Automatic Checks
ElectroBoard checks your panel in real time against 100+ rules grouped by category. Results appear in the Validation panel — the colour-coded panel in the bottom-right corner of the editor.
Reading the validation panel
Checks are grouped by severity:
- 🔴 Safety — critical errors that can lead to fire, electric shock or equipment damage. Must be fixed
- 🟡 Problem — situations that may cause nuisance tripping or unstable operation. Fixing is recommended
- 🔵 Recommendation — advice for improving the design. May be ignored, but better taken into account
Click any check to expand the details. The details explain the cause of the problem and suggest a solution. Some checks have a button that jumps to the relevant device.
💡 Standard adaptation: Message texts adapt to the regulatory standard chosen in the panel settings. For NEC, for example, the wire-colour warning shows NEC 200.6 / 250.119 and the black/red/blue scheme, while for IEC it shows IEC 60445 and the brown/black/grey scheme. Thresholds (voltage drop, RDF, phase balance) also differ by standard: NEC has a tighter 3% / 2% voltage-drop limit versus 5% / 3% under IEC. When several standards are active, the strictest one applies. This is the behaviour of the RegionalProfile architecture — adding a new regional standard needs a single new descriptor file, not edits across dozens of detectors.
[screenshot: validation panel with examples of different warning types]
Selectivity (5 checks)
Selectivity is the principle that, during a fault, only the device closest to the fault trips — not everything upstream.
💡 Note: The rating and curve checks (items 1, 2, 4, 5) apply only to protective devices — MCB (mcb), RCBO (rcbo), AFDD (afdd), fuse (fuse). RCDs, contactors and relays are excluded from these checks because they do not perform overload protection.
1. Child rating exceeds parent rating 🔴
Example: the "Water heater" MCB (25 A) connected to a 16 A incoming MCB.
Problem: on a water-heater overload the incoming MCB trips and disconnects the whole group (including other circuits) instead of only the water-heater MCB.
Solution: lower the child rating or raise the parent rating.
2. Same rating on parent and child 🟡
Example: a parent MCB (16 A) and a child MCB (16 A).
Problem: on overload it is undefined which trips first — the whole group may be disconnected.
Solution: make the child rating lower than the parent.
3. RCD without an upstream circuit breaker 🟡
Example: an RCD connected to a contactor (not to an MCB).
Problem: an RCD is not rated for short-circuit currents and may be damaged.
Solution: add an MCB ahead of the RCD, or replace it with an RCBO.
💡 Clarification: the check walks the RCD's entire ancestor chain through non-protection devices (voltage relay, contactor, transfer switch, 1-0-1 isolator). If an MCB / RCBO / fuse is found at any level upstream, the warning does NOT fire. For example, the chain "incoming MCB → voltage relay → RCD" is correctly protected.
4. Curve conflict 🟡
Example: a parent with curve B, a child with curve D.
Problem: on a short circuit the parent (curve B, fast) trips before the child (curve D, slow) and disconnects the whole group.
Solution: the parent curve must be the same as or slower than the child curve. For example: parent C or D, child B or C.
5. Sum of child ratings far exceeds the parent 🟡
Example: a 40 A incoming MCB has five 16 A child MCBs (sum = 80 A > 40 A ÷ DF(0.7) ≈ 57 A).
Problem: if all circuits switch on at once, the parent device may trip.
Solution: check the diversity factor — if not all circuits run simultaneously, this may be fine. Otherwise, raise the parent rating.
💡 Diversity factor (DF) per IEC 61439-1: ElectroBoard applies the DF automatically based on the number of outgoing circuits on the parent device:
Outgoing circuits DF 1 1.0 2–3 0.8 4–5 0.7 6–9 0.6 10+ 0.5 The parent-overload threshold is the sum of child ratings against
parent rating ÷ DF. For five children (DF = 0.7) the threshold for a 40 A device is ≈ 57 A.
Inrush current (1 check)
6. Inrush current exceeds the breaker's tripping threshold 🔴/🟡
Example: the "Washing machine" MCB (16 A, curve C) with a motor whose inrush current is ~80 A.
Problem: when the washing machine starts, the motor inrush current exceeds the curve-C band (threshold 80–160 A). The breaker may trip on every switch-on.
Solution: change the breaker curve (e.g. to D) or raise the rating.
Cable system (3–5 checks)
7. Cable may overheat 🔴
Example: a 1.5 mm² cable (in a wall, 16 A ampacity) under a 20 A breaker.
Problem: the breaker rating exceeds the cable's permissible current — on overload the cable reaches a dangerous temperature before the breaker trips.
Solution: increase the cable cross-section or lower the breaker rating.
💡 Transfer switch / changeover: for devices with two inputs (main + reserve source), checks 7–10 apply to both cables independently — primary and secondary. Messages for the secondary (reserve) cable are tagged "reserve cable".
8. Cable running at the limit 🟡
The calculated load current is close to this cable's ampacity. It will work, but with no margin.
