Direct Answer

You are torn between hardwired interlocking and platform-based remote alarming — afraid of over-design but also of insufficient safety redundancy. What is the criterion? The answer: judge by whether the failure consequence can tolerate waiting for the network response — personal-safety and fire-spread consequences require hardwiring (it must act even when the network is down); actions that tolerate second-level response (exhaust fans, notifications, load shedding) can use the platform; spend the limited budget on the few circuits that "must act even when the network is down," rather than hardwiring every circuit.

At one plant's fire-interlocking retrofit: the fire alarm and circuit-breaking loops were hardwired (relay direct output, not through the network); exhaust fans and audible/visual notifications used platform interlocking. During a network-outage drill: hardwired loops acted as usual (cut the affected circuits); platform loops were delayed (executed after the network recovered) — verifying the design intent. Conclusion: hardwiring governs "must act," the platform governs "can wait." The decision's core is grading by failure consequence — only circuits that must act even when the network is down get hardwired; the rest go through the platform, precise budget with no waste.

Because:

  • Hardwiring is "reliable even when the network is down": no network dependency, millisecond response;
  • Platform interlocking "depends on the network": fails when the network is down, second-level response;
  • Consequence grading: personal safety/fire spread = must hardwire; exhaust/notification/shedding = platform can tolerate;
  • Budget logic: hardwiring is expensive (cables + terminals + commissioning); give it only to circuits that "must act."

Key insight: "must act even when the network is down" is the only reason to hardwire. Grade by failure consequence — a few circuits hardwired, most via the platform; safety and cost both achieved.

At one plant, all interlocking was made platform-based to save hardwiring cost. During a network fault that coincided with a distribution-cabinet temperature over-limit, the platform interlock did not execute (network down); manual response was delayed by minutes. Rectification: the temperature over-limit interlock was changed to hardwired (direct trip/load cut); exhaust and notifications stayed on the platform. Lesson: do not save where hardwiring is required — for circuits that "must act even when the network is down," the platform cannot substitute.

1. Response and Reliability Comparison of the Two Approaches

Step one: what are the characteristics of each.

Hardwired interlocking:

  • Principle: relay contact direct output (not through the network);
  • Response: millisecond level (relay action time);
  • Reliability: no network dependency (acts even when the network is down);
  • Cost: high (cables, terminals, commissioning);
  • Applicable: personal safety, fire breaking, etc.

Platform remote interlocking:

  • Principle: the platform issues commands → actuators act;
  • Response: second level (network transmission + command processing);
  • Reliability: network-dependent (fails when the network is down);
  • Cost: low (reuses network + platform);
  • Applicable: exhaust, notifications, load shedding, etc.

Comparison points:

  • Response speed: hardwired milliseconds vs platform seconds;
  • Network dependency: hardwired none vs platform dependent;
  • Action certainty: hardwired certain vs platform depends on the network;
  • Cost: hardwired high vs platform low.

Key insight: hardwired = reliable even when the network is down + millisecond; platform = network-dependent + second-level. The reliability difference is the root of the decision.

2. Decision Criterion: Consequence Tolerance

Step two: how to judge whether to hardwire.

Consequence grading:

  • Personal safety (electric shock/fire injuring people): must hardwire;
  • Fire spread (uncontrolled spread if cutting is late): must hardwire;
  • Equipment damage (sustained over-temperature/overload): hardwire preferred;
  • Production impact (load shedding/stoppage): platform can tolerate;
  • Notification type (audible/visual/SMS): platform suffices.

Tolerance judgment:

  • Ask "can you accept no action when the network is down":

- Cannot accept (safety/fire): hardwire; - Can accept (production/notification): platform;

  • Ask "is a few seconds' delay fatal":

- Fatal (fire/shock): hardwire; - Not fatal (exhaust/shedding): platform.

Judgment formula:

  • Consequence severity × network-failure probability = risk;
  • High risk (unacceptable): hardwire;
  • Low risk (acceptable): platform.

Key insight: "must act even when the network is down" is the watershed. Circuits that cannot accept no-action-on-outage get hardwired; those that can wait go to the platform — consequence tolerance decides the investment.

3. Which Circuits Must Be Hardwired

Step three: specifically which circuits.

Must hardwire:

  • Fire breaking: fire-interlocking cuts the affected circuits;
  • Temperature over-limit trip: critical equipment over-temperature direct cut;
  • Leakage/insulation-fault trip: personal-safety related;
  • Emergency-stop circuits: must act under any condition;
  • Over-limit trip: protective action cannot wait for the network.

Platform-applicable:

  • Exhaust interlock: temperature/smoke triggers exhaust (second-level tolerable);
  • Audible/visual notification: alarm indication (notification nature);
  • Load-shedding strategy: cutting non-critical loads (acceptable delay);
  • SMS/email: notifying operations (asynchronous);
  • Reports/records: post-analysis (no real-time requirement).

Grading example:

  • Cabinet temperature over-limit: hardwire (cut load);
  • Exhaust start: platform (second-level tolerable);
  • Audible/visual alarm: platform (notification nature);
  • Emergency stop: hardwire (must act under any condition).

