Three-phase supplies for farm grain stores and workshops.

How do I get three-phase to a grain store?

The first call is to the network operator, because the supply itself is their equipment. Round here that is Northern Powergrid. Changing a single-phase supply to three-phase counts as altering an existing connection, and a store with no supply at all needs a new connection.

They'll ask how much power you need. Work it out before applying, from the dryer, the fans, any heaters and the workshop, allowing for what might be added later. I'll go through it with you at the survey, so the figure on the application matches what the store will draw.

Their quote covers the cable to your property, the new cut-out and any work on their own network. The meter belongs to your energy supplier, who fits or swaps it once the new supply is live.

An independent connections provider can quote for some or all of the connection work as well, so you can set their price against the network operator's.

Who pays for a three-phase upgrade

The farm pays for the part that serves it. Since Ofgem's connection charging reforms took effect in April 2023, a customer asking for more capacity generally pays for the new assets that connect them and no longer pays towards strengthening the wider network, unless the reinforcement cost goes above a cap.

Distance and spare capacity drive the figure. A yard near a transformer with room to spare is a smaller job than one that needs a new transformer or a long cable run, and only the network operator's quote tells you which you've got.

The wiring on your side is separate, and it gets its own written quote after I've looked at the meter position and the route to each building.

What I wire after the meter

Once the supply is in, the installation on your side starts with a main switch and a three-phase distribution board sized for what you'll run, with spare ways for later.

From the board, armoured cable runs out to each building, buried or clipped high where vehicles and stock can't damage it. Each motor gets its own circuit and a switch beside it that can be locked off, because Electricity at Work regulation 12 calls for a way of cutting off and isolating equipment before anyone works on it.

Loads need spreading across the three phases. A board with every big motor on one phase overloads that phase while the other two carry little, so the circuits are balanced when the board is laid out and checked again at the test.

On a long run out to a store, the cable size allows for voltage drop as well as current, so a motor at the far end of the yard still gets enough voltage to start cleanly.

Each outbuilding fed from the board has its earthing arrangement assessed, because steel frames, water troughs and wet concrete change what counts as safe on a farm.

Grain dryer electrics

A dryer is usually the biggest single load on a farm, and it works hardest at harvest, when everything else is running too. Its fan motors draw far more current for a moment as they start than they do once running, so the cable and the protection are sized for both.

Grain dust settles on everything in a store. The HSE warns that disturbed deposits can form an explosive cloud, so the store should be assessed under DSEAR, and its guidance favours dust-protected enclosures for roof-level lights and extraction fans.

Aeration fans tend to arrive one bay at a time over several seasons. Spare ways in the board and a spare duct across the yard save digging the same trench twice.

Workshops and three-phase machines

Welders and compressors bought second-hand from industry often expect three-phase. Check the rating plate before you buy, because on a single-phase farm the supply decides what the workshop can run.

A three-phase electrical panel works like the board in a house, with three live busbars where a house has one. Each machine gets its own breaker, and its starter is wired so the machine stays off when the power comes back after a cut.

Where the network quote is out of reach, some farms run a three-phase machine from a single-phase supply through a phase converter, or change a small motor for a single-phase one. Both have limits on size, and I'd look at the load before recommending either.

Before you apply

If the existing board and the cables out to the sheds are old, a Section 705 farm inspection of what's already there shows whether they'll take the extra load or need replacing at the same time.

Ventilation fans in pig and poultry sheds can run on three-phase too, and their alarm circuits are best planned in from the start.

On a brand-new farm building, the three-phase board goes in as part of the new installation, from first fix to certificate.

Solar panels on the shed roofs go through our solar partner, so mention them at the survey if they're planned.

Where I wire three-phase supplies

I'm a three-phase electrician working out of Bridlington, and I take on farm jobs across Driffield and the Wolds and south through Holderness to Hedon and Withernsea.