Why a commercial electrician plans the shutdown before the cabling
People sometimes ask whether the work can just be done live so nothing has to go off. Usually the answer is no, and that is not an electrician being awkward.
Regulation 14 of the Electricity at Work Regulations 1989 only allows work on or near live conductors where it is unreasonable for them to be dead, reasonable to work on them live, and suitable precautions are in place.
All three conditions have to be met, and inconvenience to trading rarely clears that bar.
So the useful question is when the power goes off, and how much of the building loses it. The answer is usually some mix of these:
Doing the isolations themselves early, late or at a weekend, with the preparation done in normal hours.
Splitting the building so one floor, bay or group of circuits is dead while the rest stays up.
Temporary supplies to the few things that genuinely cannot stop, such as refrigeration, a server or a sump pump.
Before any of that is priced, write down what must stay on. Access control, lifts, door entry and fire alarm panels are the ones people forget.
A monitored alarm that loses its mains supply can also raise a fault at the monitoring centre, so give them the dates in advance.
Cat A, Cat B, and whose electrics they are
Anyone taking on office space will hear these two terms. A Category A fit-out is what a landlord or developer hands over: a blank floor with distribution, general lighting and basic small power in place.
Category B is the occupier's own layout, which on the electrical side means power and data to desks, meeting rooms and kitchens, plus feature lighting and its controls.
The trap is that partitions move everything. Cat A lighting laid out for an open floor often has to be repositioned once the Cat B walls go up, and somebody pays for the same ceiling twice.
If you are the landlord and a tenant is already lined up, see their layout before the Cat A lighting is finished.
If you are the tenant, two lease points matter before anything is fixed to the building: whether alterations need the landlord's consent, and whether you will have to strip the work out again when you leave.
That second conversation is far easier years later with the handover records described further down. Our own fit-out work includes power, data and feature lighting for an office in Leeds, for JLL.
CDM 2015 covers electrical work too
The Construction (Design and Management) Regulations 2015 apply to all construction work, and installing or altering electrics counts.
A business commissioning that work is the client under those rules, with duties of its own: chiefly making sure the project is properly arranged and that contractors get the information they need before they start.
Where more than one contractor will work on the project, the client has to appoint a principal designer and a principal contractor in writing. An electrical job carried out by one firm with no subcontractors does not trigger that, but a fit-out with joiners, ceiling fixers and plumbers alongside the electricians usually does.
The project must also be notified to HSE on an F10 if it is expected to last more than 30 working days with more than 20 workers on site at once, or to exceed 500 person days. The client is the one who notifies, although someone else can submit it on their behalf.
Will the supply cope with what you are adding?
Businesses grow into their electrics one machine at a time: a second compressor, a bigger oven, a kiln, fleet chargers, a heat pump.
At some point the question stops being about cable sizes and becomes whether the site has the capacity at all.
On a larger business supply metered through current transformers, the bill shows an agreed supply capacity in kVA. You pay for that capacity every month whether you use it or not, and running over it can bring excess capacity charges on top. Adding load without looking at that figure is how a business finds out through an invoice rather than a tripped main switch.
The sensible order is to measure before designing. Logging existing demand across a normal working period, which is what our energy usage surveys do, shows how much headroom is really there. Capacity is not only a total, either.
Older units are sometimes badly balanced, with one of the three phases near its limit while the other two have room to spare, and moving circuits across can make space on the overloaded phase without touching the supply.
Staggered start-ups and load management can do the same. Where none of that is enough, it becomes an application to Northern Powergrid for more capacity, and that belongs at the very start of the programme, because from then on the network's timescale sets the start date rather than anything on site.
Relighting a commercial unit: the EPC rules in 2026
If you let commercial property, lighting is tied up with the Minimum Energy Efficiency Standards. Since 1 April 2023 a landlord cannot continue to let a non-domestic property with an EPC rating below E, subject to the seven-year payback test and registered exemptions.
The longer-term picture changed in June 2026. The government dropped the planned move to EPC C in 2027.
Instead, rented non-domestic buildings over 1,000 square metres are to need EPC B from 2031 where that is cost-effective, while smaller buildings stay at E with no date set for any rise.
None of that is law yet, because it still needs secondary legislation. Anyone who budgeted for a C by 2027 should revisit the plan.
Lighting is one of the things an assessor models on a commercial EPC, and unlike a home assessment, controls such as presence detection and daylight dimming are counted. Keep the product data sheets and lighting design from the job, because an assessor with real efficacy figures can use them.
Design the emergency lighting into the new layout as well, rather than leaving it wherever the old fittings happened to be. The large industrial unit we relit for Barnsley Council went to high-bay LED throughout, with new power installed alongside.
Industrial sites run to their own rules
On a working industrial site the electrician is a guest inside somebody else's safety system. Expect a site induction before any tools come out, risk assessments and method statements sent over in advance, and a permit to work before anything is isolated, with hot works and working at height often under separate permits.
None of that is paperwork for its own sake. On a process site, switching off the wrong feeder can stop a plant or leave a process in an unsafe state.
Our work on sites like this includes power, containment and external works across a live process and energy site in Merseyside for Vital Energi, and cable containment and first-fix on a large commercial unit for Amazon.
When a main contractor or facilities team pre-qualifies an electrical firm, the useful evidence is competence, insurance and health and safety accreditation.
Ours is NICEIC approved contractor status for the electrical work itself, CHAS for health and safety pre-qualification, and JIB, the industry body behind electricians' grading.
What you should be handed at the end
New circuits should come with an Electrical Installation Certificate to BS 7671, together with the schedules of inspection and test results. Smaller work that adds no new circuit gets a Minor Electrical Installation Works Certificate instead.
On a bigger project, add as-fitted drawings and the manufacturers' information for the operation and maintenance file. Those are the documents an insurer, a landlord or your next EPC assessor will ask to see. The scope of what we install, from fit-outs and distribution to containment and three-phase power, is set out under commercial and industrial electrical installations.
For a tenant, this pack is also what makes the reinstatement conversation at the end of a lease straightforward. Ongoing fixed-wire testing is a subject of its own, covered on our test and inspection service page.
Commercial electrician across South Yorkshire and further afield
With our base in Wath upon Dearne, the nearest commercial work is in Rotherham, Barnsley, Sheffield and Doncaster. Larger projects take us further: the jobs above were in Leeds and Merseyside, and our retail fit-outs run from a unit in Eldon Square, Newcastle, down to Southampton. Photographs of several are on our projects page, and every town we cover is listed on areas we cover.
A failed three-phase board is dealt with under distribution board and consumer unit replacement, and if a site loses power without warning, our emergency electrician page covers what to check first. Fire alarms and security systems for business premises sit under CCTV and fire alarm installation.