9. Voltage drop exceeds 5% 🔴
Solution: increase the cable cross-section or reduce the circuit length.
10. Voltage drop 3–5% 🟡
For lighting, keeping the drop below 3% is recommended. For socket circuits — below 5%.
11. Non-standard cable cross-section 🔵
An informational message about the use of a non-standard cross-section.
11a. Larger cable cross-section recommended 🔵
The current cross-section will carry the breaker current, but with no margin. For example, a 25 A MCB recommends 6 mm² but 4 mm² is installed — it will work, yet close to the limit. This is advice for the future, not an error.
Cable — installation physics (4 checks)
Universal installation-physics checks per IEC 60364. Always active (independent of the chosen regulatory standard); some fire only when the corresponding installation conditions are set in the panel settings.
11b. Conductor may burn out on a short circuit 🔴
Rule (IEC 60364-4-43): the let-through energy (I²t) of the protective device on a short circuit must not exceed the conductor's thermal withstand k²×S² (the adiabatic criterion). Otherwise the conductor insulation degrades faster than the protection trips.
Example: a protection device with high let-through energy over a thin conductor (e.g. 1.5 mm²).
Solution: increase the conductor cross-section (each is checked — L, N, PE separately) or fit faster protection — a gG fuse or a lower rating.
11c. Cable grouping reduces ampacity 🟡
Rule (IEC 60364-5-52 §523.5): when several cables run in a common bundle or tray, their mutual heating reduces the ampacity (grouping factor Cf). The check activates when the number of cables in the group (more than one) is set in the panel settings.
Problem: the calculated current exceeds the ampacity with Cf applied (although without grouping this cable would carry it).
Solution: increase the cross-section or reduce the number of cables in the group.
11d. Current exceeds ampacity at elevated temperature 🟡
Rule (IEC 60364-5-52, Table B.52.14): at an ambient temperature above the standard 30 °C, the cable ampacity is reduced by factor k1. The check activates when the installation temperature is set in the panel settings.
Solution: increase the cross-section or change the installation conditions (lower ambient temperature).
11e. N conductor too small for a harmonic load 🔴
Rule (IEC 60364-5-523, Annex E): with a significant share of triplen harmonics (3rd, 9th — from switch-mode power supplies, LED drivers, variable-speed drives) the neutral current may exceed the phase current. For 33–45% harmonics the N cross-section is multiplied by a factor of 1.45.
Problem: the N conductor is smaller than required for the harmonic load — a risk of neutral overheating.
Solution: increase the N conductor cross-section to the recommended value.
Earthing (3 checks)
12. Device incompatible with the earthing system 🔴
Some devices do not work with certain earthing systems. For example, an RCD does not work in a TN-C system (where N and PE are combined) — differential protection physically cannot operate on a leakage.
12a. No shock protection in a TT system 🔴
In a TT earthing system the only reliable protection against indirect contact is a residual-current device (RCD or RCBO). If the panel has no RCD at all, there is no protection on an insulation fault to an enclosure.
Solution: add an incoming RCD with a rated residual current ≤ 300 mA, or a per-group RCD ≤ 30 mA.
13. Earthing-system limitation 🔵
The device can work, but with limitations for the chosen earthing system. For example, in TN-C an RCD/RCBO cannot be used, and bathrooms and kitchens cannot be protected by differential protection. If possible, consider moving to TN-C-S (splitting PEN into N + PE).
Phase conflict (2 checks)
14. Child on a different phase than the parent 🔴
Example: an RCD on phase L1, and a child MCB on phase L2.
Problem: the child device is not fed from the parent. The RCD does not see the current flowing through the MCB.
Solution: move the child to the same phase as the parent, or change the parent device.
15. Incompatible connection variant 🟡
The child's connection variant does not match the parent's phases.
Panel structure (9 checks)
16. No incoming device 🔵
The panel has no isolator or MCB at the incomer. Recommendation — add one so the panel can be safely de-energised.
17. RCD with no connected breakers 🟡
An RCD or contactor parent has no child devices. It occupies a rail position but serves no function.
18. Device without upstream protection 🔵
A device that should be protected (e.g. an MCB) is not connected to any parent.
19. Cable cross-section not specified 🔵
For a device with an outgoing cable, the cable parameters are not set. Without them, the cable's overheat protection cannot be checked.
19a. Control-circuit target deleted 🟡
A controller device (contactor switch, relay, etc.) references a contactor that has been removed from the panel.
19b. Control-circuit target is not a contactor 🟡
A controller device references a device that is not a contactor. Control circuits are supported only for contactors (with an A1/A2 coil).
19c. Device controls itself 🟡
A device references itself as the control-circuit target.
19d. Fed from a device with no output 🟡
The device is connected as a child of an SPD (varistor shunt), socket, meter or relay — that is, a device that has no output terminal for supplying a load and does not pass current onward.
Solution: move the device to a real upstream source — the same incoming device or busbar that feeds the SPD.
