WAGO 789 Ground Resistance Signaling Module

Technical Overview

Ground resistance signaling module detecting insulation faults in 24VDC control circuits with potential-free contact output for PLCs.

Key Features

Ground fault alarm via digital output.
Signals falling below an asymmetric isolation resistance between +24 V or 0 V and ground.
Potential-free (Iso OK) contact for evaluation via PLC.
Status LEDs for operation status (green "Status OK", red/yellow "Iso Alarm").
Push-in CAGE CLAMP connection technology.
Suitable for DIN-35 rail mounting.
Can operate with grounded or ungrounded control circuits.
RoHS compliant with exemptions.
Conforms to UL 61010-2-201.
Meets EMC immunity (EN 61000-6-2) and emission (EN 61000-6-3, EN 61000-6-4) standards.

Technical Specification Matrix

Parameter	Value
Nominal Supply Voltage	DC 24V (SELV)
Supply Voltage Range	DC 18...31.2V
Current Consumption at Nominal Supply Voltage	≤ 40mA
Current at Ground Fault (24 VDC)	max. 56mA
Maximum Switching Voltage (Iso OK contact)	48 VDC (SELV)
Continuous Current (Iso OK contact)	500mA
Power Loss	≤ 1.7W
Test Voltage (Supply/Iso OK contact)	1.5kVAC
Protection Type	IP20
Ambient Temperature (Operation)	-40...+70°C
Ambient Temperature (Storage)	-40...+85°C
Mounting Type	DIN-35 Rail
Connection Technology	Push-in CAGE CLAMP
Conductor Size (Connection 1)	0.25...1.5mm² / 24...14 AWG (Solid/Fine-stranded)
Conductor Size (Connection 2)	0.2...2.5mm² / 24...12 AWG (Solid/Fine-stranded)
Strip Length	8...9mm / 0.31...0.35 inches
Response Value for Alarm (Ungrounded/Grounded)	4kΩ (at US = 24 V)
Response Time (Ungrounded Circuit)	1s
Response Time (Grounded Circuit)	10s
MTBF	> 600,000 h (per MIL-HDBK-217F2)
Conformity Marking	CE
Physical Weight (kg)	0.05
Dimensions L x W x H (cm)	5.1 x 1.8 x 9

Industrial Applications

1. Industrial Machinery Safety Monitoring

The WAGO 789-665 module ensures safety and uptime in industrial machinery by monitoring 24VDC control circuits for insulation degradation or ground faults. Its potential-free contact integrates seamlessly with PLCs for immediate alarm signaling or system shutdown.

Problem Solved

Prevents catastrophic equipment failure, electrical hazards, and unplanned downtime by providing early detection of ground faults in critical 24VDC control systems, utilizing its 4kΩ alarm response value and potential-free output.

24VDC control circuitsGround fault detectionInsulation monitoringPLC integrationMachine safetyPreventive maintenance

2. Critical Process Automation Systems

For continuous process automation, this signaling module offers reliable insulation monitoring for 24VDC power supplies in diverse industrial environments. Its wide operating temperature range of -40 to +70°C ensures consistent performance.

Problem Solved

Maintains system integrity and prevents costly interruptions in continuous processes by accurately identifying and signaling ground faults in 24VDC systems. The ability to function in extreme temperatures (-40...+70°C) supports robust operation in various industrial settings.

Process control24VDC power supplyInsulation resistanceFault diagnosticsContinuous operationHarsh environments

3. Distributed Building Automation Systems

Effectively monitors extensive 24VDC networks in building automation, allowing for rapid fault localization in distributed I/O modules and sensors. Its compact 18mm width and DIN-rail mounting simplify integration into existing control panels.

Problem Solved

Reduces troubleshooting time and enhances system reliability in large building automation infrastructures by quickly pinpointing ground faults in the 24VDC supply lines. The DIN-35 rail mounting and compact dimensions (18mm width) facilitate easy installation and scalability.

Building managementDistributed I/O24VDC systemsFault localizationSystem reliabilityDIN-rail mounting