Offline Monitoring

Continuous monitoring of de-energised loads and conductors

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, insulation faults may occur at the supply line or at the load itself due to humidity or other impacts. If these insulation 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-energised 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.

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 minimises risk of fire and injury
  • Optimised 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 Flyer Offline Monitoring EN 1.7 MB EN13.05.2019 10:30:59
Technical article Technical paper: Avoiding failure of drive systems 335.5 KB EN13.05.2019 10:29:22


Insulation monitoring


Offline monitor (earth fault lock-out) for monitoring de-energised loads in TN,TT and IT systems

ISOMETER® iso685…
ISOMETER® iso685…

Insulation monitoring device for inverter applications and large industrial plants


System components


Extension of the nominal voltage range of ISOMETER® to AC 0...7200 V


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