ZB4-BZ102
ActiveHarmony XB4 1NC Contact Block
Single contact block with 1 normally closed (NC) contact for Schneider Harmony XB4 series. Screw clamp terminals.
Common Applications
Contact block with 1NC (Normally Closed) contact — the circuit is complete until the button is pressed. Used for stop buttons and emergency stops where the default safe state is "circuit closed" (fail-safe design). If the wire breaks, the circuit opens and the machine stops — same as pressing the button. Always wire NC contacts in series with the safety circuit. Can be stacked with a 1NO block on the same button for simultaneous start/stop signaling.
Commonly Found On
Compatibility
Same compatibility as ZB4-BZ101. NC version for stop/safety circuits. Stacks with ZBE elements for 1NO+1NC on a single button.
Repair & Maintenance
Replace when button operates intermittently. Silver contacts pit over time from arcing. Check with multimeter: NC should show <1 ohm when not pressed, open when pressed. Replace the entire block — dont try to file contacts.
Specifications
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Certifications
Third-party safety certifications. UL = required for US NEC installations. CE = EU compliance. CSA = Canadian standards.
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UL, CSA, CE
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Contact Configuration
Normally Closed — circuit is on until you press. Standard for stop/emergency functions. Wire in series with safety circuits.
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1NC
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Current rating
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10A
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Terminal Type
How you connect wires. Screw clamp is most common in industrial. Spring cage is faster but requires proper ferrules.
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Screw Clamp
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Max Voltage
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600V
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Specs with this icon are linked to the manufacturer's original source page
You'll Also Need
This is a modular component. For a complete assembly, you may also need:
Installation Quick Reference
Mounting: Snap onto the rear of any compatible button body in the same series. The latch clicks audibly when properly seated. Some models require a mounting adapter.
Wiring: Terminals are marked NO (11/12) or NC (21/22). Use 0.5-2.5mm² wire with ferrules. Tighten to 0.8 Nm. Verify with a multimeter before energizing.
Dimensions
Wiring Diagram
Troubleshooting
Intermittent switching
Silver contacts are pitted from arcing. Replace the contact block — they are consumable parts. If arcing is severe, check that the switched load doesn't exceed the contact rating (typically 6A at 120VAC).
Contact block won't snap onto button body
Verify the contact block series matches the button head series (e.g., Schneider ZB4 blocks fit ZB4 heads only, not ZB5). Check for debris or damage on the mounting tabs.
Where to Buy
Price range
$1.31 — $15.35
across 4 distributors
Quick Specs
- Certifications
- UL, CSA, CE
- Contact Configuration
- 1NC
- Current rating
- 10A
- Terminal Type
- Screw Clamp
- Max Voltage
- 600V
What People Are Saying
“Keep spares of these. Contact blocks are consumable parts — the first thing to check when a button starts acting intermittent. Cheap replacement, saves troubleshooting time.”
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Data Sources
Specifications and product data sourced from the following references.
