Local/remote switching failures are among the most confusing actuator faults: switched to local, the valve still obeys remote; hand-driven to about 10% opening, it "returns" by itself. A Bernard actuator case (12 replies) walks through the full troubleshooting logic.
Bottom line: a Bernard actuator switched to LOCAL yet still driven from remote, “returning to position” after local operation — in all likelihood the local/remote transfer never took effect. Start with the zero-cost test (disconnect the remote command cores and try local), then ring out the cabling for cross-connections and earth faults. In this case the cause was cross-wiring inside the terminal boards: the device stayed in “remote” all along, and the “auto-return” was a remote command operating the valve.
A Bernard electric control valve, selector switched to local, still responds to remote commands; when hand-driven locally to about 10% opening, the valve "returns" to its previous position by itself.
| # | Perspective | Analysis / action |
|---|---|---|
| 1 | Zero-cost test | Disconnect the remote command cores and try local: “returning” stops = the actuator still obeys remote — the transfer never happened (or a remote-priority setting holds it); fix: change the parameter or replace the selector |
| 2 | Cross-wiring analysis (the thread’s best reply) | After verifying remote↔local and control-room↔field wiring, operate from remote: nothing moves = equipment fault; it moves and local operation “returns” it = cross-wired local/remote terminal boards keep the device in “remote”; the “return” is a remote full-open/close command operating the valve |
| 3 | Parameter view | Settings such as “valve closes when switched to local” or “remote control effective” — sometimes a setting, not hardware, cements remote priority |
| 4 | Earthing & insulation (peer case) | A control valve local-ok yet DCS-side full-open/close, normal when moved elsewhere — traced to an earthed core; five fault families: external wiring, internal wiring, settings, command signal, interference |
| 5 | Vendor view | Bernard’s official account: handwheel unit or main-board wiring — substitute spares to isolate |
| Order | Action | Cost / verdict |
|---|---|---|
| 1 | Disconnect remote command wires, try local | Zero cost; instantly settles “does the actuator still obey remote?” |
| 2 | Ring out remote↔local and control-room↔field wiring | Hunt cross-connections and earth faults |
| 3 | Inspect the selector switch and remote-priority parameters | Rules out setting causes |
| 4 | Substitute spares: handwheel unit, selector, main board | Last resort, per the vendor |
"Local/remote" is fundamentally an arbitration of control authority. Note the mirror image: this case is crosstalk letting remote override local, while the AUMA article shows insulation faults creating phantom commands. Cable and ground checks remain the best value-for-money tools in actuator diagnostics.
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