When is a cooling sleeve needed and how do you calculate the required cooling flow for submersible motors?

Mode of operation

The heat loss generated by the submersible motor must be dissipated to the pumped medium by means of convection. If the minimum cooling speed along the submersible motor cannot be guaranteed, it is mandatory to install a cooling jacket in order to generate sufficient cooling.

Inadequate cooling can have the following causes:

• insufficient flow rate

• well diameter too large

• water inflow from above (top feeding)

• open water (lake, reservoir, river, tank)

To provide cooling, the pump-motor unit is supplemented by a cooling jacket. This separate „sheet metal jacket“ is sealed above the pump inlet. The pumped medium is thus sucked in from below and directed past the motor in order to dissipate the generated motor heat loss (convection).

Appropriate brackets and inlet strainers are available for horizontal installation in an open body of water, e.g. a tank, a lake or a flowing body of water.

Required cooling flow

The minimum cooling flow values for Franklin Electric motors can be found in the following overview:

Calculation of the cooling flow

To calculate the required cooling flow, the following formula can be used: