Do you need a permit or an inspection for a backup generator at work?

Only when it crosses a regional threshold: the permit depends on power, running hours and fuel tank, while an inspection applies to every backup generator. Our guide to emergency power supply for your business compares UPS, generator and battery; this article covers the paperwork. A business battery takes over the short cuts, so the generator starts less often.

Perhaps the generator stood behind the building when you took over the site, or the electrician connected it after the last power cut. Nobody mentioned a permit, until the inspector asks for the hour log or the insurer asks whether the fuel tank is declared.

The exemption only holds as long as the generator stays a pure emergency machine.

Which rules apply to a backup generator at a company in Belgium?

Five sets of rules, from different authorities. The region sets the environmental permit, the federal electrical code the inspection, the grid operator the link with the grid. Fuel tank and noise have rules of their own.

Each region reads another number. Flanders looks at the power in kVA and the thermal input, Wallonia at the thermal input, Brussels at the engine power.

Do you need a backup generator permit in Flanders under VLAREM?

Usually not, if it is a true emergency generator of less than 400 kVA that runs less than 100 hours a calendar year. The Departement Omgeving states that such generators are not classified in VLAREM rubric 12.1 (electricity production). You must record the hours they run.

The engine has a rubric of its own, 31.1 (stationary engines), from 300 kW thermal input. Engines under 1 MW thermal input that drive an emergency generator and run less than 100 hours a year are not classified either. Both limits apply per generator.

Between 100 and 500 hours a year, an emergency generator counts for only 50% of its power. That matters when you add up the power of the whole site.

VLAREM defines an emergency generator as a machine that keeps the power on during problems with the grid supply. The Departement Omgeving was asked about a generator that also runs 2 to 4 hours a week for production. Its answer: then it is not an emergency generator.

Above those limits the generator is classified: a notification (melding) or an environmental permit, depending on its power. Your municipality tells you which applies to your site.

What about a backup generator permit in Wallonia or Brussels?

Both regions catch smaller generators than Flanders, and neither has the same 400 kVA exemption. Check a standby generator against the environmental permit rules before you buy, not after.

Wallonia classifies a generator as a combustion installation, based on its nominal thermal input. From 0.1 MW up to 1 MW thermal it is class 3: a declaration to your municipality, valid for 10 years. From 1 MW it is class 2, which needs a permit, and the rubric makes no exception for emergency use.

Thermal input is not the number on the sales sheet; check the plate or ask the supplier. With typical diesel figures (power factor about 0.8, electrical efficiency about 33%, Departement Omgeving), 0.1 MW thermal is roughly 40 kVA.

Brussels lists emergency generators with an engine of at least 20 kW under rubric 104: a declaration or an environmental permit. Bruxelles Environnement adds conditions:

• Use the generator only when the grid fails, or for test runs; never for peak shaving.
• Fit an hour meter and keep the yearly running hours (in Flanders only needed for the exemption).
• Have it checked and maintained at least once a year, as the manufacturer prescribes.
• Inside a building, the room has walls, floor and ceiling with one hour of fire resistance. The exhaust sits at least 8 metres from any opening or fresh-air intake.

Does the fuel tank of your generator need its own permit?

An integrated tank of up to 2,000 litres usually does not, a separate tank often does. In Flanders, a tank built into the generator as one CE-marked unit is not a storage place under VLAREM, up to 2,000 litres.

A bigger integrated tank, or a separate tank refilled on site, is a storage place. Diesel almost always carries the flammable pictogram GHS02, so rubric 17.3.2.1.1 applies. For a business that is class 3 from 100 kg up to 20 tonnes. At 0.833 kg per litre (the Departement Omgeving figure), 100 kg is about 120 litres.

In Wallonia diesel storage is class 3 from 3,000 to 25,000 litres, and class 2 from 25,000 to 250,000 litres. In Brussels, a day tank built into the generator is not a separate depot. An existing depot up to 3,000 litres is tolerated in the generator room; new depots go elsewhere.

Does an emergency generator need an AREI inspection, and what must the grid operator know?

Yes. A fixed back-up generator is part of your electrical installation, so the AREI applies. A recognised inspection body checks it before use and after an important change or extension.

After that, non-household installations are inspected every 5 years. Mobile, movable or temporary installations get a yearly check, like explosion zones and high voltage. So a generator moving between sites is inspected every year.

When the generator keeps safety equipment running, the AREI adds conditions for a safety source. It must switch on automatically, stand in a suitable, ventilated room reserved for it, and be tested under load at least once a year. Our article on inspecting an emergency generator and the rest of your back-up lists them.

For the grid operator, one question counts: does the generator ever run in parallel with the grid? A changeover switch that disconnects the grid before the generator takes over keeps the two apart.

Synergrid C10/11 calls a unit that only feeds an island an emergency power system. It may run in parallel only rarely and briefly, for example at most 5 minutes per switchover. Every parallel connection goes into a logbook.

How loud may a backup generator be?

New generators under 400 kW must stay under an EU noise limit, and every generator carries its guaranteed sound power level on a label. That is the European outdoor noise directive 2000/14/EC. Compare that label before you choose a machine.

Where it stands is the other half of the generator noise rules. In Flanders, classified installations follow the VLAREM noise rules, and exempt emergency engines under 1 MW must still meet part of them. For other unclassified machines, local police or municipal rules can apply.

Neighbours hear the test runs, not the rare real cut: plan them on weekdays during working hours and keep them short.

How does a battery change the permit story for your generator?

A battery takes the short cuts and the daily work, so the generator can stay a true emergency machine. The generator only starts when a cut lasts longer, so its running hours stay low.

It also solves a Brussels problem: a back-up generator may not do peak shaving there, but a battery may. In Flanders the same split protects the emergency status.

There is one trap. A generator that charges the battery every day, or cuts a peak, becomes a production installation. Other thresholds, noise and emission rules then apply, and in Flanders it is no longer an emergency generator.

That can still be the right choice. In Maasmechelen our semi off-grid system (24 kVA, 30.8 kWh) makes an emergency generator useful. The customer chooses the grid or the generator to charge the battery.

The farm in St-Georges-sur-Meuse shows the other direction. With no connection in the street, it ran fully on a generator. With solar panels and a battery of 46.2 kWh, the generator now only serves as back-up. Our article on combining a generator with a battery explains how they share the work.

Above a certain size the battery has its own environmental conditions, inspection and fire safety measures. A battery that cuts peaks daily is a storage system, not an emergency power system: in Flanders you report it to Fluvius. Our article on business battery safety, permits and inspection covers that side.