Sarel
Electrical enclosures
Sarel Enclosures Guide
Sarel Enclosures Installation
Selection of enclosures is generally regarded as a
simple process, determined by the requirement of size together with a
passing, often misguided reference to IP ratings.
Enclosure technology, although perceived as being
relatively simple, is continually evolving to meet the demands of
new applications which not only raise new questions concerning
potentially adverse environmental conditions but which also create
the requirement for an increasing array of new features.
The materials of construction are in themselves a whole area of
technological involvement, with welded mild and stainless steels;
hot press moulded GRP and complex plastic mouldings in ABS, PVC,
polycarbonate, polystyrene etc. Outdoor
Installations
In many instances the automatic choice for
enclosures is mild steel but the use of such enclosures outdoors is
questionable but continues for reasons which have little to do with
the enclosure itself – cost, convenience, habit and familiarity. All
are valid reasons but each is self-limiting, and still ignores the
fact that steel rusts. Despite the best in
preparation, painting, plating and handling, ultimately the
corrosive propensity of the basic material may affect the
suitability of the application performance, which is, basically to
provide a protective envelope housing sensitive or potentially
harmful electrical equipment. Mild steel
enclosures therefore are not ideal, but they do offer advantages and
are apparently a cost-effective solution in many instances. So what
are the alternatives, and what can be done to improve the chances of
a successful installation with a mild steel enclosure left alone to
the mercy of the elements? Use a corrosive
resistant material instead; there is a wide range of products, which
Sarel can offer, principally glass fibre reinforced polyester and
stainless steel. Such materials drastically reduce or completely
eliminate problems of corrosion where conditions would be too
problematical for mild steel.
One key additional advantage is that cost
differentials have narrowed over recent years. Moulding techniques
and material advances now ensure that GRP enclosures are of more
than adequate strength for most applications including street and
trackside furniture.
They offer a measure of additional safety where
vandalism is concerned; a damaged steel enclosure can become live, a
GRP one cannot. For added strength, GRP enclosures
such as root pillars are simply made of thicker material with
reinforcing ribs but without the weight penalties of steel.
Consequently, in many cases where the capital cost is not the prime
consideration, use of a corrosion resistant product can be
inherently more satisfactory and can also work out cheaper by
eliminating maintenance costs. Aspiration &
Condensation
These two phenomena frequently combine to produce
substantial quantities of water within the enclosure. Aspiration
occurs as a consequence of rising and falling temperatures; when the
daytime temperature is high the air in the enclosure expands and
some is expelled – creating a partial vacuum; when the temperature
falls, cool moisture laden air is drawn in, and when it reaches its
dewpoint the moisture condenses and is deposited on components and
the enclosure. The whole process is cyclical and can eventually
produce an incredible amount of water.
The consequence, apart from the very real danger
of electrical shorting, is to cause internal corrosion in steel
installations; correct use of thermal management equipment can help
prevent these problems. Working On The Enclosure
The following are common sense tips, which can
help to ensure a successful installation: Inspect
outer packaging on delivery as damaged wrapping may mean the
enclosure itself has been damaged in transit. Do
not insert a knife into the packaging, e.g. to cut tape, as there is
a risk of scoring the paint finish. Do not drag
the enclosure across workshop floors – use approved lifting methods.
Clear swarf from workbenches and make sure work surfaces are free
from debris. Empty the enclosure of any swarf or
filings before installation as condensation may corrode them.
When marking out do not score paint surfaces.
Repaint bared hole edges. Use sharp cutting tools
to avoid cracking paint. Use punches in preference
to drills. Seek manufacturer’s advice on care of
seals and paint selection before removing seals or overpainting.
Remember all work should be such as to maintain the IP integrity.
Check the loading of equipment to be fitted, as distortions of
mountings or doors may affect the sealing. Final
inspection should be conducted before transportation from the
workshop. Site Installation
Ensure walls/floors are plumb and level and in
good condition. On external locations, site on the
lee side of buildings where possible. Canopies are recommended to
deflect direct rainfall, as are pedestals to raise enclosures from
wet floors. Floor standing enclosures which are
not designed to be free standing should be bolted back to a wall or
stanchion for stability. Cable entries must be
supported outside the box, so that no stress is caused to the
enclosure, as deformation may degrade the sealing.
Earthing continuity should conform to relevant local standards.
The installation should comply with the relevant standards as
specified by the user. Selection of the enclosure should conform to
the relevant BS or equivalent standard. A planned
maintenance programme is advisable, checking gaskets, paintwork,
hinges, locks etc, for signs of physical damage, tampering or
corrosion. Further Information
For further information on Sarel products, please
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Electrical enclosures wall mounted floor standing rack steel grp boxes
Technical information associated with:
Sarel - A Guide to Enclosure Selection & Installation
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