Electrical faults remain one of the most significant identifiable causes of fires in non-domestic buildings. Official fire statistics for England reveal that electrical faults were the largest recorded cause of non-domestic fires in 2024/25, linked to around 20% of incidents, or approximately 2,750 fires.
These fires were responsible for 130 separate injuries, highlighting not only the serious risk to people and property, but also the potential liability employers may face if electrical risks are not properly managed.
Preventive fire protection is now an essential part of company security. Fire-related operational disruptions and property damage can threaten business continuity and, in severe cases, a company's long-term viability. Those responsible for electrical safety should therefore set high standards for preventive fire protection.
For effective fire protection in electrical installations, continuous residual current monitoring of essential installations, installation parts and devices is the preferred approach. Residual current monitors or residual current monitoring systems should be installed alongside existing protective devices to support early detection and reduce fire risk.
1. In locations where, in accordance with Chapter 42, a particular risk of fire exists, preventive protection measures against the risk of fire are required. This may also apply to other locations of the electrical installation, depending on a risk analysis. The selection of protective and monitoring devices shall take into account the nature of the load and the likelihood of the device to operate, for example, fault currents of higher frequencies, DC fault currents or increased leakage currents. (See also Regulation 331.1.)
2. In section “532.3 Residual current monitors (RCMs) for protection against fire risks in IT systems”: “In IT systems. RCMs may be used as an alternative to RCDs in accordance with Regulation 532.2, provided that the location is supervised by one or more skilled or instructed person(s). RCMs shall be in accordance with BS EN 62020 and operate in conjunction with switchgear suitable for isolation. RCMs shall be installed at the origin of final circuits. The rated residual operating current shall not exceed 300mA. Audible and visual signals shall be provided by the RCMs.
3. In section “532.4 Insulation monitoring devices (IMDs) for protection against the risk of fire in IT systems”: Insulation monitoring devices applied in IT systems for protection against the risk of fire shall comply with the requirements of Section 538. A fault location system in accordance with the requirement of Regulation 538.2 able to locate the faulty circuit, may also be used.
1. Preventive safety and asset protection
Continuous residual current monitoring or insulation monitoring supports preventive fire protection by helping to protect people, machinery and electrical equipment from the hazards of electric current. It also improves operational reliability and availability by enabling insulation faults to be detected and addressed at an early stage, helping to reduce maintenance and operating costs and minimise the risk of unexpected operation of existing protective devices. “Where a circuit is permanently monitored by an RCM or an IMD it is not necessary to measure the insulation resistance if the functioning of the RCM or IMD is correct. The functioning of the RCM or IMD shall be verified.” BS 7671, section 651.2
2. Immediate visibility of insulation deterioration
By monitoring residual current in systems and devices within electrical installations, insulation deterioration becomes visible immediately and can be signalled. Instead of relying on insulation resistance testing at long intervals, continuous monitoring helps maintain a high insulation resistance level.
3. Compliance support and legal assurance
In applications where an RCD cannot be used for technical reasons, RCMs can help meet normative requirements and support compliance with the Low Voltage Directive. In the event of damage, this can contribute to a stronger legally secure position.
4. Insurance and damage-prevention alignment
Meeting or exceeding property insurers’ damage-prevention directives, such as BS 7671 and The Electricity at Work Regulations 1989 requirements, may also help reduce insurance premiums.
5. Guidance for compliant electrical protection
Further information is available in the BS 7671 requirements. These documents provide guidance on damage prevention, protective devices for fire protection in electrical installations, and insulation fault protection in electrical installations with electronic equipment.
