Handbook of Electrical Installation Practice - BeKnowledge

Standby Power Supplies 137
plant room is vitally important in view of the large amount of radiated heat from
generating sets and the need to circulate large volumes of cooling air through
radiators. Ideally, radiators are mounted as close to an outside wall aperture as
possible and if for any reason this cannot be done then a suitable ducting system
should be provided. An additional extraction system may be provided to keep
the plant room cool, particularly in the case of installations with heat exchanger
systems or remote radiators.
If the plant room is at ground level or in a basement, the foundations are probably
adequate to carry the set. It is recommended that concrete plinths are erected
to lift the set above ground level to provide for drip trays and access beneath. If the
set is installed above ground level the question of floor loading needs careful consideration
and discussion with the architect and it may be necessary to fit resilient
mountings so that vibration is not transmitted to the building. The height of the set
also determines the fuelling supply arrangements. Bulk storage tanks are normally
installed at ground level and circulation of oil to the generating set service tank may
require fuel transfer pumps as an alternative to gravity feed.
Exhaust systems should be short with the minimum number of bends and the
bend radius maximised to avoid back pressure. If a long exhaust run is necessary
the cross-sectional area of the pipe must be increased to compensate. The connection
between the exhaust run and the engine manifold must always include a
flexible section, otherwise vibration from the engine will damage the exhaust
installation. For multiple set installations each engine must be provided with its own
exhaust system and in no circumstances should exhausts be paralleled at any point.
Exhaust pipe temperatures can reach 500°C close to the engine and exhaust system
runs should be lagged to prevent radiated heat from raising the temperature of the
plant room. Normal industrial silencers are usually satisfactory but for residential
areas a special additional silencer may be required.
Safety codes must be strictly observed in the operation of standby sets and display
notices should be erected giving the usual precautions against fire and electric shock.
A special notice is also required advising personnel that a standby generating set
can start automatically at any time without warning.
The electrical cable run from the generator terminal box should ideally use a
flexible type cable to withstand vibration from the generator. Free-standing control
panels should be mounted close to the set. Mains standby installations should
include bypass switches to allow the load transfer contactors to be made dead for
safe maintenance work.
Commissioning
Following familiarisation with the plant by study of operating manuals, instruction
books, diagrams, etc., preparation for the first run includes checking batteries,
filling with oil and fuel, bleeding the injection system, checking air cleaners, fitting
guards, etc.
The initial run should be short, for a minute or two, to check for leaks in the fuel
and water systems followed by a 15 minute run ideally at about one-third load, under
close observation. During this run the water temperature should reach normal value
controlled by the thermostat. Following examination and oil check, the set can then