Temporary Generator Power for Manufacturing Facilities: A Practical Planning Guide

A manufacturing site can lose power for many reasons: a network fault, transformer failure, switchboard work, a failed standby generator or a planned maintenance shutdown. The effect is rarely limited to the lights going out. A sudden stop can interrupt production, leave material in process, trigger lengthy resets and affect cooling, extraction, compressed air, controls, IT or product quality.

Temporary generator hire can bridge the gap while permanent power is unavailable or critical equipment is repaired. However, a factory is not simply a larger office. Motors, drives, heaters, compressors, pumps, refrigeration, process controls and sensitive electronics create different starting and running demands. The temporary arrangement must be planned around the real site, not selected from a single total-load figure.

This guide explains the information a temporary-power provider will need, the decisions manufacturing teams should make and the checks that help turn a hired generator into a dependable operating plan.

Quick answer: what does temporary power planning involve?

Temporary power planning for a manufacturing facility means identifying the loads that must remain available, confirming their electrical characteristics, designing a safe connection and changeover arrangement, checking access and cable routes, planning fuel and resilience, then testing the complete setup before relying on it. For a large or complex site, a survey and load assessment are usually the fastest route to a defensible answer.

When might a manufacturing facility need temporary power?

Temporary generators can support both emergencies and planned work. Common situations include:

1. an unexpected mains, transformer or switchgear failure
2. a standby generator that has failed or is unavailable for repair
3. planned substation, switchboard or electrical-distribution maintenance
4. replacement of an ageing generator or automatic transfer switch
5. a factory extension or additional production line awaiting a permanent supply
6. seasonal or project-based increases in demand
7. contingency cover during higher-risk engineering work
8. temporary resilience while a permanent critical-power project is designed and commissioned

An emergency response is sometimes unavoidable, but advance planning creates more options. It gives the team time to survey the load, agree what can be shed, prepare a connection point, plan the shutdown window and test the temporary arrangement before production depends on it.

Why manufacturing temporary power needs detailed planning

Manufacturing power requirements vary widely. One site may need to preserve cold storage and a small control network; another may need to restart several large motors, ovens or compressed-air systems in a controlled sequence. P&I's manufacturing power solutions therefore need to be considered in the context of the process, the site infrastructure and the consequences of an interruption.

A generator can appear large enough when only the normal running load is added up, yet still struggle when several motors start together. Sensitive controls may also need stable power while a generator is starting and a changeover device is transferring the load. Cable length, voltage drop, protection settings, earthing, fuel logistics and the route back to mains all affect the final solution.

1. Define the critical, essential and deferrable loads

The first question is not 'How large is the factory?' It is 'What must remain operational, and for how long?' Powering the entire site may be possible, but it is often faster and more efficient to prioritise the loads that protect people, the process, product and recovery.

A useful starting point is to separate critical, essential and non-essential loads. The labels must be defined for the specific facility, but the groups may include:

• Safety and environmental systems: emergency lighting, alarms, ventilation, extraction, containment or other site-specific protective systems.
• Process-critical equipment: control systems, pumps, cooling, refrigeration, compressed air, lubrication, trace heating and equipment needed to hold a process in a safe state.
• Business-critical services: servers, communications, access control, security, dispatch and selected offices.
• Deferrable loads: non-urgent charging, comfort loads, secondary production lines or equipment that can remain isolated during the temporary arrangement.

Ask which loads cannot tolerate even a short interruption, which can be supported by a UPS while the generator starts, which can restart after the supply stabilises and which can be shed. This classification controls generator size, connection design, fuel use and the production restart sequence.

2. Confirm the load profile, not only the total kW

A list of equipment nameplates is useful, but the generator selection should reflect how the site actually operates. The temporary-power provider may need:

1. supply voltage, frequency and number of phases
2. running demand in kW and apparent power in kVA
3. power factor and the type of connected load
4. the largest motors, compressors, pumps, transformers or other high-starting-current equipment
5. the sequence and size of load steps during restart
6. sensitive electronic or non-linear loads that may affect power quality
7. expected operating hours, load variation and future changes during the hire
8. any existing UPS, generator, ATS or load-shedding controls

Where current readings, trend data or a load survey are available, they can provide a more realistic picture than connected-load totals alone. P&I's generator sizing and selection guide provides useful background, but a complex manufacturing load should be reviewed by a competent specialist before equipment is selected.

3. Plan the connection, changeover and isolation

A hired generator still needs a safe route into the electrical system. A purpose-designed temporary generator connection point can shorten deployment time. Without one, additional temporary works may be required before power can be restored.

The connection plan should consider the switchgear, protection, earthing and neutral arrangement, phase rotation, cable sizes, isolation points and prevention of back-feeding. It should also define whether the site will use a manual changeover, an ATS or another controlled transfer arrangement, and how it will return to the normal supply.

The Health and Safety Executive states that work on electrical equipment, machinery or installations should be planned and carried out by people who are competent for the task. Temporary generator connections should therefore be designed, installed and tested by competent persons. A controlled shutdown may be necessary to isolate, connect and prove the arrangement safely.

4. Create a controlled production restart sequence

A generator may support the normal running load but trip when several large loads start at once. Manufacturing teams should agree a restart sequence before the changeover takes place. A typical sequence may be to:

• stabilise the temporary supply and confirm acceptable voltage and frequency
• energise safety systems, controls, communications and essential auxiliaries
• start the largest motors or process loads one at a time in the agreed order
• confirm pressures, temperatures, cooling and extraction before restarting production
• restore secondary loads only when adequate capacity remains
• keep agreed headroom for normal load variation and unexpected demand

The sequence should be documented and assigned to named people. It is also worth recording the safe fallback position if a load does not start correctly or the generator alarms during the process.