19e. Both transfer-switch inputs from the same source 🟡
Example: on a transfer switch, both the main and the reserve input are tied to the very same physical device.
Problem: redundancy does not work — when supply to that device fails, both transfer-switch inputs lose power simultaneously.
Solution: tie the main and reserve inputs to different sources (e.g. incoming MCB + generator).
💡 Difference from check 50: check 50 fires when the two inputs have the same source role (both "Grid"), whereas this one fires when both inputs point to the same device.
Allocated power (1 check)
20. Allocated power exceeded 🔴
The panel's total load exceeds the allocated power. With all devices running at once, the supplier's incoming breaker may trip. Reduce the load, use timers, or ask the supplier to increase the allocated power.
Loading (3 checks)
22. Breaker overloaded 🔴
The calculated current through the breaker exceeds its rating. The breaker is running in an overload condition.
23. Breaker close to the limit 🟡
The calculated current is close to the rating. Increasing the rating or redistributing the load is recommended.
23a. Enable the diversity factor 🔵
When many outgoing circuits are connected to one parent device, calculating at 100% simultaneity overstates the total current — in practice not all circuits run at once.
Solution: enable the diversity factor (DF) in the toolbar — the load calculation becomes more realistic per IEC 61439-1. This is advice, not an error.
Phase balance (2 checks, three-phase only)
24. Phase imbalance > 30% 🟡
One of the phases is loaded significantly more than the others. This raises the neutral current and lowers supply quality.
25. Phase imbalance 15–30% 🔵
Noticeable unevenness; redistributing the load is recommended.
Busbar combs (19 checks)
💡 Comb type: the comb type (1P / 3P / 1P+N / 3P+N) is determined automatically from the actual conductor set of the breakers in it — not from the pole count of the first breaker. For multi-phase panels each phase (L1/L2/L3) may have a separate comb if their positions do not coincide. This removes false type detection for mixed groups.
26. Comb breaker does not exist 🔴
A breaker was deleted from the panel but remained in the comb. Delete the comb and create a new one.
27. Breaker not on the comb's rail 🔴
A breaker was moved to another rail and is no longer on the comb's rail.
28. Conductors do not match the comb 🔴
After changing a breaker's connection (e.g. from 1P to 3P), its conductors no longer match the comb type.
29. Different feed direction in the comb 🔴
Breakers in the same comb have different feed directions — one is fed from the top, another from the bottom.
29a. N comb fed from an unsuitable device 🔴
Rule: an N comb fed from a device (rather than from an N bar) is valid only when that device is a distributor of N — it has a neutral-distribution role (RCD, transfer switch, cross-module, changeover) and its own N pole.
Example: an N comb fed from an ordinary 1P+N MCB (passthrough) or an SPD (shunt).
Problem: passthrough devices have 1–2 output terminals on N — not intended for branching. An SPD physically has a varistor shunt and does not pass N current outward.
Solution: re-tie the comb feeder to an N bar or to a distributor (e.g. a 4P cross-module that has an N pole and output terminals).
29b. Comb with no supply source 🔴
The input comb has no explicit source (feeder). A comb needs a breaker or N bar to feed from — check the comb properties panel.
29c. Reference to a non-existent source 🔴
The comb's supply source (feeder) references a breaker, bar or comb that is not on the panel (e.g. after deletion). Choose an existing source.
29d. RCBO in a shared N group 🔴
An RCBO has its own internal N channel. A shared RCBO comb with ordinary breakers shorts this internal N — the RCBO's differential protection breaks (IEC 60364-5-53). Remove the RCBO from this comb, or make all its members RCBOs.
29e. N comb without an N bar 🔴
An N comb needs a neutral source selected: the panel's N bar (the common bar or the RCD's own N bar). Choose a source in the comb properties.
29f. Comb Inc exceeded 🔴
The sum of the connected breaker ratings is greater than the comb's rated withstand (Inc). Thermal withstand is not guaranteed (IEC 61439-1 cl. 9.3). Increase the comb Inc or split the breakers across two combs.
29g. Cascade cyclic reference 🔴
The comb is indirectly fed from itself through a chain of sources (comb → comb → … → itself). Choose an N bar directly or another comb higher in the cascade.
29h. Comb cascade too deep 🔴
The comb-cascade depth exceeds 5 levels. Per IEC 61439-1 cl. 9.3, thermal-withstand coordination is not guaranteed. Shorten the chain.
29i. Device poles do not intersect the comb conductors 🔴
A breaker's conductors (e.g. L2) are absent from the comb (e.g. L1-only). The breaker cannot be a member of this comb — remove it or change its connection type.
29j. Combined-comb phase without a source 🔴
A combined comb (1P+N / 3P+N) declares a phase conductor, but the source cannot provide it — e.g. the phase is routed through an N bar that does not carry L. Choose a phase source for the phase.
