Data Sheet | Item Number: 789-665 Ground resistance signaling module; Ground fault alarm via digital output; Supply voltage: 24 VDC; Module width: 18 mm https://www.wago.com/789-665 Short description: WAGO's module signals a value falling below a non-adjustable, asymmetric isolation resistance between +24 V or 0 V of the supply voltage and ground with a potential-free (Iso OK) contact and status LED. The Iso OK contact can be evaluated via a PLC. This status is maintained until the next measurement interval. Operation with Grounded Control Circuit (Functional Potential Equalization) • The module establishes an internal connection between the 0 V (X2.2) and ground (X2.1) connections via a semiconductor switch. • At 10 s intervals, this connection between 0 V and ground is interrupted for 0.5 s, and the isolation resistance between +24 V (X1.3) or 0 V (X2.2) of the supply voltage and earth (X2.1) is determined. • The grounding connection on the module does not meet the requirements of a protective earth terminal (PE). It serves as a functional ground. The measurement method does not involve the module establishing any permanent connection between 0 V and ground. Operation with Ungrounded Control Circuit • In this operating mode, the semiconductor switch to establish a connection between 0 V (X2.2) and ground (X2.1) is deactivated. At 1 s intervals, the isolation resistance offset is determined for 0.5 s. • The module does not meet the requirements of an isolation monitoring device per EN 61557-8. “Iso OK" Contact • The potential-free contact serves the purpose of supporting evaluation (e.g., via a PLC) of looming isolation faults. • This contact must not be used to switch safety-related products that could cause the circuit to switch off. Page 1/5 Version 07.03.2024 Continued on next page

Data Sheet | Item Number: 789-665https://www.wago.com/789-665 Power supply Nominal supply voltage US Page 2/5 Version 07.03.2024 Continued on next page

Data Sheet | Item Number: 789-665https://www.wago.com/789-665 Connection data Connection type 1 Page 3/5 Version 07.03.2024 Continued on next page

Commercial data Country of origin GTIN Customs tariff number Environmental Product Compliance RoHS Compliance Status Compliant,With Exemption Approvals / Certificates General approvals Declarations of conformity and manufacturer's declarations Approval Standard Certificate Name Approval Standard Certificate Name mity WAGO GmbH & Co. KG Underwriters Laboratories Inc. (ORDINARY LOCATIONS) Approvals for hazardous areas Approval Standard Certificate Name Underwriters Laboratories Inc. (HAZARDOUS LOCATIONS) Page 4/5 Version 07.03.2024 Continued on next page

Data Sheet | Item Number: 789-665 https://www.wago.com/789-665 Item No.: 2009-110 Marking strips; for Smart Printer; on reel; not stretchable; plain; snap-on type; white Item No.: 210-719 Operating tool; Blade: 2.5 x 0.4 mm; with a partially insulated shaft Subject to changes. Please also observe the further product documentation! Current addresses can be found at:: www.wago.com