{"id":3297,"date":"2026-09-24T11:00:00","date_gmt":"2026-09-24T11:00:00","guid":{"rendered":"https:\/\/cnsuton.com\/?p=3297"},"modified":"2026-09-28T02:30:01","modified_gmt":"2026-09-28T02:30:01","slug":"coordenacao-da-selectividade-de-interruptores-diferenciais","status":"publish","type":"post","link":"https:\/\/cnsuton.com\/pt\/blog\/rccb-selectivity-coordination\/","title":{"rendered":"Seletividade de RCCB: Coordena\u00e7\u00e3o de Dispositivos a Montante e a Jusante"},"content":{"rendered":"

RCCB selectivity<\/strong> means a downstream residual-current device should clear the local fault while the upstream device remains closed when the coordination objective requires continuity. Achieving it depends on sensitivity ratio, intentional time delay, device type, residual-current waveform, fault magnitude and the manufacturer’s tested or declared coordination data. A downstream 30 mA device and an upstream 300 mA device are not automatically selective. Check the exact products and every operating mode before approving the settings. State the coordination boundary in the panel schedule and obtain approval from the responsible engineer.<\/p>\n

Define total or partial selectivity<\/h2>\n

First state whether the project needs total selectivity across the expected fault range or only partial selectivity up to a declared residual-current level. Total selectivity is a demanding claim and may require a time-delayed or selective upstream device, a sensitivity ratio and manufacturer evidence. Partial selectivity can be acceptable when the limiting current is documented and the installation risk is understood. Do not write \u201cselective\u201d on a schedule without the boundary.<\/p>\n

\n\n\n\n\n\n\n\n\n\n
Coordination input<\/th>\nWhy it matters<\/th>\nEvidence to request<\/th>\n<\/tr>\n
Downstream sensitivity<\/td>\nSets the local residual-current operating threshold<\/td>\nExact RCCB type and declared I\u0394n<\/td>\n<\/tr>\n
Upstream sensitivity<\/td>\nMust not operate before the downstream device for the target fault range<\/td>\nUpstream setting, ratio and manufacturer table<\/td>\n<\/tr>\n
Time delay<\/td>\nCreates a separation window between devices<\/td>\nDelay curve, tolerance and non-operating time<\/td>\n<\/tr>\n
Waveform and device type<\/td>\nOperating response can vary with residual-current shape<\/td>\nType, test conditions and product instructions<\/td>\n<\/tr>\n
Fault magnitude<\/td>\nCoordination may end at a stated current limit<\/td>\nStudy, test evidence and partial-selectivity boundary<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<\/div>\n
\"Two
Article-specific product-reference cover based on original SUTON product photography.<\/figcaption><\/figure>\n

Use the manufacturer’s tested or declared coordination data for the exact combination. Do not infer selectivity from nominal mA values alone.<\/small><\/p>\n

Use sensitivity and delay together<\/h2>\n

A higher upstream threshold creates separation only if the device’s actual operating and non-operating limits support it. An intentional delay can help, but it must remain compatible with the required disconnection time and touch-voltage protection. Review the full tolerance bands rather than subtracting nominal values. Normal leakage, transient leakage and waveform can also affect which device sees the residual current first.<\/p>\n

Electrical Installation’s coordination guide<\/a> describes the need to coordinate residual-current devices by sensitivity and time. ABB’s RCD selectivity material<\/a> shows why manufacturer-specific tables and selective device types matter. These are technical references, not substitutes for SUTON combination data.<\/p>\n

Check normal leakage and operating modes<\/h2>\n

Calculate or measure leakage with all loads operating, including filters, drives, power supplies, long cables, standby and transfer modes. A high upstream setting does not fix a downstream device that sees excessive normal leakage. For generators, PV or multi-source systems, identify whether source bonds and return paths change the residual-current seen by each device.<\/p>\n

Test the intended sequence with the approved equipment and record which device trips. Do not create a test fault without a controlled procedure. The RCCB sensitivity guide<\/a> covers threshold choice, and the two-pole versus four-pole RCCB guide<\/a> covers conductor arrangements.<\/p>\n

Document the coordination boundary<\/h2>\n

Record upstream and downstream model codes, pole arrangement, sensitivity, delay, waveform type, installation mode, fault range, evidence revision and the intended continuity objective. If the combination is not tested, mark the limitation and obtain engineering approval before calling it selective. Recheck coordination after changing a device, setting, cable, source, accessory or enclosure arrangement.<\/p>\n

IEC 60947-2:2024<\/a> provides product-standard context, while HSE electrical-safety guidance<\/a> reinforces competent work and safe isolation. Apply the project edition and local rules.<\/p>\n

Selection workflow<\/h2>\n
    \n
  1. State total or partial selectivity and the current boundary.<\/li>\n
  2. Identify upstream\/downstream model codes and residual-current types.<\/li>\n
  3. Compare sensitivity, delay, tolerances and waveform response.<\/li>\n
  4. Check normal leakage and every source\/transfer mode.<\/li>\n
  5. Obtain manufacturer coordination evidence.<\/li>\n
  6. Record settings, test results and limitations.<\/li>\n<\/ol>\n