| Name | Category | Size | Language | Timestamp | D-/B-Number |
|---|---|---|---|---|---|
| Product Overview ISOMETER®/ISOSCAN® | Product Overviews | 5.3 MB | EN | 2024/02/1616.02.2024 | |
| Product Overview - Residual Current Monitoring | Product Overviews | 4.2 MB | EN | 2026/02/1111.02.2026 |
Products
Multichannel AC, pulsed DC and AC/DC sensitive residual current monitor
Multichannel AC, pulsed DC and AC/DC sensitive residual current monitor
Multichannel AC, pulsed DC and AC/DC sensitive residual current monitor with one alarm contact per channel
Multichannel AC, pulsed DC and AC/DC sensitive residual current monitor with one alarm contact per channel
AC/DC sensitive residual current monitor (type B) with 6 integrated measuring current transformers
AC/DC sensitive modular residual current device for MRCD applications
AC/DC sensitive residual current monitoring modules for monitoring applications
AC/DC sensitive residual current monitoring module with integrated split-core measuring current transformer
AC/DC sensitive residual current monitoring module for electric vehicle charging systems
DC sensitive residual current monitoring module for electric vehicle charging systems
Modular residual current device type B for additional protection (protection against indirect contact) in earthed systems (TN and TT systems)
AC/DC sensitive residual current monitor for TN and TT systems (AC, DC, pulsed DC currents)
AC/DC sensitive residual current monitor for TN and TT systems (AC, DC, pulsed DC currents)
Residual current monitor for TN and TT systems (AC and pulsed DC currents)
AC/DC sensitive residual current monitoring for AC charge stations
AC/DC sensitive residual current monitoring for AC charge stations
AC/DC sensitive residual current monitoring module for measuring AC and DC currents up to ±100 mA
Insulation monitoring device for inverter applications and large industrial plants
Insulation monitoring device for inverter applications and large industrial plants, variant for coupled systems
Insulation monitoring device for inverter applications and large industrial plants, variant for coupled systems and insulation fault location
Insulation monitoring device tailored to the requirements of railway rolling stock applications
Insulation monitoring device especially for railway applications
Insulation monitoring device with instantaneous tripping, frequency nominal system voltage 60 Hz
Insulation monitoring device for offline monitoring of de-energised loads
Insulation monitoring device for measuring high-resistance insulation resistances up to 10 GΩ and to monitor long parallel cable
Insulation monitoring device for subsea cables and umbilicals.
Device combination for insulation monitoring in medium-voltage systems
Insulation monitoring device for unearthed systems in photovoltaic installations up to AC 1000 V/DC 1500 V
Insulation monitoring device for mobile, insulated elevating work platforms and ungrounded work platforms, e.g., in hydrogen electrolysers or in the chemical industry
Insulation monitoring device for unearthed AC, AC/DC and DC power supplies (IT systems)
Insulation monitoring device for unearthed DC systems (IT systems) DC 0 V to 400 V. Suitable for DC charging stations according to CCS or CHAdeMO
Insulation monitoring device with coupling device for unearthed DC systems (IT systems) DC 0 V to 1000 V Suitable for DC charging stations according to CCS or CHAdeMO
Insulation monitoring device for railway applications up to AC/DC 440 V
Insulation monitoring device for unearthed AC/DC control circuits
Insulation monitoring device for batteries up to DC 400 V
Insulation monitoring device for medical IT systems
Offline monitor (earth fault lock-out) for monitoring de-energised loads in TN,TT and IT systems
Insulation monitoring device for mobile generators up to AC 300 V
Insulation monitoring device for photovoltaic systems up to AC 690 V/DC 1000 V
Insulation monitoring device for unearthed AC control circuits
Insulation monitoring device for unearthed AC, AC/DC and DC systems (IT systems) for energy storage devices up to AC/DC 400 V
Insulation monitoring device for unearthed AC, AC/DC and DC systems (IT system)
Insulation monitoring device for mobile generators up to 3(N)AC, AC/DC 400 V
Insulation monitoring device for unearthed AC, AC/DC and DC main and control circuits
Insulation monitoring device for mobile generators
Insulation monitoring device for unearthed DC drive systems in electric vehicles
Insulation monitoring device for unearthed DC drive systems in electric vehicles
Insulation monitoring device for photovoltaic systems up to AC 793 V/DC 1100 V
