A submersible motor is attached to the bottom of the pump. This makes the pump intake water from above the motor. To properly cool the motor, the water needs to flow past the motor before entering the pump. This means the water needs to flow upward in the well, past the bottom of the motor before entering the pump intake.
If the pump/motor is installed above the perforations or above the bottom of the well casing, then all the water that enters the pump will flow past the motor before entering the pump, and the motor will be properly cooled.
If the pump/motor is set below the perforations or below the bottom of the well casing, it is very possible that the well will be feeding the pump from above. When the pump is top-feeding, the water around the motor can be boiling. In this way the motor can overheat, even while the pump is moving cool water up the discharge pipe to the surface.
A flow inducer or cooling shroud is simply a piece of PVC pipe that is large enough to go over the pump/motor, yet small enough to fit inside the well casing. A shroud is clamped and sealed with tape just above the pump intake. The bottom of the shroud extends at least to the bottom of the motor, and can extend even further if needed. A flow inducer or shroud forces the flow past the motor to keep it cool, even when the well is feeding the pump from above.
Over the years Franklin kept shortening their motors until the new 1 HP is only 11.73” long. That means the bottom of the motor is only 11.73 inches below the water intake on the pump. Franklin says their motors are now so short they don’t need a shroud, even in a top feeding application. Of course they like to sell motors, which is the main reason they shortened their motors to the bare minimum length to begin with. So their advice that a flow inducer is not needed should be taken with a grain of salt.
With a 4” pump, (which is actually 3.5” OD) in 4” casing, (which is actually 4” ID) there is no room for a flow inducer or shroud. Care must be taken to make sure the pump is set high enough in the well that flow comes to it from below, so the motor stays cool. In this case, it is better to have just 3’ of water above the pump rather than 23’ or more.
The best practice in 4” casing is to set the end of the motor above the perforated casing. When that is not possible, I do a well test and set the pump as high in the well as I can, but still low enough the pump will not suck air.
With a 3” pump, (which is actually 3 5/16” OD), in 4” casing, a 3” shroud can be used.
When installed in 5” or larger casing, a 4” shroud can be used with a 4” pump.
With a flow inducer or shroud attached, the pump/motor can be set as close to the bottom of the well as possible. This way sufficient flow for cooling will still go past the motor.
When using a Cycle Stop Valve or a 1 GPM Dole valve, the pump can be producing only 1 GPM. 1 GPM is sufficient to cool 2HP motors or smaller, but it is important that the 1 GPM flows past the motor before entering the pump. This is why we recommend a flow inducer or shroud anytime one will fit in the casing. But if the well is feeding the pump from below, a shroud is not required.
And again, Franklin says 2HP and smaller motors are now short enough that there will be sufficient flow to cool the motor, even without a shroud, and even in top feeding conditions. So a shroud is not mandatory when using a Cycle Stop Valve. But we highly recommend a shroud if you have the option.
