Generators: physical and environmental considerations

In many data centres, generators are a vital complement to UPSs; if adequately fuelled and supported, they can continue to provide electrical power for as long as needed during extended blackouts or utility power problems. However, they can be relatively large, diesel-operated items that can affect the environment and people around them without sufficient planning to mitigate their impact. This starts with seeking local authority planning permission; requirements vary according to location. Local regulations must be checked before installing or operating a standby generator. If fuel is to be stored on site then the local fire officer may also need to inspect the proposed generator and fuel positions. The local electricity supply company must also be advised that a generator is to be installed on the site. Installation starts with providing adequate and regulation-compliant fuel storage facilities. In England the Control of Pollution (Oil Storage) (England) Regulations 2001 require oil storage tanks to have a secondary containment facility such as a bund or drip tray to prevent oil escaping into the water environment. The regulations apply to all oil storage containers greater that 200 litres located above ground at an industrial, commercial or institutional site. Different regulations apply in Scotland and in Northern Ireland, however there are currently no equivalent regulations in Wales. A generator supplied with a standard double bunded day tank that can provide eight to 24 hours’ full power run-time is relatively straightforward to position and install, however, the siting of bulk fuel tanks with their associated fire valves and fuel pumps will require specialist advice. Depending on size, the generator may need special delivery vehicles and lifting equipment during delivery. Even a smaller, 100kVA generator weighs several tonnes and is the size of a small car. It requires careful consideration for its positioning, and delivery into the chosen position. The generator must be installed on a flat, level surface, and may require secure floor fixings. Accordingly, generators are often installed on a purpose-built concrete slab. As a minimum, a power cable rated to carry full generator power and a signal cable to carry generator start/stop signals must be run between the generator and the AMF panel and/or the essential services board. If the generator power cable is long then its rating may need increasing to reduce the volt drop along it. This increases the generator’s electrical installation costs, so it should be located as close as practically possible to the AMF panel and/or the essential services board. Acoustic noise can be an issue, depending on the generator’s proximity to occupied areas, and its likelihood of operating at night. Acoustic housings with various noise attenuation ratings are available for standby generators, but costs rise with higher attenuation ratings. A generator, when running, produces heat as well as electrical power. Almost all standby generators are air-cooled, so enough cooling air must be provided. Accordingly, most standby generators are housed outside the building in weatherproof and acoustically-shielded enclosures. Generators also create exhaust gases, which must be vented safely. Any exhaust system fitted has to avoid disturbance to nearby people, while ensuring that fumes are minimised and vented safely. Long exhaust pipe runs or bends in the exhaust pipe call for an increase in the pipe’s cross-sectional area. Any part of the exhaust pipe passing through a building must be lagged to minimise the problems of heat and fumes. Specialist advice is required when exhaust pipes pass through, or attach to, a building. Considering the importance of getting the installation right, and the multiple disciplines needed to do so, it makes sense to use a supplier such as UPSL. They can not only deliver a matched UPS–generator pair, but also provide the installation and commissioning services necessary to ensure a trouble-free implementation.