3.7 DISTRIBUTION AND LIGHTING
PANEL BOARDS DISTRIBUTION
PART 1 GENERAL
3.7.1 .1 DESCRIPTION OF WORK
Installation comprise panel boards for distribution and lighting for protection of circuits, including fixing and supporting materials and materials for termination of feeders, sub circuits and branch circuits.
3.7.1.2 STANDARDS
Panel boards generally are to comply with the requirements of IEC 439-1 Factory Built Assemblies for LV Switchgear and Control Gear for voltages up to and including 1000 V a.c. And 1200 V d.c.
DESIGNATIONS:
Panel boards are designated on Drawings and in Schedules, as follows:
3.7.1.3 SCHEDULES
Indicate the designation and required type of panel board using the following criteria:
- Type of construction (MCB or MCCB), referring to type of branch circuit-breakers.
- Voltage, number of phases and wires
- Branch circuit-breaker, trip rating and wire size
- Main circuit breaker, trip rating and frame size (maximum continuous rating) for MCCB.
- Short-circuit interrupting capacity (IC) in kA at point of application
- Special arrangement or provisions
3.7.1.4 EQUIPMENT DATA :
Submit for approval comprehensive data including, but not limited to, the
Following:
- Manufacturers' catalogues indicating specific equipment selected.
- Types of panel boards and circuit breaker characteristics include duties and ratings compensation at and above 40 deg. C ambient conditions and corresponding temperatures within the enclosures
- Dimensions of panels and specific contents of each panel board
- Integrated equipment tabulations for coordinated short-circuit series combinations of circuit breakers.
3.7.1.5 TESTS AND CERTIFICATES
Provide complete certified manufacturer's type test and routine test records in compliance with the Standards.
3.7.1.6 SHOP AND CONSTRUCTION DRAWINGS
Submit drawings for approval including, but not limited to, the following:
- exact composition of each panel board, indicating busbar rating frame or continuous rating and trip ratings of all circuit breakers
- Typical installation details of panel boards, indicating main feeder ,branch circuit conduit connections, terminal provisions, tags, labels, mounting methods and materials used.
3.7.1.7 APPROVED MANUFACTURERS:
Obtain panel boards from one of the following:
Shnider group (EGYPT )
ABB (EGYPT)
Or other equal and approved.
PART 2 PRODUCTS AND SYSTEM
3.7.2.1 DISTRIBUTION AND LIGHTING PANELBOARDS
RATED INSULATION VOLTAGE:
To be in accordance with the respective Standards specified.
3.7.2.1.1 PANEL BOARDS:
To be totally enclosed, dead front type, protection code IP 31 for indoor installations and IP 55 for outdoor installations, in accordance with IEC 144 all interiors with expansion of main incoming and the branching C.B's shall be completely factory assembled with neutral bar, connection busbars and earth bar connector.
3.7.2.1.2 EARTHING BAR:
To be provided in every panel board.
3.7.2.1.3 PROTECTION:
Is to be fully rated throughout the systems.
3.7.2.1.4 SERIES (CASCADE) COORDINATED PACKUP PROTECTION:
Will only be acceptable within final branch circuit panel boards, between branch circuit breakers and the main incoming circuit breaker, in accordance with an integrated series combination chart prepared by the manufacturer, tested and certified in the country of origin by an internationally authorized organization, where short-circuit ratings are beyond available fully rated types specified and upon Engineer's approval.
3.7.2.1.5 CIRCUIT BREAKERS:
Are to be non-fused type.
3.7.2.1.6 CIRCUIT BREAKER ARRANGEMENT:
Panel boards are to have one main incoming circuit breaker and the number of branch circuit breakers arranged as shown on the Schedules including spare circuit-breakers and not less than spare spaces for future expansion.
Three-phase panel boards are to be designed for sequence phase connection of branch circuit devices.
3.7.2.1.7 BRANCH CIRCUIT NUMBERING:
On 3-phase panel board schedules, circuits 1 and 4 are to be connected to red (R) phase, 2 and 5 to yellow (Y) phase, 3 and 6 to blue (B) phase etc., to conform with branch circuit wiring numbering shown on the Drawings.
3.7.2.1.8 PANELBOARD ENCLOSURES
TYPE:
General purpose type suitable for relevant ambient conditions, flush or surface mounting as shown on the Drawings, comprising box, trim, or trim and door to approved manufacturer's standards and sizes.