29k. Combined-comb N without a source 🔴
A combined comb (1P+N / 3P+N) declares N, but the source cannot provide it — e.g. N is routed through a phase bar that does not carry the neutral. Choose a neutral source (an N bar) for N.
29l. N comb under an RCD on the common bar 🟡
An N comb whose members are under an RCD is fed from the panel's common N bar rather than from that RCD's own N bar.
Problem: a shared neutral with other groups breaks selective leakage protection (IEC 60364-5-53 cl. 531) — the RCD sees foreign current and may nuisance-trip.
Solution: re-tie the N comb to that RCD's own N bar.
29m. Comb crosses a zone boundary 🟡
Breakers of different room zones are grouped in one comb (e.g. bathroom and living room).
Solution: for ease of maintenance, make separate combs for each zone. This is a best-practice recommendation, not a connection error.
29n. Comb feeder on a different rail 🔵
The comb's supply source (feeder) is on a different rail than the comb itself. This is allowed but may lead to long inter-rail wire crossings — check the routing.
29o. Comb supply-hierarchy break 🟡
In a combined comb (1P+N / 3P+N) the phase and N sources have no common ancestor in the supply tree — L and N come from topologically independent cascades.
Problem: independent supply chains on one comb can create a short circuit between cascades.
Solution: feed the comb's phase and neutral from a common source (one device or a linked hierarchy).
PE/N bars (2 checks)
30. Bar terminals overflow 🟡
The number of connected devices exceeds the number of terminals on the bar. The system will offer to increase the terminal count to the nearest standard size.
31. PE bar missing 🟡
The panel has devices that need earthing (SPD), but there is no PE or PEN bar. Add a bar of the appropriate type.
Electrical safety (IEC 60364) (4 checks)
Checks for compliance with fundamental electrical-safety requirements. Always active; no manual enabling needed. Framed against IEC 60364 and the related IEC standards.
32. RCD differential selectivity 🔴
Rule (IEC 61008-1 §7.6): the rated residual current of the parent RCD (IΔn) must be at least three times that of the child RCD (S-type vs general selectivity).
Example: an incoming RCD (IΔn = 30 mA) with a child RCD (IΔn = 30 mA) — a violation. Required: parent ≥ 100 mA (since 30 × 3 = 90 mA).
Problem: without a sufficient spread of tripping currents, a leakage trips both RCDs at once, de-energising the whole panel instead of one group.
Solution: fit an incoming RCD with IΔn ≥ 100 mA (fire protection) or 300 mA, and 30 mA group RCDs.
33. Wet zones without an RCD ≤ 30 mA 🔴
Rule (IEC 60364-7-701): circuits in wet locations (bathroom, laundry) must be protected by an RCD with IΔn ≤ 30 mA.
Example: the "Water heater" MCB with a "Bathroom" zone is connected to a parent device with no RCD in the protection chain.
Problem: the absence of differential protection in a wet location — a risk of electric shock.
Solution: connect the device under an RCD or RCBO with IΔn ≤ 30 mA. For enhanced protection (bathroom) IΔn = 10 mA is recommended.
34. Device labelling 🔵
Every protective device should carry a label that identifies the circuit it protects. Without labelling, the purpose of a circuit cannot be identified during maintenance or a fault.
Problem: the device has no name (the "Name" field is empty).
Solution: give the device a descriptive name (e.g. "Kitchen sockets", "Corridor lighting").
34a. Bedroom without AFDD protection 🔴
Rule (IEC 60364-4-42 §421.4): circuits in bedrooms must be protected by an arc-fault detection device (AFDD) — because of the raised fire risk from arcing faults in damaged wiring at night.
Problem: a device in a "Bedroom" zone is not protected by an AFDD — neither the device itself nor any of its ancestors is an AFDD (or an RCBO with an AFDD function).
Active for: standards that require an AFDD in bedrooms.
Solution: add an AFDD or an RCBO with an AFDD function upstream of this breaker.
Cross-modules (2 checks)
35. Cross-module connection count exceeded 🔴
The number of child devices on one terminal (conductor) of the cross-module exceeds its physical number of outputs per pole. For example, more circuits than a 12-output pole can take.
Solution: reduce the number of child devices, choose a cross-module with more outputs, or route N to a separate bar.
💡 On current overload: the total load current is checked separately — in the "Loading" section (checks 22–23). A cross-module has no "sum of ratings > module rating" check, because the sum of ratings is not the simultaneous current (12×16 A ≠ 192 A at once).
36. Child device phase incompatibility 🔴
A child device requests a conductor (phase) that the cross-module does not have. For example, a three-phase device connected to a single-phase cross-module.
Solution: change the child device connection, or use a cross-module of the matching pole count (4P for three-phase circuits).
N routing (17 checks)
Checks for correct routing of the neutral (N) conductor through the device hierarchy.
37. N conductor not connected 🔴
The device has an N pole, but the N route is undefined. The system points to the root of the problem — the highest ancestor where N breaks.