Key insight: hardwiring goes to "safety-critical," the platform to "operational convenience." Grade by circuit nature — safety class hardwired, convenience class platform.

4. Cost Differences

Step four: where the money differs.

Hardwired cost composition:

  • Cables (independent wiring per circuit);
  • Relays/terminals (per circuit);
  • Construction/commissioning (on-site wiring + testing);
  • Later maintenance (terminal tightening, circuit testing).

Platform-interlock cost composition:

  • Network reuse (no extra cables);
  • Platform functions (software configuration);
  • Actuators (shared with hardwiring);
  • Configuration/commissioning (platform logic setup).

Cost comparison:

  • Hardwired: hundreds to thousands of yuan per circuit (depending on distance);
  • Platform: low marginal cost (reuses the existing network);
  • All-hardwired vs hybrid: hybrid saves 60%–80% of wiring cost;
  • Budget logic: spend on the few circuits that "must act."

Key insight: hardwiring is "high per-circuit cost," the platform is "low marginal cost." Hardwiring every circuit is waste — configure only the critical ones; most of the budget is saved.

5. Typical Configuration Example

Step five: what is the most reasonable configuration.

Example scenario (a plant's distribution system):

  • Incoming main breaker: hardwire (fire breaking/emergency stop);
  • Temperature over-limit circuit: hardwire (cut load);
  • Leakage-trip circuit: hardwire (personal safety);
  • Exhaust interlock: platform (second-level tolerable);
  • Audible/visual notification: platform (notification nature);
  • Load-shedding strategy: platform (acceptable delay).

Configuration principles:

  • Safety-critical circuits: hardwire (must act even when the network is down);
  • Convenience circuits: platform (act when the network is available);
  • The two complement each other: hardwiring guarantees the bottom line, platform expands coverage;
  • Periodic testing: regular action tests on hardwired circuits (reliability verification).

Acceptance points:

  • Network-outage test on hardwired circuits (verify no network dependency);
  • Platform-interlock delay test (verify second-level response);
  • Circuit-list check (correct grading);
  • Redundancy check (dual channels for critical circuits).

Key insight: the typical configuration is "safety hardwired + convenience on the platform." Clear grading, tested and verified — interlocking is both reliable and economical.

6. Product Landing: Digital Electrical Intelligent Supervision System

FEXLINK products land interlocking grading:

  • ESF Electrical-Fire Monitoring & Control Device (relay output): hardwired breaking for fire/temperature over-limit;
  • Platform interlocking: exhaust/notification/load-shedding strategies;
  • Circuit-list management: hardwired/platform grading labels;
  • Interlock testing: periodic test records (reliability verification).

Design principle in one sentence: "hardwiring guarantees the bottom line, the platform expands coverage." Circuits that must act even when the network is down get hardwired — safety has a fallback, budget is not wasted.

Common scenario Q&A:

  • Q: For temperature over-limit interlocking, is a platform trip enough? A: Not recommended for critical equipment — when the network is down the platform fails and temperature keeps rising; hardwiring cuts the load directly and is more reliable.
  • Q: How much does full hardwiring cost? A: Billed per circuit (cables + terminals + commissioning); full hardwiring is several times the hybrid cost; configure only the "must-act" circuits.
  • Q: Is platform interlocking completely unreliable? A: No — with the network normal, second-level response suffices; it only fails when the network is down, so safety-critical circuits cannot depend on it.
  • Q: Do hardwired circuits need maintenance? A: Yes — periodic action tests (prevent contact oxidation/circuit breaks), with test records in the maintenance ledger.
  • Q: How do I present this investment to leadership? A: Explain that the few "must-act-even-when-the-network-is-down" circuits protect the safety bottom line, and the rest use the platform to save budget — safety and cost both win.

7. Common Decision Misconceptions

  1. All-platform to save cost: all interlocking via the platform. Consequence: safety circuits do not act when the network is down. Correct: hardwire safety-critical circuits.
  2. All-hardwired for safety: hardwiring every circuit. Consequence: wasted cost (convenience circuits do not need it). Correct: grade by consequence.
  3. Construction cost only: ignoring network-outage risk. Consequence: save small money, take a big risk. Correct: include reliability value in the decision.
  4. Hardwired without testing: installed and ignored. Consequence: contact oxidation/circuit breaks unknown. Correct: periodic action tests.
  5. Grading undocumented: configured by feel. Consequence: unclear circuit attribution (hardwire-required circuits on the platform). Correct: manage a graded circuit list.

Scope and Limitations

This article provides a decision framework for hardwired interlocking vs platform-based remote alarming (response/reliability comparison, consequence-tolerance criterion, circuits that must be hardwired, cost differences, typical configuration example) for distribution-system interlock design, fire-interlock retrofit, and budget allocation. Specific circuit grading must be determined per on-site safety requirements, process continuity, and code requirements; design and construction of hardwired circuits must comply with applicable electrical and fire codes; interlock testing must be performed by qualified personnel per procedures. All cases are anonymized (a certain plant) and do not refer to any specific customer.