5. Check access, positioning and cable routes

Generator availability is only part of the problem. The equipment must reach the site, be positioned appropriately and connect without creating new hazards or blocking operations. Review:

• vehicle and HIAB access, gate widths, height restrictions and delivery times
• ground condition, level and available space for the generator and fuel equipment
• safe exhaust discharge, ventilation and separation from occupied or sensitive areas
• noise constraints and neighbouring premises
• distance to the connection point and the effect on cable size and voltage drop
• vehicle, forklift and pedestrian routes that cables must cross
• cable ramps, barriers, weather protection and security
• access for inspection, maintenance and refuelling throughout the hire

Photographs, drawings and a measured cable route help a provider plan the delivery. For larger or awkward sites, a survey can prevent a generator arriving only to find that it cannot be positioned or connected as expected.

6. Plan fuel autonomy and refuelling

The required runtime should be based on the expected load, the generator's consumption at that load and the fuel capacity available to the arrangement. A multi-day hire also needs a refuelling plan that works outside normal hours.

• How many hours must the facility operate between deliveries?
• Can fuel vehicles reach the generator while the site is running?
• Who monitors fuel level and who receives low-level alarms?
• What happens if the outage lasts longer than expected?
• Are spill controls, secondary containment and site environmental procedures in place?
• Is theft or tampering a risk at the proposed location?

Oil-storage obligations depend on the location and arrangement. In England and Wales, GOV.UK guidance on business oil storage says the rules apply to standby generators with a connected oil supply tank of 201 litres or more. Separate guidance applies in Scotland and Northern Ireland, so the requirements for the site should be checked as part of the plan. P&I can also support ongoing operation through its generator refuelling service.

7. Decide how much resilience the temporary system needs

A single generator may be appropriate for a short planned shutdown where a controlled stop remains available. It may be insufficient where one generator failure would create an unacceptable safety, environmental or production consequence.

Higher-criticality arrangements may use N+1 capacity, synchronised sets, a ready standby generator or a UPS to bridge no-break loads. N+1 means the system can still support the required load after one necessary component is unavailable. The right arrangement depends on the consequence of failure, not simply the size of the factory.

The contingency plan should also cover cable, switchgear, connection and fuel risks. Adding a second generator does not remove every single point of failure if both sets depend on the same unprotected connection or fuel route.

8. Commission and test the complete arrangement

Delivery is not the end of the job. Before production relies on temporary power, the installation and operating sequence should be inspected, tested and recorded. The exact test plan will be site-specific, but it may include:

• visual and electrical inspection of the installation
• confirmation of protection, earthing, neutral arrangement and phase rotation
• functional testing of the changeover and return-to-mains process
• staged application of representative loads
• monitoring voltage, frequency and generator response during load steps
• checking alarms, emergency stops, telemetry and escalation routes
• confirming the agreed production restart and shutdown sequence
• recording responsibilities, contacts, fuel checks and inspection intervals

A load bank test can help prove generator performance under controlled electrical load. It does not automatically replace functional testing of the full site arrangement, including changeover, controls and the real restart sequence.

Planned hire and emergency hire require different information

For a planned shutdown

Allow time for a site survey, load assessment, drawings, cable-route planning, delivery access, RAMS, inductions, fuel arrangements and a witnessed test. Agree the isolation and return-to-mains windows with production, facilities, electrical and health-and-safety teams. Where practical, prepare and label a temporary connection point before the shutdown begins.

For an emergency

Make the site safe, follow the business continuity plan and record what happened. Capture generator or switchgear alarms, identify the minimum load that must be restored, share drawings or photographs and confirm site access. Do not bypass protection or improvise a connection. The immediate temporary solution should be treated as a managed bridge while the underlying fault is investigated.

Temporary power call checklist for manufacturing sites

Providing the following information can help a temporary-power specialist assess the requirement more quickly:

• site address, operating hours and the best on-site contact
• reason for the hire and when power is required
• expected hire duration and hours of operation per day
• load schedule, recent readings or details of the equipment that must run
• voltage, phase, frequency and largest starting loads
• existing generator, UPS, ATS and switchgear details
• connection-point photographs, drawings and approximate cable distance
• delivery restrictions, lifting needs and proposed generator location
• critical-load priority and agreed production restart sequence
• fuel autonomy, refuelling access and environmental controls
• required redundancy, standby arrangements and on-site monitoring
• shutdown window, site induction and permit or RAMS requirements

How P&I Group supports temporary manufacturing power

P&I Group provides temporary and emergency generator hire for commercial and industrial sites. The hire service can include generators, cables, distribution boxes, ATS panels, fuel tanks and load banks, supported by delivery, positioning, fuel management and on-site monitoring options. P&I also supports manufacturers with generator and UPS design, installation, maintenance and repair, which is useful when a temporary arrangement is bridging a wider system fault or replacement project.

The aim is not simply to place a generator outside the building. It is to create a temporary power arrangement that matches the load, works with the site and can be operated, tested and recovered in a controlled way.

Frequently asked questions

Plan temporary power before production is at risk

Temporary generator power is most reliable when it is treated as an engineering and operational plan, not an equipment-only hire. Define the critical loads, confirm the real load profile, prepare the connection, plan fuel and access, decide the resilience level and test the full arrangement before relying on it.

If you are preparing for a planned shutdown or need urgent temporary power for a manufacturing site, contact P&I Group with the site, load and access information you have available. The team can help assess the next practical step.