CONSTRUCTION:
Box, trim and doors where required, are to be electro- galvanized sheet steel of gauges not less than specified and in accordance with the Standards. Welded joints are to be galvanized after manufacture. Gutter spaces are to conform to the Standards, but are not to be less than 100 mm on all sides. Enclosure is to have pre-designed angles or threaded end studs to support and adjust mounting of interior panel board assembly.
TRIMS:
Are to cover and overlap front shield, covering all terminals and bus compartments, to form a dead front panel. Trims are to be fixed to cabinet/box by quarter-turn clamps engaging flange of box (use of screws engaging holes in flange of box is not acceptable). Screws where used are to be oval-head, countersunk and flush. Trims for flush mounted panel boards are to overlap box and front shields by at least 20 mm. Trims for surface mounted panel boards are to be exactly sized to form a flush fit to box.
DOORS:
Are to have concealed hinges integral with trim and flush combination cylinder lock and catch. Doors over 1000 mm high are to have vault-type handle and multiple point latch mechanism. Locks are to be keyed alike.
FINISH :
Inner and outer surfaces of cabinet/boxes, trims, doors etc. are to be cleaned, phosphatized, chrome passivated and treated with a final thermosetting epoxy powder modified by polyester resins providing high resistance to mechanical in jury, heat, acid and alkali solvents, grease, ageing and corrosion and of standard grey color to Engineer's approval.
DIRECTORIES:
Under glassine, or an approved alternative durable arrangement, are to be provided on inside face of doors, or in metal label holders when trim without doors is specified. Directories are to be typed to identify panel boards and clearly indicate circuit number and description of load.
OUTDOOR ENCLOSURES:
Are to be heavy duty sheet steel cabinets, minimum 2 mm thick, fully weatherproofed (IP55), without knockouts, but with removable sealed/gasketed bottom gland plates and gasketed doors.
3.7.2.1.9 BUSBARS
TYPE:
One piece, 98% pure electrolytic copper, based on maximum total temperature rise of 40 deg. C over an ambient of 50 deg. C at full continuous rating, and maximum current density of 1.25 A/mm2. Bolted or clamped contact surfaces are to have maximum current density of 0.25 A/mm2. Aluminum is not to be used for busbars or panelboard parts.
DESIGN:
Busbars are to be shrouded/insulated and rigidly designed so that branch circuit devices can be removed without disturbing adjacent units or changed without additional machining, drilling or tapping. Busing is to be full size without reduction. Busing and blank plates are to allow installation of future circuit devices, where indicated on the Drawings.
RATING:
Busbar rating is to be at least equal to main-circuit- breaker frame size. Where no main circuit breaker is required, busbars are to be provided with main lugs or a disconnect switch, with a nominal rating equal to standard circuit-breaker frame sizes, and as shown on the single line diagrams and panels schedule.
SHORT-CIRCUIT DUTY:
Bus bars are to carry maximum short-circuit duty of main protective device, which is to be at least maximum short- circuit at point of application for a period of one second, without showing any signs of degradation.
TERMINALS AND CONNECTIONS:
Are to be of the anti-turn, solder less screw-pressure type. Screws and bolts used for making copper/copper connections are to be hard copper alloy with lock washers (riveted bus connections are not acceptable).
NEUTRAL BAR:
Is to be solid and fully insulated from cabinet or box. One solder less box type set-screw connector is to be provided for neutral wire of each branch circuit and one bolted clamp-type connector or anti-turn lug with set-screw for main incoming neutral wire. Neutral is to be fully sized and rated as for phase busbars.
EARTHING BAR:
Is to be copper, brazed to panelboard cabinet, with bolted pressure connector for main conductor and one set-screw-type tunnel terminal for each outgoing conductor, to provide a secure and reliable contact with all metal parts and enclosure.
3.7.2.1.10 MOULDED CASE CIRCUIT BREAKERS (MCCB
TYPE:
Totally enclosed, molded case, constructed from high quality, high temperature tropicalized molded insulating materials, for continuous normal operation at 100% rated current at ambient temp 40 oC inside the enclosure. For within enclosures and provided with front operated single toggle type handle mechanism for manual operation of main contacts in addition to automatic operation under over current conditions. Multi-pole breakers are to have a common integral trip bar for
Simultaneous operation of all poles. Ampere rating is to be clearly visible. All terminals are to be box lug or clamp type with set screws.
