KEY POINTS
- Review the complete supply path, not just the nearest spare breaker.
- Use operating data and the new equipment schedule together.
- Agree isolation, temporary supply and commissioning before the connection work.
A spare space in a distribution board does not establish spare electrical capacity. Before ordering a new production line, compare its operating requirements with the existing supply, transformer, switchboards and feeders. The result should identify what can be retained and what needs investigation or modification.
Build an equipment schedule
Ask the machine supplier for rated voltage, phase arrangement, input power, starting characteristics and connection requirements. Include supporting loads such as extraction, compressed air, cooling and material handling. Identify which machines will run together and which are standby units.
The Electrical Installation Guide distinguishes installed power from the maximum demand expected in use. Record the assumptions behind the demand calculation. A list of nameplate ratings and a measured demand profile answer different questions; both can be useful.
Check the complete power path
| Part of the system | Information to review |
|---|---|
| Incoming supply and transformer | Available supply capacity, equipment ratings and representative peak demand |
| Main and intermediate boards | Busbar and breaker ratings, equipment condition, spare ways and existing loading |
| Feeders and final circuits | Cable size, installation conditions, route length and proposed connection |
| Protection | Fault levels, device settings and coordination with upstream equipment |
Cable capacity depends on its installation and operating conditions. The conductor-sizing guide explains why cable selection and protective-device selection need to be considered together. Have the responsible designer assess the revised arrangement; increasing a breaker rating alone does not establish that the circuit is suitable.
Measure a representative operating period
Record the equipment running during the survey, production shifts and any unusual shutdowns. A quiet week may not capture the demand of a busy production period. Where a seven-day load survey is proposed, agree whether that period represents the operating cycle and whether seasonal or future loads need separate assessment.
Turn the findings into a decision
The review may support new circuits within the existing capacity, a feeder or switchboard modification, or an application for additional supply. Ask for the assumptions, required work and unresolved items in writing. Confirm utility processing, equipment procurement and inspection dates for the specific site; a general approval timeline is not a reliable project commitment.
Plan the connection and return to service
Agree the affected circuits, approved isolation arrangements, shutdown window and testing responsibilities. If temporary power is needed, identify the loads it must support and how the changeover will be managed. Spare ways do not mean that work can safely proceed on energised equipment.
Keep the equipment schedule, current single-line diagram and planned commissioning date together when discussing industrial electrical work or a switchboard upgrade.
Questions before committing to the new line
Can existing drawings be used?
Yes, as a starting point. Identify modifications made since the last revision and arrange site verification where the records do not match the installation.
Does a new line always require a larger transformer?
No. The answer depends on the assessed demand, the equipment ratings and the limits elsewhere in the distribution system.
What should be settled before installation is booked?
Confirm the design, equipment availability, approvals, access arrangements, isolation plan and acceptance tests with the responsible teams.
ETES services for this work
References & further reading
Primary publications used in this guide. Confirm the requirements and editions applicable to your project.
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