. The conductors are stranded, not solid, so the cable can flex as the water level and the pump move.

Two-wire and three-wire are not the same job

A two-wire pump has the starting components built into the motor, so the cable carries two conductors plus ground and lands directly on the motor leads. A three-wire pump needs a control box at the surface with the start capacitor and relay, so the cable carries three conductors plus ground and one of them is the start winding.

That is why 12/2 and 10/3 are the two sizes most often in stock, and why a roll of 10/3 cannot substitute for 12/2 on a two-wire pump. When a lot is described, the conductor count matters more than the gauge. A seller who says only ten-gauge has described half of what a buyer needs.

Depth, gauge and the splice that decides the life

Well depth sets the gauge. A shallow jet conversion in a forty-foot well may take 12/2; a three-hundred-foot submersible needs heavier conductors to keep voltage drop within reason, and the run from the wellhead to the pressure tank is part of the calculation. A pump that fails early is often a voltage-drop failure rather than a motor failure.

The other weak point is the splice. Cable is joined to the motor leads with a sealed splice kit, and that splice sits in water. A replaced pump leaves the old cable in the well or hauls it out in one piece, and a cable that comes out with a swollen, hardened splice at the bottom is a cable that has been wet on the inside.

Farm and rural water work

Sandusky County and the flat, drain-tiled ground around Fremont run on wells: farmsteads, grain operations, rural residences and small water systems. Every pump replacement strands a length of drop cable, and much of it is pulled, coiled and stored in a barn against the day it is needed again.

That stored cable is usually a single length cut at the pitless adapter, which makes it measurable. What it is not is tagged, and a coil of flat cable in a barn has no print left on the outside face because the print was on the side that faced the pipe.

• Conductor count and gauge, for example 12/2 or 10/3
• Flat or round, and whether the jacket is intact end to end
• Length as cut, and whether the splice end is included
• Condition of the bottom end: swollen, hardened or clean
• Whether the cable was pulled from a working well or a failed one