CIRCUIT BREAKER TRIP UNITS:
Unless otherwise specified or shown on the Drawings, circuit breakers up to and including 250 A frame size, are to be electronic thermal-magnetic type, having bi-metallic inverse time delay over current element for small overloads and in stantaneous magnetic over current trip element for operation under short-circuit conditions on each pole. Circuit breakers 250amp and larger are to have adjustable instantaneous trips.
SWITCHING MECHANISM:
Quick-make, quick-break type, with positive trip-free operation so that contacts cannot be held closed against excess currents under manual or automatic operation. Contacts are to be non-welding silver alloy provided with approved arc quenching devices of metallic grid construction.
TRIP CURRENT RATING (AMPS):
Indicates nominal maximum rating at which the overload element is set to operate.
FRAME SIZE:
Is defined as the maximum continuous current rating of a circuit breaker which corresponds with the maximum of its trip range listed below and which is to be related to minimum acceptable short-circuit interrupting ratings, based on fully rated interrupting duties; normal duty (N), high break (H), or current limiter (L), as specified hereunder.
TRIPPED POSITION:
When tripped automatically by over current condition, operating mechanism of circuit breaker is to assume an intermediate position clearly indicated by the handle between ON and OFF positions.
INTERCHANGEABLE TRIPS:
All circuit breakers have interchangeable trip units.
COMPENSATION:
Thermal over current trips are to be ambient temperature compensated between 25 and 50 deg. C.
ELECTRONIC TRIP UNIT:
Applicable to circuit breakers 800 A frame size and larger, are to be solid state trip units with long time delay settings, between 0.4 to 1 times maximum trip rating, short time delay range of 3 to 10 times maximum trip rating with a maximum clearing time of 0.2 seconds, and instantaneous protection adjustable from 2 to 10 times continuous rating. Solid state trip units are to be insensitive to changes in ambient temperature between -20 and +55 deg.C. Earth fault protection is to be built into trip unit where specified, and is to be suitable for connection to an external current sensor. Push-to-trip button is to be provided on cover for testing the trip unit.
ACCESSORIES:
Circuit-breakers are to be designed to accommodate standard attachments, including shunt-trip, under-voltage release, combined auxiliary and alarm switches, and electrical operator to any circuit breaker of rating (frame size) 100 A and over. Padlocking devices are to be provided as additional accessories, where shown on the Drawings.
3.7.2.1.11 OPERATED EARTH RESIDUAL CURRENT LEAKAGE TRIP DEVICES (RCDs):
Are provided as add-on where required and as shown on the Drawings. Protection against earth fault current, in addition to over current and short- circuit protection, is to be in accordance with the Regulations. Trip current sensitivity on breakers for branch circuits is to be 30 mA. Circuit breakers are to include current transformer with tripping coil assembly, test button and trip free mechanism to ensure circuit breaker cannot be held closed against earth faults.
3.7.2.1.12 CURRENT LIMITING CIRCUIT BREAKERS:
Molded case type without fusible elements. When operating within current limiting range, the I2t of let-through current is to be less than that of 1/2 cycle wave of symmetrical protective short- circuit current as compatible with breaker construction.
3.7.2.1.12 .1 CURRENT LIMITING CIRCUIT BREAKERS:
Are to have, on each pole, adjustable inverse time-delay over-current characteristics for overload protection and instantaneous trip for short-circuit protection. Operation of main contacts is to be based on electro-magnetic repulsion forces between contacts created by fault current. Ratings are specified at rated voltage for an rms value of prospective short circuit current.
3.7.2.1.13 MINIATURE CIRCUIT BREAKERS (MCBS )
TYPE:
Thermal magnetic non-adjustable type tested in accordance with IEC-157-1, IEC 947-2.
MINIMUM SHORT-CIRCUIT BREAKING CAPACITIES:
Are to be as follows:
10 - 100 A MCB: 10 or 16 kA at 220 V . A . C .
CONSTRUCTION:
MCBs are to be tropicalized for continuous normal operation at 100% rated current at ambient temp 40oC outside the enclosure. and humidity to 95%, and are to be constructed from high quality, high temperature, molded insulating materials. Guaranteed duties and characteristics are to be submitted for temperatures above 40 deg. C. MCBs and combinational devices are to be modular, of unified profile and mounted to standard DIN rail.
