Switchboard form checker
Check separation, access and clearances for a switchboard.
Reads AS/NZS 3000:2018. Tables checked 26 Sept 2026.
Try a job 5
Each job fills in example values. Replace them with your values.
- Check the access to a main switchboardThe access clearances and separation rules for an 800 A main switchboard.
- Check access to a house switchboardThe clear space a domestic switchboard needs.
- Check a long board for two exitsWhether a 3.6 m board needs two exits.
- Check a board in a cupboardThe access for a 400 A board that is not in a room.
- Check the impulse clearancesThe clearance for a 6 kV impulse withstand.
Inputs
Worked example with the default inputs. The live calculator replaces it when the page loads.
- Board rating per phase
- 400 A
- Board length
- 2 m
- Domestic installation
- No
- Rated impulse withstand voltage Uimp
- 6 kV, origin of installation
- Board sits in a room you must enter to reach it
- Yes
- Clear space in front of the board
- 0 m
Cl 2.5.5 applies to this board
No
- Incoming supply conductors, Cl 2.5.5.1
- Not required
- Internal separation, the Cl 2.5.5.2 route
- Not required
- Forms that suit that route, App K example
- 3b or 4a or 4b
- Clearance from every face that needs access
- 1m
- Unimpeded space around the board
- 0.6m
- Emergency exit paths
- Enough to get clear, no count set
- Clearance at Uimp 6 kV, App K example
- 5.5mm
This result is a design aid. Verify it against the current standard.
Calculation steps
- Cl 2.5.5 applies to this boardResultNo
AS/NZS 3000:2018 Cl 2.5.5
- Insulate or separate the incoming supply conductors, Cl 2.5.5.1Not required
AS/NZS 3000:2018 Cl 2.5.5
- Internal separation, the Cl 2.5.5.2 routeNot required
AS/NZS 3000:2018 Cl 2.5.5
- Accepted forms of separation, use any one, App K example3b or 4a or 4b
AS/NZS 3000:2018 App K Para K6.2
- Accepted form suffixes, App K examplei, h, ih
AS/NZS 3000:2018 App K Para K6.2
- What each form separates, App K exampleTable K2
AS/NZS 3000:2018 App K Table K2
- Clearance from every face that needs access1m
AS/NZS 3000:2018 Cl 2.10.2.2
- Unimpeded space around the board0.6m
AS/NZS 3000:2018 Cl 2.10.2.2
- Emergency exit pathsEnough to get clear, no count set
AS/NZS 3000:2018 Cl 2.10.2.2
- Minimum clear doorway widthNo figure for this board
AS/NZS 3000:2018 Cl 2.10.2.2
- Minimum clear doorway heightNo figure for this board
AS/NZS 3000:2018 Cl 2.10.2.2
- Overvoltage category at Uimp 6 kV, App K exampleIV
AS/NZS 3000:2018 App K Para K6.4
- Clearance at Uimp 6 kV, App K example5.5mm
AS/NZS 3000:2018 App K Para K6.4
- Alternative test voltage at Uimp 6 kV, kV r.m.s., App K example5.1
AS/NZS 3000:2018 App K Para K6.4
- Creepage at Ui 440 V, pollution degree 3, material group III, App K example6.3mm
AS/NZS 3000:2018 App K Para K6.5
About this calculator
How this is calculated
The tool checks whether Clause 2.5.5 of AS/NZS 3000:2018 asks for separation inside a switchboard. It also reads the access and exit figures of Clause 2.10.2.2 and the Appendix K examples.
- Scope. It compares the board rating with the Cl 2.5.5 threshold. At or above it, Cl 2.5.5 applies.
- Incoming conductors. Where Cl 2.5.5 applies, the incoming supply conductors are insulated or separated (Cl 2.5.5.1).
- Internal separation. The tool says if the Cl 2.5.5.2 route needs internal separation. It lists the forms that suit that route, from Paragraph K6.2 and Table K2.
- Access. From Cl 2.10.2.2 it gives the clearance from each face that needs access. It also gives the unimpeded space around the board. A domestic board has its own front clearance.
