Do I need a three-phase supply?
You need three-phase if you run equipment that's built for it, or if your total load is more than a single-phase supply can safely carry. Most homes and small shops run on single-phase at 230V. Three-phase supplies 400V between phases and spreads the load across three lines, which suits large motors and heavy loads.
The equipment that most often needs it:
- Workshop machinery
- Lathes, milling machines, saws, spray booths and larger welders.
- Compressors
- Bigger air compressors in garages, body shops and small factories.
- Commercial kitchens
- Combination ovens, large fryers and dishwashers in cafés and takeaways.
- 22kW EV chargers
- Faster charging for fleets or businesses. Single-phase chargers top out around 7kW.
- Heat pumps
- Larger units for big homes or commercial buildings.
- Large homes
- Where heat pumps, EV chargers and electric heating add up to a heavy load.
How do I get a three-phase supply installed?
If your building doesn't already have three-phase, the new supply has to come from the network operator. In Leicestershire, that's National Grid Electricity Distribution (formerly Western Power Distribution). You or your electricity supplier apply to them, and they quote and charge for the supply directly.
Lead times vary a lot. A simple connection where three-phase is already in the street can be fairly quick. If the local network needs reinforcing, or the road needs digging up, it can take months. We can help you work out the load figures the application asks for, and we'll plan our part of the work to fit their dates.
Many industrial units, older workshops and some commercial premises already have a three-phase supply that's simply not being used fully. Checking that is one of the first things we do at the survey.
What three-phase work do you do?
We do everything after the meter: boards, cables, isolators and the final connections to your equipment. The supply itself, up to and including the meter, belongs to the network operator and your energy supplier.
- Distribution boards
- New three-phase boards, or replacing old ones, with suitable protection.
- Sub-mains
- Cables feeding a workshop, outbuilding or second board from the main supply.
- Machine connections
- Isolators, starters and connections for lathes, compressors and similar.
- Industrial sockets
- Three-phase plug-in points so equipment can be moved or swapped.
- EV chargers and heat pumps
- Dedicated circuits for three-phase chargers and larger heat pumps.
- Upgrades and additions
- Adding new machines to an existing three-phase installation.
Can I run a three-phase machine on a single-phase supply?
Sometimes. A phase converter or inverter drive can run some three-phase motors from a single-phase supply. This is common for a lathe or mill in a home workshop.
It depends on the machine, the size of the motor and how it starts. It won't suit everything, and it won't help if your total load is simply too big for the supply. We'll look at the motor plate and tell you honestly whether a converter is practical or whether a three-phase supply is the better long-term answer.
What affects the cost of a three-phase installation?
The main factors are the size and number of machines, the distance from the supply to where they'll be used, and whether the existing board can take the extra load. Every job is different, so we price after a survey visit and give you one fixed price for our work.
Network operator charges for a new supply are separate and come from them directly. These are the things that drive our price:
- Number of machines
- Each one needs its own circuit, isolator and connection.
- Cable distance and route
- Long sub-mains, ducts or runs to outbuildings add materials and time.
- Board size and type
- Larger loads need bigger boards and heavier protective devices.
- Existing installation
- Older boards may need replacing before anything new can be added.
- Working around your business
- Phased work to keep you trading is planned into the price.
What happens at the survey visit?
We look at your incoming supply, your existing board and where the equipment will go, and we talk through what you plan to run now and in the future. Afterwards you get one written fixed price for our work, with anything the network operator needs to do listed separately so there are no grey areas.
To help us price accurately, have these ready if you can:
- Equipment details
- Make, model and power rating from each machine's plate or manual.
- Planned layout
- Where each machine will sit, even a rough sketch.
- Supply information
- Recent electricity bill and any letters from the network operator.
- Future plans
- Extra machines or EV chargers you may add later.
What regulations apply to three-phase work?
All three-phase work is designed, installed and tested to the current Wiring Regulations (BS 7671, 18th Edition), and you get an Electrical Installation Certificate when it's finished. In a home, new circuits are also notifiable under Part P of the Building Regulations.
In business premises, Part P doesn't apply, but the Electricity at Work Regulations do. They put a duty on the business to keep its electrical system safe. A properly certified installation, clear labelling and isolators you can reach quickly all help you meet that duty. Because three-phase runs at 400V between phases, good labelling matters even more, so anyone working on the system later knows exactly what they're dealing with.