Submain and consumer mains voltage drop
A guide for allocating voltage drop across Australian consumer mains, submains and downstream circuits without turning the allocation into a final compliance decision.
When allocation matters
Submain and consumer mains checks are different from a single final-circuit voltage-drop calculation. The reviewer is usually asking how much of the project allowance is used upstream, and how much remains for downstream circuits or equipment runs.
The useful record separates segments. It shows the demand current, supply voltage, one-way route length, cable data and target for the upstream run, then keeps the downstream allowance visible. That prevents a low downstream result from hiding a long upstream route, or an upstream result from consuming too much of the total allowance.
Allocation sequence
- Identify the point of supply, main switchboard, distribution board and downstream loads involved in the record.
- Confirm the voltage and phase basis for the upstream run.
- Use demand current or another reviewed current basis that suits the submain or consumer mains record.
- Enter the installed one-way route length for the upstream segment.
- Enter cable data that belongs to the upstream candidate.
- Enter the total project target and downstream allowance used for this review stage.
- Review upstream percentage, downstream allowance and total allocation together.
Segment record table
| Field | What to record | Why it matters |
|---|---|---|
| Upstream segment | Point of supply, board, route and candidate cable | Separates submain pressure from final circuits |
| Current basis | Demand current, measured current or reviewed design value | Current controls voltage-drop arithmetic |
| Voltage basis | Single-phase or three-phase value used for percent | Percent is not repeatable without voltage |
| Cable data source | mV/A/m or R/X values for the segment | Data must match the upstream cable context |
| Downstream allowance | Percentage or voltage reserved for downstream runs | Shows whether the upstream route leaves room |
| Total allocation | Upstream result plus downstream allowance | Keeps the whole installation context visible |
Reading allocation pressure
If the upstream result is low and the total allocation has margin, the record can move forward for project review with the current, route and cable data source attached. If the upstream run consumes most of the allowance, the project team may need to review route length, board location, demand current, candidate cable data or downstream allowance before changing a conductor.
If the total allocation is above the entered target, do not decide the answer from one number. Name the pressure point. The issue might be a long consumer mains route, a submain candidate, downstream circuit allowance, voltage basis or demand current source.
Boundaries
- Do not use allocation arithmetic as a final installation decision.
- Do not mix current basis from one board with cable data from another segment.
- Do not hide downstream allowance when the record is meant to describe a total installation path.
- Do not copy controlled cable table values into the public worksheet.
- Do not ignore DNSP, local authority, manufacturer or project requirements.
Submain and consumer mains voltage drop in Australian work
Explain how to record upstream and downstream voltage-drop allocation for Australian submain and consumer mains calculations. The useful record is not just the final number or definition; it is the combination of the entered value, the supply arrangement, the equipment or circuit reference and the decision that still needs project review.
submain and consumer mains voltage drop workflow for Australian cable allocation records Keep the wording in Australian English, use metric units, and treat 230/400 V a.c. at 50 Hz as the ordinary low-voltage context unless the project information states a different value.
Checks that belong beside this page
- Regional scopeAustralia; Australian English; DNSP, local authority, project and equipment requirements can override worksheet assumptions.
- Standards contextAS/NZS 3000 and AS/NZS 3008 context noted for project review; current standards, DNSP requirements, installation conditions and project documents remain controlling sources.
- Review timingReview cadence: Annual or when submain voltage-drop calculator fields, voltage-drop charts, Australian standards context, DNSP practice or project documentation practice changes.. Update trigger: Calculator field or chart change, standards update, DNSP requirement change, allocation practice change or project feedback.
Practical use sequence
For Submain and consumer mains voltage drop, begin with the circuit, board, load, cable route, equipment item or measurement record named by this topic. Record the value basis, such as current, voltage, kW, kVA, route length, test value, product rating, tariff value or worksheet field, then note the review boundary so another person can see what this page explained and what still needs a project decision.
The strongest Submain and consumer mains voltage drop record is specific enough to be reviewed later. It names the Australian context, keeps the entered assumptions visible, separates calculation support from compliance decisions and shows where a calculator, table, chart or term definition should be opened next.
Record detail to capture
Keep the Submain and consumer mains voltage drop note attached to Australia; Australian English; DNSP, local authority, project and equipment requirements can override worksheet assumptions.. When the page is used during design, estimating, testing, review or study work, write the entered assumption, the source that supplied it, the circuit or equipment label and the person or role that must review the following action.
For Submain and consumer mains voltage drop, the review cadence is Annual or when submain voltage-drop calculator fields, voltage-drop charts, Australian standards context, DNSP practice or project documentation practice changes. and the update trigger is Calculator field or chart change, standards update, DNSP requirement change, allocation practice change or project feedback.. If the topic connects to Submain voltage drop, open that page after the current definition, input basis or boundary has been recorded, so the next calculation inherits the right Australian context.
A complete Submain and consumer mains voltage drop record leaves four facts visible: why the page was opened, which Australian supply or equipment context applies, which value remains user-entered and what later change would alter the result. That makes the page useful as a working note instead of a loose reference copied away from the project evidence.
- InputsWrite down the entered values and their units before comparing results across calculators or reference pages.
- LocationKeep the value tied to the board, circuit, cable run, equipment terminal, supply point or worksheet row it describes.
- Authority checkCompare the record with current Australian requirements, DNSP or local authority conditions and product information.
- Review trailRetain the date, edition context and reason for the calculation so later changes can be traced.
Connected AUWiring pages
Use the related pages for Submain and consumer mains voltage drop when the topic needs a calculator input, lookup table, formula chart or supporting term before the project record is complete. Open Submain voltage drop first when that page owns the next value or definition.
- Submain voltage dropReview upstream and downstream voltage-drop allocation.
- Voltage dropCalculate voltage drop for one cable run.
- Cable sizeReview the candidate cable after allocation pressure is known.
- Australian supply voltageConfirm voltage basis before comparing percentages.