Solution: change the ancestor's connection variant (e.g. 1P → 1P+N) or add an N bar.
38. Direct N under an RCD (2 direct) 🟡
Two child devices are set to "Direct" under an RCD/transfer switch/changeover. Physically — one N terminal, two wires on it: electrically permissible (with a WAGO/ferrule combination), but adding an N bar is better.
Solution: move one of the children to "Via bar" (the bar is created automatically).
38a. Direct N under an RCD — overload (3+ direct) 🔴
Rule: 3+ child devices in "Direct" mode under an RCD/transfer switch/changeover. Physically impossible — one N terminal cannot take 3+ wires.
Solution: create an N bar for this RCD (UI hint: "3+ — bar"). The children switch to bus routing automatically.
💡 N-bar life cycle: the N bar of an RCD/RCBO/transfer switch/changeover exists only while at least one child is in "Via bar" mode. If all children move to "Direct", the bar is deleted automatically. This prevents "orphan" bars accumulating as the panel is edited.
39. Direct N but the parent has no N 🟡
"From parent" mode is chosen, but the parent has no N conductor in its connection scheme. The system points to the highest ancestor without N.
Solution: change the ancestor's connection variant or the N connection mode.
40. Parent deleted (N-from-parent mode) 🟡
The device is set to N-from-parent, but the parent no longer exists.
Solution: assign a new parent or change the mode to "Via bar".
41. Passive N with no source 🟡
The device has no N pole but has a cable/loads that need N, and there is no N conductor in the parent chain.
Solution: change the ancestor's connection variant (e.g. 1P → 1P+N).
💡 SPD (shunt) exception: if the parent device is an SPD, this check does not fire. The SPD's children physically take N from the common N bar, not through the SPD's N pole — so overloading its N terminal is impossible by design.
42. Passive load on an N terminal 🔵
2+ child devices are connected to one device's N output without a separate bar. Adding a group N bar is recommended.
43. N bypasses the parent 🟡
The N conductor goes to the common bar, bypassing a parent that has an N pole. The phase is protected through the hierarchy, but N is not.
Solution: change the mode to "From parent" or add a separate N bar.
💡 Exceptions: the warning is inactive when the parent is an SPD (shunt: physically no direct path) or a pure distributor (a cross-module without its own N bar: N is not switched, the bypass avoids no protection). The warning is valid only for devices that break N on a pole (RCD, RCBO, transfer switch, changeover).
44. Reference to a non-existent N bar 🔴
The device is tied to an N bar that has been deleted.
Solution: detach the bar in the properties panel, or create a new one.
45. N bar tied to a PE bar 🔴
The N tie points to a PE bar instead of N. An incorrect connection.
Solution: detach and choose the correct N bar.
46. N bar missing 🔴
The board has no N (neutral) bar, but there are devices that need N.
Solution: add an N bar from the component palette.
47. PE bar missing 🔴
The board has no PE (earth) bar, but there are devices with PE.
Solution: add a PE bar from the component palette.
47a. N input and output on different bars 🔴
Rule: a device that "owns" an N bar must not simultaneously receive N from another bar — this means the device feeds one bar and takes N from another, which is a topology error.
Example: a cross-module assigned itself one N bar, but through the hierarchy N enters from another (e.g. laid down by an SPD ancestor).
Solution: leave one bar for the device, or remove the tie via "Detach" in the properties.
47b. Closed N loop 🔴
Rule: N input and output on the same bar → a closed loop. Physically N circulates within itself — usually the result of two devices in the hierarchy being assigned the same "group N bar".
Example: a 4P incoming MCB is tied to bus-1; a cross-module below is also tied to bus-1. The hierarchy resolves the cross-module input as bus-1 = output → a loop.
Solution: remove the tie on one of the owners via "Detach". UI guard: the "group N bar" dropdown does not show a bar whose selection would form a loop.
47c. Parallel neutrals of sources 🔴
Rule (IEC 60364-5-55 §551.4.3.2): a standalone source (generator/inverter) with an internal N bond whose neutral is common with the mains neutral. The neutral of such a source must be switched (a 4-pole transfer switch / an interlocked ATS), not connected in parallel with the mains one.
Problem: parallel neutrals create a circulating current — the RCD sees a current difference and does not operate correctly on a leakage.
Solution: add a transfer switch that switches N, with a mechanical interlock.
47d. N bar with no owner (orphan) 🟡
An N bar has consumers (devices that take neutral from it), but no device has marked it as its own via "group N bar". This is usually a leftover after "Detach": an RCD/transfer switch no longer feeds the bar, while children still take N from it.
Solution: assign the bar to another device as its "group N bar", switch the consumers to another bar or direct mode, or delete the bar from the palette.
47e. N bar detached despite N consumers 🟡
A device explicitly gave up its own N bar (opt-out), but its child devices still need the neutral that this bar was meant to distribute.
Solution: press "Attach N bar" in the device properties to cancel the opt-out and restore the N bar for the children.