    Use the SUTON ETM1L product page<\/a> as a product starting point. Request a model-specific selectivity confirmation before approving the schedule.<\/p>\n

    The circuit-breaker types guide<\/a> is the parent overview for the RCCB coordination decision.<\/p>\n

    At handover, retain the upstream and downstream model codes, sensitivity, delay, coordination table revision, test result and stated selectivity boundary. If a device, setting, source or cable changes later, repeat the coordination review before describing the arrangement as selective.<\/p>\n

    Where evidence is unavailable, mark the limitation clearly and obtain engineering approval. A nominal 30 mA versus 300 mA comparison is useful context, but it is not a substitute for the declared operating curves and the actual installation study.<\/p>\n

    Ask the supplier to identify whether the combination has total or partial selectivity, the residual-current level at which coordination ends, the test conditions and any required upstream delay. Keep that answer with the panel schedule and commissioning record.<\/p>\n

    Do not call a combination selective solely because the upstream threshold is higher. Confirm the time tolerance, waveform response, normal leakage and source mode for the exact products before release and handover with signoff by the owner and engineer for records and QA and review before release and delivery securely for clarity and audit later for all users now.<\/p>\n

    Build an approval record that can be audited<\/h2>\n

    Record the exact catalog code, frame, rated current, poles, voltage, residual-current function, settings, terminals, accessories, mounting arrangement and document revision. Keep the as-designed, as-installed and as-left information separate. A family brochure is not enough when several sensitivities, pole arrangements or trip units share an enclosure.<\/p>\n

    The technical file should include the single-line diagram, fault-current study, protection study, conductor schedule, panel drawing, manufacturer instructions and commissioning results. If a value comes from a calculation, state the source inputs and revision. If it comes from a manufacturer table, identify the exact table and device combination.<\/p>\n

    Commissioning and safe-work boundary<\/h2>\n

    Before energization, verify device identity, settings, pole arrangement, conductor placement, terminal preparation, tightening method, barriers, labels, handle operation, auxiliary functions and mechanical interlocks. Testing and fault studies must be carried out or approved by qualified people under the adopted rules. This article supports specification work and does not authorize energized work.<\/p>\n

    After a serious fault or unexplained trip, do not simply reset the device. Investigate the cause, inspect the RCCB and connected equipment as required by the manufacturer, and confirm that settings remain correct.<\/p>\n

    Information to include in an RFQ<\/h2>\n

    Give bidders the system voltage and frequency, AC or DC duty, poles and neutral arrangement, normal current, calculated maximum and minimum fault current, residual-current sensitivity and time delay, required breaking capacity, conductor and terminal details, accessories, control voltage, mounting, ambient conditions and required documents. Ask for a completed compliance schedule rather than an unqualified family datasheet.<\/p>\n

    Require the offered model to be decoded in full. Options such as electronic residual-current modules, test buttons, auxiliary contacts, shunt trips and time delays can change the product code and wiring. An accessory shown in a brochure photograph is not automatically part of the quotation.<\/p>\n

    Close the evidence loop before purchase approval<\/h2>\n

    Place each supplier answer beside the project requirement and classify it as compliant, conditional or noncompliant. Do not treat a blank cell as compliance. Resolve alternative offers with the same technical review applied to the base offer, and retain the approved schedule with the purchase order. Confirm that the datasheet revision, drawing, setting sheet and installation instructions all describe the same catalog code and option package.<\/p>\n

    Ask who owns the protection calculation, who sets the device, and which operating modes were included. Record assumptions that still depend on vendor data. This discipline prevents a late discovery about neutral sensing, pole arrangement, leakage, delay or an accessory from becoming a panel change after shipment.<\/p>\n

    At handover, keep the final model code, settings, test results, marked-up single-line diagram and commissioning record together. Future maintenance staff should be able to see exactly which conductors, sources and residual-current functions were included in the decision. If a later replacement uses a different trip technology or accessory, repeat the review instead of assuming the original coordination still applies.<\/p>\n

    Where the quotation offers alternatives, ask the supplier to identify every changed interface and every changed assumption. A different pole arrangement, sensitivity selector, delay module or terminal kit can alter the panel drawing, coordination study and test plan even when the front label appears similar.<\/p>\n

    Do not close the review with a generic statement that the device is \u201csuitable.\u201d State the intended protection objective, the selected value, the evidence source, the operating modes covered and the limitation that remains. That record makes later troubleshooting and replacement safer.<\/p>\n

    \"Original
    Original SUTON product photo for model-specific verification.<\/figcaption><\/figure>\n
    \"Original
    Original SUTON product photo for model-specific verification.<\/figcaption><\/figure>\n

    Related SUTON technical resources<\/h2>\n

    Use the linked product and related guides as procurement starting points, then verify the offered device against the project study. Similar-looking RCCBs can have different ratings, terminals, trip functions and approvals.<\/p>\n

    Educational video<\/h2>\n

    The following neutral educational video supports the electrical principle discussed here. It does not replace project calculations or manufacturer instructions.<\/p>\n