OPERATION:
Under overload conditions, thermal tripping is to provide close protection of insulated conductors. Under short-circuit conditions, the magnetic trip is to operate at 5 - 10 times normal rated current (type 3 characteristic). Magnetic operation is to be in the current limiting region and opening time is not to exceed 5 milli-seconds.
RATINGS:
Preferred rated currents are to be 10, 16, 20, 25, 32, 40, 50, 60, 80 and 100A, calibrated at 40 deg. C, available as 1p, 2p, 3p and 4-pole circuit breakers. Derating above 40 deg. C is not to exceed 1% per deg. C, and loading is not to exceed 80% of circuit breaker rating.
RESIDUAL CURRENT DEVICES:
For earth leakage protective circuit breakers are to be add-on devices or built-in and integral with the standard circuit breaker. Non-adjustable sensitivities of 30 mA, 100 mA and 300 mA are to be available for all ratings of 2-pole and 4-pole circuit breakers.
AUXILIARIES:
Where required or shown on single line diagram are to include alarm switch, auxiliary switch, shunt trip, under voltage trip and similar units which are to be modular additions to the circuit breakers.
3.7.2.1.14 MOULDED CASE SWITCH (MCS )
MOULDED CASE SWITCH:
Is to be a non-automatic on-off switching device of equal construction to an equivalent circuit- breaker, having no over current or fault protective elements, but marked with a maximum current withstand and voltage rating.
SHORT CIRCUIT RATINGS:
Circuit breakers are to be rated for symmetrical r.m.s service short current breaking capacity 100% of the ultimate short circuit current breaking capacity as per IEC 947-2.
3.7.2.15 PANELBOARD ASSEMBLIES
DISTRIBUTION PANELBOARDS ( D P )
Distribution panelboard is to have an insulation grade of 600 V a.c., 240 V. d.c. conforming to IEC 439 and BS 5486: Part 1 class 3 surface mounted to wall, with doors, unless otherwise shown on the Drawings, suitable for ratings of main circuit breaker and busbars 3-phase, 4-wire as shown in schedules, suitably and orderly arranged for any selected combination of branch MCCBs ranging and short-circuit interrupting ratings as shown on the schedules.
CONSTRUCTION:
Cabinet/box is to be minimum 2 mm thick sheet steel suitable for mounting relevant C.B's. Trim or trim and door are to be of minimum 2 mm thick sheet steel. Fronts are to be single or twin covers to shield circuit breakers, terminals and live ends.
INTERIOR:
Of panelboard is to be a pan assembly consisting of chassis of minimum 2mm thick folded galvanized sheet steel, flanged and reinforced, with busbars vertically arranged and fixed mounted on molded insulators. Assembly is to be removable, fixed to four threaded studs or similar arrangement, and is to allow in and out adjustment inside the cabinet.
MOULDED INSULATORS:
Are to have minimum temperature rating of 130 deg. C and insulation grade of 3.5 kV for one minute.
CIRCUIT BREAKERS:
Are to be mounted in suitable arrangement (except for larger circuit breakers) and bolted rigidly to copper cross and centre bus connectors.
3.7.2.16 LIGHTING PANEL BOARDS
ARRANGEMENT:
Panelboard is to comprise a set of homogeneous branch circuit-breakers with unified profile and base, and one main circuit breaker. Single and multi-pole circuit breakers or other devices are to occupy modular spaces.
Accommodation of contactors and split-bus arrangement or other devices is not to change regularity of standard box width.
INDOOR ENCLOSURE:
To be of minimum 1.0 mm thick sheet steel (suitable for mounting the C.B as shown in schedules) for box/cabinet and minimum 1.5 mm thick sheet steel for front shield, trim and door. Fixings for flush trim are to be adjustable to allow for misalignment between box and wall surface. Wiring spaces (gutters), at least 100 mm wide. Larger gutters are to be provided where tap-off insulated split connectors are required. Knockouts are to be provided in top or bottom sides of enclosures and are to provide a neat and uniform conduit/cable terminal arrangement.