Terminal overload (1 check)
48. 3+ connections on one terminal 🟡
A device terminal has 3 or more connections (inputs or outputs). The physical limit is a maximum of 2 wires per terminal.
Solution: add a cross-module or a distribution bar for branching.
💡 Exception: the cross-module is excluded from this check — branching to many outputs (5/7/11/12/15/16 outputs per pole) is its direct purpose.
Terminal bridges (4 checks)
A bridge (jumper) is a connection between two of a device's own terminals declared in its properties. These checks catch dangerous or meaningless bridges. All are universal physics / data integrity, independent of the chosen regulatory standard.
48a. Short circuit between terminals 🔴
Example: a bridge connects an L terminal to an N terminal (or L↔PE, N↔PE).
Problem: connecting terminals of different conductors is a short circuit. Applying voltage instantly damages equipment or causes electric shock.
Solution: remove the bridge or reassign the terminals.
48b. Bridge touches a control terminal 🔴
A bridge may connect only power terminals (L / N / PE). One of its terminals is a control terminal (coil, auxiliary contact, current transformer, channel), which is not a power conductor.
Solution: remove the bridge.
48c. Bridge points to a non-existent terminal 🟡
The bridge references a terminal that is not in the device configuration. It has no effect and will be removed automatically the next time the device is edited.
48d. Duplicate bridge 🟡
The same terminal bridge is declared several times. The duplicate has no effect.
Solution: remove the redundant bridge.
Source roles (12 checks)
These checks apply when the panel has incoming sources (a root breaker or a secondary transfer-switch/changeover parent) with a role assigned via the "Power source" section in the properties panel.
49. Source role not assigned 🟡
The incoming device has child devices, but the source type (grid / transformer / generator / inverter / UPS / solar / battery) is not chosen.
Solution: open the incoming device's properties panel → "Power source" section → choose a role.
Why it matters: the AI assistant receives information about sources in the query context ("tell me about the backup system"), and on the canvas roles are shown as coloured markers for quick navigation.
50. Transfer switch with two identical sources 🟡
A transfer switch or 1-0-1 switch has two inputs with the same source role (e.g. both "Grid").
Problem: redundancy makes no sense — on a fault of one source the other is the same.
Solution: choose different roles for the main and reserve inputs (e.g. "Grid" + "Generator", "Grid" + "Inverter", "Solar" + "Battery").
51. Inverter/generator without an upstream protective breaker 🔴
Rule: a device with a source role of inverter / generator / solar / battery / UPS is not itself a protective device (e.g. a changeover, contactor, isolator flagged with a sourceRole) and has no MCB/RCBO/fuse upstream.
Problem: on a short circuit on the inverter/generator side there is no overcurrent protection.
Solution: add an MCB/RCBO/fuse ahead of the flagged device, or change the device itself into an MCB with a sourceRole (an MCB protects the source's entry point itself).
51a. 2P (L+N) switch in a TN-C system 🔴
Rule: in a TN-C earthing system the neutral and protective conductor are combined (PEN). Switching the N pole in 2P (L+N) mode breaks the PEN during source transfer — dangerous (protective earthing is lost).
Solution: use 1P (L only) or 4P (L1+L2+L3+N) in a three-phase variant.
51b. Single-phase 2P (L+N) feeds a three-phase load 🔴
Rule: a single-phase breaker in 2P (L+N) mode is semantically equivalent to 1P+N — it cannot feed a three-phase load. If the child device has 2+ active phases, then on a short circuit the single-phase device will not switch all phases → a residual contact = a hazard.
Solution: switch the device to 4P (L1+L2+L3+N) mode, or change the load to single-phase.
51c. Transfer-switch reserve collapses a multi-phase load onto one phase 🔴
Rule: a terminal bridge is declared on the transfer switch's reserve input — all poles are shorted onto one phase. A multi-phase load on the reserve:
- three-phase (motor, EV charger) — will not get a rotating magnetic field and will burn out within seconds;
- two-phase — loses the potential difference between phases; line loads (220/380 V between phases) will not work, damage is possible.
Solution: move this load to a separate input without redundancy, or change the load type to single-phase.
51d. Incorrect terminal bridge 🔴
A declared device terminal bridge is invalid:
- the bridge points to a non-existent terminal — the terminal number is absent from the device configuration;
- the bridge is between identical conductors — both terminals map to the very same conductor, so the bridge has no effect.
Solution: check the terminal numbers or remove the redundant bridge.
52. N unavailable through a 2P L1+L2 🟡
Rule: the child device has an N pole, but there is a 2P device in the ancestor chain in L1+L2 mode (no N) — a split-phase inverter — and the panel has no common N bar to back up the walk-through.
Solution: add an N bar (the system finds it automatically via walk-through), or change the 2P ancestor's mode to L+N.
52a. Transfer-switch reserve input has a different pole count 🟡
Example: a three-phase transfer switch (4P), with a single-phase (2P) reserve input.