- Exits. A switchroom can pass the rating or length trigger. Then the tool gives the exit count and doorway size.
- Clearance example. It reads the Appendix K clearance for the impulse voltage you pick (Paragraphs K6.4 and K6.5).
| Step | Table or clause | What it decides |
|---|---|---|
| Scope and separation | AS/NZS 3000 Cl 2.5.5 | Whether the board needs separation |
| Forms | App K Para K6.2 and Table K2 | The forms that suit |
| Access and exits | Cl 2.10.2.2 | Clearances, exits and doorways |
| Clearances | App K Para K6.4 and K6.5 | The worked examples |
Worked example
A 1000 A commercial board in a switchroom. Cl 2.5.5 applies and internal separation is required. Forms 3b, 4a or 4b suit. The tool gives 2 exit paths, set well apart. The Appendix K clearance at 6 kV is 5.5 mm.
Limits
- Appendix K is informative. Its clearance and creepage figures are examples. Verify them to AS/NZS 61439.1.
- The tool holds the Cl 2.5.5.2 route only. Cl 2.5.5.1 offers other routes.
- Under the trigger, the tool gives no exit count and no doorway size.
- Measure each clearance with the doors and gear in the positions the clause names.
- Door swing and hold-open rules appear as warnings only.
See also: Industrial switchboards, Switchboard fault rating and busbar withstand and the fault rating calculator.
Questions
Each answer describes what this tool calculates. The result is a design aid. Verify against the current standard.
When does a switchboard need internal separation?
AS/NZS 3000:2018 Clause 2.5.5 covers a switchboard at or over 800 A per phase. Enter the rating and AmpSize tells you whether the board meets that trigger. Clause 2.5.5.1 also asks you to insulate or separate the incoming supply conductors, on every route. Clause 2.5.5.2 then sets out the internal separation the board needs.
Which forms of separation are accepted?
Appendix K Paragraph K6.2 names Form 3b, Form 4a and Form 4b, and the same forms with the i, h and ih suffixes. Table K2 shows what each form separates. Appendix K is informative, so treat these as an example route to Clause 2.5.5.2 rather than a figure the standard sets.
How much space is needed around a switchboard?
Clause 2.10.2.2.1 sets 1.0 m from every face that needs access. A domestic installation may use 0.6 m at the face of the board. AmpSize applies that relief to the front face. Other faces keep 1.0 m. The clause sets a 0.6 m unimpeded space around the board. Read the clause for the door and switchgear positions it assumes.
When are two emergency exit paths needed?
Clause 2.10.2.2.2 sets two exit paths, well apart, where you must enter a room to reach the board. That applies from 800 A per phase, or over 3 m long. One path is enough if 3 m stays clear in front with doors open and gear drawn out. Other boards need enough exit paths, with no set count.
Which edition does the tool read, and what does it leave out?
The tool reads AS/NZS 3000:2018 incorporating Amendments 1, 2 and 3. Amendment 2 rewrote Clause 2.10.2.2. Amendment 3 only removed the AS/NZS 3439 references from Clause 2.5.5. The tool holds Clauses 2.5.5 and 2.10.2.2 and Appendix K Paragraphs K6.2, K6.4 and K6.5. Rated diversity factor and temperature rise checks sit in the AS/NZS 61439 series, so the tool holds neither.
Clauses and tables this tool reads
- AS/NZS 3000:2018 App K Para K6.2Form of internal separation
- AS/NZS 3000:2018 App K Para K6.4Overvoltage category
- AS/NZS 3000:2018 App K Para K6.5Creepage
- AS/NZS 3000:2018 App K Table K2Internal separation, the least each form needs
- AS/NZS 3000:2018 Cl 2.10.2.2Switchboard access and emergency exits
- AS/NZS 3000:2018 Cl 2.5.5Protection against arcing faults inside a switchboard
- AS/NZS 3000:2018 Cl 2.5.5, Cl 2.10.2.2 and App K Table K2Switchboard internal separation, access and clearances
Every clause and table, with how each was verified
Tables last checked on 26 Sept 2026.
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