Grundfos Troubleshooting Tips for "CR" Pumps


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  1. The pump runs - but at a reduced capacity or does not deliver water
    • Wrong rotation - Check wiring for proper connections, correct wiring.
    • Strainers, check valves, or foot valves are clogged - Remove strainer, screen or valve and inspect. Clean and replace. Reprime pump.
    • Pump impeller or guide vane is clogged - Disassemble and inspect pump passageways. Remove any foreign materials found.
    • Incorrect drain plug installed - If the proper drain plug is replaced with a standard plug, water will recirculate internally. Replace with proper plug.
  2. The pump squeals when it starts and stops:
    • Stack height adjustment is wrong - Disconnect power, remove coupling, loosen set screws in shaft seal, readjust stack height per I&O instructions, tighten set screws at shaft seal, reattach coupling.
  3. Fuses blow or circuit breakers or overload relays trip:
    • Pump is bound - Turn off power and manually rotate pump shaft. If shaft does not rotate easily, check coupling setting and adjust as necessary. If shaft rotation is still tight, remove pump and inspect. Disassemble and repair.
  4. Noise in pump that sounds like gravel:
    • Pump is cavitating
      • Insufficient inlet pressure at pump - choke back on pump discharge valve to lower NPSHR (net positive suction head required)
      • Clogged strainers on pump inlet piping - remove strainer, screen or valve and inspect. Clean and replace. Reprime pump.