Problem: a reserve of a different pole count will feed only part of the phases — a three-phase load on the reserve will run on one phase only.
Solution: use a reserve device of the same pole count as the transfer switch, or set the transfer switch to a lower pole count.
52b. Phase-terminal bridge in a TT/IT system 🔵/🟡
In TT and IT earthing systems, bonding (bridging) phase terminals has specific requirements. The check reminds you to verify the design against the standards (in particular IEC 60364-4-41). The level (🔵 or 🟡) depends on the active standard.
52c. Bridge declared without a reason 🔵
A terminal bridge is declared on the device, but the source does not require bonding — all ancestors have the same pole count and are not two-phase standalone sources. The bridge is probably redundant.
52d. Source type not marked 🔵
The input node has no assigned source type (grid / generator / inverter / UPS / solar). Mark the source for correct scheme analysis and AI-assistant hints.
💡 Difference from check 49: check 49 (🟡) fires for an incoming device that already has child devices; this one (🔵) is a softer hint for any input node.
Core neutral invariants — IEC 60364 (5 checks)
These checks activate depending on the chosen standard. For IEC 60364 all five are active.
53. PEN switched on a device 🔴
Rule (IEC 60364-4-41, IEC 60364-5-54 §543): the PEN conductor must not be broken in an MCB/RCD/isolator before the point where it splits into N and PE.
Solution: use 1P instead of 2P, or split PEN into N + PE higher in the hierarchy.
PEN split point (TN-C-S). In most apartments PEN is split into N and PE already at the building's main distribution board, so separate N and PE already arrive at the panel — switching N there is permitted. So the system does not show a false warning, set the split point for TN-C-S in the panel settings (⚙): "Upstream" clears this warning, while "In this board" (a combined PEN at the incomer, typical for a private house on an overhead line) keeps the check active. The safer "In this board" option is on by default, so a real hazard is never silently hidden.
54. Incomer without 4P in a TT/IT system 🔴
Rule (IEC 60364-4-46): in TT and IT systems the incoming device must be four-pole — switching all phases together with N.
Solution: replace the incoming device with a 4P one.
55. N not isolated between zones of different RCDs 🔴
Rule (IEC 61008-1): the neutral conductor between groups of different RCDs must be isolated — a shared N bar between two RCDs causes nuisance tripping.
Solution: create a separate N bar for each RCD group.
56. PEN bar after the split point 🔴
Rule (IEC 60364-4-41, IEC 60364-5-54 §543): after PEN is split into N + PE, returning to PEN is prohibited.
Solution: replace the PEN bar with separate N and PE bars.
57. Transfer switch without an interlock 🔴
Rule (IEC 60947-6-1 §7.2.1): a transfer switch (ATS, changeover) must have a mechanical or electrical interlock that prevents both sources being closed at once.
Solution: enable the "Interlock" parameter in the transfer-switch/changeover properties.
Comb safety (2 checks)
58. Comb bypasses the RCD via N 🔴
A feeder comb is fed from a point upstream of the RCD/transfer switch, so the N of the comb breakers does not pass through that RCD. The phase L passes through the RCD (via the parent hierarchy) while N does not. Differential protection is broken: the device will not trip on a real leakage.
Solution: re-tie the comb feeder to a device downstream of the RCD, or move the MCB upstream of the RCD.
59. Direct N connections in a 1P+N/3P+N comb 🟡
Members of an N-carrying comb under an RCD count as 1 physical wire on the RCD's N terminal (via the comb), not N separate wires. This is taken into account in the direct-N threshold count.
Phase bars L1/L2/L3 (4 checks)
Soft validation of phase distribution bars (L1/L2/L3) — all warnings are "Problem" 🟡 level. It does not block the design, but shows issues in the Validation panel with links to the standards.
60. Phase not connected 🟡
Rule: the phase source is explicitly set to "not assigned", and automatic source detection (from parent / bar) yielded no result.
Solution: in the device properties, choose a phase source (a parent distributor or a phase bar) in the "SOURCE" dropdown.
61. Reference to a deleted phase bar 🟡
Rule: the device references an L bar that has been deleted from the board.
Autofix: "Fix" writes "not assigned" — the user explicitly chooses a new source.
62. Phase bar of a different type 🟡
Rule: the device is tied to a bar of a type that does not match the phase (e.g. an L1 input pointing to an N bar).
Solution: choose a bar of the matching type, or remove the tie.
63. Phase-bar overload 🟡
Rule (IEC 61439-1 §5.4): the sum of device ratings on a phase bar must not exceed bar rating × DF (default 63 A, RDF per the active standard).
Solution: split the load across two phase bars, or replace the bar with a higher rating.
Binding N invariants to the standard
The N invariants (items 53–57) are controlled by the "Standard" parameter in the panel settings:
| Standard | Active N invariants |
|---|---|
| IEC 60364 (default) | all 5 |
| HD 60364 (CENELEC) | all 5 |
| NEC / BS 7671 | technically critical only |
If no standard is chosen, the N-invariant checks are not active.
