1.
Introduction:
This specification covers the supply of metal waterproof cabinets required for the installation therein of energy meters and the KAHRAMAA incoming service, comprising electrical service cable, MCCB, earth and neutral terminals, and the customer‟s cable.
2.
Climatic Conditions:
The service electrical cabinet will be used in the following climatic conditions : Maximum Direct Sunlight Temperature : 75 0C
Maximum Ambient Air Temperature : 50 0C Maximum Relative Humidity : 100%
Occasional sandstorms with height salt content. Occasional fog mixed with salty sea water mist. Occasional torrential rain in winter and up to 15 cm per year. Prolonged periods with temperatures between 30 0C and 50 0C with humidity simultaneously between 30% and 100%
3.
Electrical Systems:
The electrical system to which the equipment installed in the cabinets will be connected will be nominally 250 / 433 Volts, 03 Phase, Star Connected and with Solid Neutral Earth.
4.
Mounting Facilities:
The cabinets shall be suitable for mounting in a recess in the boundary wall of domestic premises, or on occasions directly inset into the wall of a building. For this purpose the cabinet will have holes in the sides to permit the use of bolts or screws to secure it to the wall. At the front of the cabinet there shall be a lip intended to conceal irregularities in the gap between the wall and the cabinet.
5.
Materials and Finish:
The cabinet shall be of Sheet Aluminium of a thickness sufficient to make the completed cabinet rigid and robust.
The following is a guide to the finish to be used. It represents a minimum standard.
All ferrous surfaces and edges shall be cleaned of scale and rust by shot blasting and shall be treated on the same day, without outdoor exposure, with a zinc spray. The zinc chromate shall be applied by a flame gun process and shall be a thickness of ZN4 in accordance with BS 2569: (Specification For Sprayed Metal Coatings).
And BS 2569 - 2:1965 (1997) (Protection Of Iron And Steel Against Corrosion And Oxidation At Elevated Temperatures ).
This treatment shall be followed by the application of one coat of zinc chromate base priming paint and an undercoat and a final coat of durable oil and weather resisting paint. The colour of the final coat shall be Light Aircraft Grey Code 627 of BS 381C : 1996 ( Specification For Colours For Identification, Coding And Special Purposes ), or of a similar colour. The paint shall have a matt finish.
The inside of the cabinet shall have applied a coating of resin of GRP which shall cover the whole of the inside surface. This will be applied before the placing of the interior wood panel.
Where an alternative finish specification is offered, the manufacturer shall bear in mind the need for the electrical service cabinet to provide long service in the arduous conditions stated above. It is essential that the finish shall be of the highest quality.
In the event that the electrical service cabinet is found to suffer from deterioration in service, Qatar General Electricity & Water Corporation
“KAHRAMAA” reserve the right to reject the supplied and installed electrical
service cabinet.
Where an alternative specification is offered, this shall be declared to Qatar General Electricity & Water Corporation “KAHRAMAA” at approval stage, and be subject to approval.
6.
General Description:
The cabinet shall be of the shape and the dimensions as shown in the Sketch No. (14). It shall have a door at the front containing:
1. A clear wired glass window for reading the meter, no alternative to clear wired glass in acceptable.
2. A small door having on the outside a unique pattern lock, and on the inside a bolt, to allow access to the MCCB operating handle whilst preventing access to any live terminals. Two keys shall be for the unique lock. The door shall have a seal to prevent the ingress of water.
3. Weather rendering and weather proofing and vermin proof ventilation. Means shall be provided to prevent ingress of water through the main door and the small door. This shall generally be by a seal of neoprene or similar durable material.
4. Means of locking the main door which shall comprise two 8 mm triangular locks and a facility for fitting a padlock having a 7 mm hasp.
The cabinet shall have mounted inside a plywood panel for the purpose of mounting the major electrical components of the installation.
The supply of the meter, MCCB and terminals is not included in this specification. The cabinet shall have attached to its inner, lower surface :
1. a terminal capable of accommodating 3 separate 35 mm² conductors for earthing purposes.
2. a clamp for accommodating and earthing the armour of the customer‟s cable.
Both of these shall be securely fixed in placed by welding or brazing and shall form a secure electrical contact with the body of the cabinet.
There shall be an electrical connection between the body of the cabinet and the main door for the purpose of ensuring that the door is earthed.
This shall be of flexible braid of adequate size. Two cable access holes, diameter 10 cm, for the main and consumer cable entries.
A wide lip shall be provided at the top of the cabinet so positioned as to prevent water from running down the wall and flooding the top of the main door.
The identity of the manufacturer or his representative shall be clearly indicated on the cabinet, either inside or outside.