TYPE:
Panelboard for 220 V. a.c. or up to 380 V a.c. service voltage, lighting type single-phase and neutral (SPN) or 3-phase and neutral (TPN), 2-pole or 3-pole MCCBs on branch circuits and 2-pole or 3-pole MCCB on main incoming, or as shown in schedules.
BRANCH CIRCUIT BREAKERS:
Are to be 1p, 2p or 3p, rated 100A frame size with trip ratings between 10 A and 100 A, and compatible ICs, selected from normal (N), high-break (H) or current-limiter (L) range are to din rail mounted.
MAIN CIRCUIT BREAKER:
Is to be 2p, 3p or 4p, rated as shown in schedules, 225/250 A or 400 A continuous rating (frame size) with trip ratings and fully rated non-current limiting ICs of the normal (N) or high-break (H) ranges, with or without residual current device (RCD) as indicated on schedules.
INTERNAL ASSEMBLY:
To consist of removable back plate or back pan of rigid construction, attached to enclosure by four captive screws through keyhole fixings, and provided with DIN rails in horizontal arrangement for SPN panels and in vertical arrangement for TPN panels. Assembly is to be complete with neutral terminal block, earthing bar and one piece insulated bolt-on/comb- type phase busbar. Busbars are to be single- phase or 3-phase with spare connectors for fixing by tightening a single screw on circuit breaker.
Insulation is to be of high thermal rating, capable of carrying maximum short-circuit current for one second without overheating beyond acceptable limits required by the Standards.
3.7.2.17 SPN TYPE PANELBOARDS:
Are to be suitable for 220 V maximum service voltages, single-phase and neutral, with MCBs on branch circuits and main incoming.
3.7.2.18 TPN TYPE PANELBOARDS:
Are to be suitable for up to 380 V a.c. maximum service voltage, 3-phase and neutral, with MCBs on branch circuits and 3-pole or 4-pole MCB or MCCB main incoming, as shown in the Schedules or on the Drawings.
3.7.2.19 CONTACTORS:
2-pole or 3-pole, electro-magnetic type, class AC 3 to IEC 947-4, designed to withstand large initial currents of tungsten lamp loads or discharge lamp loads and rated not less than the overload setting of the protective device upstream. Contacts are to be double break silver cadmium plated, having self-cleaning wiping action. Control is to be provided by means of phase-neutral (maximum 220V) split coil, for on-off activation by local and/or by remote direct-wired on-off push-buttons. Contactor is to be mechanically latched. Control circuit is to be fused. Auxiliaries are to include local pilot light, parallel remote indicating circuit, two N.O. and two N.C. auxiliary contacts.
PART 3 FIELD AND INSTALLATION WORK
3.7.3.1 FIXING GENERLLY :
- Align, level and securely fasten panel boards to structure
- Fix surface mounted outdoor panel boards at least 25 mm from wall ensuring supporting members do not prevent flow of air
- do not use connecting conduits to support panel boards.
- Close unused openings in panelboard cabinets.
3.7.3.2 PANELBOARD INTERIORS:
Do not install in cabinets until all conduit connections to cabinet have been completed.
3.7.3.3 WIRING INSIDE PANELBOARDS:
Shall be factory made.
3.7.3.4 TRIM:
Fix plumb and square prior to painting. Fix trim for flush mounted cabinets flush with wall surface finish.
3.7.3.5 PROTECTION:
Treat concealed surfaces of recessed cabinets with heavy field application of water-proof compound prior to installation.
3.7.3.5 INSPECTION AND TESTS ON SITE
GENERALLY:
Carry out sample tests, as required by the Engineer, on panel boards after installation, to verify short-circuit capability of circuit breakers and busbars. Inspect conditions within panel boards and verify insulation conditions by use of a megger
CIRCUIT BREAKERS:
Tests are to include operation of every circuit breaker manually. Check automatic operation of selected circuit breakers, as required by the Engineer, by applying necessary short-circuit, overload, and/or earth leakage current for tripping circuit breaker, and compare with manufacturer's data/characteristic curves. Measure and report ambient temperature inside enclosure.
INSULATION TESTS:
Carry out insulation tests on all busbars between phases, between phases and earth/cabinet, and between neutral and earth. Record all readings, using a 500 V megger for equipment used on 240 V systems and a 1000 V megger for equipment used on systems up to 600 V.
Labeling: to be engraved type for all incoming C.B and outgoing C.B
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