Multi-profile validation
Since April 2026 validation supports several standards at once on one panel. This lets you design against multiple standards in parallel and see only the warnings that are truly critical for the chosen codes.
Standard selector
In "Panel settings" → "Validation standards" section there is a checkbox list:
- ✅ IEC 60364 (default) — international
- ☐ Regional codes — NEC, BS 7671 and others, selectable per market
You can choose one or several. The active set is shown as a chip indicator in the validation-panel header — for example "IEC + NEC". Clicking the chip scrolls straight to the selector in the settings.
How it works
- Filter by standard: each Issue carries a tag of the standard it is bound to. Before the Validation panel renders, Issues whose standard is not in the active set are filtered out. The detectors themselves stay agnostic to the set — there is one filter, at the formatting boundary.
- Panel-level state: the choice is saved with the panel.
- Defaults in a new project: inherited from UI Prefs — the user sets a global default in the profile settings, and a new panel picks it up.
Selectivity strictness
When several standards are active, the system chooses the strictest DF (diversity factor) among them. This "pickStrictest" algorithm guarantees that one scenario does not hide errors that would fire under one of the standards on its own.
Checks by the chosen standard
3 checks are bound to specific standards. They activate only when the corresponding standard is chosen.
64. RCD class for a DC load 🟡
Rule (IEC 61008-1): a type-AC RCD does not detect DC leakage currents. Circuits with inverters/EV chargers/PV need a type B or F RCD.
Active for: IEC
Solution: replace the RCD with type B (for PV, EV) or type F (for variable-speed drives).
65. RCD in a TT/IT system without an N pole (4P required) 🔴
Rule (IEC 60364): in TT and IT earthing systems the differential protection (RCD/RCBO) must switch the neutral together with the phases. Without an N pole the RCD cannot reliably disconnect the circuit on a leakage.
Active for: IEC
Solution: replace the RCD with a 4-pole model (with a neutral).
66. Legacy wire colours 🔵
Rule (IEC 60445): the modern palette is required: brown L1, black L2, grey L3, blue N, green-yellow PE. A legacy colour code (e.g. white/black/red for phases) is an info-warning.
Active for: standards mandating the modern palette
Solution: change the colour standard in Wire Mode → "Colour standard" section → IEC.
Reinforcing existing checks
Improvements to three checks with multi-standard support:
- 51. Inverter without an upstream protective breaker — now counts an AFDD as an OCPD; standard-dependent refs (IEC/NEC).
- 53. PEN switched — an extended set of offending devices, a more precise message about the PEN cut point.
- 69. Portable generator without 4P — for portable generators (a separate flag) the incoming device must be 4P (all poles together with N).
Short-circuit currents — calculation and checks
ElectroBoard calculates short-circuit (SC) currents and checks two key electrical-safety requirements: automatic disconnection time and breaking capacity of the protective devices. Results are available in two places — as separate checks in the validation panel and as a detailed ⚡ "Short-circuit currents" calculator (a toolbar button in the editor).
Source parameters (network impedance / SC current at the incomer) are set in Panel settings → "SC source" — see the Network settings section for more. If the source is not set, the calculation uses typical values (marked with an asterisk *).
67. Automatic disconnection time not ensured 🔴
Rule (IEC 60364-4-41 §411): on a fault to an enclosure, the protective device must disconnect the circuit within the required time. For TN systems the condition Zs ≤ U0 / Ia is checked — the earth-fault loop impedance is no greater than the ratio of voltage to the device's tripping current. For TT via an RCD — RA · IΔn ≤ 50 V (the touch voltage does not exceed the safe limit).
Solution: reduce the loop impedance (larger cross-section or shorter cable), fit an RCD, or choose a device with a lower instantaneous tripping current.
68. Insufficient breaking capacity 🔴
Rule (IEC 60947-2, IEC 60898-1): the device's rated breaking capacity (Icu / Icn) must be no less than the prospective short-circuit current at the point of installation — Icu ≥ Ik(max). Otherwise the device may be destroyed during a short circuit without breaking the circuit.
Solution: fit a device with a higher breaking capacity (e.g. 6 kA → 10 kA), or apply back-up protection upstream.
The "Short-circuit currents" calculator
The ⚡ toolbar button opens a panel with a table for each device: Zs (Ω), Ik (A), Ia (A), a disconnection verdict, Ik max (kA), Icu (kA) and a withstand verdict. The source of the values is marked as measured / set / transformer / typical. A dash — means an incomplete SC path (missing cable data), an asterisk * means a default value.
v1 limitations: the calculation is R-dominant (no reactive component X, fixed conductor temperatures); gG fuses and the IT earthing system are not yet supported; the loop impedance is counted up to the panel boundary (the final conductor to the load is not modelled).
Tip: you do not have to fix every recommendation (🔵). But all safety errors (🔴) should be resolved before using the design for a real installation.