AIM Manual

Motor Application » Three-Phase Motors (Page 38)

Inline Booster Pump Systems (Continued)

  • 10. Motor Overload Protection: Submersible motors require properly sized ambient compensated Class 10 quick-trip overloads per Franklin’s AIM manual guidelines to protect the motor. Class 20 or higher overloads are NOT acceptable. Franklin’s SubMonitor is strongly recommended for all large submersibles since it is capable of sensing motor heat without any additional wiring to the motor. Applications using Soft Starters with a SubMonitor require a start-up bypass - consult the factory for details. SubMonitor can not be used in applications using a VFD control.
  • 11. Motor Surge Protection: Properly sized, grounded and dedicated motor surge arrestors must be installed in the supply line of the booster module as close to the motor as possible. This is required on all systems including those using soft-starters and variable speed drives (inverter drives).
  • 12. Wiring: Franklin’s lead assemblies are only sized for submerged operation in water to the motor nameplate maximum ambient temperature and may overheat and cause failure or serious injury if operated in air. Any wiring not submerged must meet applicable national and local wiring codes and Franklin Cable Chart Tables 16-21. (Notice: wire size, wire rating, and insulation temperature rating must be known when determining its suitability to operate in air or conduit. Typically, for a given size and rating, as the insulation temperature rating increases its ability to operate in air or conduit also increases.)
  • 13. Check Valves: Spring-loaded check valves must be used on start-up to minimize motor upthrusting, water hammer, or in multiple booster (parallel) applications to prevent reverse flow.
  • 14. Pressure Relief Valves: A pressure relief valve is required and must be selected to ensure that, as the pump approaches shut-off, it never reaches the point that the motor will not have adequate cooling flow past it.
  • 15. System Purge (Can Flooding): An air bleeder valve must be installed on the booster sleeve so that flooding may be accomplished prior to booster start-up. Once flooding is complete, the booster should be started and brought up to operating pressure as quickly as possible to minimize the duration of an upthrust condition. At no time should air be allowed to gather in the booster sleeve because this will prevent proper cooling of the motor and permanently damage it.
  • 16. System Flush – Must Not Spin Pump: Applications may utilize a low flow flushing operation. Flow through the booster sleeve must not spin the pump impellers and the motor shaft. If spinning takes place, the bearing system will be permanently damaged and the motor life shortened. Consult the booster pump manufacturer for maximum flow rate through the pump when the motor is not energized.
  • 17. Open Atmosphere Booster Pump Systems: When an open booster is placed in a lake, tank, etc. that is open to atmospheric pressure, the water level must provide sufficient head pressure to allow the pump to operate above its NPSHR requirement at all times and all seasons. Adequate inlet pressure must be provided prior to booster start-up.
Table 38 Franklin Cable chart (See item 12 Wiring above)
#10 AWG#8 AWG#6 AWG#4 AWG#2 AWG
753-LEAD (DOL)40A28A#8 AWG40A76A52A100A68A136A92A
6-LEAD (Y-∆)69a48a97a69a132a90a173a118a236a159a
903-LEAD (DOL)44a32a64a44a84a60a112a76a152a104a
6-LEAD (Y-∆)76a55a111a76a145a104a194a132a263a180a
1253-LEAD (DOL)66A46A77A53A109A75A153A105A195A134A
6-LEAD (Y-∆)114A80A133A91A188A130A265A181A337A232A
  • Based on 30 °C maximum ambient with cable length of 100 feet or less.