Continuous monitoring of de-energized loads and conductors

Permanent monitoring of de-energized loads and lines

Many types of loads that are temporarily or mainly disconnected (standby mode) must function reliably when needed. This applies, for example, to fire pumps, slide-valve drives, lift motors or emergency power generators. However, during prolonged downtimes, ground faults may occur at the supply line or at the load itself due to humidity or other impacts. If these ground faults are not detected, when connecting the installation the protective device triggers and operation is not possible. In more severe cases, engine fires may occur.

"Offline monitors" can prevent this since they monitor the insulation resistance of de-energized loads in order to report faults at an early stage. Special ISOMETER®s (IR420-D6, IR425-D6, IRDH, iso685 series) are used for this purpose. For this solution it is irrelevant whether the temporarily or mainly disconnected loads are supplied by TN, TT or IT systems.

Offline Monitoring

Your benefits

  • Continuous monitoring instead of insulation measurement based on random samples during recurrent testing
  • Avoiding expensive and unplanned system shutdowns
  • Higher productivity
  • Two-stage reporting minimizes risk of fire and injury
  • Optimized maintenance thanks to early detection
  • Avoiding operational interruptions and emergency actions
  • Less damage to property due to defective motors, longer service life
  • Reducing operating and maintenance costs
  • Less storage costs for spare parts (motors)

Areas of application

  • Pumps (sprinkler systems, lifting pumps, etc.)
  • Emergency slide-valve drives in crane systems (e.g. on ships)
  • Slide-valve drives in supply lines (gas, water, oil, etc.)
  • Lifts
  • Flue gas dampers
  • Emergency power generators
  • Cables and conductors


Flyer Offline Monitoring
Product overview ISOMETER®
Technical paper Avoiding failure of drive systems



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For further information, refer to our technical papers!