Siemens Unstable Transfer / Hunting Between Sources

Generator transfers load but then drops out and re-transfers back to utility repeatedly (hunting).

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Safety Warning

This repair may involve working with high voltage components or water connections. Always unplug the appliance before removing any panels.

If you are not confident in your ability to perform this repair safely, we strongly recommend contacting a professional technician.

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Possible Causes

Tight utility voltage/frequency thresholds, Intermittent generator sensing, Loose sensing wiring, Incorrect ATS time delays

How to Fix / Troubleshooting

Safety first: Repeated transfers can stress equipment. Place the system in manual mode and isolate from load while adjusting settings.

  • Review controller thresholds: In the Siemens controller, widen the acceptable voltage and frequency bands slightly within manufacturer limits to prevent nuisance transfers.
  • Adjust time delays: Increase transfer and retransfer time delays so that brief disturbances do not cause immediate switching.
  • Inspect sensing wiring: Tighten all voltage and frequency sensing connections at both generator and utility sides.
  • Monitor stability: After adjustments, observe operation during a controlled test to ensure stable transfer behavior.
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Repair Difficulty

Medium 3/5

Required Part

ATS Control Board
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