The following is a letter from Kevin Price of Sun-Star Electric, Inc.
Also available: Original Scanned Letter (pdf)
May 20, 2010
Dear Mr. Austin:
All submersible motors require cooling flow past the motor to dissipate heat generated within the motor. Hitachi has a standard for ambient temperature and required flow dependent on load. And although the specifications of your application are not covered on this chart we have performed extensive testing covering ranges outside the chart.
In your application (5 GPM, 7" shroud, 6" motor with an actual O.D. of 5.5") the flow velocity past the motor will be .109 feet per second. At this flow velocity at an ambient temperature of 95°F the service factor of the of the motor will be .82 and the motor must be de-rated from 10 HP to 8.2 HP with no service factor. Your application of 6 HP at 60-77°F at this same flow is well within the allowable limits of the motor rating at this reduced flow and temperature. We would expect lower internal motor temperatures, which will actually increase your service factor in this operating temperature range (60-77°F). We have performed research at temperatures above and below 77°F with "No-Flow" and the motor has performed satisfactorily. We anticipate no problem with your operating range.
Thans you for this opportunity to be of service. If you have any questions or desire additional information, please do not hesitate to contact this office.
Kevin P. Price
Vice President Sales & Service
Sun-Star Electric, Inc.