Installing a generator safely: location, ventilation, connection

Install the generator outdoors or in a dedicated, ventilated room, away from windows and air intakes. Set it on flat, stable ground. Earth it, and fit a changeover switch, manual or automatic, so that no power can flow back into the grid. Exhaust gases contain carbon monoxide, an odourless and deadly gas: never run a generator inside a house or garage.

Where should a generator go?

A generator belongs outdoors, sheltered from rain, or in a dedicated, well-ventilated plant room. This keeps exhaust fumes away from people and gives the engine the air it needs to stay cool.

• A soundproof set is protected from the weather by its canopy, so it can stay outdoors.
• An open-frame set must be installed under a shelter or in a ventilated room.
• Air must flow freely around the set. Keep the clearances the manufacturer specifies.
• The exhaust must discharge away from windows, doors, air intakes and neighbours.
• The ground must stay clear of water in heavy rain. A raised concrete base stops water pooling under the set.
• Never in a house, garage or basement, even with the door open.

The differences between the two versions are covered in our guide to soundproof or open-frame generators.

What base does a generator need?

The base must be flat, stable and able to carry the weight of the set with its fuel. According to our data sheets, a 100 kVA soundproof set weighs 1,920 kg. A 500 kVA set weighs 5,900 kg.

Figures from the data sheets of our Perkins-engine diesel generators. Each product page gives the model's dimensions and weight, soundproof and open frame. For a large set, have the concrete base designed by a professional.

How is the generator connected to the electrical system?

A qualified electrician makes the connection, with earthing and a changeover switch. The switch disconnects the building from the grid before connecting it to the generator.

Without a changeover switch, generator power can flow back into the grid. This backfeed can electrocute technicians working on the line. It can also damage the generator when mains power returns.

• A manual changeover switch is operated by hand at each outage.
• An automatic transfer switch (ATS) moves the supply to the generator when the grid fails, then back to the grid when it returns.
• Never connect a generator to a wall socket with a cable that has a plug at each end.

Cables and breakers are sized for the current the generator delivers. A 20 kVA set at 400 V delivers about 29 A per phase at full load, a 100 kVA set about 144 A. The calculation is in our kVA vs kW guide.

On a three-phase set, spread the single-phase circuits across the three phases. Our single-phase or three-phase guide explains why.

How should fuel be stored?

Store fuel in closed containers designed for it, away from any source of heat.

• Keep fuel well away from the exhaust and the engine.
• Never refuel with the engine running or still hot.
• Petrol is more volatile than diesel and needs even more care.
• Clean fuel protects the filters and the injectors.
• Keep a fire extinguisher suited to fuel fires near the set.

How much noise should you expect?

The data sheets of our Perkins-engine sets give one sound level per model: 75 dBA from 13 to 100 kVA, up to 85 dBA from 1,250 to 2,000 kVA. The measurement conditions are on each data sheet.

Point the exhaust and the hot-air outlet away from homes and offices. Near neighbours, choose a soundproof set.

Who commissions the generator?

We install the generators we supply on site, connect them and commission them. We then train your users to operate them. See our installation and commissioning service.

Once the set is in place, regular maintenance keeps it reliable. Follow our generator maintenance schedule, or see all our services.

Sources: manufacturers' data sheets (Perkins-engine generator sets).