Insulation monitoring device for installations with a low-resistance insulation level
Multichannel AC, pulsed DC and AC/DC sensitive residual current monitor
Multichannel AC, pulsed DC and AC/DC sensitive residual current monitor
Multichannel AC, pulsed DC and AC/DC sensitive residual current monitor with one alarm contact per channel
Multichannel AC, pulsed DC and AC/DC sensitive residual current monitor with one alarm contact per channel
AC/DC sensitive residual current monitor (type B) with 6 integrated measuring current transformers
AC/DC sensitive modular residual current device for MRCD applications
AC/DC sensitive residual current monitoring modules for monitoring applications
AC/DC sensitive residual current monitoring module with integrated split-core measuring current transformer
AC/DC sensitive residual current monitoring module for electric vehicle charging systems
DC sensitive residual current monitoring module for electric vehicle charging systems
Modular residual current device type B for additional protection (protection against indirect contact) in earthed systems (TN and TT systems)
AC/DC sensitive residual current monitor for TN and TT systems (AC, DC, pulsed DC currents)
AC/DC sensitive residual current monitor for TN and TT systems (AC, DC, pulsed DC currents)
Residual current monitor for TN and TT systems (AC and pulsed DC currents)
AC/DC sensitive residual current monitoring for AC charge stations
AC/DC sensitive residual current monitoring for AC charge stations
AC/DC sensitive residual current monitoring module for measuring AC and DC currents up to ±100 mA
Insulation monitoring device for inverter applications and large industrial plants
Insulation monitoring device for inverter applications and large industrial plants, variant for coupled systems
Insulation monitoring device for inverter applications and large industrial plants, variant for coupled systems and insulation fault location
Insulation monitoring device tailored to the requirements of railway rolling stock applications
Insulation monitoring device especially for railway applications
Insulation monitoring device with instantaneous tripping, frequency nominal system voltage 60 Hz
Insulation monitoring device for offline monitoring of de-energised loads
Insulation monitoring device for measuring high-resistance insulation resistances up to 10 GΩ and to monitor long parallel cable
Insulation monitoring device for subsea cables and umbilicals.
Device combination for insulation monitoring in medium-voltage systems
Insulation monitoring device for unearthed systems in photovoltaic installations up to AC 1000 V/DC 1500 V
Insulation monitoring device for mobile, insulated elevating work platforms and ungrounded work platforms, e.g., in hydrogen electrolysers or in the chemical industry
Insulation monitoring device for unearthed AC, AC/DC and DC power supplies (IT systems)
Insulation monitoring device for unearthed DC systems (IT systems) DC 0 V to 400 V. Suitable for DC charging stations according to CCS or CHAdeMO
Insulation monitoring device with coupling device for unearthed DC systems (IT systems) DC 0 V to 1000 V Suitable for DC charging stations according to CCS or CHAdeMO
Insulation monitoring device for railway applications up to AC/DC 440 V
Insulation monitoring device for unearthed AC/DC control circuits
Insulation monitoring device for batteries up to DC 400 V
Insulation monitoring device for medical IT systems
Offline monitor (earth fault lock-out) for monitoring de-energised loads in TN,TT and IT systems
Insulation monitoring device for mobile generators up to AC 300 V
Insulation monitoring device for photovoltaic systems up to AC 690 V/DC 1000 V
Insulation monitoring device for unearthed AC control circuits
Insulation monitoring device for unearthed AC, AC/DC and DC systems (IT systems) for energy storage devices up to AC/DC 400 V
Insulation monitoring device for unearthed AC, AC/DC and DC systems (IT system)
Insulation monitoring device for mobile generators up to 3(N)AC, AC/DC 400 V
Insulation monitoring device for unearthed AC, AC/DC and DC main and control circuits
Insulation monitoring device for mobile generators
Insulation monitoring device for unearthed DC drive systems in electric vehicles
Insulation monitoring device for unearthed DC drive systems in electric vehicles
Insulation monitoring device for photovoltaic systems up to AC 793 V/DC 1100 V
Insulation monitoring device for installations with a low-resistance insulation level
Contact our experts to find out how continuous monitoring can help strengthen your electrical fire safety strategy.
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