Schneider Preventa XPS — Safety Relay Won't Reset

Schneider · beginner · 20 min

A Preventa XPS safety relay that won't energize its outputs usually has an open Y1-Y2 feedback loop, a dual-channel input that isn't fully made, or the wrong reset wiring. Read the LEDs and check the loop.

⚠️ The XPS won't close its safety outputs until every monitored condition is satisfied — that's the point. Read the LEDs to see which condition is missing, then fix the wiring, not the relay.

Read the LEDs first

A Schneider Preventa XPS safety relay module has four LEDs that indicate status, faults, and synchronization, giving you the monitoring-circuit status for fast diagnosis. Before touching wiring, read them — they show the state of power, the input channels, and the outputs, so they tell you which condition is holding the relay open.

The three usual reasons it won't reset

1. Open Y1-Y2 feedback loop

The XPS monitors an external Y1-Y2 feedback loop — typically the normally-closed auxiliary contacts of the controlled contactors/actuators (and, in many wirings, the reset/start circuit). If this loop is open, the relay will not energize its outputs. A welded or stuck external contactor (its NC aux stays open), a broken wire in Y1-Y2, or a missing link is the classic "it won't reset" cause. Verify the feedback loop is closed with the machine in its safe/off state.

2. A dual-channel input not fully made

Safety inputs (E-stop, guard) are usually two channels that must both close for the relay to allow a reset. If one channel is open — a pressed E-stop, an open guard, a broken channel, or a discrepancy — the relay stays tripped. Confirm both channels of the input device are made together.

3. Wrong reset mode / wiring

The XPS offers automatic or manual reset, selectable by wiring. If it's wired for manual reset, the outputs only close after a reset/start pulse — so nothing happening on power-up can simply mean it's waiting for the reset button. If it's wired for automatic reset, it should reset itself once inputs and feedback are satisfied. Confirm the start-function wiring matches the intended behavior.

Step-by-step

  1. Read the four LEDs — identify whether power, an input channel, or the output/feedback is the missing condition.
  2. Check the 24 VDC control supply to the module.
  3. Verify both safety input channels are made (no pressed E-stop, guard closed, both channels healthy).
  4. Check the Y1-Y2 feedback loop is closed — inspect the external contactor NC aux contacts (watch for a welded contactor holding it open) and the loop wiring.
  5. Confirm reset mode — if manual reset, give the reset/start pulse; if automatic, confirm the start wiring.
  6. Outputs close once inputs and feedback are satisfied and the reset condition is met.

Verify

With inputs made, the feedback loop closed, and the reset satisfied, the XPS energizes its safety outputs (the corresponding LEDs turn on). If it drops again immediately, a monitored contactor is likely welded (feedback opens) — check the external actuator.

Never do this

Do not jumper out the Y1-Y2 feedback loop or bridge a safety input channel to force a reset. The feedback loop exists to catch a welded contactor; defeating it removes the protection.

Key points

  • The XPS four LEDs show power, input-channel, output, and fault/sync status — read them to see which condition holds the relay open.
  • An open Y1-Y2 feedback loop (e.g. a welded external contactor's NC aux, or broken loop wiring) is the classic 'won't reset' cause.
  • Dual-channel safety inputs must both close — a pressed E-stop, open guard, or a single-channel fault keeps it tripped.
  • Reset is automatic or manual by wiring — a manual-reset module simply waits for the reset/start pulse.
  • Never jumper the Y1-Y2 loop or bridge an input channel to force a reset; the loop catches a welded contactor.

Codes and symptoms

Won't reset / no output — Safety outputs stay open
A monitored condition is unmet — open Y1-Y2 feedback loop, a dual-channel input not fully made, or awaiting a manual reset pulse.